Ōmoriskala

from Wikipedia, the free encyclopedia

The Ōmori scale was developed in 1900 by the Japanese scientist Fusakichi Ōmori to estimate the seismic intensity of earthquakes in Japan .

The Ōmori scale is a seven-part scale that primarily considers the effects of earthquakes on typical Japanese construction methods and also on the landscape. It combines these effects with the maximum acceleration caused by earthquake shocks on the ground. Based on the Ōmori scale, the Japan Meteorological Agency (JMA) developed the forerunner of the JMA scale, which was used in Japan and Taiwan until 1996, in 1951 . Since the Ōmoris scale primarily assesses damage, it does not contain any levels that correspond to levels I to V of the Mercalli scale , which are based on earthquake effects that do not cause any damage. Level I of the Ōmori scale is therefore roughly equivalent to Mercalli's level VI.

In contrast to magnitude scales , such as the well-known Richter scale , an intensity scale describes the effects of an earthquake on the landscape, streets or buildings that can be perceived without instruments ( macro-seismics ). Depending on the local conditions, a single earthquake classified according to such a scale can have different strengths in different places. Examples of other intensity scales are the Mercallis scale , the European Macroseismic Scale (EMS) or the Rossi-Forel scale .

Degree of strength Max. Acceleration * ( mm / s ²) observation
I. 300 The tremor is so strong that most people inside buildings are frightened and flee outside. Slight wall cracks and plaster damage on poorly built brick buildings, normal wooden houses crunch loudly. Furniture falls over, pendulum clocks stop, badly built, tall chimneys (e.g. factory chimneys) fall over. Trees tremble visibly and the water in ponds and pools becomes muddy.
II 900 Wall cracks on normal wooden houses, old wooden houses are crooked. Some Japanese tombstones and other towering objects such as stone lanterns fall over, and some thermal and mineral springs change their behavior. Normal factory chimneys still hold up.
III 1200 Around a quarter of all factory chimneys are damaged. Badly built brick houses are partially or completely destroyed. Some wooden bridges are damaged, some tombstones and other towering objects such as stone lanterns fall over. Japanese paper-covered doors break, roof tiles slip and light rockfalls are observed on some mountain slopes.
IV 2000 All factory chimneys are damaged. Most brick houses will be partially or completely destroyed, some wooden houses will be completely destroyed. Wooden sliding doors jump out of their guides, normal stone lanterns fall over and wooden bridges are partially destroyed. Gaps with a width of five to eight centimeters open in level and soft ground, here and there dams and embankments are damaged.
V 2500 All normal brick houses are very badly damaged, about three percent of the wooden houses are completely destroyed. Some Buddhist temples collapse. Dams and embankments are badly damaged. Railroad tracks are easily bent, brick walls damaged, and ordinary tombstones topple over. In some places there are large crevices in the ground along watercourses that can be up to 60 cm wide. The water from streams and rivers sloshes onto the bank, well water becomes cloudy. There are landslides.
VI 4000 Most of the Buddhist temples collapse. 50 to 80 percent of the wooden houses are completely destroyed. Dams and embankments are almost completely destroyed. Paths and roads through rice fields are severely damaged and interrupted by cracks and crevices to the extent that riding animals or vehicles on them prevent traffic. Railway tracks are severely bent, large iron bridges are destroyed. Wooden bridges are partially or completely destroyed and stable gravestones also fall over. Meter-wide crevices open in the ground and are sometimes accompanied by sand or water fountains. Most of the iron or ceramic underground tanks will be destroyed. All the low-lying levels are shaken horizontally and vertically in such a way that sometimes all trees and plants die, resulting in numerous landslides.
VII ≫ 4000 All buildings except some wooden structures are destroyed. Some doors or wooden houses are pushed 30 to 90 cm wide. Large landslides fall from the mountain flanks and large demolitions arise in the ground.

* The maximum acceleration indicates the acceleration generated by earthquake waves and acting on the earth's surface. The horizontal acceleration forces acting parallel to the earth's surface are of particular importance for the damaging effects of an earthquake.

Individual evidence

  1. ↑ Integrated practical course III: Earthquake (Experiment D), Figure 2.6: Comparison of the frequently used intensity scales. Swiss Seismological Service (SED) ( Memento from March 15, 2002 in the Internet Archive )

literature