Investigating geological structure in the shallow layer using tomographic technique of seismic explosion survey

摘要

The detailed P-wave velocity structure of the surface layers in the Kyusyu sea area,Japan was analyzed using the 3-D tomographic method for seismic refraction survey in this paper.The greater than one thousand P wave arrival times received from 14 seismic explosion surveys were used in the structure analysis of the 2-D profile.In the present analysis,the pseudo-bending method,a fast algorithm for two point ray tracing is used in forward modeling.The method can find an accurateray path in a full three-dimensional velocity structure even where lateral variations in velocity are severe.The conjugate gradient (CG) algorithm was employed to solve the discrete linearized equation about the traveltime differences.The velocity structure result in the present analysis indicates that the velocity structure obtained from the tomographic technique of the seismic wave velocity emerges evidently lateral heterogeneity.It also implies that the tomographic technique of the seismic explosion survey can character the complicated geological structure.The tomographic inversion of the explosion survey is avail for the geological structure analyses of the shallow layer.