1. SICHUAN EARTHQUAKE May 12, 2008
BBC
Science

2. fault area x slip x rigidity
Science
USGS
1. Find the seismic moment
M0 = 8.9 * 10^20 Nm
SEISMIC MOMENT M0 =
fault area x slip x rigidity
MOMENT MAGNITUDE Mw =
2/3 x (log M )
University of Nevada

3. 2. Predict the rupture length (km) and average displacement (m)
Wells and Coppersmith, 1994
500 km
10 m
3*10^11 * 500*10^3 * w * 10 = 8.9 * 10^20 --> w = 593 m ~ 1/2 km
2. Predict the rupture length (km) and average displacement (m)
3. Use these and the moment to predict the downdip dimension (fault width). Use rigidity = 3*1010 Pa (1 Pascal=N/m2)

4. 4. How do the intensity & aftershock distributions compare to the fault parameters you estimated?
USGS
350 km vs. 500 km

5. 5. How does the slip distribution from body wave modeling compare to the fault parameters you estimated?
7 m vs. 10 m
w: 20 km vs. 1/2 km hmmm
20*10^3 * 280*10^3 * 7 * 3*10^10 = 11.8 * 10^20 = M0 --> Mw = 8.0
USGS

6. 6. What type of faulting did it involve?
7. Which plane did it occur on?
8. What’s the tectonic cause?
USGS
Zhang et al., 2004
GPS site velocities wrt Eurasia