Abstract：The parameters of orientation and density of stratum fracture development can be evaluated based on the character and information of S-wave splitting.These two parameters have important meaning in increasing recovery factor of oil gas in fractured reservoir.When using converted wave data of 2-D single source to evaluate the fracture parameters,we usually supposed that a certain relation of time difference and amplitude might exist between the fast and slow S-waves which often do not exist in reality,especially the relation of time difference can not be certain.Therefore,on the basis of polarization of fast and slow S-wave being orthonormal polarization,the paper presented an orthonormal basis rotation method,deduced an analytic expression of the angle between geometry co-ordinate and natural co-ordinate,which finished the separation of fast and slow S-waves and evaluated the developed orientation of stratum fracture.The synthetic records and real cases showed that the method has both feasibility and practicality for evaluation of main orientation of fracture.
