Source model of the 2009 Mw 7.6 Padang intraslab earthquake and its effect on the Sunda megathrust
Dreger, Douglas S.
Date of Issue2012
We investigate the source of the Mw 7.6 Padang earthquake by inverting three-component global positioning system (GPS) data and broad-band regional seismic-displacement waveforms. The earthquake involved oblique-reverse slip either on an E–W, south-dipping plane, or on a N–S, west-dipping plane. Finite-fault inversions indicate that the rupture primarily propagated downdip and southwest from the hypocentre, with a scalar seismic moment between 3.4 and 3.7 × 1020 N m (Mw 7.62–7.65). Analysis of the seismic and geodetic data do not allow for unique identification of the causative focal plane. Aftershock patterns strongly suggest the E–W plane was the causative focal plane, but aligned geological structures in the downgoing plate favour the N–S plane. In either case, this unusually large intraslab earthquake has moved closer to failure the deepest portion of the overlying megathrust, which last ruptured during a great earthquake more than two centuries ago and is late in its seismic cycle.
Geophysical journal international
© 2012 The Authors. This paper was published in Geophysical Journal International and is made available as an electronic reprint (preprint) with permission of the authors. The paper can be found at the following official DOI: [http://dx.doi.org/10.1111/j.1365-246X.2012.05600.x]. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper is prohibited and is subject to penalties under law.