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?