Mercalli scale
The Mercallis scale is now a twelve-point scale of earthquake intensity, which divides the visible and tangible effects (strength) of earthquakes on the earth's surface based on the observed events and the changes caused and is used to describe damage. The information is subjective and depends on the observer, on the geological characteristics and on the local development.
history
The Mercalli scale was introduced when there were no precise measuring instruments and no international measuring network. It is named after the Italian volcanologist Giuseppe Mercalli (1850–1914). Mercalli developed the scale based on the Rossi-Forel scale in the second half of the 19th century by documenting and tabulating the damage caused by earthquakes. This enabled him to determine the approximate origin of the quake, because the further away a place is from the epicenter , the less damage is usually caused. Mercalli published his ten-point scale in 1902, which describes the direct impact of earthquakes on people and buildings.
In 1904, the Italian geophysicist Adolfo Cancani suggested expanding the scale to twelve levels in order to be able to provide a more differentiated description of very strong earthquakes. This scale came to be known as the Forel-Mercalli scale and the Cancani scale . In 1912 the German geophysicist August Heinrich Sieberg carried out a comprehensive revision of this scale, which also took into account the effects of tremors on plants. After this scale was revised, it was called the Mercalli-Cancani-Sieberg scale (MCS scale) from 1923 . In a translation into English and revision of the MCS scale by the seismologists Harry O. Wood and Frank Neumann , the Mercalli-Wood-Neumann scale (MWN scale) was created in 1931 , which the authors themselves called the Modified Mercallis scale (MM scale or MM-31) gave.
In 1958, Charles Francis Richter published a thorough overhaul of the Modified Mercallis Scale, which took into account the effects of earthquakes on buildings of varying strength. Since his name was already used journalistically as a designation for the local magnitude scale ( Richter scale ), he suggested the name Modified Merkalliskala von 1956 (MM-56). This identity of names had the disadvantageous effect that it was often no longer clear to which MM scale scientific papers referred. This problem was exacerbated by further revisions of the scale while retaining the name.
Classification
The individual levels of the Modified Mercalli Scale are described as follows:
| step | designation | description |
Acceleration (1 g ≈ 9.81 m / s²) |
|---|---|---|---|
| I. | imperceptibly | Perceived only by a few people under particularly favorable circumstances | <0.001 g |
| II | very easy | Occasionally noticeable (upper floors of high-rise buildings), is occasionally noticed by people who are resting | 0.001-0.002 g |
| III | light | Can be clearly felt, especially on the upper floors of buildings, even if mostly not recognized as an earthquake. Standing cars and hanging objects swing slightly, vibrations similar to those of a passing truck | 0.002-0.005 g |
| IV | moderate | In buildings by many, outside during the day by some people, some sleepers wake up. Dishes, windows and doors tremble or clink, walls make creaking noises. Stationary cars sway clearly, vibrations like those when a truck collides with a house | 0.005-0.01 g |
| V | pretty strong | Felt by almost everyone, many sleepers wake up. Dishes and window panes can shatter, unstable objects fall over, and pendulum clocks can stop. Trees sway, doors and windows can open and close | 0.01-0.02 g |
| VI | strong | Felt by everyone, many people are scared, walking becomes difficult. Slight damage to buildings, cracks and similar damage in the plaster . Heavy furniture can shift, objects fall off shelves and pictures fall off the walls. Trees and bushes sway. | 0.02-0.05 g |
| VII | very strong | Noticeable even in moving cars, it becomes difficult to stand. Damage to furniture, loose bricks falling down. Buildings that are inadequately built or have been designed incorrectly will be severely damaged, with light to medium damage to normal buildings. Damage is negligible if the design and type are good | 0.05-0.1 g |
| VIII | destructive | Driving becomes difficult. Slight damage to buildings of good construction and type, considerable damage to normal buildings up to and including partial collapse. Major damage to buildings that are inadequately constructed or with a faulty structural design. Collapse of chimneys, factory chimneys, columns, monuments and walls possible. Heavy furniture falls over. Branches are broken off, water level changes in wells possible, cracks in steep terrain on wet ground | 0.1-0.2 g |
| IX | devastating | Significant damage to buildings with good construction methods and types, even well-planned structural structures warp. Great damage to stable buildings up to partial collapse. Houses are being moved from their foundations, damage to underground pipelines and dams, cracks in the ground | 0.2-0.5 g |
| X | devastating | Even well-executed wooden frame constructions are partially destroyed, most of the masonry objects and structural constructions are destroyed along with their foundations. Railway tracks are bent, some bridges are destroyed. Severe damage to dams, large landslides, water in lakes, rivers and canals overflows, and cracks in the ground are widespread | 0.5-1 g |
| XI | catastrophe | Almost all masonry buildings collapse, bridges are destroyed, railway tracks are severely bent, large cracks in the ground, supply lines are destroyed | 1-2 g |
| XII | big catastrophe | Total destruction, major changes on the surface of the earth, objects are thrown into the air, the surface of the earth moves in waves, large masses of rock can start moving | > 2 g |
Web links
- August Sieberg: The Effects of a Severe Earthquake. University of Jena, accessed April 7, 2013 (watercolor).
Individual evidence
- ^ Roger MW Musson, Gottfried Grünthal, Max Stucchi: The comparison of marcoseismic intensity scales. In: Journal of Seismology. Volume 14, Issue 2, 2009, pp. 413–428, digital version online (PDF; 472 kB) at archives-ouvertes.fr (English).
- ^ The Modified Mercalli Intensity Scale . USGS , October 27, 2009; archived from the original on May 5, 2010 ; accessed on March 6, 2010 (English).
- ^ The Modified Mercalli (MM) Intensity Scale . In: Natural Resources Canada . Canada Government , accessed September 22, 2019 .
- ↑ Seismology. Karl-Franzens-Universität Graz, archived from the original on February 20, 2012 ; Retrieved November 30, 2015 (original website no longer available).