Simulation of Microtremor H/V Response to Three Simple Sediment/Structure Models

Abstract eng:
In order to evaluate the 2D effects of sediment thickness variation on the resonant frequency of the horizontal to vertical spectral ratio (H/V) of the microtremor measurements, we numerically simulated the ambient noise superposition and interference in three sediment models: the flat layer sediment, a dip layer sediment and a thrust fault, with the 2D finite difference time domain (FDTD) method. First, we created the sediment/structure model. Second, we used the FDTD method to simulate the propagation of the ambient noise with the excitation of the randomly distributed noise sources in the uppermost part of the crust. The responses of the model were recorded at the receiver arrays on the surface. Then, the synthetic ambient data were processed with the horizontal to vertical component H/V spectral ratio method to extract the variation of the resonant frequency for a given sediment structure. We compared the H/V derived sediment thickness results with the initial models and found that simulation results can produce credible images of the subsurface structure which can matched with the initial models in a great agreement. We conclude that numerical simulation of microtremors with the FDTD method can provide a reference model for the purpose of planning real-world field measurement and assisting the comprehension of field H/V results. This work is supported by the Ministry of Science and Technology of China with Project No. 2006DFA21650 and the Institute of Earthquake Science with Project No. 0207690229.

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