2016 Fiscal Year Final Research Report
Mechanism of high Vp/Vs anomalies in subducting oceanic crusts
| Project/Area Number |
26400492
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Research Field |
Geology
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| Research Institution | Toho University |
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Principal Investigator |
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| Research Collaborator |
MIZOGUCHI Kazuo
NISHIMURA Kaya
KAWASHIMA Kenji
SHITAMORI Hazuki
ARIGA Hanae
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| Project Period (FY) |
2014-04-01 – 2017-03-31
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| Keywords | スロースリップ / 地震波速度異常 / プレート沈み込み帯 / 地震波速度測定実験 / 室内岩石実験 / Vp/Vs比 / 亀裂 |
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| Outline of Final Research Achievements |
We conducted laboratory measurements of P and S wave velocity Vp and Vs under confining pressure, Pc, and Pp (up to 50 MPa) for water-saturated dolerite specimens with various fracture distributions by heating (300, 500 and 700 deg C), in order to investigate the effect of fracture distribution on the relationship between Pp conditions and Vp/Vs. We also observed microstructures of the specimens and obtained fracture densities in order to characterize the fracture distributions in detail. We have demonstrated how Vp/Vs depends on Pp and porosity, and that there is a threshold value of initial porosity, or “critical porosity”, around 3% or less, under which Vp/Vs is not close to observed high Vp/Vs anomalies, even if an effective pressure is small (Pp is high and close to Pc). We expect the findings and suggestions of this study to improve interpretations of Pp and void structure conditions in oceanic crusts at subduction zones in deep based on seismic observations.
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| Free Research Field |
構造地質学，実験岩石力学，岩石物性（力学・水理），断層力学
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