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Possible large near-trench slip during the 2011 M_w 9.0 off the Pacific coast of Tohoku Earthquake

Lay, Thorne and Ammon, Charles J. and Kanamori, Hiroo and Xue, Lian and Kim, Marina J. (2011) Possible large near-trench slip during the 2011 M_w 9.0 off the Pacific coast of Tohoku Earthquake. Earth Planets and Space, 63 (7). pp. 687-692. ISSN 1343-8832.

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The 11 March 2011 off the Pacific coast of Tohoku (M_w 9.0) Earthquake ruptured a 200 km wide megathrust fault, with average displacements of ∼15-20 m. Early estimates of the co-seismic slip distribution using seismic, geodetic and tsunami observations vary significantly in the placement of slip, particularly in the vicinity of the trench. All methods have difficulty resolving the up-dip extent of rupture; onshore geodetic inversions have limited sensitivity to slip far offshore, seismic inversions have instabilities in seismic moment estimation as subfault segments get very shallow, and tsunami inversions average over the total region of ocean bottom uplift. Seismic wave estimates depend strongly on the velocity structure used in the model, which affects both seismic moment estimation and inferred mapping to slip. We explore these ideas using a least-squares inversion of teleseismic P-waves that yields surprisingly large fault displacements (up to ∼60 m) at shallow depth under a protrusion of the upper plate into the trench. This model provides good prediction of GPS static displacements on Honshu. We emphasize the importance of poorly-constrained rigidity variations with depth for estimating fault displacement near the trench. The possibility of large slip at very shallow depth holds implications for up-dip strain accumulation and tsunamigenic earthquake potential of megathrusts elsewhere.

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Lay, Thorne0000-0003-2360-4213
Kanamori, Hiroo0000-0001-8219-9428
Additional Information:© 2011 The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences; TERRAPUB. Received April 7, 2011; Revised May 22, 2011; Accepted May 25, 2011; Online published September 27, 2011. This work made use of GMT, SAC and Coulomb 3 software. The IRIS DMS data center was used to access the FDSN seismic data. This work was supported by NSF grant EAR0635570 and USGS Award Number 05HQGR0174. We thank the editor and two anonymous reviewers for their constructive reviews of the manuscript.
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Subject Keywords:2011 Tohoku Earthquake; megathrust faults; subduction zones; earthquake rupture process; tsunami earthquakes
Issue or Number:7
Record Number:CaltechAUTHORS:20120104-113747751
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:28650
Deposited By: Jason Perez
Deposited On:04 Jan 2012 21:11
Last Modified:03 Oct 2019 03:34

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