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标题：The 2011 off the Pacific coast of Tohoku Earthquake related to a strong velocity gradient with the Pacific plate
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作者：Makoto Matsubara ; Kazushige Obara
期刊名称：Earth, Planets and Space
电子版ISSN：1880-5981
出版年度：2011
卷号：63
期号：7
页码：663-667
DOI：10.5047/eps.2011.05.018
出版社：Springer Verlag
摘要：We conduct seismic tomography using arrival time data picked by NIED Hi-net, including earthquakes off the coast, outside the seismic network.For these offshore events, we use the NIED F-net focal depth.We detect two low- V .zones in the uppermost subducting oceanic crust.The landward low- V zone with a large anomaly corresponds to the western edge of the coseismic slip zone of the 2011 off the Pacific coast of Tohoku Earthquake.The asperities of the previously known Off-Miyagi and Off-Fukushima earthquakes with magnitudes around 7.0 are also located at the boundary of the low- V and the eastern high- V zones.The initial break point (hypocenter) is associated with the edge of a slightly low- V and low- V p / V s zone.The trenchward low- V and low- V p / V s zone extending southwestward from the hypocenter may indicate the existence of a subducted seamount.The high- V zone and low- V p / V s zone might have accumulated the strain and resulted in the huge coseismic slip zone of the 2011 Tohoku Earthquake.The low- V and low- V p / V s zone is a slight fluctuation within the high- V zone and might have acted as the initial break point of the 2011 Tohoku Earthquake. Key words Seismic tomography the 2011 off the Pacific coast of Tohoku Earthquake high- V coseismic slip zone seamont NIED Hi net low V oceanic crust asperity.
关键词：Seismic tomography ;the 2011 off the Pacific coast of Tohoku Earthquake ;high-V coseismic slip zone ;seamont ;NIED Hi net ;lowVoceanic crust ;asperity