Puget Sound Faults
The Puget Sound faults under the densely populated Puget Sound region (also known as the Puget Lowland) in Washington State form a complex of contiguous seismically active geological faults that can trigger earthquakes. These include (listed on the adjacent map from north to south; the "F" used in the abbreviations comes from the English "fault" = "rejection"):
- Devils Mountain Fault (DMF)
- Strawberry Point Fault and Utsalady Point Fault (SPF and UPF)
- Southern Whidbey Island Fault (SWIF)
- Rogers Belt (Mount Vernon Fault / Granite Falls Fault Zone) (RB)
- Cherry Creek Fault Zone (CCFZ)
- Rattlesnake Mountain Fault Zone (RMFZ)
- Seattle Fault (SF)
- Tacoma Fault (TF)
- Saddle Mountain Faults (SMF)
- Olympia structure (OS; possibly a fault)
- Doty Fault (DF)
- Saint Helens Zone and Western Rainier Zone (SHZ and WRZ)
General background
Sources of and danger from earthquakes
The Puget Sound region in western Washington forms the economic backbone of the state because of its population concentration; seven percent of the US's international trade goes through this region. ("The Puget Lowland is a north-south oriented structural basin that is flanked by Mesozoic and Tertiary rocks of the Cascade Range in the east and by Eocene rocks of the Olympic Mountains in the west." The Georgia Basin in the north is structurally connected, but topographically by the Chuckanut Mountains near Bellingham .) This region is at risk from earthquakes due to three sources:
- a large subduction earthquake like the one in 1700 , magnitude 9 on the Richter scale , caused by sliding the entire Cascadia subduction zone from an estimated Cape Mendocino in Northern California to Vancouver Island in British Columbia
- Earthquakes within a tectonic plate (intra-crustical; Wadati-Benioff zone ) such as the 2001 Nisqually earthquake with a magnitude of 6.7 on the Richter scale, which occurred on one or a fracture of a small part of a subducting plate at a depth of about 50 kilometers
- relatively shallow earthquakes in the earth's crust, generally less than 25 kilometers deep, caused by unrest and faults in near-surface structures in the earth's crust; the energy released depends on the depth of the fault; the faults discussed here are believed capable of triggering earthquakes with magnitudes of 6 or 7
While the large subduction events release a lot of energy (with a magnitude of 9), this energy is spread over a large area, most of which is close to the coast. The energy of the much smaller Benioff earthquakes is also weakened and spread over a relatively large area. The most violent intra-crustal earthquakes have about the same total energy (which is about one hundredth of a subduction event), but because they occur closer to the surface, they produce more powerful vibrations and therefore greater damage.
A seismic vulnerability study of bridges in the Seattle – Tacoma area estimated that magnitude 7 earthquakes in the Seattle or Tacoma faults would cause nearly the same damage as a magnitude 9 subduction earthquake because the two faults directly below the highest If the population and economy are concentrated in the region, greater damage would be expected, but all of the faults discussed here could cause severe damage locally and disrupt regional infrastructure such as motorways, railways and pipelines. (For links to more information on various hazards, see the Seattle Fault article .)
Not only does the Puget Sound region have potentially seismic activity, it is actually seismically active. A map from the Pacific Northwest Seismic Network shows that the majority of the earthquakes in western Washington are concentrated in four locations: in two nearby zones under Mt. Saint Helens and Mt. Rainier , along the DDMFZ, and under the Puget Sound between Olympia and close to the Southern Whidbey Island Fault. The southern border runs roughly on the southern border of the Pleistocene glaciation; the seismic activity may reflect the uplifting of the upper crust by the glacial masses after the depression.
discovery
Huge deposits of glaciers and other springs, lush vegetation, urban development, and a topography of sharp relief and rapid erosion obscure the superficial signs of faults in this region and have hampered its discovery. The first sure signs of most faults are from a 1965 grave map, and their likely existence was noted on 1980 and 1985 maps. Until 1985 only the Saddle Mountain faults showed Holocene activity (since the last glaciation about 12,000 years ago). Until 1992, the first of the lowland faults, the Seattle Fault, was not recognized as a true fault with Holocene activity, or even a minimum known about its history.
The discovery of the faults was greatly helped with the development of LIDAR , a technique that can normally penetrate the vegetation cover, including the canopy of forest canopies, and map the surface of the earth with the unprecedented resolution of about one foot (30 cm). An informal consortium of regional authorities coordinated a lidar mapping of much of the central Puget Lowland, which resulted in the discovery of numerous fracture levels of faults, which were subsequently explored through excavations and subsequent paleoseismological studies. Marine surveys using reflection seismics in Puget Sound, where it is cut by various faults, have provided cross-sectional views of the structure of some of these faults, and an intensive, large-scale combined near / offshore study (Seismic Hazards Investigation in Puget Sound, SHIPS) carried out in 1998 a three-dimensional model of much of the geometry hidden beneath the surface. Aeromagnetic surveys, seismic tomography and other survey methods have also contributed to the localization and understanding of these faults.
Geological structure
The ultimate driver of the tensions that cause earthquakes are the movements of the tectonic plates : material from the earth's mantle strives to the surface in mid-ocean ridges and moves away from the ridge as plates of the oceanic crust , which ultimately under the more upwelling plates of the continental crust is subducted. West Washington lies over the Cascadia subduction zone , where the Juan de Fuca plate is subducted under the eastern part (see graphic on the right). This is obliquely pushed over by the North American plate coming from the northeast , which has formed a curve in the subducted plate and the forearc basin above it . This curvature deformed the subducted floe into an arch that lifted the Olympic Mountains and saved them from subduction. During the past 50 million years (since the early Eocene ), the subduction pressed them upwards against the North Cascades (“fixed block” in the graphic), which sit on the North American plate. This forms a pocket or trough - what a local geologist called the "big hole between the mountains" - between the Cascades to the east and the Olympic Mountains and Willapa Hills to the west. This pocket holds a stream of terrans (crust blocks about 20 ... 30 kilometers thick) that were pushed with the Pacific plate over the western border of North America, and in the process a clockwise rotation of southwest Washington and most of Mediate Oregon; the result was described as the wreck of a train. These terranes were overlaid by the basalts of the Crescent Formation (parts of Siletzia ). Folding and warping have brought these basalts to the surface in places (the black areas in the graphic); the basins in between were filled with various sediments, some of which were eventually lifted up. Glacial deposits and deformed fillings cover most of the lowlands on Puget Sound. These form the Puget Lowland. The principal effects of this complex interaction of forces on the near-surface crust under the Puget Lowland are:
- The basement of the Crescent Formation is raised on the southern, eastern and northern flanks of the Olympic Mountains and in several folds.
- Some formations in the outer crust of the earth (such as the Western and Eastern Melange Belts, see map ) would be pressed onto the older (pre- tertiary ) base of the North Cascades.
- There is a general north or north-east directed compression within the lowland forming folds which eventually breakup, to dip-slip -Verwerfungen (vertical movement), thrusts or reverse faults to be.
- Some blade shifts (horizontal movement) are expected along the peripheral faults (as in the case of the Southern Whidbey Island and Saddle Mountain faults).
This is further complicated by a feature of unknown structure and origin, the Olympic-Wallowa Lineament (OWL). It is a seemingly coincidental sequence of topographical features, which runs roughly from the north side of the Olympic Peninsula east-southeast to the Wallowa Mountains in northeast Oregon. It coincides with the West Coast Fault and the Queen Charlotte Fault system of leaf displacement zones (similar to the San Andreas Fault in California) on the west side of Vancouver Island, but shows no significant or continuous horizontal motion itself. It is of interest here because the various strands of the Seattle Fault switch orientations as they appear to cross the OWL. Several other features such as the Rosedale monocline and the Olympia structure, as well as a large part of the topographical features, have parallel alignments. It could also be the original location of the Darrington-Devils Mountain Fault (the dashed line marked “X” at the top of the following map). The OWL appears to be a deep structure over which the shallow crust of the Puget Lowland is pushed, but this remains speculative.
A pattern of elevations and pelvis
Most of these "faults" are actually zones of complex faults at the boundaries between sedimentation basins ( synclines ) and uplifts of the crust ( anticlines ). There is a general pattern by which most of these faults divide up a series of basins and uplifts, each about 20 km wide. From north to south these are (see map on the right):
- Devils Mountain fault zone (including Strawberry Point and Utsalady Point faults)
- ∪ Everett Basin
- Southern Whidbey Island Fault (SWIF)
- ∩ "Elevation of unknown origin" (Port Ludlow)
- Kingston Arch (Eng. About "Kingston Arch"; Lofall Fault - Because of the geometry of the SWIF and Kingston Arch, the "uplift of unknown origin" between them is smaller and the fault that separates the uplift from the arch [the Lofall fault , discovered not long ago by Brocher et al. (2001)] is shorter; it is not remarkably seismically active.)
- ∪ Seattle Basin
- Seattle Fault Zone (approximately the lines EF)
- ∩ Seattle uplift
- Tacoma Fault Zone (approximately Line C)
- ∪ Tacoma Basin
- Olympia fault (roughly line A)
- ∩ Black Hills uplift
- Doty Fault / Scammon Creek Fault (dashed lines; strictly speaking, the southern limit of the Black Hills uplift would be the southeast trending Scammon Creek fault which converges with the east trending Doty Fault at Chehalis. At the angle between these is the smaller Lincoln Creek uplift, the Doty Hills, and, farther west, an impressive chunk of crescent basalt. If the pattern is continued southwest, along junction AA 'in Pratt's Figure 11 [and the mapped course of Doty Fault is ignored], then the next basin is at Grays Harbor [not listed here]. The Doty Fault / Chehalis Basin complex follows intersection XX 'on the map )
- ∪ Chehalis Basin
The Hood Canal Fault (and its possible extensions) and the Saddle Mountains Faults to the west are believed to be the western limit of all of this. To the east, the Devils Mountain Fault joins the south-trending Darrington Fault (not shown) which runs to the OWL, and the Southern Whidbey Island Fault extends over the Rattlesnake Mountain Fault Zone (dashed line) out to the OWL. No definitive eastern border has yet been found south of the OWL; there are some signs that it cannot be determined. (For example, the Olympia Fault is associated with a series of faults between Olympia and Chehalis that could extend as far as the Columbia River ; it also appears to be its northernmost limit. There is also evidence that the Tacoma Fault coincides with the White- River / Naches River Fault on the east side of the Cascade Range.)
The uplift and basin pattern continues to the west and southwest with the Grays Harbor Basin, Willapa Hills uplift, and Astoria Basin, but it is not known whether these faults in the same way as in the Puget Sound region are limited.
Structural models
Thrust cover hypothesis
It is believed that all of these faults, folds, basins and uplifts are related. According to the outstanding model, the “Puget Lowland Thrust Nappa Hypothesis”, these structures (faults etc.) occur within a clod of the earth's crust at a depth of about 14 ... 20 kilometers, which has separated from deeper crustal structures and was pushed over them. Most of this thrust cover consists of the Crescent Formation (which in turn corresponds to the Siletz River volcanoes in Oregon and the Metchosin Formation on Vancouver Island), a huge volcanic Eocene basalt eruption (approx. 50 million years old), which comes either from a chain of submarine mountains or from a "rifting" (the opening of a rift ) on the continental margin (see Siletzia ). This " basement " is covered by sedimentary deposits similar to the Chuckanut Formation and more recent (typically Miocene ) volcanic deposits. The Seattle Uplift, and possibly the Black Hills Uplift as well, are comprised of basalts from the Crescent Formation that came to the surface when pushed over some sort of ramp. This ramp could either have been less deep-lying crustal blocks or consisted of the broken and pushed thrust cover. Faults and folds may have developed where the thrust cover is bent, or where its leading edge pushed over softer, weaker sediments and then broke up and fell.
If, as the model suggests, the various faults are connected to the thrust cover, then there is the possibility that one earthquake could trigger more. This view is particularly astonishing, as it would explain several seismic events in close succession about 1,100 years ago.
Seismotectonic modeling
In the previous study, seismicity, surface geology and geophysical data were modeled to model the fault structures of the upper crust of the earth. Another model - more complementary than competing with the first - used seismic and other data to create a 3-D tectonic model of the entire earth's crust; this was later analyzed with the help of finite elements in order to determine the regional geodynamic features.
A principal finding is that "the crust seismicity in the southern Puget Sound region appears to be blocked by a block of the Crescent Formation in a key position just south of the Seattle Fault." More precisely, this means that the concentration of Seismicity under Puget Sound south of the Seattle Fault is associated with the uplift of this block, bounded by the Seattle, Tacoma, and Dewatto Faults to the north, south, and west (the eastern boundary is undetermined). It is also believed that the Great Quake in Seattle about 1,100 years ago, as well as other related seismic events in southern Puget Sound around this time, affected the entire block; the magnitude was about 8, the quake was possibly triggered by an earthquake in the deeper crust of the earth.
Very little is known about the structure of the earth's deeper crust (below about 30 kilometers), although this and other seismotomographic studies (such as Ramachandran (2001)) provide tempting glimpses.
The Quaternary fault and fold database (QFFDB) of the USGS , which contains details of the discovery, a technical description and a bibliography for each fault, is the primary source for the following overviews ; a specific link (if available) will be provided at the end of each section.
Devils Mountain Fault
The Devils Mountain Fault (DMF) runs about 125 km from the small town of Darrington in the foothills of the Cascade Range west to the northern tip of Whidbey Island and on to Victoria, British Columbia . It is believed to merge there with the Leech River fault system at the south end of Vancouver Island. In Darrington it is connected to the Darrington-rejection, which is about 110 km south passes and with the Creek rejection Straight (SCF) is merged to finally close Easton to change the direction and at the Olympic-Wallowa-lineament to be connected ; collectively, this complex is referred to as the Darrington-Devils Mountain Fault Zone (DDMFZ).
