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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 hazard
Focal depth: 10 m
Duration of ground shaking: > 80 sec.
Magnitude: 7.8 / 8 / 8.3
Speed of crustal movement: 3.1 km / sec
(3x speed of voice)
Death toll: > 69, 000
No. of quake lakes / landslide dams formed: 34
The hazard
Felt over: 1500 km away
The affected area: > 1-2 x the size of the HKSAR
Hazard prone area: 417 counties, 19 severe zones
The epicenter:
- where several faults ruptured together in the zone
for about 300 m to the N
- the most active seismic zone in China
The relief
Lungmanshan 5000 m
Sichuan Basin 500 m
Tibet plate
South China plate
Indian plate
4 mm / yr
How reliable is earthquake prediction?
The most successful one in China
Haicheng (NE China) Quake in winter, 1975
An earthquake warning was issued 9 hours
before the strike.
The government evacuate million of people
away from the epicenter
What are the signs?
Freaky behaviour in animals
Before 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, 1960s
e.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 reports
amateurish report
lack of rigorous and reductionistic investigation
lack of statistics on false alarms
Measurement of earthquake prediction
seismic events
seismic velocity ratio
electrical resistivity
groundwater flow
radon emanation rate
crustal movement
electromagnetics
Prediction vs. warning
Prediction ~ scientific methods involved
Warning ~ 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?