Effect of the free surface on the earthquake energy: A case study of reverse faulting |
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Authors: | Li YanHeng Shi BaoPing Zhang Jian |
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Institution: | (1) Graduate University of Chinese Academy of Sciences, Beijing, 100049, China;(2) Institute of Crustal Dynamics, Chinese Earthquake Administration, Beijing, 100085, China |
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Abstract: | Based on the representation theorem of seismic energy radiation, in this study, we have quantitatively investigated the effect
of free surface on the radiation energy distribution due to a coupling interaction between free surface and near surface finite
fault for the reverse earthquake faulting. Corresponding to the finite faulting, a 2-D pseudostatic-reverse-fault-dislocation
solution has been used in the calculation of the work done by the seismic response against free surface. The results indicate
that, due to a strong coupling interaction between the free surface and near surface fault, the total radiated seismic energy
E
R is much larger than that radiated only from the fault itself (E
F), especially for the shallow reverse faulting. In convention, E
F is commonly used in the estimation of earthquake energy radiation. However, when the fault depth H, the distance between the free surface and top of fault location, increases, the effect of the coupling interaction between
the fault and free surface decreases gradually. Therefore, the total radiated energy E
R approaches to the E
F when the depth H is about 2 times the fault length I. The current study could provide us a partial explanation of the apparent stress discrepancy observed at the far field and
near field in the recent large earthquake. Moreover, the current study also has a significant implication of how to quantitatively
describe the near fault strong ground motion and associated seismic hazard from the earthquake source energy point of view.
Supported by the Institute of Crustal Dynamics, China Earthquake Administration (Grant No. ZDJ2007-1), Hundred Talent Program
of Chinese Academy of Sciences, and National Natural Science Foundation of China (Grant No. 40574022) |
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Keywords: | energy partitioning representation theorem thrust fault apparent stress response of surface |
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