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The 2009 Samoa–Tonga great earthquake triggered doublet

Lay, Thorne and Ammon, Charles J. and Kanamori, Hiroo and Rivera, Luis and Koper, Keith D. and Hutko, Alexander R. (2010) The 2009 Samoa–Tonga great earthquake triggered doublet. Nature, 466 (7309). pp. 964-968. ISSN 0028-0836.

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Great earthquakes (having seismic magnitudes of at least 8) usually involve abrupt sliding of rock masses at a boundary between tectonic plates. Such interplate ruptures produce dynamic and static stress changes that can activate nearby intraplate aftershocks, as is commonly observed in the trench-slope region seaward of a great subduction zone thrust event1. The earthquake sequence addressed here involves a rare instance in which a great trench-slope intraplate earthquake triggered extensive interplate faulting, reversing the typical pattern and broadly expanding the seismic and tsunami hazard. On 29 September 2009, within two minutes of the initiation of a normal faulting event with moment magnitude 8.1 in the outer trench-slope at the northern end of the Tonga subduction zone, two major interplate underthrusting subevents (both with moment magnitude 7.8), with total moment equal to a second great earthquake of moment magnitude 8.0, ruptured the nearby subduction zone megathrust. The collective faulting produced tsunami waves with localized regions of about 12 metres run-up that claimed 192 lives in Samoa, American Samoa and Tonga. Overlap of the seismic signals obscured the fact that distinct faults separated by more than 50 km had ruptured with different geometries, with the triggered thrust faulting only being revealed by detailed seismic wave analyses. Extensive interplate and intraplate aftershock activity was activated over a large region of the northern Tonga subduction zone.

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URLURL TypeDescription DOIArticle
Lay, Thorne0000-0003-2360-4213
Kanamori, Hiroo0000-0001-8219-9428
Rivera, Luis0000-0002-0726-5445
Additional Information:© 2010 Macmillan Publishers Limited. Received 23 February; accepted 24 May 2010. This work made use of GMT and SAC software and Federation of Digital Seismic Networks (FDSN) seismic data. The Incorporated Research Institutions for Seismology (IRIS) Data Management System (DMS) and the F-Net and Hi-Net data centres were used to access the data. C. Ji kindly shared details of his model. Z. Duputel wrote the W-Phase software version used in this study. We thank H. Savage and E. Brodsky for discussions of frictional conditional stability. This work was supported by NSF grant EAR0635570 and USGS Award Number 05HQGR0174. Author Contributions: All authors contributed equally to the analysis and preparation of this paper.
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Issue or Number:7309
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ID Code:19707
Deposited By: Tony Diaz
Deposited On:04 Sep 2010 03:56
Last Modified:09 Mar 2020 13:19

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