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Zhang C.,Wuhan University | Zhang S.,Wuhan University | Zhang S.,Key Laboratory of Environment and Geodesy
Acta Seismologica Sinica | Year: 2014

The thermal conductivity and expansion coefficients are two significant parameters that have influence on the dynamic process of slab subduction. Due to the heterogeneity of Earth medium, these two coefficients are usually variable with depth. Unfortunately, such variations are often ignored in current modeling studies of geodynamics. The present study refers to the temperature-dependent thermal conductivity and expansion to simulate the dynamic process of slab subduction. The impact of thermal parameters and viscosity on slab geometry and the corresponding characteristics of mantle convection are analyzed. The modeling results show that the temperature-dependent thermal conductivity and expansion affect the subduction angle by changing the thermal and viscosity structure. The viscosity plays a critical role in controlling the slab dynamic evolution. The mantle convection is affected by viscosity structure and exhibits different patterns, such as layered convection and local multiple convection loops, etc. Source

Zhang C.,Wuhan University | Zhang S.-X.,Wuhan University | Zhang S.-X.,Key Laboratory of Environment and Geodesy | Carminati E.,University of Rome La Sapienza | Gao B.-Y.,Wuhan University
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2014

The present study calculated the thermal structure, the distribution of buoyancy, and P-wave velocity anomalies in Japan Trench subduction zone using finite difference method, and predicted the range of metastable olivine according to whole and layered mantle convection models. We analyzed the influences of multiple coefficients, such as thermal conductivity, thermal expansion, and heat sources on the thermal structure. The relation between the buoyancy of subduction zone and its shape were also discussed. Interesting results for layered mantle convection model demonstrated that the modeled P-wave velocity anomalies not only matched seismic tomography results much better, but also highly correlated to the distribution of deep-focus earthquakes in Japan Trench subduction zone. The areas of metastable olivine inside slabs became larger with decreasing values of thermal conductivity and thermal expansion coefficients and ignoring phase change heating and shear heating would also induce larger areas of modeled metastable olivine. The maximum value of negative buoyancy reached the depth of about 400 km. The metastable olivine resulted in the decrease of negative buoyancy, or even positive buoyancy within the subduction zone against the penetration of the subduction zone into the 660 km discontinuity. ©, Science Press. All right reserved. Source

Zhang S.,Wuhan University | Zhang S.,Key Laboratory of Environment and Geodesy | Zhang C.,Wuhan University | Zhang Y.,Wuhan University | And 4 more authors.
Journal of Earth Science | Year: 2015

The present study aims to reveal the recovering period of the postseismic fluid pressure in fault zone, offering an insight into earthquake recurrence. Numerical modeling is performed based on a 2D simple layered fault-valve model to simulate the fluid activities within the earthquake fault. In order to demonstrate the features of postseismic fluid pressure in natural state, the interference of tectonic movements is not considered. The recovering period of postseismic fluid pressure includes a suddenchanging period and a much longer fluctuating period. Modeling results show that fault permeability and porosity are sensitive parameters and reversely proportional to the recovering period of the fluid pressure in earthquake fault zone. When the permeability reduces from 10-15 to 10-18 m2, the recovering period increases from 400 to 2 000 yrs, correspondently. The upper and lower fluid pressures are separated by the valve seal, causing their fluctuations in opposite tendencies. © 2015, China University of Geosciences and Springer-Verlag Berlin Heidelberg. Source

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