Coseismic slip distribution of the 2011 off the Pacific Coast of Tohoku Earthquake (M9.0) refined by means of seafloor geodetic data

[1] On 11 March 2011, the devastating M9.0 Tohoku Earthquake occurred on the interface of the subducting Pacific plate, and was followed by a huge tsunami that killed about 20,000 people. Several geophysical studies have already suggested that the very shallow portion of the plate interface might have played an important role in producing such a large earthquake and tsunami. However, the sparsity of seafloor observations leads to insufficient spatial resolution of the fault slip on such a shallow plate interface. For this reason, the location and degree of the slip has not yet been estimated accurately enough to assess future seismic risks. Thus, we estimated the coseismic slip distribution based on terrestrial GPS observations and all available seafloor geodetic data that significantly improve the spatial resolution at the shallow portion of the plate interface. The results reveal that an extremely large (greater than 50 m) slip occurred in a small (about 40 km in width and 120 km in length) area near the Japan Trench and generated the huge tsunami. The estimated slip distribution and a comparison of it with the coupling coefficient distribution deduced from the analysis of the small repeating earthquakes suggest that the 2011 Tohoku Earthquake released strain energy that had accumulated over the past 1000 years, probably since the Jogan Earthquake in 869. The accurate assessments of seismic risks on very shallow plate interfaces in subduction zones throughout the world can be obtained by improving the quality and quantity of seafloor geodetic observations.

[1]  Y. Ito,et al.  3D modeling of the cycle of a great Tohoku‐oki earthquake, considering frictional behavior at low to high slip velocities , 2011 .

[2]  T. Matsuzawa,et al.  Coupling coefficient, hierarchical structure, and earthquake cycle for the source area of the 2011 off the Pacific coast of Tohoku earthquake inferred from small repeating earthquake data , 2011 .

[3]  J. Nakajima,et al.  What controls interplate coupling?: Evidence for abrupt change in coupling across a border between two overlying plates in the NE Japan subduction zone , 2009 .

[4]  Tomokazu Kobayashi,et al.  Coseismic and postseismic slip of the 2011 magnitude-9 Tohoku-Oki earthquake , 2011, Nature.

[5]  Osamu Fujiwara,et al.  Marine incursions of the past 1500 years and evidence of tsunamis at Suijin-numa, a coastal lake facing the Japan Trench , 2008 .

[6]  J. Nakajima,et al.  Anomalous low‐velocity zone and linear alignment of seismicity along it in the subducted Pacific slab beneath Kanto, Japan: Reactivation of subducted fracture zone? , 2006 .

[7]  Kaj M. Johnson,et al.  A Fully Bayesian Inversion for Spatial Distribution of Fault Slip with Objective Smoothing , 2008 .

[8]  H. Kanamori,et al.  Possible large near-trench slip during the 2011 Mw 9.0 off the Pacific coast of Tohoku Earthquake , 2011 .

[9]  Kenji Satake,et al.  Linear and nonlinear computations of the 1992 Nicaragua earthquake tsunami , 1995 .

[10]  Sarah E. Minson,et al.  The 2011 Magnitude 9.0 Tohoku-Oki Earthquake: Mosaicking the Megathrust from Seconds to Centuries , 2011, Science.

[11]  Akira Hasegawa,et al.  Nearly complete stress drop in the 2011 Mw 9.0 off the Pacific coast of Tohoku Earthquake , 2011 .

[12]  Akira Asada,et al.  Displacement Above the Hypocenter of the 2011 Tohoku-Oki Earthquake , 2011, Science.

[13]  J. Nakajima,et al.  Three‐dimensional structure of Vp, Vs, and Vp/Vs beneath northeastern Japan: Implications for arc magmatism and fluids , 2001 .

[14]  Hiroo Kanamori,et al.  A rupture model of the 2011 off the Pacific coast of Tohoku Earthquake , 2011 .

[15]  Chen Ji,et al.  Focal mechanism and slip history of the 2011 Mw 9.1 off the Pacific coast of Tohoku Earthquake, constrained with teleseismic body and surface waves , 2011 .

[16]  T. Sagiya,et al.  Slip distribution of the 2011 off the Pacific coast of Tohoku Earthquake inferred from geodetic data , 2011 .

[17]  Masaya Matsuura,et al.  Geodetic data inversion using a Bayesian information criterion for spatial distribution of fault slip , 1992 .

[18]  M. Kikuchi,et al.  Asperity map along the subduction zone in northeastern Japan inferred from regional seismic data , 2004 .

