Abstract
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.
Original language | English |
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Pages (from-to) | 172-185 |
Number of pages | 14 |
Journal | Physics of the Earth and Planetary Interiors |
Volume | 184 |
Issue number | 3-4 |
DOIs | |
Publication status | Published - 2011 Feb |
Keywords
- Crustal earthquake
- Magma and fluids
- Seismic anisotropy
- Seismic tomography
- Slab dehydration
- The 2008 iwate-Miyagi earthquake
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Geophysics
- Physics and Astronomy (miscellaneous)
- Space and Planetary Science