Wairarapa Fault

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Map of the North Island Fault System with the location of the Wairarapa Fault

The Wairarapa Fault is a geological fault in the Greater Wellington region of the North Island of New Zealand .

geography

The fault, which is part of the North Island Fault System , runs on the southeast flank of the Remutaka Range , parallel to the mountain range in a southwestern direction. It begins north of the small settlement of Mauriceville , around 25 km north of Masterton and ends around 20 km northeast of Turakirae Head , at the western end of Palliser Bay . The Wairarapa Fault thus extends over a length of around 80 km.

geology

The North Island of New Zealand lies on the eastern edge of the Australian Plate , under which the Pacific Plate shifts in the so-called Hikurangi Trench at 38 mm to 50 mm per year in a south-westerly direction. The displacements in this subduction zone create tensions in the Australian plate, which lead to fractures, faults and, as a result, earthquakes. The Wairarapa Fault , along with the Wellington Fault , the Ohariu Fault and the Carterton Fault, is one of the larger faults in the south of the North Island. It is shifting at a rate of 39 mm per year in a south-westerly direction, with elevations on the western side of the fault mostly occurring in a north-westerly direction. Due to these elevations, the Remutaka Range continues to gain height, while the extensive Wairarapa Valley with Wairarapa Lake continues to develop on the southeast side . The depth of the fault is assumed to be up to 20–30 km.

Historical earthquakes

The largest earthquake recorded on land in New Zealand since the earthquake was recorded was the Wairarapa earthquake in 1855 . With a thickness from 8.2 to 8.3  M W , it changed the landscape along a more than 100 km long fault line significantly. Terrain elevations of up to just over 6 meters led z. B. at Palliser Bay to significant shifts of the shoreline towards the lake. The two sides of the fault shifted horizontally by up to 18 meters.

Two other major earthquakes occurred later in 1942 ( Wairarapa earthquake of 1942 ) with magnitudes of 7.0 and 7.2  M S with the epicenter near Masterton .

Today, however, it is assumed that a major earthquake caused by the Wairarapa Fault has a higher probability of not happening again in the next hundred years, since the earthquake of 1855 significantly reduced the tension in the fault. Russ Van Dissen , a geologist and earthquake specialist with GNS Science , put the probability of a similar earthquake at 1 to 2%.

See also

literature

  • JJ Aitken : Plate Tectonics for curious kiwis . Ed .: Institute of Geological & Nuclear Sciences Limited . Lower Hutt 1996, ISBN 0-478-09555-4 (English).
  • Tim Little, John Begg : 1855 Wairarapa Earthquake Symposium: All-day Field-trip to the Wairarapa Fault and 1855 Rupture Sites . Ed .: Greater Wellington Regional Council . Wellington 2005, ISBN 0-909016-88-7 (English, online PDF 12.2 MB [accessed October 14, 2014]).
  • Timothy Little, Liz Schermer, Russ Van Dissen, John Begg, Rachel Carnel : Field Trip 5 - Southern Wairarapa Fault and Wharekauhau Thrust (Palliser Bay) . In: Geoscience Society of New Zealand (Ed.): GeoSciences '08 Field Trip Guides . Wellington 2008, p. 75–120 (English, online PDF 6.5 MB [accessed October 14, 2014]).

Individual evidence

  1. ^ Major Faults in New Zealand . GNS Science , accessed October 14, 2014 .
  2. ↑ a b Little, Begg : 1855 Wairarapa Earthquake Symposium . 2005, p.  4 (English).
  3. ↑ Little, Schermer, Van Dissen, Begg, Carnel : Field Trip 5 . 2008, p.  78 (English).
  4. ↑ M 8.2 - 8.3, Wairarapa, January 23, 1855 . GeoNet , accessed October 14, 2014 .
  5. ↑ Little, Begg : 1855 Wairarapa Earthquake Symposium . 2005, p.  6 (English).
  6. ↑ Wairarapa region - Wairarapa fault . Te Ara - the Encyclopedia of New Zealand , November 14, 2012, accessed October 14, 2014 .
  7. ^ M 7.2, Wairarapa I, June 24, 1942 . GeoNet , accessed October 14, 2014 .
  8. ^ M 7.0, Wairarapa II, August 2, 1942 . GeoNet , accessed October 14, 2014 .
  9. ↑ Don Farmer : 1855 quake cuts repeat risk . Wairarapa Times-Age , August 22, 2012, accessed October 14, 2014 .