Historic Earthquakes: Tectonic Summary

Magnitude 7.1 TAIWAN REGION
2002 March 31 06:52:50 UTC

This thrust earthquake occurred off the north-east shore of the island of Taiwan in a tectonicly complex region known as the Taiwan Collision Zone. This region is highly seismic. There are an average of five earthquakes per year with magnitude 5 or greater occurring within a 1 by 1 degree zone surrounding the epicenter. The high seismicity results from the convergence of the Philippine Sea plate and the Eurasian plate. The Philippine plate is moving NW at a rate of about 7 cm per year relative to the Eurasian plate. The complex region near the epicenter contains several substantial tectonic features including, the Ryukyu trench, Manila trench, and the Okinawa trough.

Given the earthquake's fault mechanism and depth, it likely resulted from slip on the boundary between the subducting Philippine plate and the overlying Eurasian plate (see the cross-section link to the left). The surface expression of this contact is the east-west trending Ryukyu trench which is about 200 kilometers southeast of the epicenter.

The tectonic environment of this earthquake differs from that of the more destructive magnitude 7.7 earthquake that occurred on September 20, 1999; the latter earthquake occurred in the crust of the Eurasian plate within the island of Taiwan.