Precise positioning in double-layer horizontal media

The existing source positioning models for earthquakes and rock bursts are based on homogeneous media. In order to improve source positioning accuracy, a source positioning method in double-layer horizontal media is proposed. Using the isochron concept in the process of deriving the law of refraction based on the Huygens principle and the approximate determination method of refraction point which is widely used in engineering, we get a travel time equation by which the depth and horizontal coordinates are obtained. Based on the specific distribution solution of monitoring stations, the travel time equation is simplified into linear equations. Reasonable assumptions and geometric means are adopted to revise the calculated results of source depth. The positioning accuracy of double-layer media model is significantly higher than that of classical linear positioning method under a variety of conditions. The analysis of the calculated results of double-layer media model under various positioning conditions shows that: (1) when the wave velocity ratio and station spacing are different, there is an optimal value range for source positioning; (2) the double-layer media model is especially suitable for deep source positioning with large buried depth; (3) when the ratio of horizontal to vertical distance between station and source is larger, the positioning accuracy is worse. It is suggested to build stations on the areas where earthquakes are easily prone to happen; (4) there is no advantage when the ratio of distances from interface of the source and stations is too large or small, so it is suggested to use the classic linear positioning method. Further optimization of double-layer media model and promotion to multi-layer media one will improve the precise positoning.