The relationship between the deep-level structure in crust and brewing of strong earthquakes in Xingtai area |
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| Authors: | Lan-Xi Xiao Yuan-Qing Zhu Shao-Quan Zhang Xu Liu and Yu Guo |
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| Institution: | (1) Institute of Geophysics, China Seismological Bureau, 100081 Beijing, China;(2) Seismological Bureau of Shanghai, 200062 Shanghai, China;(3) Seismological Bureau of Shandong Province, 250014 Ji’nan, China |
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| Abstract: | In this paper, crust medium is treated as Maxwell medium, and crust model includes hard inclusion, soft inclusion, deep-level
fault. The stress concentration and its evolution with time are obtained by using three-dimensional finite element method
and differential method. The conclusions are draw as follows: (1) The average stress concentration and maximum shear stress
concentration caused by non-heterogeneous of crust are very high in hard inclusion and around the deep fault. With the time
passing by, the concentration of average stress in the model gradually trends to uniform. At the same time, the concentration
of maximum shear stress in hard inclusion increases gradually. This character is favorable to transfer shear strain energy
from soft inclusion to hard inclusion. (2) When the upper mantle beneath the inclusion upheave at a certain velocity of 1
cm/a, the changes of average stress concentration with time become complex, and the boundary of the hard and soft inclusion
become unconspicuous, but the maximum shear stress concentration increases much more in the hard inclusion with time at a
higher velocity. This feature make for transformation of energy from the soft inclusion to the hard inclusion. (3) The changes
of average stress concentration and maximum shear stress concentration with time around the deep-level fault result in further
accumulation of maximum shear stress concentration and finally cause the deep-level fault instable and accelerated creep along
fault direction. (4) The changes of vertical displacement on the surface of the model, which is caused by the accelerated
creep of the deep-level fault, is similar to that of the observation data before Xingtai strong earthquake. |
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| Keywords: | Maxwell medium stress concentration inclusion deep-level fault numerical simulation |
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