Distributed acoustic sensing (DAS) is being applied in an increasing number of geoscientific fields. We present herein preliminary results of applying DAS to monitor microseismicity in underground mines. We installed 275 m of fiber optic cable approximately 1500 m below the surface in an operational mine and recorded mine seismicity for two weeks during November of 2018. The first approximately 50 m was tied to the sidewall safety mesh and a further 225 m was grouted into a down-dipping borehole alongside four three-component geophone sensors with 14 Hz high-sensitivity elements. The geophone sensors are located 132 m, 154 m, 176 m and 198 m down the borehole. We show that, for the larger seismic events (M_W > −0.1), there is relatively good agreement in the data collected with DAS compared to the geophone data. There is some amplitude variation, especially at higher frequencies, but the phase of the recordings match well. We were able to include the DAS data in processing select events using PhaseNet, a machine-learning based algorithm, to pick phase arrivals and then locate these events using a recently developed interferometric method. In our comparison of the background noise of the DAS and that of the geophones, we found that the DAS as installed in our experiment has a noise floor orders of magnitude higher than the seismic background of the mine. Furthermore we compared the recordings in the different fiber sections (tied to the safety mesh and grouted, respectively) to analyze the feasibility of using existing mining communication infrastructure as sufficiently accurate seismic sensors. Fiber optic communication cables are typically tied to the sidewall mesh in the absence of dedicated conduits, and thus our mesh-coupled section was a suitable proxy for this scenario. We found extremely limited utility in the recordings of the mesh coupled fiber.

分布式声学传感 (DAS) 正在越来越多的地球科学领域得到应用。我们在此展示了应用 DAS 监测地下矿山微震活动的初步结果。我们在一个运营矿井的地表以下约 1500 m 处安装了 275 m 的光缆，并在 ​​2018 年 11 月期间记录了两周的矿井地震活动。前约 50 m 与侧壁安全网相连，另外 225 m 被灌浆到一个下倾钻孔，旁边是四个带有 14 Hz 高灵敏度元件的三分量地震检波器传感器。地震检波器传感器位于钻孔下方 132 m、154 m、176 m 和 198 m 处。我们表明，对于较大的地震事件（ M _W > -0.1)，与地震检波器数据相比，DAS 收集的数据具有较好的一致性。有一些幅度变化，特别是在较高频率下，但记录的相位匹配得很好。我们能够使用基于机器学习的算法 PhaseNet 将 DAS 数据包含在处理选择事件中，以选择相位到达，然后使用最近开发的干涉测量方法定位这些事件。在我们比较 DAS 和地震检波器的背景噪声时，我们发现我们实验中安装的 DAS 的本底噪声比矿井的地震背景高几个数量级。此外，我们比较了不同纤维部分（分别连接到安全网和灌浆）中的记录，以分析可行性使用现有的采矿通信基础设施作为足够精确的地震传感器。光纤通信电缆通常在没有专用导管的情况下连接到侧壁网格，因此我们的网格耦合部分是这种情况的合适代理。我们发现在网状耦合光纤的记录中的效用极其有限。