The large aftershocks triggered by the 2011 Mw 9.0 Tohoku-Oki earthquake,Japan |
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| Institution: | 1. School of Geodesy and Geomatics, Wuhan University, Wuhan, Hubei 430079, China;2. State Key Laboratory of Geodesy and Earth’s Dynamics, Wuhan, Hubei 430077, China;3. Key Laboratory of Geospace Environment and Geodesy, Ministry of Education, Wuhan University, Wuhan, Hubei 430079, China;1. Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Bologna, Via Donato Creti, 12, 40128 Bologna, Italy;2. Department of Earth Sciences, University of Oxford, South Parks Road, OX1 3AN Oxford, UK;1. National Center for Research on Earthquake Engineering, 200, Sec. 3, HsinHai Rd., Taipei 10668, Taiwan, ROC;2. Department of Earth and Environmental Sciences, National Chung Cheng University, 168, University Rd., Min-Hsiung, Chia-Yi County 62102, Taiwan, ROC;1. Department of Earth and Environmental Sciences, National Chung Cheng University, Chiayi 621, Taiwan;2. Institute of Earth Sciences, Academia Sinica, Taipei 115, Taiwan;3. Institute of Space Science, National Central University, Jhongli 320, Taiwan;4. Center for Space and Remote Sensing Research, National Central University, Jhongli 320, Taiwan;5. Department of Real Estate and Built Environment, National Taipei University, New Taipei City 237, Taiwan;6. Institute of Geophysics, National Central University, Jhongli 320, Taiwan;7. Seismological Center, Central Weather Bureau, Taipei 100, Taiwan;1. Department of Geophysics, Banaras Hindu University, Varanasi, India;2. Department of Earth Sciences, Indian Institute of Technology Roorkee, Roorkee, India;3. Wadia Institute of Himalayan Geology, Dehradun, India;4. Ministry of Earth Sciences, New Delhi, India |
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| Abstract: | The Mw 9.0 Tohoku-Oki earthquake that occurred off the Pacific coast of Japan on March 11, 2011, was followed by thousands of aftershocks, both near the plate interface and in the crust of inland eastern Japan. In this paper, we report on two large, shallow crustal earthquakes that occurred near the Ibaraki-Fukushima prefecture border, where the background seismicity was low prior to the 2011 Tohoku-Oki earthquake. Using densely spaced geodetic observations (GPS and InSAR datasets), we found that two large aftershocks in the Iwaki and Kita-Ibarake regions (hereafter referred to as the Iwaki earthquake and the Kita-Ibarake earthquake) produced 2.1 m and 0.44 m of motion in the line-of-sight (LOS), respectively. The azimuth-offset method was used to obtain the preliminary location of the fault traces. The InSAR-based maximum offset and trace of the faults that produced the Iwaki earthquake are consistent with field observations. The fault location and geometry of these two earthquakes are constrained by a rectangular dislocation model in a multilayered elastic half-space, which indicates that the maximum slips for the two earthquakes are 3.28 m and 0.98 m, respectively. The Coulomb stress changes were calculated for the faults following the 2011 Mw 9.0 Tohoku-Oki earthquake based on the modeled slip along the fault planes. The resulting Coulomb stress changes indicate that the stresses on the faults increased by up to 1.1 MPa and 0.7 MPa in the Iwaki and Kita-Ibarake regions, respectively, suggesting that the Tohoku-Oki earthquake triggered the two aftershocks, supporting the results of seismic tomography. |
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| Keywords: | Tohoku-Oki earthquake InSAR Slip distribution inversion Coulomb stress change Aftershock triggering |
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