The Devils Mountain Fault separates two similar but different ensembles of Mesozoic (i.e., pre-tertiary, that is, pre-dinosaur extinction) or older rocks. In the north it is the Helena-Haystack-Melange (HHM; in the graphic on the right: HH mélange, violet), in the south it is the West- and East-Melange-Belt (WEMB, blue). There are some interesting relationships here. The HHM rocks were found in the Manastash Ridge , 110 km south (the small purple spot in the lower part of the graph). In addition, the Chuckanut Sedimentary Formation (part of the NWCS, green) north of the DMF correlates with the Suak and Roslyn Formations just north of the Manastash Ridge. All of this is explained by a dextral (right-handed) leaf shift on the Straight Creek Fault, which began about 50 ... 48 million years ago. That is exactly the time after which the terran bearing the Olympic Mountains came into contact with the North American continent. These mélanges could have been offshore islands or submarine mountains sandwiched between the Olympic Terran and the North American continent and autopsied across the continent . Other similar rocks have been found at Rimrock Lake Inlier (in the graphic below), in the San Juan Islands, and in the Pacific Coast Complex along the West Coast Fault on the west side of Vancouver Island. It appears that the entire DDMFZ and Leech River fault system have been shifted from their original position along the OWL to the early continental margin. This is a significant observation because the Strawberry Point, Utsalady Point, Southern Whidbey Island and various other unnamed faults that lie between the DDMFZ and the OWL - all converging at the west end of the DDMFZ - intermediate stages seem to be the DDMFZ.
The movement of the southern segment of the DDMFZ, which converges with the SCF - the Darrington Fault - was, like that of the SCF itself, right-handed. And as with the SCF, the blade shift ended 44… 41 million years ago (due to plutonic collapses). The western segment, however - the Devils Mountain Fault - has a sinistral ( left, meaningful) movement. This is because the Olympic Terran is moving northeast (relative to North America); its continued clockwise rotation resembles a gigantic wheel rolling along the west side of the crystalline core of the North Cascades. Geology also suggests that the DMF is moving at an incline over a ramp rising to the east, perhaps a long-gone stretch of coastline.
The Devils Mountain Fault is seismically active and there is evidence of Holocene dropouts in this activity. If the entire 125 km broke apart in a single event, the resulting earthquake could have been up to 7.5 in magnitude. However, there is evidence that the fault is segmented, which would have limited both the fracture and the earthquake magnitude.
Strawberry Point and Utsalady Point Faults
Strings of the eastbound Devils Mountain Fault traverse the northern tip of Whidbey Island at Dugualla Bay and the north side of Ault Field (Whidbey Island Naval Air Station). Just four miles (6 km) south of the town of Oak Harbor , several piers span the Utsalady Point Fault (UPF) as they point roughly southeast towards Utsalady Point on the north end of Camano Island. And between these two, the Strawberry Point Fault (SPF) bypasses the south side of Ault Field, splits into several strands that brace Strawberry Point, and eventually disappears (or ends) under the Skagit River delta . Both SPF and UPF are ascribed a sloping course, that is, the faults show both horizontal and vertical movements, as the crust blocks are pressed against each other. These faults also form the northern and southern boundaries of the uplifted pre-tertiary rock, suggesting that the faults collide at greater depth, broadly like a model of the Seattle and Tacoma faults, but on a smaller scale . Sea seismic reflection studies on either side of Whidbey Island extend the known length of these faults to at least 26 and 28 km, respectively. The real length of the UPF is possibly twice as great as it forms the southern limit of an aeromagenetic high which extends another 25 km to the southeast. The trench formation at the UPF (at a stage identified with the help of LIDAR) shows at least one, possibly two woodane earthquakes with your magnitude of 6.7 or greater, the younger of which occurred between 1550 and 1850 and possibly by the Cascadia earthquake of 1700 was triggered. These earthquakes may have caused tsunamis, and several nearby locations show evidence of tsunamis that are not correlated with other known quakes.
Because there is a piece of uplifted pre-tertiary rock between the SPF and the UPF, it doesn't really match the uplift and basin patterns described above because it is on a smaller scale (more than 2 km wide than around 20) and the uplift is complete here how a wedge was pushed out between two nearly vertical faults instead of being pushed over a ramp like the Seattle and Tacoma faults. In addition, there is no significant basin between these and the Devils Mountain Fault. Based on marine seismic reflections from the Juan de Fuca Strait exploration, it was assumed that the DMF, SPF and UPF are structurally connected (at least in the Whidbey Island crossing segment).
Southern Whidbey Island Fault
The Southern Whidbey Island Fault (SWIF) is a notable terran boundary that manifests itself as a zone of complex transpressional faults with at least three strands approximately four miles (6.4 km) wide . Research on marine seismic reflections indicates that it is sweeping northwest across the east end of the Strait of Juan de Fuca. Exactly south of Victoria, British Columbia, it intersects the westbound Devils Mountain Fault (see above) and either merges with or traverses (and perhaps cuts off) to merge with the Leech River Fault . The Leech River Fault has been identified as the northern edge of the Crescent Formation (also called the Metchosin Formation and part of the Siletzia Terran under much of western Washington and Oregon). Seismic-tomographic studies show that this part of the SWIF marks a strong contrast of the seismic transit times, so that the basalts of the Crescent Formation are expected to have contact with the metamorphic basement of the geological province of the Cascade Range in the east. (This contact represents the coast-range-boundary fault, see below.)
To the southeast, the SWIF passes the Admiralty Inlet (behind Port Townsend ) and crosses the southern part of Whidbey Island to cross the mainland between Mukilteo and Edmonds . This section of the SWIF forms the southwest side of the Everett Basin (see map ), which is remarkably so aseismic that no significant shallower earthquakes (less than 12 kilometers deep) there or in the section where the SWIF reaches it first 38 years of instrumental observation. Equally noteworthy so far is that "most of the seismicity in northern Puget Sound along and southwest of the Southern Whidbey Island Fault typically occurs at depths of 15 ... 27 kilometers within the deeper part of the Crescent Formation."
The contrast of seismic propagation velocities as in the northwest is missing in this section, so that it is obvious that there is no contact with the Coast Mountains or the cascade chain. The meaning of this - whether the edge of the Crescent Formation (and implicitly that of the Siletz Terran) turns south (see the discussion below ) or whether the metamorphic basement is being displaced by other volcanic rocks - is unknown. It has been suggested that a corresponding change in the nature of the SWIF might reflect a change in the orientation of regional pressures on the crust. Prior to 2000, prominent aeromagnetic anomalies strongly suggested that the fault zone continued to the southeast, possibly to the small town of Duvall , but this was uncertain as it is largely hidden and the faint superficial traces have usually been overbuilt by urban development. After 2000, investigations using LIDAR and high-resolution aeromagnetic data identified fracture stages near Woodinville , the incisions of which were confirmed to be tectonic and geologically young.
The subsequent mapping shows that the SWIF winds around the east end of the Seattle Basin , then merges with the Rattlesnake Mountain Fault Zone (RMFZ); The RMFZ is today, apart from the turn deflected by about 15 ° and another connection, taken for the southern extension of the SWIF. (see maps of Fall City, North Bend and Carnation) The calculated length of the SWIF between Victoria and Fall City is around 150 km.
It was suggested that the SWIF could extend beyond its intersection with the RMFZ (only with peripheral strands that connect to the RMFZ) and further across the cascades, in order to eventually cross or be united with the Olympic-Wallowa Lineament ; an examination of regional peculiarities suggests such a pattern. (Blakely et al. 2011; their preferred interpretation is that the SWIF has a right-hand gap along the RMFZ.) However, detailed mappings just beyond the intersection show only a complex and confusing pattern of faults, with no evidence of an existing or non-existent continuous one Rejection. There are currently no plans to map areas further east that could elucidate this pattern.
Paleoseismological studies are summarized below. One study compared the relative height of two marshes on opposite sides of Whidbey Island and found that about 3,000 years ago an earthquake with a magnitude of 6.5 ... 7.0 caused an uplift of 1 ... 2 meters. Another study identified an unusually broad band of escarpment running between Bothell and Snohomish , several of which in the vicinity of the controversial regional sewage treatment plant at Brightwater had at least four, possibly nine seismic events on SWIF over the past 16,400 years. These seismic events were a major problem in choosing the location of the plant, as it was placed between two active strings and the inflow and outflow pipelines cross several zones of unsafe subsoil.
Rogers Belt
To the north of Everett there is an area of parallel mountain ranges and drainage basins that are roughly NW-SE oriented and stand out clearly even on non-geological maps. (Interstate 5 runs almost exactly north from Everett to Mount Vernon , with the exception of a stretch southeast of Conway that runs parallel to one of these low folds . In some places, such as along the South Fork Stillaguamish River between Arlington and Granite Falls, there is There are also drastic geological features.) These chains (part of a larger regional pattern reflecting the base of the former Calkins Range ) are formed by sediments that accumulated in the Everett Basin in the Eocene and finally by northeastward compression against older Cretaceous and Jurassic rocks in the East bounding the Puget Lowland were folded. At the boundary of these older rocks is the Rogers Belt, a geologically interesting zone stretching from the Sultan area (just east of Everett) to Mount Vernon (north of the belt in the Devils Mountain Fault ) enough. Taking into account these topographical peculiarities, some parallel gravity gradients and a “very active zone of low seismicity”, William Rogers concluded in 1970 that there was a “fault or other significant structural feature”.
The Bellingham Bay / Chaplain fault zone was first mapped by Cheney in 1976 as running north-northwest from nearby Chaplain Lake (north of Sultan) to beyond Bellingham Bay . Doubts about the connections of these faults led to the name no longer being used from 1986 when Cheney opened the Mount Vernon Fault (MVF) from near Sultan northwest over Lummi Island (on the west side of Bellingham Bay, visible in the map above ) and the Devils Mountain Fault ( DMF , part of the Darrington / Devils Mountain Fault Zone) near Mount Vernon. Cheney also mapped the Lake Chaplain Fault, which runs parallel to and just east of the MVF from Lake Chaplain to Granite Falls .
Detailed mapping of this area since 2006 has revealed a complex pattern of faults. At the north end, the right-shifting McMurray Fault Zone (MFZ) spans Lake McMurray, just south of the Devils Mountain Fault; it is believed to be an important limiting fault. This boundary coincides with a topographical fracture structure that runs from Mount Vernon in the north to the town of Granite Falls and Lake Chaplain (just north of Sultan).
The Woods Lake Fault , which extends beyond Lake Chaplain, corresponds very closely to the mapped location of the southern end of Cheney's Mount Vernon Fault. Subsequent mapping, however, indicated that the Woods Creek Fault (WCF), a four mile (6.4 km) wide strip of transient faults and blade faults running to the west and just below Sultan , the more significant fault and better aligned with Mount Vernon seems. These two faults (and several others) appear to end at the leftward shifting Sultan River Fault on the western edge of the north- northeast facing Cherry Creek Fault Zone (CCFZ; see next section). (The location of some previously mapped faults has been adjusted on the latest maps.) The main fault zone extends from the Woods Creek Fault to the Granite Falls Fault Zone (GFFZ), a short distance from the WCF and trending under Granite Falls. Although the interrupting section has not been mapped, geologists believe the GFFZ is connected to the McMurray Fault Zone to the north and forms the eastern boundary of the Everett Basin.
These faults cut through the Western Mélange Belt (WMB; blue area on the map ), which emerges from North Bend (on Interstate 90) to Mount Vernon. The WMB is a mixture of late Jurassic and Cretaceous rocks (some of which are up to 166 million years old) formed in an accretion wedge (or prism) of a subduction zone. The presence of rock debris from the Idaho batholith indicates that it used to be closer to what is now southern Idaho. Some of the faults may have developed in the Mesozoic era when these deposits took place in the accretion wedge; the north-east and north-north-east trending faults that form the individual basins stem from a subsequent change in transtension.
Early Eocene volcanic units in the area appear to be part of a 49… 44 million year old magmatic belt that emerged immediately after the arrival of Siletzia and is possibly linked to the event.
The strongly pronounced topographical lineaments at the northern end of the Rogers Belt pose a confusing problem, as they do not have a defined distance at the point where they are divided into two by the left-handed oblique-slip Devils Mountain Fault. The alternative that more recent faults in the Rogers Belt are at a distance from the DMF - Cheney said that the MVF are at a distance to the DMF of 47 kilometers to the north beyond Lummi Island - is contrary to the general consensus that there is no distance to the DMF . (OFR 98-5, Bow and Alger)
Cherry Creek Fault Zone
The Cherry Creek Fault Zone (CCFZ) was discovered in 2010 when the area at the northern end of the Rattlesnake Mountain Fault Zone (RMFZ) was mapped. From a point immediately north of Carnation, the east side of the CCFZ (here about three quarters of a mile [1.2 km] wide) can be traced up Harris Creek, crossing the upper reaches of Cherry Creek and finally reaching the small town of Sultan. Here the main strand of the west side joins the Sultan River Fault under the Sultan River . The extension of the zone is believed to be beyond Lake Chaplain, possibly to the east end of Mount Pilchuck . It is seen as an "important or potentially active" structure.
In the jumble of active and potentially active fault zones discovered in the lower Snoqualmie Valley, the Cherry Creek Fault Zone is notable in part because it lies east of Duvall (where it forms the northwest trending Johnsons Swamp Fault Zone, the most easterly in the RMFZ, crosses) a hotspot of seismic activity where the Duvall earthquake of 1996 occurred with a magnitude of 5.3 on the Richter scale. (Additional details in Dragovich et al. (2010b) and in the map of the epicentres in Dragovich et al. 2012) The distances to the east-west oriented Monroe Fault (on the south side of the Skykomish River ), the earthquake-causing detachments of the fault levels from each other and kinematic signs show that the CCFZ represents a left-handed blade shift, possibly with some oblique movement (upwards on the east side).
The CCFZ appears to be related to the parallel Tokul Creek fault zone in the south; both appear to be conjugate faults (i.e. secondary faults branching off opposite sides of a blade shift at roughly the same angle; here the Cherry Creek and Tokul Creek fault zones on the east side of the RMFZ appear conjugate to the SWIF on the west side) to the northwest trending To be SWIF. The Tokul Creek Fault (TCF) strikes north-northeast from Snoqualmie with a possible distance to the Western Melange Belt and with a valley that breaks through to the Skykomish River; it is now believed to be of regional importance.
