Focal depths and mechanisms of Tohoku-Oki aftershocks from teleseismic P wave modeling |
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| Authors: | Ling Bai Lorena Medina Luna Eric A Hetland Jeroen Ritsema |
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| Affiliation: | 1. Key Laboratory of Continental Collision and Plateau Uplift, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, 100101, China
2. Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, 48109, USA
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| Abstract: | Aftershocks of the 2011 Tohoku-Oki great earthquake have a wide range of focal depths and fault plane mechanisms. We constrain the focal depths and focal mechanisms of 69 aftershocks with M w > 5.4 by modeling the waveforms of teleseismic P and its trailing near-surface reflections pP and sP. We find that the “thrust events” are within 10 km from the plate interface. The dip angles of these thrust events increase with depth from ~5° to ~25°. The “non-thrust events” vary from 60 km above to 40 km below the plate interface. Normal and strike-slip events within the overriding plate point to redistribution of stress following the primary great earthquake; however, due to the spatially variable stress change in the Tohoku-Oki earthquake, an understanding of how the mainshock affected the stresses that led to the aftershocks requires accurate knowledge of the aftershock location. |
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