A study of large earthquake sequences in the Sumatra subduction zone and its possible implications

Abstract

Large subduction earthquakes have repeatedly occurred along the Sumatra subduction zone, where the Australian oceanic plate is subducting beneath the Sunda continental plate. We have analyzed two years (2009 to 2011) earthquake data from a regional seismic network along the Sumatra region that provided by the Badan Meteorologi, Klimatologi, dan Geofisika (BMKG) of Indonesia. Based on those data, a regional one-dimensional velocity model was refined first. Then, all events have been relocated based on the hypocenter double difference technique. Based on the relocated earthquake catalogue, three large earthquake sequences with magnitude greater than Mw 7.5 were well identified with one of them induced significant tsunami, thus, the 30 September 2009 Mw 7.6 Padang earthquake, the 7 April 2010 Mw 7.8 Banyak Islands earthquake, and the 25 October 2010 Mw 7.8 Mentawai tsunami earthquake. The characteristics of these earthquake sequences were analyzed and its possible implications were discussed in this study. A statistical analysis of polynomial linear fitting has been proposed to identify lineation of earthquake pattern in this study. Results indicated that a northwest-southeast dipping of earthquake lineation was identified within the Banyak Islands earthquake sequence and considered as the activity of the upper splay fault. Limited earthquake activity was identified at the Mentawai gap region and considered as a locked asperity. Those faults could be as a major threat of a great source of tsunamigenic fault. This region is considered as a high potential candidate to generate destructive earthquake and tsunami on the Sumatra subduction zone in future.