can earthquakes be predicted?. hku roundtable forum on sichuan quake 2008 brief notes by elaine wong
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Can earthquakes be predicted?
HKU Roundtable forum on Sichuan Quake 2008
Brief notes by Elaine Wong
The General fact of the Quake
12 May, 2008
The hazardFocal depth: 10 mDuration of ground shaking: > 80 sec.Magnitude: 7.8 / 8 / 8.3Speed of crustal movement: 3.1 km / sec
(3x speed of voice)Death toll: > 69, 000 No. of quake lakes / landslide dams formed: 34
The hazardFelt over: 1500 km awayThe affected area: > 1-2 x the size of the HKSARHazard prone area: 417 counties, 19 severe zonesThe epicenter: - where several faults ruptured together in the zone for about 300 m to the N
- the most active seismic zone in China
The reliefLungmanshan 5000 mSichuan Basin 500 m
Tibet plate South China plate
Indian plate
4 mm / yr
How reliable is earthquake prediction?The most successful one in ChinaHaicheng (NE China) Quake in winter, 1975An earthquake warning was issued 9 hours before the strike.The government evacuate million of people away from the epicenterWhat are the signs?
Freaky behaviour in animalsBefore the Sichuan Quake (2008) in a zoo:
‘ 鴕鳥成群狂奔、大雁集體絶食、 亞洲象不斷長鳴、長角羚焦躁不安… ..’
Animal prediction centres in China, 1960se.g. successful use of pigeons and cats
‘ 深圳街蟾蜍上街’ (25/5/08)
How reliable is earthquake prediction?mostly post-shake reportsamateurish reportlack of rigorous and reductionistic investigationlack of statistics on false alarms
Measurement of earthquake predictionseismic eventsseismic velocity ratioelectrical resistivitygroundwater flowradon emanation ratecrustal movement electromagnetics
Prediction vs. warningPrediction ~ scientific methods involvedWarning ~ interpretation of prediction
~ public policies
Think about it ~In the case of the U.S., no warning of 1 single event of earthquake prediction is made so far.Why?
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