An ancient shallow slip event on the Mentawai segment of the Sunda megathrust, Sumatra
Natawidjaja, Danny H.
Suwargadi, Bambang W.
Hill, Emma M.
Edwards, R. Lawrence
Date of Issue2012
The outer-arc islands of western Sumatra rise during great megathrust earthquakes, due to large slip on the underlying megathrust. In contrast, the islands subsided up to a few centimeters during the recent tsunamigenic earthquake of October 2010, due to slip far updip, near the trench. Coral microatolls on one of the islands recorded a much larger subsidence, at least 35 cm, during an event in approximately A.D. 1314. We calculate a suite of slip models, slightly deeper and/or larger than the 2010 event, that are consistent with this large amount of subsidence. Sea level records from older coral microatolls suggest that these events occur at least once every millennium, but likely far less frequently than their great downdip neighbors. The revelation that shallow slip events are important contributors to the seismic cycle of the Mentawai segment further complicates our understanding of this subduction megathrust and our assessment of the region's exposure to seismic and tsunami hazards.
DRNTU::Science::Geology::Volcanoes and earthquakes
Journal of geophysical research
© 2012 AGU. This paper was published in Journal of Geophysical Research and is made available as an electronic reprint (preprint) with permission of American Geophysical Union. The paper can be found at: DOI [http://dx.doi.org/10.1029/2011JB009075]. 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.