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
