Abstract:The anisotropy of medium in HBC area in Sichuan Province was found in the processing and interpretation of P and SH wave data. Shear wave passing through anisotropic medium splits into two different waves:fast shear wave whose polarization direction is parallel to fracture trend in formations, and the slow shear wave that polarues in the direction perpendicular to fracture trend. Fast and slow shear wave sections can be respectively obtained by using different layouts and data processing methods. The anisotropy coefficient can be derived from the travel times of fast and slow S-waves arriving at the same interface;it can also be obtained from the ratio of SH-wave velocity to converted wave velocity. Anisotropy coefficient reflects fracture density. Then the direction of fracture zone can be determined by making both X, Y-component detection in data acquisition and coordinate revolution in data processing. Without the above measures taken, we can roughly determine the direction of fracture zone in the light of structure-line trend.