Rattlesnake Mountain Fault Zone
The Rattlesnake Mountain is a protuberant north-west ridge running due west of North Bend (about 25 mi (40 km) east of Seattle). It coincides with and is possibly a result of uplift at the Rattlesnake Mountain Fault Zone (RMFZ). The RMFZ is a band of at least eleven faults showing both dipping (vertical) and right-handed blade displacement movements (See the map attached in Dragovich et al. (2009); in the map above, these faults are indicated by the pair of dotted lines at the bottom Another mountain and fault zone of the same name is near Pasco ;
The southern end of Rattlesnake Mountain is cut off by the Olympic-Wallowa Lineament (OWL) and the faults turn eastward to merge with the OWL. The north end of the mountain range drops off where it crosses the east end of the Seattle Fault, which in turn closes the RMFZ; Rattlesnake Mountain forms the eastern edge of the Seattle Uplift (see Geological Maps of Fall City and North Bend).
The RMFZ continues north-northwest beyond Fall City and Carnation, where strands of the RMFZ make a slight turn 15… 20 ° west to meet the Southern Whidbey Island Fault Zone (SWIF, see above); the RMFZ is therefore considered to be an extension of the SWIF. The relationship between these two fault zones is not fully understood. Movements along the SWIF should continue east-southeast until it merges with the OWL, but instead appear to take a shortcut ("step to the right") along the RMFZ. This happens where the SWIF meets the edge of the Western and Eastern Melange Belts (which are remnants of a Mid-Cretaceous subduction zone); the RMFZ is where the Seattle uplift is pushed against the Western Melange Belt. (Whether the RMFZ simultaneously establishes the contact between the crescent formation and the cascade chain and thereby to the coast range boundary fault depends on whether the crescent formation extends that far. Gravity studies do not suggest this, or at least not close to the surface The situation at depth is unknown. There is a suggestion of a shear at about 18 kilometers, but on a similar shear further south [below the SWCC ] the rocks below are believed to be pre-tertiary.)
To the north, the Melange Belt manifests as the Rogers Belt , a zone of low amplitude folds and elongations from Monroe to Mount Vernon; the apparent western edge of this zone follows the strike of the RMFZ. South of Monroe, the Rogers Belt folds are hidden by subsequent volcanic formations, but other faults parallel to the RMFZ (e.g. the Snoqualmie Valley and Johnson's Swamp Fault Zones) extend the general trend of north-northwest trending faults to at least after Monroe.
(The Rattlesnake Mountain Fault Zone is not included in the QFFDB.)
Coast Range Boundary Fault
The Coast-Range-Boundary- Fault (CRBF) is theoretically expected on the basis of tectonic considerations that could partially correlate with one or more known faults or belong to a previously undiscovered fault. Put simply, the bedrock on the west side of Puget Sound does not match that on the east side. To the west of Puget Sound, the tectonic bedrock of the Coast Range geological province is formed from approximately 50 million year old marine basalts of the Crescent Formation, which are part of the Siletzia Terran under western Washington and Oregon. To the east of Puget Sound, the Cascade Range Province's subsurface consists of various pre-tertiary metamorphic rocks more than 65 million years old. Somewhere between the Puget Sound and the foothills of the Cascade Range, there is contact between these two geological provinces. (According to Johnson et al. (1996) "must exist".) Since the juxtaposition of various disparate tectonic structures in Northwest Washington requires significant blade displacement, this contact zone is still expected to be one of the major faults.
The north end of the Crescent Formation (also known as the Metchosin Formation) has been identified as the east-west trending Leech River Fault on the southern tip of Vancouver Island. This turns and runs exactly south of Victoria, almost in line with the SWIF. Investigations using seismic tomography across the north end of the SWIF suggest that it is also part of the contact zone between the Coast Range and the Cascade Range. Therefore it seems plausible that the remainder of the SWIF (and its apparent extension, the RMFZ) constitute this contact zone and (since these faults are active) the CRBF.
One problem with this is that the parts of the SWIF east of Puget Sound show no differences in the speed of seismic wave propagation that different rock types would indicate. Another problem with the SWIF / RMFZ as CRBF is that a major westward move is needed to connect the RMFZ to the Saint Helens Zone (SHZ; see map ), whereas the RMFZ turns eastward to apply to align the OWL. (There is some evidence of shear [horizontal separation] at 18 kilometers, and it is possible that the surface fault patterns do not reflect the faults or structures below the shear.) The second problem is partially resolved because there is a location the seismicity and putative folding that extends from the north end of the SHZ to the north end of the Western Rainier Zone (see Figure 48 ), which runs along the edge of a formation known as the Southern Washington Cascades Conductor (SWCC). (The SWCC appears to be made up of tertiary marine sediments rather than the pre-tertiary metamorphic rocks of the Cascade Province; this would make it part of the Coast Range Province and shift the contact zone between the Coast Range and Cascades to the east However, the SWCC is of shallow thickness [no more than 15 km deep] and likely spread over the pre-tertiary basement. The crescent formation is expected to have contact with the pre-tertiary rocks along the SHZ at depth.)
However, data from gravity and other readings suggest that the point of contact of the Crescent Formation near the southern tip of Whidbey Island could turn away from the SWIF, and that reentry even below north Seattle is possible (this condition cannot be met at depth to form the northwestern side of the Seattle Basin and possibly join the recently described “Bremerton Trend” of faults that run from the south end of the Hood Canal through Sinclair Inlet ( Bremerton ) and across Puget Sound. The Crescent Formation boundary could also simply (and tacitly) run south-southeast under Seattle to the WRZ. Further seismic tomographic surveys have tantalizingly revealed indications of north trending strands beneath Seattle and another one directly east of Lake Washington. While there is no direct evidence of any northbound trending fault below Seattle, the geological community appears to agree with this prospect (such as Dragovich et al. (2002) and some regional maps).
How the CRBF might run north of Seattle (particularly north of the OWL, which grazes Seattle) is unknown; it is even questionable whether it does it at all, since there is no direct evidence of such a rejection. (There is a preliminary report of aeromagnetic and gravity mapping that the eastern edge of the Siletzia Terran is under Lake Washington.) There is a fascinating view from Stanley et al. (1999) that the distances from the edge of the Crescent Formation to the west along the Seattle Fault with the Seattle Basin arise from a gap between the main part of Siletzia and a northern broken block.
Seattle Fault
The Seattle Fault is a zone of complex thrusts (English "thrust faults.") And reverse faults (English "reverse faults.") - between the lines E and F on the map km wide up to 7 and more than 70 km long - which represents the north edge of the Seattle uplift. It stands out in relation to the east-west orientation, the depth down to the basement and the danger for a densely populated area. It is the most widely studied fault in the region, so it will be discussed in more detail.
The Seattle Fault was first identified in 1965, but was not documented as an active fault until 1992, when a series of five articles described that about 1,100 years ago (AD 900 ... 930) an earthquake with a magnitude of 7 or more restoration points and Alki Point raised, lowered West Point (the three white triangles in the Seattle Basin on the map ), caused rockfalls in the Olympic Mountains, landslides in Lake Washington, and triggered a tsunami in Puget Sound. (See Adams (1992) and additional references in the main Seattle Fault article .) It extends eastward to (and possibly ends) the Rattlesnake Mountain Fault Zone (RMFZ; the southern extension of the SWIF) near Fall City . It seems geologically justifiable that both SWIF and RMFZ represent the contact zone between the tertiary base of the Crescent Formation in Puget Sound in the west and the older Mesozoic (pre-tertiary) base of the Mélange Belt under the cascade chain in the east (see geological maps of Fall City and North Bend).
structure
Due to the large number of investigations, there are several models for the Seattle Fault about its structure, which could also be relevant for other faults. In the wedge model by Pratt et al. (1997) an approximately 20 km thick block of rock - mainly basalts of the Crescent Formation - is pushed over a "main ramp" of denser material; this forms the Seattle uplift. The Seattle fault zone is on the leading edge of this floe, which lies at the top of the ramp, breaks off and slides into the Seattle Basin. In this model, the Tacoma fault zone is primarily the result of local adjustments as the clod bends upward at the base of the ramp.
The model of the passive double roof by Brocher et al. (2001) (expanded by Brocher et al. (2004) and Johnson et al. (2004a)) is based on seismic-tomographic data from the experiment "Seismic Hazards Investigation in Puget Sound" (SHIPS), also uses the concepts of the displaced floe and the main ramp, but interprets the Tacoma fault zone as a "reverse fault" or "back thrust", which tilts northward against the southward sinking Seattle fault (see figure); as a result the Seattle-raising as a Horst pushed upward.
Although the two models differ in a few details, they make it clear that the Seattle Fault itself is capable of triggering a magnitude 7.5 earthquake. However, if the Seattle Fault breaks up along with other faults (see discussion above ), significantly more energy would be released and the magnitude of the earthquake would be around 8.
The question of western limits
Determining the western boundary of the Seattle Fault has been problematic and has implications for discussion of the entire western side of the Puget Lowland. Originally it was unspecified and was rather vaguely determined west of Restoration Point (i.e. west of Puget Sound). An early view was that "the Seattle fault appears to be cut off by the Hood Canal fault ... and does not extend into the Olympic Mountains." This seems well founded, as the Hood Canal forms a salient physiographic boundary between the Olympic Mountains and the Puget Lowlands and is believed to be the site of a major fault. Subsequent authors were sufficiently convinced to follow the fault west of Bremerton to north of Green Mountain (the northwest corner of the Blue Hills uplift - see "E" on the map - a topographically protruding uplifted basalt) and just before the Hood Canal . (Interestingly, Johnson et al. (1999) failed to determine any characterizing evidence of a fault zone in the seismic reflection profiles on the Hood Canal, claiming that "the Seattle fault does not extend westward to the Hood Canal". [Emphasis added]) They were reluctant to map the fault further west, however, because the distinctive aeromagnetic lineament used to locate the Seattle fault no longer exists immediately west of Bremerton.
Investigations of the Seattle Fault west of Bremerton have revealed the complexity of the geological structure and faults. Several studies show that the southernmost strand of the SF, once located beyond Green Mountain, turns southwest towards the Saddle Mountain and Frigid Creek faults. (Wildcat Lake; Holly) The Saddle Mountain fault zone is not really facing in the opposite direction, however. (The Frigid Creek Fault appears to be more directly in line with this southwest facing extension of the Seattle Fault, but geologists appear to have missed a connection.) It aligns more north where it runs from west to east hits trending faults (including the Hamma-Hamma fault zone ) so that it appears to be a westward extension of the Seattle fault zone. This alignment continues northward where the Pleasant Harbor lineament appears to terminate other westward extensions of the SFZ. Further investigations show faults from the SF towards the northwest and west-northwest against Dabob Bay; these are now recognized as part of the Dabob Bay fault zone. While some coherence is being developed, this question has not yet been fully resolved: the faults identified are not responsible for much of the regional seismicity.
Another view is that the Dewatto Fault is the western edge of the relatively rigid Seattle uplift (see map ). The presence of deformations (displacement) between the Seattle Fault and the Saddle Mountain Deformation Zone is likely to be common across the more resilient sediments in the Dewatto Basin; this fact and the greater depth of the crescent formation may account for the suppressed expression of the Seattle Fault west of Green Mountain.
Tacoma fault zone
The Tacoma Fault (on the right of the graphic; also between lines C and D on the Uplift and Basin map, above ) just north of the city of Tacoma has been described as "one of the most active geophysical anomalies in the Puget Lowland". The western portion is an active east-west trending north-dipping fault that separates the Seattle uplift from the Tacoma Basin, with approximately 50 kilometers of identified superficial fissures. It is believed to be capable of causing earthquakes with a minimum magnitude of 7, and there is evidence of such an earthquake about 1,000 years ago. Possibly the same quake documented for the Seattle Fault , 38 km north. This is probably not accidental because the Tacoma- and the Seattle Fault converge at depth in the way (see illustration above) that the north-south directional compression, the Seattle-raising pushes up so that it waste and faults in both fault zones follow.
The Tacoma Fault was first identified by Gower et al. (1985) identified as a grave anomaly ("Structure K") running eastward across the northern peaks of Case and Carr Inlet, then south-east under Commencement Bay and towards the small town of Puyallup . Its character as a fault zone was not recognized until 2001, and only in 2004 did the opening of a trench betray any Holocene activity. (See also Brocher et al. (2001))
Stages of the Tacoma Fault associated with the Holocene uplift were traced westward to Prickett Lake (southwest of Belfair , see map) (cf. Sherrod et al. (2003), the base of Sherrod et al. (2004)). The Tacoma Fault was originally believed to be the result of a weak magnetic anomaly west of the Frigid Creek Fault, but is now believed to be associated with a steep gravitational, aeromagnetic and seismic velocity gradient northward to Green Mountain (Blue -Hills elevation). This is the Dewatto lineament believed to result from an eastward dipping shallow thrust at a point that pushed the western flank of the Seattle uplift into the northwest corner of the Tacoma Basin. It appears that the Seattle uplift acts as a rigid block with the Tacoma, Dewatto and Seattle faults as the south, west and north edges, respectively. This could explain why the Seattle and Tacoma faults appear to be ruptured around the same time.
The interpretation of the eastern part of the Tacoma fault is not fully accepted. (The QFFDB, citing the lack of consensus, ignores this eastern part.) Most scientists associate it with the strong gravity anomaly (the reflections of which typically occur when the fault is composed of juxtaposed rocks of different densities) and the topographic lineament under Commencement Bay in harmony. This follows the front of the Rosedale Monocline, a slightly southwest tilting formation that forms the cliffs on which Tacoma was built.
In addition, the contrasting character of the east and south-east trending segments is worrying, and the change in orientation is somewhat difficult to reconcile with the observed fault traces, especially since data on seismic reflection (see Johnson et al. (2004a), cf. also the Differences between the AA '(west) and BB' (east) profiles in Fig. 17) show that some faults extend eastward across Vashon Island and the East Passage of Puget Sound (the East Passage Zone , EPZ) to Federal Way and continue an eastward trending anticline. It is not yet clear whether the faults will continue eastwards. The EPZ is active and was the location of the Point Robinson earthquake with a magnitude of 5 in 1995.
There is evidence of links between the Tacoma Fault and the White River Fault (WRF) beyond the EPZ and Federal Way, as well as under the Muckleshoot Basin (see map ), and on to the Naches River Fault . (Alternatively, the Tacoma Fault could be just a breakline that continues as the main part of the WRF to west-northwest beyond Kent and Bremerton.) If so, it would become a major fault system (over 185 km long) that would Puget Lowland connects to the Yakima Fold Belt on the other side of the Cascade Range, and has potential effects on both the Olympic-Wallowa Lineament (which it runs parallel to) and geological structures south of the OWL.
