TY - JOUR
T1 - Seismic tomography and anisotropy in the source area of the 2008 Iwate-Miyagi earthquake (M 7.2)
AU - Cheng, Bin
AU - Zhao, Dapeng
AU - Zhang, Guowei
N1 - Funding Information:
Previous studies have demonstrated that seismic velocity and Poisson's ratio in the crust are closely related to factors such as composition, temperature, crack density, saturation rate, and fluid content ( O’Connell and Budiansky, 1974; Toksoz et al., 1976; Moos and Zoback, 1983; Zhao et al., 1996; Gupta et al., 2009a; Xu and Zhao, 2009 ). The low-Vs and high- σ anomaly below the source area might reflect the existence of fluids within fractured rocks ( Zhao et al., 1996, 2002; Wang and Zhao, 2006; Xia et al., 2008; Gupta et al., 2009b ) that contributed to the initiation of the mainshock rupture. This conjecture has been supported by evidence from seismological, geophysical and hydrological studies.
PY - 2011/2
Y1 - 2011/2
N2 - In order to understand the generation mechanism of the Iwate-Miyagi earthquake (M 7.2) that occurred on 14 June 2008 in Northeast Japan, we determined high-resolution 3D seismic velocity (Vp, Vs) and Poisson's ratio (σ) structures as well as P-wave azimuthal anisotropy in and around the source area using 246,623 P-wave and 189,153 S-wave high-quality arrival times from 1941 aftershocks of the 2008 Iwate-Miyagi earthquake as well as 4878 shallow and intermediate-depth earthquakes in this area recorded by the dense High-Sensitivity Seismic Network (Hi-net) and the seismic stations of Tohoku University. Our results show that hypocenters of the mainshock and three large aftershocks are located in a boundary zone where both seismic velocity and Poisson's ratio change drastically in a short distance. A zone with pronounced low-velocity and high Poisson's ratio is revealed in the lower crust and uppermost mantle under the source area, which may reflect the arc magma and fluids ascending from the upper-mantle wedge. The P-wave azimuthal anisotropy is complex under the study area, which may also indicate the complex crustal structure there. These results indicate that the generation of the 2008 Iwate-Miyagi earthquake was influenced by the ascending arc magma and fluids associated with the dehydration reactions of the subducting Pacific slab under Northeast Japan.
AB - In order to understand the generation mechanism of the Iwate-Miyagi earthquake (M 7.2) that occurred on 14 June 2008 in Northeast Japan, we determined high-resolution 3D seismic velocity (Vp, Vs) and Poisson's ratio (σ) structures as well as P-wave azimuthal anisotropy in and around the source area using 246,623 P-wave and 189,153 S-wave high-quality arrival times from 1941 aftershocks of the 2008 Iwate-Miyagi earthquake as well as 4878 shallow and intermediate-depth earthquakes in this area recorded by the dense High-Sensitivity Seismic Network (Hi-net) and the seismic stations of Tohoku University. Our results show that hypocenters of the mainshock and three large aftershocks are located in a boundary zone where both seismic velocity and Poisson's ratio change drastically in a short distance. A zone with pronounced low-velocity and high Poisson's ratio is revealed in the lower crust and uppermost mantle under the source area, which may reflect the arc magma and fluids ascending from the upper-mantle wedge. The P-wave azimuthal anisotropy is complex under the study area, which may also indicate the complex crustal structure there. These results indicate that the generation of the 2008 Iwate-Miyagi earthquake was influenced by the ascending arc magma and fluids associated with the dehydration reactions of the subducting Pacific slab under Northeast Japan.
KW - Crustal earthquake
KW - Magma and fluids
KW - Seismic anisotropy
KW - Seismic tomography
KW - Slab dehydration
KW - The 2008 iwate-Miyagi earthquake
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U2 - 10.1016/j.pepi.2010.11.006
DO - 10.1016/j.pepi.2010.11.006
M3 - Article
AN - SCOPUS:79952739772
SN - 0031-9201
VL - 184
SP - 172
EP - 185
JO - Physics of the Earth and Planetary Interiors
JF - Physics of the Earth and Planetary Interiors
IS - 3-4
ER -