Magnitude 8.4 Great earthquake in Southern Sumatra

Wednesday, September 12, 2007 at 11:10:26 UTC

4:10:26 AM Pacific Daylight Time

Epicenter: Latitude 4.517S, 101.382E (indicated by star on map below).

Depth: approximately 30 kilometers.


Robert Butler and John Lahr


A great earthquake occurred early this morning Portland time on the subduction zone at the Java Trench 620 km (385 miles) west-northwest of Jakarta, Java, Indonesia. A small tsunami was generated. This earthquake occurred on the same plate tectonic boundary that ruptured in the December 26, 2004 great earthquake that generated the disastrous Indian Ocean tsunami that took 240,000 lives. The Java Trench forms the boundary between the India-Australia Plate and the southeastern portion of the Eurasian Plate. The rate of convergence at this plate boundary is about 6 cm/year. This is a fairly high plate convergence rate and this subduction zone is very seismically and volcanically active. For comparison, the convergence rate of the Juan de Fuca Plate beneath the North American Plate at the Cascadia subduction zone is about 3 cm/year.

















Corvallis, Oregon, AS-1 Seismogram.