Dewatto lineament
The western flank of the Seattle Uplift forms a strong gradient of gravity as well as aeromagnetic and seismic propagation velocities, which became known as the Dewatto lineament . It results from the difference between the denser and more magnetic basalts of the Crescent Formation, which were raised to the east, and the glacial sediments, which filled the Dewatto Basin to the west. The Dewatto Linement extends north from the west end of the Tacoma Fault (see map in the previous section) to Green Mountain at the west end of the Seattle Fault.
Kinematic analysis suggests that if there is a shortening of compression in the Puget Lowland, which is northeast facing (i.e., parallel to the Hood Canal and the Saddle Mountain Deformation Zone) and therefore oblique to the Dewatto lineament, it is both horizontal as well as vertical energy releases, which corresponds to a distortion. Current geophysical models assume that the Dewatto Lineament is the expression of a concealed (hidden), shallow, eastward displacement , which is referred to as the Dewatto Fault . (Originally called the Tahuya Fault.) This reflects the westward faulting of the Seattle uplift into the Dewatto Basin, a northwest extension of the Tacoma Basin. This interpretation suggests that the Seattle uplift acts as a rigid block; it may also explain the kinematic connection through which large earthquakes can crack in multiple faults: the Seattle, Dewatto and Tacoma faults represent the northern, western and southern sides of a single rock, respectively. Such connections with one another can harbor the risk of major earthquakes (in the case of the Seattle Fault with a magnitude> 7); the size of the increased risk is unknown.
Hood Canal Fault
The Hood Canal marks an abrupt change in physiography between the Puget Lowland and the Olympic Mountains to the west. Because of these geophysical anomalies, it was concluded that there must be a large active blade-displacement zone that continues on land from the south end of the Hood Canal, up Dabob Bay, and north of it. This is consistent with some interpretations of the regional tectonic conditions that set a large terran between the Olympic Mountains and the Puget Lowland, and implies a connection (either across the Discovery Bay Fault or closer to Port Townsend) to the various faults in Juan de Fuca street. This boundary would be the contact where the northward movement of the Puget Lowland basement towards the Olympic Peninsula is to be found; a significant seismological zone would be expected.
The Hood Canal Fault, however, was "largely hidden" for lack of evidence; there were no clear fractures or other signs of seismic activity. A 2001 survey using high resolution seismotomography questioned its existence. Although another 2012 study interpreted the variety of tomographic data as indicative of the Hood Canal Fault, "[other mappings] found no convincing evidence for the existence of this fault"; Contreras et al. (2010) considered this to be doubtful, Polenz et al. (2013) described it in the statistical sense “with a low degree of confidence” (see also Contreras et al. (2012b), Polenz et al. (2010b)) or excluded it completely. For these reasons, it is a questionable fault from today's point of view, so that it is only shown on the map as a dashed line.
A new perspective is currently emerging: the regional tectonic boundary is not under the Hood Canal, but to the west of it, and includes the Saddle Mountain Fault Zone (see discussion below) and associated faults. This is supported by geologically recent fractures and other evidence of active movement on the Saddle Mountains faults. A geophysical lineament has also been discovered that runs through Pleasant Harbor (south of Brinnon) and appears to cut off the strands of the Seattle Fault. (A possible extension of this lineament appears in the geological map of the Eldon Quadrant.) In this view, the Hood Canal is just a syncline between the Olympic Mountains and the Puget Lowland, and the faults found there are local and discontinuous, the main zone of faults subordinate to the west. (See also Lamb et al. (2012) for a presumptive profile.) North of the Seattle Fault could be the location of regional motion along the northwest trending Dabob Bay fault zone .
Saddle Mountain Faults
The Saddle Mountain Fault s ( "East" and "West", and not to be confused with another Saddle Mountain s -Verwerfung in Adams County , Eastern Washington - see Lake QFFDB) are a group of northeast trending thrust faults at the southeast flank of the Olympic Mountains near Lake Cushman, which were first described in 1973 and 1975, respectively. The vertical movement at these faults created prominent fractures that dammed Price Lake and (just north of Saddle Mountain) Lilliwaup Swamp. The mapped superficial tracks are only 5 km long, but LIDAR-based imagery shows longer lineaments with tracks intersecting Holocene alluvial tracks. Analysis of aeromagnetic data from 2009 suggests that the faults extend at least 35 km, from the longitude of the Seattle Fault (on the Hamma Hamma River) to about 6 km south of Lake Cushman. Additional faults to the south and southeast - the Frigid Creek Fault and (to the west) the Canyon River Fault - suggest an extensive zone of faults at least 45 kilometers in length. Although the southwest trending Canyon River fault does not appear to be directly connected to the Saddle Mountains faults, they are generally in line and both occur in a similar context to Miocene faults (in the strata of the Crescent Formation through the Olympic Mountains up) and a linear aeromagnetic anomaly. The Canyon River fault is itself one of the main faults and is associated with a 40 km long lineament and individual Late Holocene fractures of up to three meters in height (OFR 2007-1).
Although these faults lie west of the Hood Canal Fault (and were initially thought of as the western limit of the Puget Lowland), recent studies indicate that the Saddle Mountain and related faults are connected to the Seattle Fault Zone. Investigations into rift formation indicate large earthquakes (with magnitudes of 6 ... 7.8) in the Saddle Mountains faults at about the same time (± 100 years) as the great quake on the Seattle fault around 1,100 years ago (AD 900 ... 930). (USGS OFR 99-0311) shows additional data of various accompanying events, see also Loganet al. (1998).) Such quakes pose serious threats to the dams at Lake Cushman in the City of Tacoma ( Cushman Dam No. 1 and Cushman Dam No. 2 ), which lie within the fault zone, as well as anyone who travels down the Skokomish River The Canyon River Fault is believed to be responsible for a similarly sized earthquake less than 2,000 years ago; this poses a particular threat to Wynoochee Dam (to the west). The history and effects of the Frigid Creek fault are unknown.
Olympic structure
The Olympia Structure (OS) - also known as the Legislature Fault - is a 80 km long gravitational and aeromagnetic anomaly that separates the sediments of the Tacoma Basin from the basalt of the Black Hills uplift (between lines A and B on the map ) . Seismic activity has not been observed on a large scale - and indeed there is little seismicity south of the Tacoma Basin as far as Chehalis - and it is not even conclusively recognized as a fault.
This structure is included in the grave mapping from 1965, but there is no comment on it. Gower et al. (1985) labeled it "Structure L", mapped it from near Shelton (near the foothills of the Olympic Mountains) southeast of Olympia (nice and close to the right below Parliament), just below the small town of Rainier , to a point east of the Doty Fault and apparently marked the northeastern boundary of a band of southeast trending faults in the Centralia -Chehalis area. They interpreted the structure as "simple folds in the bedrock," but Sherrod (1998) saw enough similarity to the Seattle Fault to consider it a thrust. Pratt et al. (1997), while observing "remarkably sharp boundaries that we interpret as evidence of structural control", failed to view this structure as a fault. (Your model of the Black Hills uplift is analogous to your “Wedge” model of the Seattle uplift [see discussion above ], but in the opposite direction. With complete analogy, a “double roof” would also fit, and the Olympic Fault would be a thrust similar to the Tacoma Fault.)
Aeromagenetic mapping in 1999 showed a prominent anomaly (OFR 99-514) that typically shows a difference in rock type. This, along with paleoseismological evidence of a strong Holocene earthquake, led to the assumption that this structure "may be associated with a fault". One reason for warning is the fact that a detailed, serious investigation has not been able to establish whether the Olympic structure is a fault or not. Although no superficial traces of a fault were found in either the woody glacial sediments or the basalts of the Black Hills (see e.g. the map of Summit Lake; recently the suspicion was raised that it was a natural berm across the delta of the Skokomish River, which was created by a fault, which the OS would identify as an active fault. However, there is still no scientific evidence for this.) A fault was mapped on the basis of well-placed drillings that started from Offut Lake (just west of Rainier) strokes southeast; it appears to be in the same line as the easternmost mapped fault in the Centralia-Chehalis area (see East Olympia geological map).
An investigation of marine seismic reflections found indications of fault processes at the mouth of the Budd Inlet, just north of the Olympia structure, and the alignment to weak lineaments from LIDAR data. These faults are not really in line with the Olympic structure, they tend to strike N75W (285 °) rather than N45W (315 °). It is uncertain how these faults relate to the structure, and whether they are deep-seated faults or fractures resulting from the bends in the earth's crust.
It has been speculated that the OS may be linked to the seismically active Saint Helens Zone (see discussion below ), which would suggest that the OS is both blocked and strained, raising the possibility of a major earthquake. From a different perspective, the OS appears to agree with a gravity boundary in the upper crust of the earth that has been mapped trending southeast to The Dalles on the Columbia River, where there is a swarm of similar trending faults (see QFFDB 580).
The fact that Olympia and southern Puget Sound are at risk of a major earthquake is demonstrated by evidence of subsidence in several locations in southern Puget Sound about 1,100 years ago. It is unknown whether this occurred as a result of a major subduction quake, attributable to an earthquake at the Seattle Fault around this time, or a quake at a local fault (e.g. the Olympia structure); there is some evidence that there were two quakes in a short period of time. A subsidence dated between AD 1445 and 1655 has been demonstrated for Mud Bay (just west of Olympia) (see map of Summit Lake).
(The Olympic structure is not listed in the QFFDB.)
Doty fault
The Doty Fault - the southernmost of the faults discussed here, separating uplifts and basins, and located just north of the Chehalis Basin - is one of nearly a dozen faults mapped in the Centralia-Chehalis coal district in 1958. Although the small towns of Centralia and Chehalis in rural Lewis County appear distant (approximately 25 mi (40 km)) from Puget Sound, they are still part of the Puget Lowland, and these faults, local geology and underlying tectonic base seem directly linked to the Puget Sound neighborhood. Although the faults in this area show no notable seismic activity, the southeast trending faults appear to be staggered with the Olympia structure (or Olympia fault?), Heading towards the definitely active Saint Helens Zone; it appears to be a large-scale structure. The Doty Fault appears to be of particular geological interest since it was linked to an aeromagnetic anomaly, and an investigation in 2000 concluded it could be the source of a magnitude 6.7 ... 7.2 earthquake. The prospect of a major earthquake at the Doty Fault highlights the serious threat to the entire Puget Sound region as it threatens vital economic lifelines: Chehalis has only one highway (Interstate 5) and one railway line, which connects the Puget Sound region to the rest of the US west coast; the alternative routes are several times longer from the Washington State Department of Transportation about the economic damage if a flood blocked the freeway for just a few days).
The course of the Doty Fault was determined from the north side of Chehalis Airport to the west to the old logging town of Doty (just north of Pe Ell), over most of the distance from its twin, the Salzer Creek Fault , which parallel about half a distance Mile (800 m) north. Both are (vertical) faults; the rock between them was lifted up by compression forces. The Doty Fault appears to end at or merge with the Salzer Creek Fault at Chehalis; the Salzer Creek Fault can be traced an additional seven miles (11.2 km) east of Chehalis. The length of the Doty Fault is controversial: the 2000 study stated it was 65 kilometers, but without comment or source. (65 km would be the combined Doty / Salzer Creek fault plus a 24 km extension westward to South Bend on Willapa Bay. Finn (1990) identified it without identifying it, with the Doty fault and notable gravity and aeromagenetic anomalies related to Willapa Bay.) Such a length would be comparable to that of the Seattle or Tacoma faults and have the potential for magnitude 6.7 earthquakes. However, it does not appear that there has been any research into the deeper structure or current activities of these faults.
The Doty / Salzer Creek fault does not fully fit the regional basin and uplift pattern delimited by faults described above . It borders the north side of the Chehalis Basin, but the southern limit of the Black Hills uplift is better described as the southeast trending Scammon Creek Fault , which converges with the Doty / Salzer Creek Fault just north of Chehalis. At the acute angle between these are the small Lincoln Creek uplift, the Doty Hills, and an impressive block of uplifted Crescent Basalt (the reddish area on the western edge of the map). The southeast trending Scammon Creek fault appears to be terminated by the Salzer Creek fault (the exact relationship is unclear), the latter continuing an additional seven miles (11.2 km) east. However, the former is only the first of at least six other parallel southeast trending faults that cross the Salzer Creek Fault. These faults are: the Kopiah Fault (note the strange curve), the Newaukum Fault , the Coal Creek Fault, and three other unnamed faults. Just behind them lies the parallel Olympia structure, which can be traced as a geophysical lineament to a point exactly east of Chehalis; these seem to be related somehow, but the nature of this relationship is not yet known.
Although these faults could only be traced for a short distance, the southeast trending anticlines are associated with a continuation to Reef Lake near Mossyrock . They also stroke in the same direction as a swarm of other faults on the Columbia River that embrace The Dalles. Since they are all faults and thrusts, they may originate from directed regional compressions. These faults also traverse the Saint Helens Zone (SHZ), a low-lying, north-northwest oriented seismic zone that appears to represent the contact between the various blocks of the earth's crust. How they could be connected is unknown.
What distinguishes the Doty / Salzer Creek Fault (and also the short Chehalis Fault which runs just east of Chehalis) from many other faults south of Tacoma is its east-west strike; the meaning of this is unknown.
(Not included in the QFFDB. See Snavely et al. (1958) and the geological map for details.)
Saint Helens Zone, Western Rainier Zone
The highest impact densities of seismicity in the middle crust of West Washington outside of Puget Sound are found in the Saint Helens Zone (SHZ) and the Western Rainier Zone (WRZ) on the southern edge of the Puget Lowland (see the seismicity map on the right). In fact, it is mainly due to this seismicity that these faults could be found, since no faults can be found on the surface. SHZ and WRZ lie just outside the topographical basin that forms the Puget Lowland (see picture ), are not part of the uplift and basin pattern, and unlike the rest of the faults in the Puget Lowland (which are faults or thrusts, mostly due to compression they appear to be leaf displacements ; they reflect a geological context that is very different from the rest of the Puget Lowland. In particular, southeast of Mount St. Helens and Mount Rainier, they reflect a regional pattern of north-northwest oriented faults, including the Entiat Fault in the North Cascades and Portland Hills and other related faults around Portland . SHZ and WRZ could already be integral parts of the regional geology of Puget Sound, perhaps representing some deep and important facets; Likewise, they arguably represent a significant seismic hazard.
