基于单纯形-最短路径射线追踪的微震震源混合定位算法

震源定位精度是评价微震监测效果的最重要指标。最短路径射线追踪法是一种求解复杂速度模型下地震波走时场及检源路径的算法,是一种重要的地震波走时正演方法。本文将该方法引入到矿山微震监测领域,与基于平均速度模型的常规单纯形定位方法相结合,建立了单纯形-最短路径射线追踪混合定位算法。首先采用最短路径射线追踪方法,计算观测系统中每个检波点到潜在震源点的反向射线路径及走时;然后基于均匀速度模型,采用单纯形算法计算得到一个初始解;最后在初始解的一个小区间内,计算各节点"走时-到时"差之和,取求和值最小值对应的节点作为震源点。层状速度模型和空区速度模型正演模拟实验表明,最短路径射线追踪方法计算得到的检源路径符合地震波传播基本规律。基于神东某矿31101工作面坚硬顶板压裂案例,以标定炮为参考,新方法定位误差4.35m,常规单纯形方法定位误差为19.63m;该方法可为层状及含空区等复杂地层微震监测等提供重要的理论支撑和技术支撑。

A hybrid microseismic source location algorithm based on Simplex and shortest path ray tracing

Source location accuracy is the most important index to evaluate the microseismic monitoring effect. The shortest path ray tracing method is often used to solve seismic wave travel time field and source path under complex velocity model. It is an important forward modeling method for seismic wave travel-time calculation. In this study, this method is introduced into the field of mine microseismic monitoring, and a simplex-shortest path ray tracing hybrid localization algorithm has been established by combining with the conventional simplex localization method. Firstly, the shortest path ray tracing method is used to calculate the reverse ray path and travel-time from each detection point to the potential source point in the observation system. Then, a simplex algorithm is used to obtain an initial location based on the uniform velocity model. Finally, in a cell of the initial location, the sum of the difference between travel-time and backward time of each node is calculated. The node with the minimum sum value is taken as the source location. Numerical simulation results of the layered velocity model and the cavity velocity model show that the source path calculated by the shortest path ray tracing method conforms to the seismic wave propagation law. Based on the case of No. 31101 longwall panel of Shendong Mine, the location error of the new method is 4.35m, and that of the conventional simplex method is 19.63m. This method can provide important theoretical and technical support for the microseismic monitoring of complex strata such as stratigraphy and cavity-containing areas.