ABSTRACT Surface arrays became an important tool for monitoring the induced seismicity in hydraulic fracturing experiments and for assessing the impact of fluid injection on the fracturing process of microearthquakes. The layout of sensors plays a key role in this task because it controls the accuracy of event locations and retrieved seismic moment tensors. We simulate various configurations of grid sensor arrays characterized by a different number of sensors, array span, sensor spacing, depth of sources and various shear/tensile source mechanisms of events. The moment tensor inversion is carried out using synthetically calculated P‐wave amplitudes with added random noise. A bias in the solutions is evaluated by errors in the double‐couple percentage of inverted moment tensors because the double‐couple errors inform us about the sensitivity of the network to detect the shear/tensile fracturing mode of induced microearthquakes. The results show that the accuracy of the double‐couple percentage is mostly controlled by the offset‐to‐depth ratio R defined as the ratio of half of the network size to the event depth. The optimum value of R is in the range of 0.75–1.5 irrespective of the type of the focal mechanism. If 121 (11 × 11) sensors are distributed in a regular grid and recorded data are characterized by a 10% random noise, the double‐couple error is less than 6%. This error increases, if R is not optimum or if the number of sensors is reduced. However, even sparse arrays with 49 (7 × 7) or 16 (4 × 4) sensors can yield a reasonable accuracy, provided the surface grid arrays are designed to have an optimum size.

中文翻译：

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用于检索微地震精确剪切-拉伸断裂的表面网格阵列的最佳尺寸和密度

摘要 表面阵列成为监测水力压裂实验中诱发地震活动和评估流体注入对微地震压裂过程影响的重要工具。传感器的布局在这项任务中起着关键作用，因为它控制着事件位置和检索到的地震矩张量的准确性。我们模拟网格传感器阵列的各种配置，其特征在于不同数量的传感器、阵列跨度、传感器间距、源深度和事件的各种剪切/拉伸源机制。矩张量反演是使用合成计算的 P 波振幅和添加的随机噪声进行的。解中的偏差通过反矩张量的双偶百分比误差来评估，因为双偶误差告诉我们网络检测诱发微地震的剪切/拉伸断裂模式的敏感性。结果表明，双偶百分比的准确性主要受偏移深度比 R 控制，该比定义为网络大小的一半与事件深度的比率。无论聚焦机制的类型如何，R 的最佳值都在 0.75-1.5 的范围内。如果121（11×11）个传感器分布在规则的网格中，记录的数据具有10%的随机噪声特征，则双偶误差小于6%。如果 R 不是最佳值或传感器数量减少，则该误差会增加。然而，