Abstract: The velocity model is the major factor affecting the seismic source localization algorithm which is the core of microseismic monitoring technique. Based on the complex velocity model, the fast sweeping method (FSM) is an algorithm to calculate the first arrival time of the seismic wave by using the eikonal equation. This method has been widely applied in the fields of earthquake localization and geophysical exploration. In this study, this method was introduced in the field of microseismic monitoring in geotechnical engineering. Especially for layered velocity models, a fast localization technique was established based on the fast sweeping method (FSM). Firstly, the fast sweeping method (FSM) in a 3D Cartesian coordinate system was proposed to calculate the initial travel time of the point source in the single velocity model and horizontal layered velocity model. Compared with the theoretical solution, the accuracy of the algorithm and its error distribution characteristics were analyzed. The travel time results calculated by the fast sweeping method (FSM) and theoretical solutions were compared to analyze the algorithm precision and error distribution characteristics. Secondly, a rapid seismic source localization technique was put forward for the layered velocity model based on the database of the arrival time differences which were calculated by fast sweeping method (FSM). Finally, the positioning accuracy and computational efficiency between the new localization technique and traditional method based on the isotropy velocity model were compared and analyzed. This study showed that the proposed technique for the layered velocity model presented a favorable accuracy and computational efficiency, and also reduced the location time significantly compared with traditional location methods. The technique can provide significant theoretical and technical support for the microseismic source localization in complex layer and acoustic emission monitoring in the laboratory.

Key words: microseismic source location, fast sweeping method, arrival time difference, database, layered velocity model