WRZ and SHZ are associated with the Southern Washington Cascades Conductor (SWCC), a formation with increased electrical conductivity. (Several possible explanations for the increased conductivity have been suggested: Eocene marine sediments containing brine are most likely Egbert & Booker (1993) discuss evidence that the anomaly in conductivity might be larger than presented here and suggest it as a holdover an "early Cenozoic subduction zone, which corresponds to today's Olympic Peninsula".) The SWCC is roughly estimated between the Reef Lake and Mount St. Helens , Mt. Adams and Mt. Rainier , with a spur extending northward ( Borders in yellow, right). This formation, up to 15 km thick, is largely buried (between one and ten kilometers deep) and has become known mainly through magnetotellurics and other geophysical methods. The southwestern boundary of the SWCC, which is believed to be in near vertical contact with the Eocene basalts of the Crescent Formation, forms a fairly large part of the 90 km long SHZ. On the east side, where it may have contact with the pre-tertiary terrans of the North American plate, the situation is different. While there is a short (not shown) zone of weaker seismicity near the Goat Rocks (an ancient Pliocene volcano) that could be associated with the contact zone, the significantly stronger seismicity of the WRZ is associated with the important carbon river / skate mountain anticline. This anticline (or raised fold) and the reduced width of the northern portion of the SWCC reflect an episode of compression in this formation. What is of great interest here is that both the northern extension of the SWCC and the Carbon River anticline are in line against Tiger Mountain (an uplifted block of the Puget Group of sedimentary and volcanic deposits typical of the Puget Lowland) and the adjacent Raging River anticlines are directed (see map ). The deepest near-surface strata of Tiger Mountain, the Middle Eocene marine sediments of the Raging River Formation, could correspond to the SWCC. (If the Carbon River and Raging River anticlines are connected and the SWCC and Raging River formations matched each other, the RMFZ would be the east edge of the SWCC. That the RMFZ fault strands turn eastward and the seismicity jumps from contact of a fault to an anticline suggests that much remains to be learned about the OWL / WR-NR zone.)
Is there an extension of the SHZ to the north? Although the Olympia structure (a possible fault) runs against the SHZ and represents the north edge of an exposed section of the Crescent Formation, it appears to be a fold in the upper crust that is part of a pattern of folds that runs southeast across the Columbia River extends near The Dalles, and is unrelated to the SHZ in the middle and deeper crustal areas (see geological map of Washington). It has been speculated that the SHZ could extend below the Kitsap Peninsula (central Puget Sound), perhaps included in a section of the submerging Juan de Fuca record that is suspected of being stuck. The implications of this are not only "the possibility of a moderate to severe earthquake in the earth's crust along the SHZ", but that the tectonics under the Puget Sound are more complicated than previously recognized, and that the differences in regional stress patterns have not yet been reflected in the Assessment of regional earthquake hazards could reflect.
The deeper structure
Mount St. Helens and Mount Rainier lie in a loop of their associated fault zones (see map above). (Mt. Rainier is a little out of the way because the faults are at greater depth and the connections don't really reach the surface vertically.) These loops are found where they intersect a “sophisticated geological structure” that is “possibly fundamental Meaning ”, a north-northeast trending zone (line“ A ”on the map) of various faults (including the Tokul Creek fault north-northeast of Snoqualmie). It contains early Miocene (about 24 million years old) volcanic vents and plutonic bodies ( plutons and batholiths ) that extend from Portland, Oregon to Glacier Peak . (Tabor & Crowder (1969) reported - possibly citing an earlier author - of a "zone of basaltic dykes and volcanic cones oriented to the north-northeast," including Mount Rainier and Mount St. Helens "in the southwest." Evarts et al. (1987 ) found that “Mount Rainier and Glacier Peak are in line with the projection of this zone”, literally NNE or “roughly N25E.” While Mount Rainier is almost N25E from Mt. Saint Helens, the more accurate calculation of longitudes Saint Helens to Glacier Peak one direction from N21E; aligning all three volcanoes would produce a slightly curved lineament, but the peculiarities of Mt. Saint Helens [like Yale Lake and Spirit Lake] lie on N20E and thus not in line with Mount Rainier. It is more likely that Mt. Rainier, as it breached to the surface, “drifted away” from the underlying lineament, which is streaking north-northeast The corresponding lineament should not be confused with the other N50 ° E painting lineaments. ) It also marks the change in the regional orientation of the faults as described above. This lineament across the three volcanoes is believed to reflect a "long-lived deep-seated lithospheric defect which has played an important role in controlling magma flow to the outer crust in southern Washington over the past 25 million years or so"; it is also said to have an influence on the geometry of the submerged Juan de Fuca plate .
A parallel line ("B") about 15 miles (25 km) west corresponds to the western boundary of a zone of seismicity that extends from the WRZ to southwest of Portland. Curiously, the extent of line "B" north of the OWL is roughly the eastern limit of the Puget Sound seismicity, while the rest of Southwest Washington and the North Cascades are relatively aseismic (see the seismicity map above). (cf. also Stanley et al. (1999), in particular the “seismicity pattern” and Figures 46-49. The position and orientation of line “B” are only shown here approximately.) This line also marks the north-west limit of the SWCC. (The apparent gap north of Riffe Lake may be because of the overburdening of volcanic deposits from the Northcraft Formation.) North of the RMFZ, it follows a topographical lineament that can be followed to Rockport (on Highway 20). (Along a section of the Sultan River and the west end of Blue Mountain, the east side of Mount Pilchuck, the Three Fingers and Whitehorse Mountain , and - north of Darrington and the DDMF - the west side of North Mountain and a section of the North Fork Stillaguamish River. North of Highway 20, it runs parallel to Lake Shannon .) It includes the Cherry Creek Fault Zone northeast of Carnation, the epicenter of the Duvall earthquake of 1965. (According to Stanley et al. (1999), the Duvall earthquake was however, a 350 ° collision of the faults. This suggests that the quake actually occurred on the transverse Cherry Valley Fault, the northernmost part of the RMFZ and possibly an extension of the Griffin Creek Fault.) between the Cherry Creek and the parallel Tokul Creek faults there is a contact between the formations of the Western Melange Belt. The zone between these two lines, which reflects changes in regional structure, seismicity, orientation of faults and possibly the structure of the underlying lithosphere, appears to be an important structural boundary in the Puget Lowland.
Also interrupted at Mount St. Helens is a north-east (O45 °) line (shown in red) Pleistocene (approx. 4 million years old) reservoirs and a topographical lineament (partly overbuilt with Highway 12). This line is the southernmost of a family of northeast trending faults and topographical lineaments that stretch from the Oregon coast into the North Cascades. A similar line lies in line with the end of the WRZ, SHZ, and Gales Creek fault zone (northwest of Portland), with faults along the upper Nehalem River on the Oregon coast and topographical contrast on the coast (between Neahkahnie Mountain and the lower Nehalem River Valley) which is sharp enough to be seen on the seismicity map (above) (just west of Portland). Other similar lineaments (for example from Astoria to Glacier Peak) lie in the alignment of several topographical features and the change in the orientation of the faults. These lineaments have been associated with possible fault zones in the earth's crust and in the subducted plates.
These properties suggest that the southern Puget Lowland is influenced by the deeper layers of the earth's crust and even the subducted Juan de Fuca plate, but details and effects are not yet known.
Further faults
Proven
There are numerous other faults (or fault zones) in the Puget Lowland and around its boundaries that have been sporadically explored and largely unnamed. These are usually quite short and generally not considered to be significantly seismogenic. However, most of the seismic activity is not associated with any of the known faults. (Rogers (2002) writes: "... there is little evidence that fault levels are associated with spatial trends from epicentres. Instead, most of the seismicity in the earth's crust seems to occur randomly on faults, all of which respond to the same regional stresses." in zones like the one observed under Mercer Island before, or from downtown Seattle to Kirkland. However, it is generally unknown whether individual zones reflect undiscovered faults or could be the source of devastating earthquakes. The ongoing mapping reveals more and more faults. For example, mapping the Rattlesnake Mountain Fault Zone uncovered a complex network of active or potentially active faults that run across the Snoqualmie Valley (and likely beyond), including the Cherry Creek Fault Zone , the location of the Duvall earthquake from 1996 with a magnitude of 5.3. (See the Cherry Creek Fault Zone References for details .)
The San Juan Island and Leach River Fault Zones which traverse the south end of Vancouver Island are clearly and unequivocally linked to the Darrington / Devils Mountain and Southern Whidbey Island Faults, and with certainty of of particular interest to the residents of Victoria, British Columbia . However, their relevance to the Puget Sound region is unknown.
The Little River Fault is representative of an extensive zone of faults along the north side of the Olympic Peninsula and in the Juan de Fuca Strait (and likely connected to the fault systems at the south end of Vancouver Island,), but these lie to the west of the blocks of earth lying beneath the Puget Lowland. Again, the possible impact of these faults on the Puget Sound region is unknown. One of these faults, the Sequim fault zone (it runs east of the small town of Sequim ), crosses Discovery Bay (and various possible extensions of the Hood Canal fault ) and limits the Port Ludlow uplift ("uplift of unknown origin") . "Elevation of unknown origin"] on the map ); it appears to widen the Southern Whidbey Island fault.
An Everett Fault running east-northeast along the cliffs between Mukilteo and Everett - d. H. east of the SWIF and on the southern border of the Everett Basin - a complaint was made, but this does not seem to have been confirmed.
Based on the investigation of marine seismic reflections, a Lofall fault has been reported, but this has not been confirmed by the discovery of a corresponding trench. This fault appears to be associated with the Kingston Arch anticline and part of the uplift and basin pattern , but its extent has been limited by the geometry of the SWIF. It is not remarkably seismically active.
Although the largely unexplored White River Fault (WRF) appears to be just outside the Puget Lowland, it could actually lead under the Muckleshoot Basin to the East Passage Zone and the Tacoma Fault (see map ). (It could also run west-northwest in association with a topographical lineament that extends from Lake Meridian in Kent via Southworth to the Washington Narrows [at the entrance to Dyes Inlet], the western end of the Seattle Fault and the southern tip of the Toandos Peninsula. ) This would represent a significantly greater seismic hazard than currently estimated, especially since the White River Fault is believed to be connected to the Naches River Fault , which runs along Highway 410 on the east side of the Cascade Range to Yakima extends.
The Straight Creek Fault is an important structure in the North Cascades but has not been active for over 30 million years. Several other faults in the North Cascades are older (off the Straight Creek Fault) and unrelated to the faults in Puget Sound.
Supposed
The Puget Sound Fault , running through the center of Puget Sound (and from Vashon Island ), was once proposed but does not seem to be accepted by geologists. A Coast Range Boundary Fault (CRBF, see discussion above ) was concluded on the basis of differences in the basement in western and eastern Puget Sound (crescent formation - contact with the Cascadia core) and arbitrarily in various locations including the Lake Washington mapped; north of the OWL it is now generally identified with the Southern Whidbey Island Fault. Where it could run south of Seattle is unknown; an argument has been made that it might run near Seattle, but this is only speculative.
A survey of surface deformation suggests possible unmapped faults near the Federal Way that run between Sumner and Steilacoom and south of Renton .
See also
Other sources
- ML Anderson, JD Dragovich, RJ Blakely, R. Wells, TM Brocher: Where Does the Seattle Fault End? Structural Links and Kinematic Implications [Abstract T23B-2022] . In: American Geophysical Union, Fall Meeting 2007 . 2008.
- JD Dragovich, HA Littke, ML Anderson, R. Hartog, GR Wessel, SA DuFrane, TJ Walsh, JH MacDonald, JF Mangano, R. Cakir: Geologic Map of the Snoqualmie 7.5-Minute Quadrangle, King County, Washington . In: Washington Division of Geology and Earth Resources . Geological Map GM – 75, July 2009. "2 map sheets, scale 1: 24,000"
- VA Frizzell, RW Tabor, RE Zartman, CD Blome: Late Mesozoic or Early Tertiary Melanges in the Western Cascades of Washington . In: JE Schuster (Ed.): Selected papers on the Geology of Washington (= Washington DGER Bulletin ). tape 77 , 1987, pp. 129–148 ( dnr.wa.gov [PDF]).
- SY Johnson, RJ Blakely, TM Brocher: Fault number 573, Utsalady Point Fault . In: US Geological Survey (Ed.): Quaternary fault and fold database of the United States . 2003 ( geohazards.cr.usgs.gov ).
- SY Johnson, RJ Blakely, TM Brocher, RC Bucknam, PJ Haeussler, TL Pratt, AR Nelson, BL Sherrod, RE Wells, DJ Lidke, DJ Harding, HM Kelsey: Fault number 570, Seattle Fault . In: US Geological Survey (Ed.): Quaternary fault and fold database of the United States . 2004 ( geohazards.cr.usgs.gov ).
- P. Karel, LM Liberty: The western extension of the Seattle fault: new insights from seismic reflection data [abstract # T21B-1951] . In: American Geophysical Union, Fall Meeting 2008 . 2008.
- HM Kelsey, BL Sherrod, AR Nelson, TM Brocher: Earthquakes generated from bedding plane-parallel reverse faults above an active wedge thrust, Seattle fault zone. . In: Geological Society of America Bulletin . 120, No. 11/12, November – December 2008, pp. 1581–1597. doi : 10.1130 / B26282.1 .
- DJ Lidke: Fault number 552, Hood Canal fault zone . In: US Geological Survey (Ed.): Quaternary fault and fold database of the United States . 2003 ( geohazards.cr.usgs.gov ).
- R. McCaffrey, AI Qamar, RW King, R. Wells, G. Khazaradze, CA Williams, CW Stevens, JJ Vollick, PC Zwick: Fault locking, block rotation and crustal deformation in the Pacific Northwest . In: Geophysical Journal International . 169, No. 3, 2007, pp. 1315-1340.
