Abstract: An accurate microseismic (MS) source location method is the foundation of MS monitoring technology for stability analysis of rock mass, and the first-arrival travel time calculation method is one of the important factors determining the precision of MS source location. An improved linear interpolation algorithm based on the fast marching methods (FMM) and LTI ray tracing is introduced to obtain relatively accurate first-arrival travel time in complex rock masses. Moreover, this improved algorithm is verified by the uniform velocity model and the Marmousi model. On the basis of travel time calculation, Runge-Kutta method, a single-step high-precision method in the numerical algorithm of ordinary differential equations, is introduced to calculate the ray propagation path. Besides, its rationality is verified in the uniform, stratified and hollow rock mass model established by us. Finally, using the least-squares method as the objective function, the MS source location is achieved by obtaining the optimal node that makes the objective function taken the minimum value. In the Marmousi model with underground caverns established by us, the location errors for the pre-set source points are 1.41, 1.00, 2.83, 1.41 m and 1.41 m, respectively. It is verified that the method in this paper can achieve relatively accurate location in the complex rock mass and provide a new idea for improving the accuracy of microseismic location in the engineering rock mass.

Key words: MS source location, interpolation, narrow band expansion, Runge-Kutta, least-squares method