Poster of the Sulawesi, Indonesia Earthquake of 16 November 2008 - Magnitude 7.4

Tectonic Summary

The Sulawesi, Indonesia earthquake of November 16, 2008 occurred as a result of thrust faulting on a plate-boundary that is marked by the North Sulawesi trench, separating the Celebes Sea basin and the Minahassa peninsula. Eastern Indonesia is characterized by complex tectonics in which motions of numerous small plates are accommodating large-scale convergence between the Australia and Eurasia plates. At the location of today's earthquake, the Celebes Sea basin (commonly considered part of the Sunda plate) moves south with respect to the Minahassa peninsula (part of the Molucca Sea plate) at a velocity of about 30 mm/year. The lithosphere of the Celebes Sea basin is thrust beneath that of the Minahassa peninsula and is seismically active to a depth of about 250 km.

The earthquake occurred approximately 25 km off the northern coast of the Minahassa peninsula of the Island of Sulawesi in an area that has seen large earthquakes in the past. For example, a damaging magnitude 7.6 earthquake occurred on April 18, 1990 approximately 85 km east of today's earthquake. The magnitude 7.6 earthquake in 1990 was followed a year later by a magnitude 7.5 earthquake in approximately the same place. More recently a magnitude 7.0 occurred within 45 km of today's earthquake on November 25, 1997. The 1997 earthquake caused damage to at least 90 building in the Gorontalo area of northern Sulawesi.