Earthquake 2 Sept 2009

2 Sept 2009 15:00:
7.3 on the Richter scale Earthquake in Lat/Lon S8.223 LS E107.449, depth: 30 kilometer below sea level, about 142 kilometer southwest Tasikmalaya, West Java Indonesia.

An earthquake (also known as a tremor or temblor) is the result of a sudden release of energy in the Earth’s crust that creates seismic waves. Earthquakes are recorded with a seismometer, also known as a seismograph. The moment magnitude of an earthquake is conventionally reported, or the related and mostly obsolete Richter magnitude, with magnitude 3 or lower earthquakes being mostly imperceptible and magnitude 7 causing serious damage over large areas. Intensity of shaking is measured on the modified Mercalli scale (

Earthquakes can be recorded by seismometers up to great distances, because seismic waves travel through the whole Earth’s interior. The absolute magnitude of a quake is conventionally reported by numbers on the Moment magnitude scale (formerly Richter scale, magnitude 7 causing serious damage over large areas), whereas the felt magnitude is reported using the modified Mercalli scale (intensity II-XII).

Richter magnitude scale
The Richter magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs (adjustments are included to compensate for the variation in the distance between the various seismographs and the epicenter of the earthquake). The original formula is:[4]
ML = log10A − log10A0(delta),

Richter Magnitudes Description Earthquake Effects Frequency of Occurrence
Less than 2.0 Micro Microearthquakes, not felt. About 8,000 per day
2.0-2.9 Minor Generally not felt, but recorded. About 1,000 per day
3.0-3.9 Often felt, but rarely causes damage. 49,000 per year (est.)
4.0-4.9 Light Noticeable shaking of indoor items, rattling noises. Significant damage unlikely. 6,200 per year (est.)
5.0-5.9 Moderate Can cause major damage to poorly constructed buildings over small regions. At most slight damage to well-designed buildings. 800 per year
6.0-6.9 Strong Can be destructive in areas up to about 160 kilometres (100 mi) across in populated areas. 120 per year
7.0-7.9 Major Can cause serious damage over larger areas. 18 per year
8.0-8.9 Great Can cause serious damage in areas several hundred miles across. 1 per year
9.0-9.9 Devastating in areas several thousand miles across. 1 per 20 years
10.0+ Epic Never recorded; see below for equivalent seismic energy yield. Extremely rare (Unknown)

(Based on U.S. Geological Survey documents.

Approximate Magnitude
Approximate TNT for
Seismic Energy Yield
Joule equivalent Example
0.0 kg (2.2 lb) 4.2 MJ
0.5 5.6 kg (12.4 lb) 23.5 MJ Large hand grenade
1.0 32 kg (70 lb) 134.4 MJ Construction site blast
1.5 178 kg (392 lb) 747.6 MJ WWII conventional bombs
2.0 metric ton 4.2 GJ Late WWII conventional bombs
2.5 5.6 metric tons 23.5 GJ WWII blockbuster bomb
3.0 32 metric tons 134.4 GJ Massive Ordnance Air Blast bomb
3.5 178 metric tons 747.6 GJ Chernobyl nuclear disaster, 1986
4.0 kiloton 4.2 TJ Small atomic bomb
4.5 5.6 kilotons 23.5 TJ
5.0 32 kilotons 134.4 TJ Nagasaki atomic bomb (actual seismic yield was negligible since it detonated in the atmosphere)
Lincolnshire earthquake (UK), 2008
5.4 150 kilotons 625 TJ 2008 Chino Hills earthquake (Los Angeles, United States)
5.5 178 kilotons 747.6 TJ Little Skull Mtn. earthquake (NV, USA), 1992
Alum Rock earthquake (CA, USA), 2007
6.0 megaton 4.2 PJ Double Spring Flat earthquake (NV, USA), 1994
6.5 5.6 megatons 23.5 PJ Rhodes (Greece), 2008
6.7 16.2 megatons 67.9 PJ Northridge earthquake (CA, USA), 1994
6.9 26.8 megatons 112.2 PJ San Francisco Bay Area earthquake (CA, USA), 1989
7.0 32 megatons 134.4 PJ
7.1 50 megatons 210 PJ Energy released is equivalent to that of Tsar Bomba, the largest thermonuclear weapon ever tested.
7.5 178 megatons 747.6 PJ Kashmir earthquake (Pakistan), 2005
Antofagasta earthquake (Chile), 2007
7.8 600 megatons 2.4 EJ Tangshan earthquake (China), 1976
8.0 gigaton 4.2 EJ Toba eruption 75,000 years ago; which, according to the Toba catastrophe theory, affected modern human evolution
San Francisco earthquake (CA, USA), 1906
Queen Charlotte earthquake (BC, Canada), 1949
México City earthquake (Mexico), 1985
Gujarat earthquake (India), 2001
Chincha Alta earthquake (Peru), 2007
Sichuan earthquake (China), 2008 (initial estimate: 7.8)
8.5 5.6 gigatons 23.5 EJ Sumatra earthquake (Indonesia), 2007
9.0 32 gigatons 134.4 EJ Lisbon Earthquake (Lisbon, Portugal), All Saints Day, 1755
9.2 90.7 gigatons 379.7 EJ Anchorage earthquake (AK, USA), 1964
9.3 114 gigatons 477 EJ Indian Ocean earthquake, 2004 (40 ZJ in this case)
9.5 178 gigatons 747.6 EJ Valdivia earthquake (Chile), 1960 (251 ZJ in this case)
10.0 teraton 4.2 ZJ Never recorded by man.
12.0 petaton 4.2 YJ Yucatan impact (Chicxulub crater) 65 Ma ago.

