Microseismic (MS) event locations are vital aspect of MS monitoring technology used to delineate the damage zone inside the surrounding rock mass. However, complex geological conditions can impose significantly adverse effects on the final location results. To achieve a high-accuracy location in a complex cavern-containing structure, this study develops an MS location method using the fast marching method (FMM) with a second-order difference approach (FMM2). Based on the established velocity model with three-dimensional (3D) discrete grids, the realization of the MS location can be achieved by searching the minimum residual between the theoretical and actual first arrival times. Moreover, based on the calculation results of FMM2, the propagation paths from the MS sources to MS sensors can be obtained using the linear interpolation approach and the Runge–Kutta method. These methods were validated through a series of numerical experiments. In addition, our proposed method was applied to locate the recorded blasting and MS events that occurred during the excavation period of the underground caverns at the Houziyan hydropower station. The location results of the blasting activities show that our method can effectively reduce the location error compared with the results based on the uniform velocity model. Furthermore, the obtained MS location was verified through the occurrence of shotcrete fractures and spalling, and the monitoring results of the in-situ multipoint extensometer. Our proposed method can offer a more accurate rock fracture location and facilitate the delineation of damage zones inside the surrounding rock mass.

微震（MS）事件的位置是MS监测技术的重要方面，MS监测技术用于描绘围岩内部的破坏区域。但是，复杂的地质条件可能会对最终的定位结果产生明显的不利影响。为了在复杂的包含洞穴的结构中实现高精度定位，本研究开发了一种使用快速行进方法（FMM）和二阶差分方法（FMM2）的MS定位方法。基于已建立的具有三维（3D）离散网格的速度模型，可以通过搜索理论与实际首次到达时间之间的最小残差来实现MS定位。此外，根据FMM2的计算结果，使用线性插值方法和Runge–Kutta方法可以获得从MS源到MS传感器的传播路径。通过一系列数值实验验证了这些方法。此外，我们提出的方法被用于定位在后子岩水电站地下洞穴开挖期间发生的爆破和MS事件。爆破活动的定位结果表明，与基于均匀速度模型的结果相比，我们的方法可以有效地减少定位误差。此外，通过喷射混凝土裂缝和剥落的发生来验证所获得的MS位置，并且监测结果 我们提出的方法用于定位在后子岩水电站地下洞室开挖期间发生的爆破和MS事件。爆破活动的定位结果表明，与基于均匀速度模型的结果相比，我们的方法可以有效地减少定位误差。此外，通过喷射混凝土裂缝和剥落的发生来验证所获得的MS位置，并且监测结果 我们提出的方法用于定位在后子岩水电站地下洞室开挖期间发生的爆破和MS事件。爆破活动的定位结果表明，与基于均匀速度模型的结果相比，我们的方法可以有效地减少定位误差。此外，通过喷射混凝土裂缝和剥落的发生来验证所获得的MS位置，并且监测结果现场多点引伸计。我们提出的方法可以提供更准确的岩石破裂位置，并有助于划定周围岩体内部的破坏区域。