2:30 PM - 2:45 PM
[SSS12-04] Seismic imaging of the eastern Japan forearc region using S-net data
Keywords:Seismic tomography, Offshore Northeast Japan, S-net, 3-D velocity structure
We carefully picked 3754 first P-wave arrival times of 63 local earthquakes (M3.5–6.2) in the Tohoku forearc region from the continuous S-net records. Then, the newly picked data are integrated with the existing arrival-time data (Zhao et al., 2012) of 360 teleseismic and 1,180 local earthquakes recorded at 3,205 Hi-net stations on the Japanese land areas. These combined data are inverted to obtain a new 3-D P-wave velocity (Vp) model beneath the entire Northeast Japan arc by using the seismic tomography method of Zhao et al. (2012).
In this work we focus on the obtained 3-D images at depths < 40 km below the region covered by the S-net. The major results are summarized as follows.
(1) Prominent low-Vp anomalies are revealed in the off-Iwate and off-Fukushima areas. These features are consistent with those revealed by previous works (e.g., Zhao et al., 2011; Huang & Zhao, 2013; Liu and Zhao, 2018), indicating that our hand-picked arrival-time data are quite accurate and robust.
(2) A significant high-Vp anomaly is revealed along the Japan Trench especially beneath the off-Miyagi region where the 2011 Tohoku-oki earthquake (Mw 9.0) occurred, which may reflect that the sedimentary layer is very thin above the subducting Pacific plate.
Huang, Z., D. Zhao (2013) JAES, 70–71, 160–168.
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Liu, X., D. Zhao (2018) Science Advances 4, eaat4396.
Zhao, D. et al. (2011) GRL 38, L17308.
Zhao, D. et al. (2012) GJI 190, 816–828.