Historic Earthquakes: Tectonic Summary

Magnitude 7.6 IRIAN JAYA REGION, INDONESIA
2002 October 10 10:50:20 UTC

The earthquake occurred in a five-hundred kilometer wide diffuse plate boundary that accommodates the westerly motion of the Philippine Sea and Caroline plates with respect to the Australian plate. The preliminary epicenter is situated near the northwest-striking Ransiki fault, one of several major faults that have been identified in northwestern New Guinea. The focal mechanism is consistent with the earthquake occurring as right-lateral slip on a northwest-striking fault.

Damaging Historical Earthquakes

In the past few decades, several earthquakes in the area of this recent earthquake have caused human casualties. On September 12th, 1979 a magnitude 7.9 earthquake struck about 190 km to the east killing 15 people. Damage estimates for this quake ranged from $5 to $25 million. Another quake with a magnitude of 6.3 occurred 330 km to the southeast on September 9th, 1985, and killed at least 10 people. A magnitude 6.3 quake, that injured 28 people, occurred 190 km to the east on November 20th 1994. And most recently, on September 8th of this year a magnitude 7.6 struck about 1000 km to the east. This quake killed at least 6 people and generated a one meter tsunami that caused extensive damage to homes on the nearby islands

Aftershocks

Generally, large crustal earthquakes generate significant aftershocks. This event is no exception. Several large aftershocks have already occurred. Usually, the number of aftershocks decays rapidly over the first few days following the mainshock but aftershocks can occur several years later.