M 7.6 - 102 km SSE of Manokwari, Indonesia

Tectonic Summary

The October 10, 2002, M 7.6 earthquake near the north coast of Papua, Indonesia, occurred as the result of shallow strike-slip faulting within the Birds Head microplate, one of the many small microplates in the region that help to accommodate the relative motions between the major Philippine Sea, Pacific, Australia, and Sunda plates. Focal mechanism solutions indicate that rupture occurred on either a left-lateral, northeast-striking fault or a right-lateral, northwest-striking fault. Of these two possible fault orientations, finite-fault modeling of globally recorded seismic data is more consistent with slip on the northeast-striking (left-lateral) fault. At the location of the earthquake, the Pacific plate moves westward at a velocity of about 13 mm/yr relative to the Philippine plate and southwestward at a velocity of 113 mm/yr with respect to Australia.

While commonly plotted as points on maps, earthquakes of this size are more appropriately described as slip over a larger fault area. Strike-slip events of the size of the October 10, 2002 earthquake are typically about 140x20 km (length x width); modeling of this earthquake implies dimensions of about 120x15 km, predominantly up-dip of and bilaterally around the hypocenter.

In the past few decades, several earthquakes in this area have caused notable casualties. On September 12, 1979, a M 7.9 earthquake that struck about 190 km to the east resulted in 15 fatalities. Damage estimates for this quake ranged from $5 million to $25 million. Another quake with a magnitude of 6.3 occurred 330 km to the southeast on September 9, 1985, and killed at least 10 people. Most recently, a M 6.3 earthquake 190 km to the east on November 20, 1994, injured 28 people.

Hayes et al. (2016) Tectonic summaries of magnitude 7 and greater earthquakes from 2000 to 2015, USGS Open-File Report 2016-1192. (5.2 MB PDF)