[19]  Z. Altamimi,et al.  ITRF2005 : A new release of the International Terrestrial Reference Frame based on time series of station positions and Earth Orientation Parameters , 2007 .

[20]  T. Iinuma,et al.  Strain anomalies induced by the 2011 Tohoku Earthquake (Mw 9.0) as observed by a dense GPS network in northeastern Japan , 2012, Earth, Planets and Space.

[21]  Hiroo Kanamori,et al.  Frequency-dependent rupture process of the 2011 Mw 9.0 Tohoku Earthquake: Comparison of short-period P wave backprojection images and broadband seismic rupture models , 2011 .

[22]  K. Koketsu,et al.  Scaling of characterized slip models for plate-boundary earthquakes , 2008 .

[23]  Y. Fujii,et al.  Regional Difference in Scaling Laws for Large Earthquakes and its Tectonic Implication , 2000 .

[24]  F. Hirose,et al.  Outline of the 2011 off the Pacific coast of Tohoku Earthquake (Mw 9.0) —Seismicity: foreshocks, mainshock, aftershocks, and induced activity— , 2011 .

[25]  M. Kikuchi,et al.  Source process of the recurrent Tokachi-oki earthquake on September 26, 2003, inferred from teleseismic body waves , 2003 .

[26]  M. Matsu'ura,et al.  Geodetic data inversion based on Bayesian formulation with direct and indirect prior information , 2007 .

[27]  Yuji Yagi,et al.  Rupture process of the 2011 Tohoku‐oki earthquake and absolute elastic strain release , 2011 .

[28]  Yuji Yagi,et al.  A unified source model for the 2011 Tohoku earthquake , 2011 .

[29]  How did the 2011 off the Pacific coast of Tohoku Earthquake start and grow? The role of a conditionally stable area , 2011 .

[30]  Y. Kaneda,et al.  Bending of the subducting oceanic plate and its implication for rupture propagation of large interplate earthquakes off Miyagi, Japan, in the Japan Trench subduction zone , 2005 .

[31]  Motoyuki Kido,et al.  Trench‐normal variation in observed seafloor displacements associated with the 2011 Tohoku‐Oki earthquake , 2011 .

[32]  N. Umino,et al.  Spatial distribution of focal mechanisms for interplate and intraplate earthquakes associated with the subducting Pacific plate beneath the northeastern Japan arc: A triple‐planed deep seismic zone , 2001 .

[33]  Motoyuki Kido,et al.  Frontal wedge deformation near the source region of the 2011 Tohoku‐Oki earthquake , 2011 .

[34]  F. Imamura,et al.  The 869 Jogan tsunami deposit and recurrence interval of large-scale tsunami on the Pacific coast of northeast Japan , 2001 .

[35]  M. Ishiguro,et al.  A procedure for tidal analysis with a Bayesian information criterion , 2007 .

[36]  Ryota Hino,et al.  Mantle wedge structure in the Miyagi Prefecture forearc region, central northeastern Japan arc, and its relation to corner‐flow pattern and interplate coupling , 2011 .

[37]  T. Iinuma,et al.  Coseismic slip distribution of the 2011 off the Pacific coast of Tohoku Earthquake (M 9.0) estimated based on GPS data—Was the asperity in Miyagi-oki ruptured? , 2011 .

[38]  K. Shimazaki,et al.  Rupture process of the Miyagi-Oki, Japan, earthquake of June 12, 1978 , 1980 .

[39]  Gregory C. Beroza,et al.  Shallow Dynamic Overshoot and Energetic Deep Rupture in the 2011 Mw 9.0 Tohoku-Oki Earthquake , 2011, Science.

[40]  T. Furumura,et al.  Significant tsunami observed at ocean-bottom pressure gauges during the 2011 off the Pacific coast of Tohoku Earthquake , 2011 .

[41]  J. Nakajima,et al.  Revisiting the three M~7 Miyagi-oki earthquakes in the 1930s: possible seismogenic slip on asperities that were re-ruptured during the 1978 M=7.4 Miyagi-oki earthquake , 2006 .

[42]  Fred F. Pollitz,et al.  Geodetic slip model of the 2011 M9.0 Tohoku earthquake , 2011 .

[43]  Kenji Satake,et al.  Tsunami source of the 2011 off the Pacific coast of Tohoku Earthquake , 2011 .

[44]  Walter H. F. Smith,et al.  New, improved version of generic mapping tools released , 1998 .

[45]  M. Ishii.  High-frequency rupture properties of the Mw 9.0 off the Pacific coast of Tohoku Earthquake , 2011 .