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Anelastic structure of the upper mantle beneath the northern Philippine Sea |
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| Authors: | Azusa Shito Takuo Shibutan |
| Institution: | Research Center for Earthquake Prediction, Disaster Prevention Research Institute, Kyoto University, Gokasyo, Uji City, Kyoto 611-0011, Japan |
| Abstract: | We investigated the upper mantle anelastic structure beneath the northern Philippine Sea region, including the Izu-Bonin subduction zone and the Shikoku Basin. We used regional waveform data from 69 events in the Pacific and the Philippine Sea slabs, recorded on F-net and J-array network broadband stations in western Japan. Using the S–P phase pair method, we obtained differential attenuation factors, δt*, which represent the relative whole path Q. We conducted a tomographic inversion using 978 δt* values to invert for a fine-scale (50–100 km) three-dimensional anelastic structure. The results shows two high-Q regions (QP>1000) which are consistent with the locations of the Pacific and the Philippine Sea slabs. Also there is a low-Q (QP |
| Keywords: | Anelasticity Upper mantle Northern Philippine Sea Phase pair method Q |
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110) area extending to the deeper parts (350–400 km) of the model just beneath the old spreading center and the Kinan Seamount Chain in the Shikoku Basin. A small depth dependence of the laterally averaged QP was found, with values of 266 (0–250 km), 301 (250–400 km), and 413 (400–500 km).