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The 2012 Sumatra great earthquake sequence

Duputel, Zacharie and Kanamori, Hiroo and Tsai, Victor C. and Rivera, Luis and Meng, Lingsen and Ampuero, Jean-Paul and Stock, Joann M. (2012) The 2012 Sumatra great earthquake sequence. Earth and Planetary Science Letters, 351 . pp. 247-257. ISSN 0012-821X. doi:10.1016/j.epsl.2012.07.017.

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The equatorial Indian Ocean is a well known place of active intraplate deformation defying the conventional view of rigid plates separated by narrow boundaries where deformation is confined. On 11 April 2012, this region was hit in a couple of hours by two of the largest strike-slip earthquakes ever recorded (moment magnitudes Mw=8.6 and 8.2). Broadband seismological observations of the Mw=8.6 mainshock indicate a large centroid depth (∼30 km) and remarkable rupture complexity. Detailed study of the surface-wave directivity and moment rate functions clearly indicates the partition of the rupture into at least two distinct subevents. To account for these observations, we developed a procedure to invert for multiple-point-source parameters. The optimum source model at long period consists of two point sources separated by about 209 km with magnitudes Mw=8.5 and 8.3. To explain the remaining discrepancies between predicted and observed surface waves, we can refine this model by adding directivity along the WNW–ESE axis. However, we do not exclude more complicated models. To analyze the Mw=8.2 aftershock, we removed the perturbation due to large surface-wave arrivals of the Mw=8.6 mainshock by subtracting the corresponding synthetics computed for the two-subevent model. Analysis of the surface-wave amplitudes suggests that the Mw=8.2 aftershock had a large centroid depth between 30 km and 40 km. This major earthquake sequence brings a new perspective to the seismotectonics of the equatorial Indian Ocean and reveals active deep lithospheric deformation.

Item Type:Article
Related URLs:
URLURL TypeDescription
Kanamori, Hiroo0000-0001-8219-9428
Tsai, Victor C.0000-0003-1809-6672
Rivera, Luis0000-0002-0726-5445
Meng, Lingsen0000-0003-2428-0548
Ampuero, Jean-Paul0000-0002-4827-7987
Stock, Joann M.0000-0003-4816-7865
Additional Information:© 2012 Elsevier B.V. Accepted 15 July 2012. Available online 1 September 2012. Editor: P. Shearer. We thank Shengji Wei, Don Helmberger, Thorne Lay and two anonymous reviewers for helpful discussions. This work uses Federation of Digital Seismic Networks (FDSN) seismic data and CMT solutions from the Global CMT catalog. The Incorporated Research Institutions for Seismology (IRIS) Data Management System (DMS) was used to access the data. This work made use of the Matplotlib python library, of the Basemap toolkit and of the neighbourhood algorithm sampler developed by Malcolm Sambridge. Lingsen Meng and Jean-Paul Ampuero were supported by NSF Grant EAR-1015704.
Group:Seismological Laboratory
Funding AgencyGrant Number
Subject Keywords:2012 Sumatra earthquake sequence; intraplate earthquakes; earthquake source observations; seismicity and tectonics; surface waves and free oscillations
Record Number:CaltechAUTHORS:20121130-081922437
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Official Citation:Zacharie Duputel, Hiroo Kanamori, Victor C. Tsai, Luis Rivera, Lingsen Meng, Jean-Paul Ampuero, Joann M. Stock, The 2012 Sumatra great earthquake sequence, Earth and Planetary Science Letters, Volumes 351–352, 15 October 2012, Pages 247-257, ISSN 0012-821X, 10.1016/j.epsl.2012.07.017.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:35738
Deposited By: Tony Diaz
Deposited On:30 Jan 2013 19:09
Last Modified:09 Nov 2021 23:17

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