二层水平介质中震源的精确定位

现有震源定位模型均基于均匀介质,为进一步提高震源定位精度,提出了二层水平介质中震源定位方法。采用惠更斯原理推导折射定律过程中的等时线概念,结合工程中广泛采用的折射点近似确定方法,得到将震源深度与水平坐标分离的走时方程。采用特定的台站分布方案,将走时方程简化为线性方程组。采用合理假设并取几何平均数的方法修正震源深度的计算结果。二层模型在多种定位条件下的计算精度均明显高于经典线性定位方法。对各种定位条件下二层模型的计算结果分析表明,在波速比和台站间距取不同值时,存在定位效果最优的取值范围,且二层模型尤其适用于埋深较大的深震源定位。台站与震源水平、竖直距离比较大时,定位精度变差,建议在地（矿）震易发区布置台站。另外,当震源与台站距分界面距离比过大或过小时较经典线性方法不具优势,建议与经典线性定位法结合使用。二层模型的进一步优化和向多层模型推广,将进一步完善地（矿）震震源精确定位方案。

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.