2007 Fiscal Year Final Research Report Summary
Seismic velocity discontinuities beneath the Japan Islands with receuver function tomography
| Project/Area Number |
17340130
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Solid earth and planetary physics
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| Research Institution | Kyoto University |
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Principal Investigator |
HIRAHARA Kazuro Kyoto University, Graduate School of Prience, Professor (40165197)
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| Co-Investigator(Kenkyū-buntansha) |
SHIBUTANI Takuo Kyoto University, Disaster Prevention research Institute, Associate Professor (70187417)
FURUMURA Takashi University of Tokyo, Earthquake Research Institute, Associate Professor (80241404)
TODOKORO Keichi Kyoto University, Graduate School of Envnionmental Studies, Associate Professor (70324390)
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| Project Period (FY) |
2005 – 2007
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| Keywords | Receiver function / Seismic velocity discontinuities / Crust / Upper mantle / Slab / 410 km discontinuity / 660km discontinuity / Dehydrated water |
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| Research Abstract |
We investigated the method of receiver function (RF) tomography by which we simultaneously determine the smoothly varying 3-D seismic velocity structure and the velocity discontinuity surfaces. Through the investigation, we recognized the necessity of developing the raid and efficient method of synthesizing waveforms in a 3-D velocity structure including velocity discontinuities, and then developed a raid waveform synthetic method based on improved Gaussian Beam method (GBM). We applied this method to the waveforms observed in the Kii peninsula, southwest Japan, where the Philippine Sea plate is subducting with a complex 3-D configuration. We synthesized radial, transverse and vertical RFs, and compared them with the observed ones to investigate the structure of the top and the oceanic Moho of the descending Philippine Sea slab. As results, we confirmed the phases appeared in the observed radial and transverse RFs are the P to S wave converted (Ps) phases at the inclined seismic velocity discontinuities, and the phases in the vertical RFs are the P waves reflected at the surface and the inclined velocity discontinuities (PpdP).
Further, we investigated the top, the oceanic Moth and the bottom of the subducting Pacific slab by employing the RFs produced from Hi-net tiltmeters. Especially in the central Japan region where the station density is high, the analyses using bath the radial and transverse RFs revealed that dehydrated water is transported. into the mantle transition zone.
The ; low velocity zone revealed by RF analyses indicates the existence of the layer of dehydrated water. Finally, we executed 2-D simulation of earthquake cycle on a fluid-infiltrated plate interface based on a rate and state dependent friction, and investigated the relation between the fecal depth and the pore pressure distribution at depths.
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Research Products
(10 results)
