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Influence of fluids and magma on earthquakes: seismological evidence. Dapeng Zhao, O.P. Mishra, R. Sanda (2002) Presented by Penelope Burniaux. 1. 2. 3. 2. 1. Shubu, Kanto, and Tokai. Tohoku. Chugoku. 3. Shikoku. Kii. Of 161 large historic earthquakes: 70% = −3% < ΔV/V < 0
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Influence of fluids and magma on earthquakes:seismological evidence Dapeng Zhao, O.P. Mishra, R. Sanda (2002) Presented by Penelope Burniaux
1 2 3
2 1 Shubu, Kanto, and Tokai Tohoku
Chugoku 3 Shikoku Kii Of 161 large historic earthquakes: 70% = −3% < ΔV/V < 0 11% = ΔV/V < −3% 19% = 0% < ΔV/V < 1.5%
Conclusions • The existence of fluids beneath the seismogenic layer affects the long-term structural and compositional evolution of the fault zone, change the strength of the fault zone, and alter the local stress regime (Sibson, 1992;Hickman et al., 1995). • These influences enhance the stress concentration in the seismogenic layer leading to mechanical failure. • Lithological variations in the crust also contribute to the heterogeneity in the material property and stress field and cause the slow seismic velocity and the weakening of the seismogenic layer. • These many pieces of evidence suggest that the generation of a large earthquake is not a pure mechanical process, but is closely related to the physical and chemical properties of materials in the crust and upper mantle, such as water. • These results indicate that large earthquakes do not strike anywhere, but only anomalous areas that may be detected with geophysical methods.