Reverse-time ray-tracing method for microseismic source localization

Accurate source localization is a critical component of seismic monitoring. The efficiency of location algorithms is limited by several factors, such as the dimension of source parameter search space and iterative procedures of the algorithm. To avoid iterations and accelerate source localization algorithms, a reverse-time ray tracing method (RTRTM) is presented. The RTRTM estimates the particle motion direction and arrival time based on the polarization scanning method, and calculates the incident P-wave polarization vector based on the near-surface structure. It then back-traces trajectories of P waves based on the reversed direction of incident P-wave polarization vectors, and locates the mean position of converging ray terminals as the source position and the corresponding time as the original time of the event. The accuracy and efficiency of the RTRTM method are demonstrated by the source localization results of both synthetic data and data from an Mb = 1.6 local earthquake. The reliability of polarization estimation method and the effect of velocity structures on RTRTM source localization are also discussed.