- M. Polenz, BA Miller, N. Davies, BB Perry, KP Clark, TJ Walsh, RJ Carson, JF Hughes: Geologic map of the Hoodsport 7.5-minute quadrangle, Mason County, Washington . In: Washington Division of Geology and Earth Resources . Open File Report 2011-3, August 2012, p. 18. "1 map sheet, scale 1: 24,000"
- WD Stanley, SY Johnson, JM Williams, CS Weaver: Anticlinal Structures, Seismicity, and Strike-slip Faulting in the Southern Washington Cascades . US Department of Energy. P. 26. 1993 .: “Contract No. DE-AT21-92MC29267 "
- US ten Brink, PC Molzer, MA Fisher, RJ Blakely, RC Bucknam, T. Parsons, RS Crosson, KC Creager: Subsurface Geometry and Evolution of the Seattle Fault Zone and the Seattle Basin, Washington . In: Geological Society of America Bulletin . 92, No. 5, June 2002, pp. 1737-1753. doi : 10.1785 / 0120010229 .
Web links
- Preliminary Atlas of Active Shallow Tectonic Deformation in the Puget Lowland, Washington (USGS Open-File Report 2010-1149) - Maps of the faults in the region with an overview
- USGS Quaternary fault and fold database - technical descriptions and bibliographies
- The Pacific Northwest Seismic Network All About Earthquakes and Geological Hazards in the Pacific Northwest
- Earthquake locations (English)
- Northwest Washington Geological Map (GM-50 )
- Geological Map of Southwest Washington (GM-34 )
- Various maps of the Washington State Department of Natural Resources (English)
- Aeromagnetic Anomalies Maps (USGS OFR 99-514 )
- USGS QFFDB Fault # 572, Southern Whidbey Island Fault
- USGS QFFDB Fault # 574, Devils Mountain Fault
- USGS QFFDB Fault # 571, Strawberry Point Fault
- USGS QFFDB Fault # 573, Utsalady Point Fault
- USGS QFFDB Fault # 581, Tacoma fault
- USGS QFFDB Fault # 552, Hood Canal Fault
- USGS QFFDB Fault # 570, Seattle Fault
- USGS QFFDB Fault # 575, Saddle Mountain Faults
Individual evidence
- ^ A b D. Ballantyne, M. Pierepiekarz, S. Chang: Seismic Vulnerability Assessment of the Seattle-Tacoma Highway Corridor using HAZUS . 2002. Retrieved October 4, 2018.
- ^ A b c E. A. Barnett, RA Haugerud, BL Sherrod, CS Weaver, TL Pratt, RJ Blakely: Preliminary atlas of active shallow tectonic deformation in the Puget Lowland, Washington . In: US Geological Survey . Open-File Report 2010-1149, 2010, p. 32. "14 maps"
- ^ A b R. C. Bucknam, E. Hemphill-Haley, EB Leopold: Abrupt Uplift Within the Past 1700 Years at Southern Puget Sound, Washington . In: Science . 258, December 4, 1992, pp. 1611-1614. doi : 10.1126 / science.258.5088.1611 . PMID 17742525 .
- ^ MA Fisher, RD Hyndman, SY Johnson, TM Brocher, RS Crosson, RA Wells, AJ Calvert, US ten Brink: Crustal Structure and Earthquake Hazards of the Subduction Zone in Southwestern British Columbia and Western Washington . In: US Geological Survey . Professional Paper 1661-C, 2005.
- ^ RE Karlin, SEB Abella: A history of Pacific Northwest earthquakes recorded in Holocene sediments from Lake Washington . In: Journal of Geophysical Research . 110, No. B3, March 10, 1996, pp. 6137-6150. doi : 10.1029 / 95JB01626 .
- ↑ a b c d e f g h i j k l m n D. Stanley, A. Villaseñor, H. Benz: Subduction zone and crustal dynamics of western Washington: A tectonic model for earthquake hazards evaluation . In: US Geological Survey . Open-File Report 99-311, 1999.
- ^ Seismic Maps . US Geological Survey. Retrieved October 5, 2018.
- ↑ a b D. J. Harding, GS Berghoff: Fault scarp detection beneath dense vegetation cover: airborne LIDAR mapping of the Seattle Fault Zone, Bainbridge Island, Washington State . In: Proceedings of the American Society of Photogrammetry and Remote Sensing Annual Conference, Washington, DC, May, 2000 . 2000.
- ↑ a b c d e Z. F. Daneš, MM Bonno, E. Brau, WD Gilham, TT Hoffman, D. Johansen, MH Jones, B. Malfait, J. Masten, GO Teague: Geophysical Investigation of the Southern Puget Sound Area, Washington . In: Journal of Geophysical Research . 70, No. 22, November 15, 1965, pp. 5573-5580. doi : 10.1029 / JZ070i022p05573 .
- ↑ {{{publisher}}} (1980). Bedrock geologic and Quaternary tectonic map of the Port Townsend area, Washington [map]. P. 19.
- ↑ a b c d H. D. Gower, JC Yount, RS Crosson: Seismotectonic map of the Puget Sound region, Washington . In: US Geological Survey . Miscellaneous Investigations Map I-1613, 1985, p. 15. "1: 250,000"
- ↑ a b J. Adams: Paleoseismology: A Search for Ancient Earthquakes in Puget Sound . In: Science . 258, December 4, 1992, pp. 1592-1593. doi : 10.1126 / science.258.5088.1592 .
- ↑ RA Haugerud, DJ Harding, SY Johnson, JL Harless, CS Review, BL Sherrod: High-resolution lidar topography of the Puget Lowland, Washington - A Bonanza for Earth Science . In: GSA Today . June 2003, pp. 4-10.
- ↑ AR Nelson, SY Johnson, HM Kelsey, RE Wells, BL Sherrod, SK Pezzopane, L. Bradley, RD Koehler, RC Bucknam: Late Holocene earthquakes on the Toe Jam Hill fault, Seattle fault zone, Bainbridge Island, Washington Archived from the original on June 14, 2010. Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. In: Geological Society of America Bulletin . 115, No. 11, November 2003, pp. 1368-1403. doi : 10.1130 / B25262.1 . Retrieved June 9, 2010.
- ↑ a b c d B. L. Sherrod, TM Brocher, CS Weaver, RC Bucknam, RJ Blakely, HM Kelsey, AR Nelson, R. Haugerud: Holocene fault scarps near Tacoma, Washington, USA Archived from the original on June 7, 2011. Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. In: Geology . 32, No. 1, January 2004, pp. 9-12. doi : 10.1130 / G19914.1 . Retrieved September 10, 2017.
- ↑ a b S. Y. Johnson, AR Nelson, SF Personius, RE Wells, HM Kelsey, BL Sherrod, K. Okumura, R. Koehler, RC Witter, L. Bradley, DJ Harding: Evidence for Late Holocene Earthquakes on the Utsalady Point Fault, Northern Puget Lowland, Washington . In: Bulletin of the Seismological Society of America . 94, No. 6, December 2004, pp. 2299-2316. doi : 10.1785 / 0120040050 .
- ↑ a b c d e f g h i j k l m n o p q r s T. M. Brocher, T. Parsons, RJ Blakely, NI Christensen, MA Fisher, RE Wells: Upper crustal structure in Puget Lowland, Washington: Results from the 1998 Seismic Hazards Investigation in Puget Sound . In: SHIPS Working Group (Ed.): Journal of Geophysical Research . 106, No. B7, July 10, 2001, pp. 13,541-13,564. doi : 10.1029 / 2001JB000154 .
- ^ A b R. J. Blakely, RE Wells, CS Weaver: Puget Sound Aeromagnetic Maps and Data . In: US Geological Survey . Open-File Report 99-514, 1999.
- ↑ a b c d R. J. Blakely, RE Wells, CS Weaver, SY Johnson: Location, structure, and seismicity of the Seattle fault zone, Washington: Evidence from aeromagnetic anomalies, geologic mapping, and seismic-reflection data . In: Geological Society of America Bulletin . 114, No. 2, February 2002, pp. 169-177. doi : 10.1130 / 0016-7606 (2002) 114 <0169: LSASOT> 2.0.CO; 2 .
- ^ AJ Calvert, MA Fisher: Imaging the Seattle Fault Zone with high-resolution seismic tomography . In: SHIPS working group (ed.): Geophysical Research Letters . 28, No. 12, June 15, 2001, pp. 2337-2340. doi : 10.1029 / 2000GL012778 .
- ^ T. Parsons, RE Wells, MA Fisher, E. Flueh, US ten Brink: Three-dimensional velocity structure of Siletzia and other accreted terranes in the Cascadia forearc of Washington . In: Journal of Geophysical Research . 104, No. B8, August 10, 1999, pp. 18,015-18,039. doi : 10.1029 / 1999jb900106 .
- ^ MT Brandon, AR Calderwood: High-pressure metamporphism and uplift of the Olympic subduction complex . In: Geology . December 18, 1990, pp. 1252-1255. doi : 10.1130 / 0091-7613 (1990) 018 <1252: HPMAUO> 2.3.CO; 2 .
- ↑ Kathy G. Troost: The Origin of Puget Sound: Tectonics and Glaciers . Archived from the original on September 30, 2011. Retrieved October 8, 2018.
- ↑ a b c d e f g h i j k T. L. Pratt, SY Johnson, CJ Potter, WJ Stephenson: Seismic reflection images beneath Puget Sound, western Washington State: The Puget Lowland thrust sheet hypothesis Archived from the original on August 20, 2008. Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. In: Journal of Geophysical Research . 102, No. B12, December 10, 1997, pp. 27,469-27,490. doi : 10.1029 / 97JB01830 . Retrieved June 9, 2010.
- ^ A b R. W. Tabor: Late Mesozoic and possible early Tertiary accretion in western Washington State: the Helena-Haystack mélange and the Darrington-Devils Mountain Fault Zone . In: Geological Society of America Bulletin . 106, No. 2, 1994, pp. 217-232. doi : 10.1130 / 0016-7606 (1994) 106 <0217: lmapet> 2.3.co; 2 .
- ^ A b R. J. Blakely, BL Sherrod, CS Weaver, RE Wells: Connecting Crustal Faults and Tectonics from Puget Sound across the Cascade Range to the Yakima Fold and Thrust Belt, Washington: Evidence from New High-Resolution Aeromagnetic Data [Abstract GP232-02 ] . In: Eos, Transactions, American Geophysical Union . 90, No. 20, 2009.
- ↑ a b c d e R. J. Blakely, BL Sherrod, CS Weaver, RE Wells, AC Rohay, EA Barnett, NE Knepprath: Connecting the Yakima fold and thrust belt to active faults in the Puget Lowland, Washington . In: Journal of Geophysical Research . 116, no. B07105, July 7, 2011. doi : 10.1029 / 2010JB008091 .
- ↑ a b c d e f g h i j k W. D. Stanley, SY Johnson, AI Qamar, CS Weaver, JM Williams: Tectonics and Seismicity of the Southern Washington Cascade Range Archived from the original on August 20, 2011. Info: The archive link was inserted automatically and not yet tested. Please check the original and archive link according to the instructions and then remove this notice. In: Bulletin of the Seismological Society of America . 86, No. 1A, February 1996, pp. 1-18. Retrieved January 5, 2011.
- ↑ RS Babcock, RF Burmester, DC Engebretsen, A. Warnock: A Rifted Margin Origin for the Crescent Basalts and Related Rocks in the Northern Coast Range Volcanic Province, Washington and British Columbia . In: Journal of Geophysical Research . 97, No. B5, May 10, 1992, pp. 6.799-6.821. doi : 10.1029 / 91JB02926 .
- ↑ a b c d e f g h S. Y. Johnson, RJ Blakely, WJ Stephenson, SV Dadisman, MA Fisher: Active shortening of the Cascadia forearc and implications for seismic hazards of the Puget Lowland Archived from the original on June 7, 2011. Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. In: Tectonics . 23, No. TC1011, 2004, pp. 1-27. doi : 10.1029 / 2003TC001507 . Retrieved September 10, 2017.
- ↑ a b R. L. Logan, RL Schuster, PT Pringle, TJ Walsh, SP Palmer: Radiocarbon Ages of Probable Coseismic Features from the Olympic Peninsula and Lake Sammamish, Washington . In: Washington Geology . 26, No. 2-3, September 1998, pp. 59-67.
- ↑ K. Ramachandran: Velocity Structure of SW British Columbia, and NW Washington, From 3-D Non-linear Seismic Tomography [dissertation] . Univ. of Victoria. 2001.
- ↑ {{{publisher}}} (2000). Geologic map of the Snoqualmie Pass 60 minute by 30 minute quadrangle, Washington [map].
- ^ A b N. Hayward, MR Nedimović, M. Cleary, AJ Calvert: Structural variation along the Devil's Mountain fault zone, northwestern Washington Archived from the original on March 5, 2012. Information: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. In: Canadian Journal of Earth Sciences . 43, 2006, pp. 433-466. doi : 10.1139 / E06-002 . Retrieved June 9, 2010.
- ↑ a b J. D. Dragovich, AJ DeOme: Geologic map of the McMurray 7.5-minute Quadrangle, Skagit and Snohomish Counties, Washington, with a Discussion of the Evidence for Holocene Activity on the Darrington – Devils Mountain Fault Zone . In: Washington Division of Geology and Earth Resources . Geological Map GM – 61, June 2006, p. 18. "1 sheet, scale 1: 24,000"
- ↑ Utsalady Point fault . USGS. Retrieved October 15, 2018.
- ↑ JD Dragovich, GT Petro, GW Thorsen, SL Larson, GR Foster, Norman DK: Geologic map of the Oak Harbor, Crescent Harbor, and part of the Smith Iceland 7.5-minute quadrangles, Iceland County . In: Washington Division of Geology and Earth Resources . Geological Map GM – 59, June 2005. "2 sheets, scale 1: 24,000"
- ↑ RJ Blakely, BL Sherrod: Findings on the southern Whidbey Island fault zone from aeromagnetic anomalies, lidar surveys, and trenching . In: US Geological Survey . March 2006. "Presentation at USGS NSHMP (National Seismic Hazard Maps) Pacific Northwest Workshop, March 28-29, 2006"
- ↑ SY Johnson, RJ Blakely, TM Brocher, BL Sherrod, DJ Lidke, HM Kelsey: Quaternary fault and fold database of the United States: Fault number 572, Southern Whidbey Island Fault . US Geological Survey. 2004.
- ↑ a b c d e f g h i j S.Y. Johnson, CJ Potter, JM Armentrout, JJ Miller, CA Finn, CS Weaver: The southern Whidbey Island fault - An active structure in the Puget Lowland, Washington . In: Geological Society of America Bulletin . 108, No. 3, March 1996, pp. 334-354. doi : 10.1130 / 0016-7606 (1996) 108 <0334: TSWIFA> 2.3.CO; 2 .