Mercalli intensity scale

The Mercalli intensity scale is a scale used for measuring the intensity of an earthquake. The scale quantifies the effects of an earthquake on the Earth’s surface, humans, objects of nature, and man-made structures on a scale of I through XII, with I denoting not felt, and XII one that causes almost complete destruction. The values will differ based on the distance to the earthquake, with the highest intensities being around the epicentral area. Data are gathered from individuals who have experienced the quake, and an intensity value will be given to their location.

The Mercalli scale originated with the widely used simple ten-degree Rossi-Forel scale, which was revised by Italian vulcanologist Giuseppe Mercalli in 1883 and 1902. The terms [copy missing] or Mercalli scale should not be used unless one really means the original ten-degree scale of 1902.
In 1902 the ten-degree Mercalli scale was expanded to twelve degrees by Italian physicist Adolfo Cancani. It was later completely re-written by the German geophysicist August Heinrich Sieberg and became known as the Mercalli-Cancani-Sieberg (MCS) scale. The Mercalli-Cancani-Sieberg scale was later modified and published in English by Harry O. Wood and Frank Neumann in 1931 as the Mercalli-Wood-Neumann (MWN) scale. It was later improved by Charles Richter, the father of the Richter magnitude scale. The scale is known today as the Modified Mercalli Scale and commonly abbreviated MM.

The lower degrees of the MM scale generally deal with the manner in which the earthquake is felt by people. The higher numbers of the scale are based on observed structural damage. The table below is a rough guide to the degrees of the Modified Mercalli Scale. The colors and descriptive names shown here differ from those used on certain shake maps in other articles.

I. Instrumental Not felt by many people unless in favourable conditions.
II. Feeble Felt only by a few people at best, especially on the upper floors of buildings. Delicately suspended objects may swing.
III. Slight Felt quite noticeably by people indoors, especially on the upper floors of buildings. Many do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibration similar to the passing of a truck. Duration estimated.
IV. Moderate Felt indoors by many people, outdoors by few people during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rock noticeably. Dishes and windows rattle alarmingly.
V. Rather Strong Felt outside by most, may not be felt by some outside in non-favourable conditions. Dishes and windows may break and large bells will ring. Vibrations like large train passing close to house.
VI. Strong Felt by all; many frightened and run outdoors, walk unsteadily. Windows, dishes, glassware broken; books fall off shelves; some heavy furniture moved or overturned; a few instances of fallen plaster. Damage slight.
VII. Very Strong Difficult to stand; furniture broken; damage negligible in building of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken. Noticed by people driving motor cars.
VIII. Destructive Damage slight in specially designed structures; considerable in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture moved.
IX. Ruinous General panic; damage considerable in specially designed structures, well designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations.
X. Disastrous Some well built wooden structures destroyed; most masonry and frame structures destroyed with foundation. Rails bent.
XI. Very Disastrous Few, if any masonry structures remain standing. Bridges destroyed. Rails bent greatly.
XII. Catastrophic Total damage – Almost everything is destroyed. Lines of sight and level distorted. Objects thrown into the air. The ground moves in waves or ripples. Large amounts of rock may move position.
Yohan Naftali

1 comment so far


the Earthquake in Indonesia is really bad. i have some friends who live in Indonesia and they were injured because of the earthquake ~

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