M 7.6 - Sulawesi, Indonesia

Tectonic Summary

The May 4, 2000, M 7.6 earthquake near Sulawesi, Indonesia, occurred as a result of strike-slip faulting at shallow depths within the interior of the Molucca Sea microplate, part of the broader Sunda tectonic plate. Focal mechanism solutions for the earthquake indicate that rupture occurred on either a left-lateral northwest-southeast-striking fault, or along a right-lateral northeast-southwest-striking fault. Of these two possible fault orientations, finite-fault modeling of globally recorded seismic data is more consistent with slip on the southwest-striking (right-lateral) fault. Eastern Indonesia is characterized by complex tectonics in which motions of numerous small microplates are accommodating large-scale convergence among the Australia, Sunda, Pacific, and Philippine Sea plates. At the location of the May 4th earthquake, the Sunda plate moves south with respect to Molucca Sea plate at a velocity of about 30 mm/yr.

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 May 4, 2000, earthquake are typically about 140x20 km (length x width); modeling of this earthquake implies dimensions of about 100x20 km, predominantly up-dip and northeast of the hypocenter. Shallow earthquakes of this size can often have a deadly impact on nearby communities. Historically, this region has hosted several large earthquakes, with eight events of M 7.0+ within 400 km of the May 4th earthquake over the preceding 40 years. Several of these larger events caused extensive building damage, injuries, and fatalities.

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)