Application Research On Shear Wave Splitting

The structure and tectonic of Earth’s interior media are intrinsically anisotropy.Anisotropy in the crust is mainly the result of stress-aligned parallel vertical micro-cracks,which are the EDA (Extensively Dilatancy Anisotropy) cracks and widely exist in the crust.Shear wave will split when traveling through this kind of anisotropy media. And the shearwave will split into two wave trains, among which the polarization direction of fast shearwave is consistent with the crack’s direction, which means that the polarization of fastshear-wave reflects the direction of the principal compressive stress. The delay time of slowshear wave reflects the level of anisotropy. Through the parameters of share-wave splitting,we can study the characteristics of the crust media, the condition and variation of crustalstress field, etc. The study of shear wave splitting is now an important part of Geophysicalresearch.Based on correlation function analysis method, a user-friendly and stable software foranalyzing shear wave splitting which is named Swavesplit, is developed by using MATLABas developing platform. The main function of Swavesplit includes seismic waveform datamanagement, data preprocessing, data conventional calculation, filtering, correlation analysisand the result output. The data management function allows users to operate1to3seismicwaveform charts simultaneously, including data-reading, transferring, displaying, checkingand closing. The data conventional calculation function consists of numerical integration,numerical derivation, signal-to-noise ratio calculating, azimuth calculating, etc. The resultoutput function includes displaying contour map of correlation value, map of max correlationvalue and report on the results in Microsoft Word form. The Swavesplit software ischaracterized by flexible operation, steady performance and high fault tolerance.At last,53seismic waveform records within shear wave window are selected form17seismic stations in southeast part of capital area (2004.12-2005.8). All the records areanalyzed by using the software of SwaveSplit. The results are consistent with the results ofprevious researches, which demonstrating the correctness and availability of the software.