The pattern of aftershocks helps confirm the size of area that slipped during the main shock . In the case of the 2004 Indian Ocean earthquake and the 2008 Sichuan earthquake the aftershock distribution shows in both cases that the epicenter ( where the rupture initiated ) lies to one end of the final area of slip , implying strongly asymmetric rupture propagation
2008 Sichuan earthquake
2008 Sichuan earthquake
Aftershock