Focal depths and mechanisms of Tohoku-Oki aftershocks from teleseismic P wave modeling
Ling Bai1, Lorena Medina Luna2, Eric A. Hetland2, Jeroen Ritsema2
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
Focal depths and mechanisms of Tohoku-Oki aftershocks from teleseismic P wave modeling
Ling Bai1, Lorena Medina Luna2, Eric A. Hetland2, Jeroen Ritsema2
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
摘要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 Mw>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.
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 Mw>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.
基金资助:the grants of National Natural Science Foundation of China (41274086) to LB and JR, and a University of Michigan Rackham Merit Fellowship to LML
通讯作者:
Ling Bai
E-mail: bailing@itpcas.ac.cn
引用本文:
Ling Bai, Lorena Medina Luna, Eric A. Hetland, Jeroen Ritsema. Focal depths and mechanisms of Tohoku-Oki aftershocks from teleseismic P wave modeling[J]. 《地震学报》英文版, 2014, 27(1): 1-13.
Ling Bai, Lorena Medina Luna, Eric A. Hetland, Jeroen Ritsema. Focal depths and mechanisms of Tohoku-Oki aftershocks from teleseismic P wave modeling. Earthquake Science, 2014, 27(1): 1-13.