- ^ A b R. M. Clowes, MT Brandon, AG Green, CJ Yorath, AS Brown, ER Kanasewich, C. Spencer: LITHOPROBE— southern Vancouver Island: Cenozoic subduction complex imaged by deep seismic reflections Archived from the original on March 27, 2012. Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. In: Canadian Journal of Earth Sciences . 24, No. 1, January 1987, pp. 31-51. Retrieved January 13, 2013.
- ↑ THICKNESS OF UNCONSOLIDATED QUATERNARY DEPOSITS . USGS. Retrieved October 16, 2018.
- ↑ a b c d e B. L. Sherrod, RJ Blakely, CS Weaver, HM Kelsey, E. Barnett, L. Liberty, KL Meagher, KM Pape: Finding concealed active faults: Extending the southern Whidbey Island fault across the Puget Lowland, Washington . In: Journal of Geophysical Research . 113, No. B5, May 2008, p. B05313. doi : 10.1029 / 2007JB005060 .
- ^ RJ Blakely, BL Sherrod, RE Wells, CS Weaver, DH McCormack, KG Troost, RA Haugerud: The Cottage Lake Aeromagnetic Lineament: A possible onshore extension of the Southern Whidbey Island Fault, Washington . In: US Geological Survey . Open-File Report 2004-1204, 2004.
- ↑ a b B. L. Sherrod, RJ Blakely, CS Weaver, H. Kelsey, E. Barnett, R. Wells: Holocene fault scarps and shallow magnetic anomalies along the Southern Whidbey Island Fault Zone near Woodinville, Washington . In: US Geological Survey . Open-File Report 2005-1136, 2005.
- ^ LM Liberty, KM Pape: Seismic Characterization of the Seattle and Southern Whidbey Island Fault Zones in the Snoqualmie River Valley, Washington . In: US Geological Service . NEHRP, 2008. "Project Award Number 06HQGR0111"
- ↑ a b c d e J. D. Dragovich, ML Anderson, TJ Walsh, BL Johnson, TL Adams: Geologic map of the Fall City 7.5-minute quadrangle, King County, Washington . In: Washington Division of Geology and Earth Resources . Geological Map GM – 67, November 2007, p. 16. "1 map sheet, scale 1: 24,000"
- ↑ a b c d e f g h i j J. D. Dragovich, TJ Walsh, ML Anderson, R. Hartog, SA DuFrane, J. Vervoot, SA Williams, R. Cakir, KD Stanton, FE Wolff, DK Norman, JL Czajkowski: Geologic map of the North Bend 7.5-minute quadrangle, King County, Washington, with a discussion of major faults, folds, and basins in the map area . In: Washington Division of Geology and Earth Resources . Geological Map GM – 73, February 2009, p. 39. "1 map sheet, scale 1: 24,000"
- ↑ a b c d e J. D. Dragovich, HA Littke, ML Anderson, GR Wessel, CJ Koger, JH Saltonstall, JH Jr. MacDonald, SA Mahan, SA DuFrane: Geologic map of the Carnation 7.5-minute quadrangle, King County, Washington . In: Washington Division of Geology and Earth Resources . Open-File Report 2010-1, June 2010, p. 21. "1 map sheet, scale 1: 24,000"
- ↑ a b c d J. D. Dragovich, ML Anderson, SA Mahan, JH MacDonald, CP McCabe, Recep Cakir, BA Stoker, NM Villeneuve, DT Smith, JP Bethel: Geologic map of the Lake Joy 7.5-minute quadrangle, King County, Washington . In: Washington Division of Geology and Earth Resources . Map Series 2012-01, October 2012, p. 70. "2 map sheets, scale 1: 24,000"
- ↑ (The planning area for the large-scale mappings and the current status can be found under DNR Washington .)
- ^ HM Kelsey, BL Sherrod: Late Holocene displacement on the Southern Whidbey Island fault zone, northern Puget lowland . In: US Geological Survey . NEHRP, 2001. "Program Award 00HQGR0067"
- ↑ (For the county's perspective on geological events and the effects of a potential major earthquake, see the Environmental Impact Statements website .)
- ^ A b J. D. Dragovich, RL Logan, HW Schasse, TJ Walsh, WS Lingley, DK Norman, WJ Gerstel, TJ Lapen, JE Schuster, KD Meyers: Geologic Map of Washington - Northwest Quadrant . In: Washington Division of Geology and Earth Resources . Geologic Map GM-50, 2002, p. 72. "3 map sheets, scale 1: 250,000"
- ^ JH Mackin, AS Cary: Origin of Cascade Landscapes . 1965.
- ^ WP Rogers: A geological and geophysical study of the central Puget Lowland [dissertation] . Univ. of Washington, Seattle 1970, p. 123 (9 plates).
- ^ A b E. S. Cheney: Major Cenozoic faults in the northern Puget Lowland of Washington . In: JE Schuster (Ed.): Selected papers on the Geology of Washington (= Washington DGER Bulletin ). tape 77 , 1987, pp. 149–168 ( dnr.wa.gov [PDF]).
- ↑ a b c J. D. Dragovich, CL Frattali, ML Anderson, SA Mahan, JH MacDonald Jr., BA Stoker, DT Smith, CJ Koger, R. Cakir, A. DuFrane, KB Sauer: Geologic Map of the Lake Chaplain 7.5-minute Quadrangle, Snohomish County, Washington . In: Washington Division of Geology and Earth Resources . Map Series 2014–01, December 2014, p. 51. "1 map sheet, scale 1: 24,000"
- ↑ a b c d e f g h i JD Dragovich, SP Mavor, ML Anderson, SA Mahan, JH Jr. MacDonald, JH Tepper, DT Smith, BA Stoker, CJ Koger, R. Cakir, A. DuFrane, SP Scott, BJ Justman: Geologic Map of the Granite Falls 7.5-minute Quadrangle, Snohomish County, Washington . In: Washington Division of Geology and Earth Resources . Map Series 2016–03, November 2016, p. 63. "1 map sheet, scale 1: 24,000"
- ↑ JD Dragovich, SA Mahan, ML Anderson, JH Jr MacDonald, JF Schilter, CL Frattali, CJ Koger, DT Smith, BA Stoker, Andrew DuFrane, MP Eddy, Recep Cakir, KB Sauer: Geologic map of the Lake Roesiger 7.5-minute quadrangle, Snohomish County, Washington . In: Washington Division of Geology and Earth Resources . Map Series 2015-01, October 2015, p. 47. "1 map sheet, scale 1: 24,000"
- ^ JD Dragovich, DK Norman, CL Grisamer, RL Logan, G. Anderson: Geologic Map and Interpreted Geologic History of the Bow and Alger 7.5-minute Quadrangles, Western Skagit County, Washington . In: Washington Division of Geology and Earth Resources . Open-File Report 98-5, September 1998, p. 80. "1 map sheet, scale 1: 24,000"
- ↑ a b c d Joe D. Dragovich, Heather A. Littke, Shannon A. Mahan, Megan L. Anderson, James H. Jr. MacDonald, Recep Cakir, Bruce A. Stoker, Curtis J. Koger, S. Andrew DuFrane, John P. Bethel, Daniel T. Smith, Nathan M. Villeneuve: Geologic map of the Sultan 7.5-minute quadrangle, Snohomish and King Counties, Washington . In: Washington Division of Geology and Earth Resources . Map Series 2013-01, October 2013, p. 52. "1 map sheet, scale 1: 24,000"
- ↑ JD Dragovich, ML Anderson, JH Jr. MacDonald, SA Mahan, SA DuFrane, HA Littke, GR Wessel, JH Saltonstall, CJ Koger, Recep Cakir: Supplement to the geologic map of the Carnation 7.5-minute quadrangle, King County, Washington - Geochronologic, geochemical, point count, geophysical, earthquake, fault, and neotectonic data . In: Washington Division of Geology and Earth Resources . Open File Report 2010-2, June 2010, p. 42. "8 digital attachments"
- ^ A b c d E. H. Brown, JD Dragovich: Tectonic elements and evolution of northwest Washington . In: Washington Division of Geology and Earth Resources . Geological Map GM – 52, December 2003, p. 12. "1 map sheet, scale 1: 625,000"
- ↑ see QFFDB Fault # 565. )
- ↑ a b J. D. Dragovich, ML Anderson, SA Mahan, CJ Koger, JH Saltonstall, JH MacDonald, GR Wessel, BA Stoker, JP Bethel, JE Labadie, Recep Cakir, JD Bowman, SA DuFrane: Geologic map of the Monroe 7.5-minute quadrangle, King County, Washington . In: Washington Division of Geology and Earth Resources . Open-File Report 2011-1, November 2011, p. 24. "1 map sheet, scale 1: 24,000"
- ↑ a b c C. Finn: Geophysical constraints on Washington convergent margin structure . In: Journal of Geophysical Research . 95, No. B12, November 10, 1990, pp. 19,553-19,546. doi : 10.1029 / JB095iB12p19533 .
- ^ A b C. G. Mace, KM Keranen: Oblique fault systems crossing the Seattle Basin: Geophysical evidence for additional shallow fault systems in the central Puget Lowland . In: Journal of Geophysical Research . 117, no. B03105, March 2012. doi : 10.1029 / 2011JB008722 .
- ^ A b S. Y. Johnson, CJ Potter, JM Armentrout: Origin and evolution of the Seattle Fault and Seattle Basin, Washington . In: Geology . 22, No. 1, January 1994, pp. 71-74. doi : 10.1130 / 0091-7613 (1994) 022 <0071: OAEOTS> 2.3.CO; 2 .
- ↑ a b c C. M. Snelson, TM Brocher, KC Miller, TL Pratt, AM Tréhu: Seismic Amplification within the Seattle Basin, Washington State: Insights from SHIPS Seismic Tomography Experiments . In: Bulletin of the Seismological Society of America . 97, No. 5, October 2007, pp. 1432-1448. doi : 10.1785 / 0120050204 .
- ↑ a b c T. M. Van Wagoner, RS Crosson, KC Creager, G. Medema, L. Preston: Crustal structure and relocated earthquakes in the Puget Lowland, Washington, from high-resolution seismic tomography . In: Journal of Geophysical Research . 107, No. B12, December 10, 2002. doi : 10.1029 / 2001JB000710 .
- ↑ a b K. Ramachandran: Constraining fault interpretation through tomographic velocity gradients: application to northern Cascadia . In: Solid Earth . 3, 2012, pp. 53-61. doi : 10.5194 / se-3-53-2012 .
- ↑ ML Anderson, RJ Blakely, RE Wells, J. Dragovich: Eastern boundary of the Siletz terrane in the Puget Lowland from gravity and magnetic modeling with implications for seismic hazard analysis [abstract GP33B-06] . In: American Geophysical Union, Fall Meeting . 2011.
- ↑ (see also Fig. 64 available online )
- ↑ a b L. M. Liberty: The western extension of the Seattle fault: new insights from seismic reflection data Archived from the original on January 28, 2017. Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. In: US Geological Service . NEHRP, 2009. Retrieved September 10, 2017. "Project Award Number 08HQGR0075"
- ^ TM Brocher, RJ Blakely, RE Wells: Interpretation of the Seattle Uplift, Washington, as a Passive-Roof Duplex . In: Bulletin of the Seismological Society of America . 94, No. 4, August 2004, pp. 1379-1401. doi : 10.1785 / 012003190 .
- ↑ US ten Brink, J. Song, RC Bucknam: Rupture models for the AD 900–930 Seattle fault earthquake from uplifted shorelines . In: Bulletin of the Geological Society of America . 34, No. 7, July 2006, pp. 585-588. doi : 10.1130 / G22173.1 .
- ^ A b J. C. Yount, HD Gower: Bedrock Geologic Map of the Seattle 30 'by 60' Quadrangle, Washington . In: US Geological Survey . Open-File Report 91-147, 1991, p. 37. "4 panels"
- ^ A b c d S. Y. Johnson, SV Dadisman, JR Childs, WD Stanley: Active tectonics of the Seattle fault and central Puget Sound, Washington - Implications for earthquake hazards Archived from the original on January 29, 2012. Info: The archive link was inserted automatically and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. In: Geological Society of America Bulletin . 111, No. 7, July 1999, pp. 1042-1053. doi : 10.1130 / 0016-7606 (1999) 111 <1042: ATOTSF> 2.3.CO; 2 . Retrieved September 10, 2017.
- ↑ a b c d M. Polenz, E. Spangler, LA Fusso, DA Reioux, RA Cole, TJ Walsh, R. Cakir, KP Clark, JH Tepper, RJ Carson, D. Pileggi, SA Mahan: Geologic map of the Brinnon 7.5-minute quadrangle, Jefferson and Kitsap Counties, Washington . In: Washington Division of Geology and Earth Resources . Map Series 2012-02, December 2012, p. 47. "1 map sheet, scale 1: 24,000"
- ↑ a b c d e f T. A. Contreras, E. Spangler, LA Fusso, DA Reioux, G. Legorreta Paulin, PT Pringle, RJ Carson, EF Lindstrum, KP Clark, JH Tepper, D. Pileggi, SA Mahan: Geologic map of the Eldon 7.5-minute quadrangle, Jefferson, Kitsap, and Mason Counties, Washington . In: Washington Division of Geology and Earth Resources . Map Series 2012-03, December 2012, p. 60. "1 map sheet, scale 1: 24,000"
- ↑ PJ Haeussler, KM Clark: Geologic map of the Wildcat Lake 7.5 'quadrangle, Kitsap and Mason Counties, Washington Archived from the original on February 19, 2013. Information: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. In: US Geological Survey . Open File Report 00-356, 2000. Retrieved June 9, 2010. "1 map sheet, scale 1: 24,000"
- Jump up ↑ TA Contreras, SA Weeks, KMD Stanton, BW Stanton, BB Perry, TJ Walsh, RJ Carson, KP Clark, SA Mahan: Geologic map of the Holly 7.5-minute quadrangle, Jefferson, Kitsap, and Mason Counties, Washington . In: Washington Division of Geology and Earth Resources . Open File Report 2011-5, August 2012, p. 13. "1 map sheet, scale 1: 24,000"
- ↑ a b c d e f g h i j A. P. Lamb, LM Liberty, RJ Blakely, TL Pratt, BL Sherrod, K. Van Wijik: Western limits of the Seattle fault zone and its interaction with the Olympic Peninsula, Washington . In: Geosphere . 8, No. 4, June 26, 2012, pp. 915-930. doi : 10.1130 / GES00780.1 .
