Multiple CMT source analysis of the 2004 Sumatra earthquake

Abstract

While it is agreed that the great Sumatra earthquake of December 26, 2004 was among the largest earthquakes of the past century, there has been disagreement on how large it was, which part of the fault ruptured, and how the rupture took place. We present a centroid-moment-tensor (CMT) analysis of the earthquake in which multiple point sources are used in the inversion to mimic a propagating slip pulse. The final model consists of five point sources, with the southernmost sources accounting for the majority of the moment release. The presumed fault planes of the southern sources strike northwest, while those in the north strike northeast, consistent with the geometry of the subduction trench. Slip on the fault is found to be more oblique in the north than in the south. The inversion with five sources leads to a moment magnitude for the Sumatra earthquake of M_W = 9.3, consistent with estimates from long-period normal-mode amplitudes.