Approximate decomposition method of oblique incidence P, SV wave fields in observation of site borehole array

Abstract

Usually we believe that the P wave and the SV wave transform and couple mutually in the stratified medium, independent incidence field of P and SV wave may not be obtained. Firstly, radial horizontal component and transverse horizontal component are derived from tri-channel seismic data at the surface and the bedrock in borehole array by backazimuth decomposition method, and the histories of radial and vertical components are divided into two parts by S_g wave arrived time. Moreover, it is supposed that transverse horizontal components are made up of SH wave, while vertical component and radial horizontal component are constituted by P-SV wave system. Secondly, the methods of solving simultaneous equations in frequency domain are brought forward, this method combined a global-local optimization algorithm, which is genetic algorithm (GA) - Simplex Method, P, SV wave fields including SH wave are gained. At last, the preliminary rationality of this method is proved by the result coherence of another nearby borehole array at quite different site condition. This work has certain significance for study on fault characteristic, seismic phase, parameters of soft outcrop bedrock or soil-layer medium and detailed evaluation of site effect.