- ^ BJ Haug: High Resolution Seismic Reflection Interpretations of the Hood Canal-Discovery Bay Fault Zone, Puget Sound, Washington [ms thesis] . Portland State Univ. 1998.
- ↑ a b c d e f g h R. J. Blakely, BL Sherrod, JF Hughes, ML Anderson, RE Wells, CS Weaver: The Saddle Mountain Fault Deformation Zone, Olympic Peninsula, Washington: Western Boundary of the Seattle Uplift . In: Geosphere . 5, No. 2, April 2009, pp. 105-125. doi : 10.1130 / GES00196.1 .
- ↑ a b c M. Polenz, GT Petro, TA Contreras, KA Stone, G. Legorreta Paulin, R. Cakir: Geologic map of the Seabeck and Poulsbo 7.5-minute quadrangles, Kitsap and Jefferson Counties, Washington . In: Washington Division of Geology and Earth Resources . Map Series 2013-02, October 2013, p. 39. "1 map sheet, scale 1: 24,000"
- ↑ AR Nelson, SF Personius, BL Sherrod, J. Buck, L. Bradley, G. Henley II, LM Liberty, HM Kelsey, RC Witter, RD Koehler, ER Schermer, ES Nemser, TT Cladouhos: Field and laboratory data from an earthquake history study of scarps in the hanging wall of the Tacoma fault, Mason and Pierce Counties, Washington . In: US Geological Survey . Scientific Investigations Map 3060, 2008. "3 map sheets"
- ↑ BL Sherrod, AR Nelson, HM Kelsey, TM Brocher, RJ Blakely, CS Weaver, NK Rountree, BS Rhea, BS Jackson: The Catfish Lake Scarp, Allyn, Washington: Preliminary Field Data and Implications for Earthquake Hazards posed by the Tacoma Fault . In: US Geological Survey . Open-File Report 03-0455, 2003.
- ^ A b S. Carley, LM Liberty, TL Pratt: Geophysical characterization of the Muckleshoot Basin, northwestern Washington State [Abstract T51C-0694] . In: American Geophysical Union, Fall Meeting 2007 . 2007.
- ↑ LM Liberty: Seismic reflection imaging across the eastern portions of the Tacoma fault zone . In: US Geological Service . NEHRP, 2007. "Project Award Number 07HQGR0088"
- ^ A b A. P. Lamb, LM Liberty, RJ Blakely, K. Van Wijk: The Tahuya Lineament: Southwestern Extension of the Seattle Fault? [Paper No. 182-3] . In: Geological Society of America 2009 Annual meeting, Abstracts with Programs . 41, No. 7, 2009, p. 479.
- ↑ a b QFFDB, Fault # 552 . USGS. Retrieved October 30, 2018.
- ↑ TA Contreras, G. Legorreta Paulin, JL Czajkowski, M. Polenz, RL Logan, RJ Carson, SA Mahan, TJ Walsh, CN Johnson, RH Skov: Geologic map of the Lilliwaup 7.5-minute quadrangle, Mason County, Washington . In: Washington Division of Geology and Earth Resources . Open File Report 2010-4, June 2010, p. 13. "1 map sheet, scale 1: 24,000"
- ↑ a b M. Polenz, TA Contreras, JL Czajkowski, G. Legorreta Paulin, BA Miller, ME Martin, TJ Walsh, RL Logan, RJ Carson, CN Johnson, RH Skov, SA Mahan, CR Cohan: Supplement to Geologic Maps of the Lilliwaup, Skokomish Valley, and Union 7.5-minute Quadrangles, Mason County, Washington - Geologic Setting and Development Around the Great Bend of Hood Canal . In: Washington Division of Geology and Earth Resources . Open-File Report 2010-5, June 2010, p. 27.
- ↑ Fault 562a . USGS. Retrieved November 1, 2018.
- ↑ Fault 562b . USGS. Retrieved November 1, 2018.
- ^ RJ Carson: First known active fault in Washington . In: Washington Geological Newsletter . 1, No. 3, July 1973, pp. 1-3.
- ^ RJ Carson, JR Wilson: Quaternary faulting on Dow Mountain, Mason County . In: Washington Geological Newsletter . 2, No. 4, October 1974, p. 1.
- ↑ a b T. J. Walsh, RL Logan: Field data for a trench on the Canyon River fault, southeast Olympic Mountains, Washington . In: Washington Division of Geology and Earth Resources . Open File Report 2007-1, 2007. "Poster"
- ^ A b R. C. Witter, RW Givler: Final Technical Report: Two Post-Glavial Earthquakes on the Saddle Mountain West Fault, southeastern Olympic Peninsula, Washington . In: US Geological Survey . NEHRP, 2005. "Program Award 05HQGR0089"
- ↑ Stanley Fig. 64 from Stanley et al. (1999)
- ↑ a b c B. L. Sherrod: Late Holocene environments and earthquakes in southern Puget Sound [dissertation] . University of Washington, Seattle 1998.
- ↑ OFR 99-311, figures 46-50 . USGS. Retrieved November 2, 2018.
- ↑ ( Download the map on which this anomaly is shown. Further aeromagnetic and gravitational images of the Olympic and other structures are shown on the Summit Lake geological map .)
- ↑ a b B. L. Sherrod: Evidence for earthquake-induced subsidence ~ 1100 yr ago in coastal marshes of southern Puget Sound, Washington . In: Geological Society of America Bulletin . 113, No. 10, 2001, pp. 1299-1311. doi : 10.1130 / 0016-7606 (2001) 113 <1299: EFEISA> 2.0.CO; 2 .
- ↑ S. Magsino, E. Sanger, TJ Walsh, SP Palmer, RJ Blakely: The Olympia structure; ramp or discontinuity? New gravity data provide information [abstract] . In: Geological Society of America 2003 Annual meeting, Abstracts with Programs . 35, No. 6, November 2003, p. 479.
- ^ A b R.L. Logan, TJ Walsh: Geologic map of the Summit Lake 7.5-minute quadrangle, Thurston and Mason Counties, Washington . In: Washington Division of Geology and Earth Resources . Open-File Report 2004-10, June 2004. "1 map sheet, scale 1: 24,000" }
- ↑ M. Polenz, JL Czajkowski, G. Legorreta Paulin, TA Contreras, BA Miller, ME Martin, TJ Walsh, RL Logan, RJ Carson, CN Johnson, RH Skov, SA Mahan, CR Cohan: Geologic map of the Skokomish Valley and Union 7.5-minute quadrangles, Mason County, Washington . In: Washington Division of Geology and Earth Resources . Open-File Report 2010-3, June 2010, p. 21. "1 map sheet, scale 1: 24,000"
- ^ TJ Walsh, RL Logan: Geologic Map of the East Olympia 7.5-minute Quadrangle, Thurston County, Washington . In: Washington Division of Geology and Earth Resources . Geological Map GM – 56, June 2005. "1 map sheet, scale 1: 24,000"
- ↑ CR Clement: Seismic reflection imaging across steep gravity and magnetic anomaly gradients in southern Puget Sound, WA: Future fault or benign block? [abstract] . 2004.
- ↑ CR Clement, TR Pratt, MA Holmes, BL Sherrod: High-Resolution Seismic Reflection Imaging of Growth Folding and Shallow Faults beneath the Southern Puget Lowland, Washington State . In: Bulletin of the Seismological Society of America . 100, No. 4, August 2010, pp. 1710-1723. doi : 10.1785 / 0120080306 .
- ^ A b c C. S. Weaver, SW Smith: Regional Tectonic and Earthquake Hazard Implications of a Crustal Fault Zone in Southwestern Washington . In: Journal of Geophysical Research . 92, No. B12, December 10, 1983, pp. 10.371-10.383. doi : 10.1029 / JB088iB12p10371 .
- ↑ RJ Blakely, RC Jachens: Volcanism, Isostatic Residual Gravity, and Regional Tectonic Setting of the Cascade Volcanic Province . In: Journal of Geophysical Research . 95, No. B12, November 10, 1990, pp. 19.439-19.451. doi : 10.1029 / JB095iB12p19439 .
- ↑ Faults near The Dalles . USGS. Retrieved November 5, 2018.
- ↑ a b c T. J. Walsh, MA Korosec, WM Phillips, RL Logan, HW Schasse: Geologic map of Washington - Southwest Quadrant . In: Washington Division of Geology and Earth Resources . Geologic Map GM – 34, 1987, p. 28. "2 map sheets, scale 1: 250,000"
- ↑ The entire map is available online
- ↑ C. Finn, WD Stanley: Something old, something new, something borrowed, something blue - a new perspective on seismic hazards in Washington using aeromagnetic data . In: Washington Geology . 25, No. 2, June 1997, pp. 3-7.
- ↑ C. Finn: Aeromagnetic map compilation: procedures for merging and an example from Washington . In: Annali di Geofisica . 42, No. 2, April 1999, pp. 327-331.
- ^ A b I. Wong, W. Silva, J. Bott, D. Wright, P. Thomas, N. Gregor, S. Li, M. Mabey, A. Sojourner, Y. Wang: Earthquake scenario and probabilistic ground shaking maps for the Portland, Oregon, metropolitan area . In: Oregon Department of Geology and Mineral Industries . Interpretive Map Series IMS-16, 2000.
- ↑ (see the report
- ↑ a b c d C. S. Weaver, WC Grant, JE Shemeta: Crustal Extension at Mount St. Helens, Washington . In: Journal of Geophysical Research . 92, No. B10, September 10, 1987, pp. 10.170-10.178. doi : 10.1029 / JB092iB10p10170 .
- ↑ a b c W.D. Stanley, C. Finn, JL Plesha: Tectonics and Conductivity Structures in the Southern Washington Cascades . In: Journal of Geophysical Research . 92, No. B10, September 10, 1987, pp. 10.179-10.193. doi : 10.1029 / JB092iB10p10179 .
- ↑ (see the map of faults in the QFFDB)
- ^ A b G. D. Egbert, JR Booker: Imaging Crustal Structure in Southwestern Washington With Small Magnetometer Arrays . In: Journal of Geophysical Research . 98, No. B9, September 10, 1993, pp. 15.967-15.985. doi : 10.1029 / 93JB00778 .
- ^ JD Vine: Stratigraphy of Eocene rocks in a part of King County, Washington . In: Washington State Division of Mines and Geology (Ed.): Report of Investigations No. 21 . 1962.
- ^ WD Stanley, SY Johnson: Analysis of Deep Seismic Reflection and Other Data From the Southern Washington Cascades . In: US Dept. of Energy (Ed.): Fuels Technology Contractors Review Meeting, Morgantown, West Virginia, November 16-18, 1993 . 1993.
- ^ JE Schuster: Geologic map of Washington State . In: Washington Division of Geology and Earth Resources . Geological Map GM – 53, 2005, p. 44. "1 map sheet, scale 1: 500,000"
- ↑ a b c d e R. C. Evarts, RP Ashley, JG Smith: Geology of the Mount St. Helens Area: Record of Discontinuous Volcanic and Plutonic Activity in the Cascade Arc of Southern Washington . In: Journal of Geophysical Research . 82, No. B10, September 10, 1987, pp. 10.155-10.169. doi : 10.1029 / JB092iB10p10155 .
- ↑ RW Tabor, DF Crowder: On batholiths and volcanoes - Intrusion and eruption of Late Cenozoic magmas in the Glacier Peak area, north Cascades, Washington . In: US Geological Survey . Professional Paper 604, 1969.
- ↑ a b c J. M. Hughes, RE Stoiber, MJ Carr: Segmentation of the Cascade volcanic chain . In: Geology . 8, No. 1, January 1980, pp. 15-17. doi : 10.1130 / 0091-7613 (1980) 8 <15: SOTCVC> 2.0.CO; 2 .
- ↑ M. Guffanti, CS Weaver: Distribution of late Cenozoic volcanic vents in the Cascade Range: Volcanic arc segmentation and regional tectonic considerations . In: Journal of Geophysical Research . 93, No. B6, June 10, 1988, pp. 6513-6529. doi : 10.1029 / JB093iB06p06513 .
- ↑ JS Olbinski: Geology of the Buster Creek Nehalem Valley Area, Clatsop County, Oregon Northwest . Oregon State University [masters thesis]. 1983.
- ^ GC Rogers: Phase changes, fluids and the co-location of the deep and shallow seismicity beneath Puget Sound and southern Georgia Strait . In: S. Kirby, K. Wang, S. Dunlop (Eds.): The Cascadia Subduction Zone and Related Subduction Systems: Seismic Structure, Intraslab Earthquakes and Processes, and Earthquake Hazards . Open-File Report 02-328. US Geological Survey, August 2002 ( geopubs.wr.usgs.gov [PDF]).
- ^ TS Yelin: The Seattle earthquake swarms and Puget Basin focal mechanisms and their tectonic implications . Univ. of Washington, 1982 (Masters thesis).
- ↑ (see QFFDB, Fault 556 )
- ↑ see the map for the database of faults
- ^ MP Molinari, RL Burk: The Everett fault: a newly discovered late Quaternary fault in north-central Puget Sound, Washington [abstract] . In: Geological Society of America 2003 Annual Meeting, Abstracts with programs . 35, No. 6, November 2003, p. 479.
- ^ JA Vance, RB Miller: Another look at the Fraser River-Straight Creek Fault (FRSCF) [abstract] . In: Geological Society of America 1994 Annual Meeting, Abstracts with Programs . 24, 1994, p. 88.
- ^ SY Johnson: Stratigraphy, age, and paleogeography of the Eocene Chuckanut Formation, northwest Washington . In: Canadian Journal of Earth Sciences . 21, 1984, pp. 92-106. doi : 10.1139 / e84-010 . }
- ^ NJ Finnegan, ME Pritchard, RB Lohman, PR Lundgren: Constraints on surface deformation in the Seattle, WA, urban corrider from satellite radar interferometry time-series analysis . In: Geophysical Journal International . 174, 2008, pp. 29-41. doi : 10.1111 / j.1365-246X.2008.03822.x .
