Since 1991, induced earthquakes have been observed and linked to gas production in the Groningen field. Recorded waveforms are complex, resulting partly from a Zechstein salt layer overlying the reservoir and partly from free‐surface reverberations, internal multiples, interface conversions, guided waves, and waves diving below the reservoir. Therefore, picking of polarities or amplitudes for use in moment tensor inversion is problematic, whereas phase identification may be circumvented employing full waveform techniques. Although moment tensors have become a basic tool to analyze earthquake sources, their uncertainties are rarely reported. We introduce a method for probabilistic moment tensor estimation and demonstrate its use on the basis of a single event within the Groningen field, concentrating on detailed tests of input data and inversion parameters to derive rules of good practice for moment tensor estimation of events recorded in the Groningen field. In addition to the moment tensor, event locations are provided. Hypocenters estimated simultaneously with moment tensors are often less sensitive to uncertainties in crustal structure, which is pertinent for the application to the Groningen field, because the task of relating earthquakes to specific faults hitherto suffers from a limited resolution of earthquake locations. Because of the probabilistic approach, parameter trade‐offs, uncertainties, and ambiguities are mapped. In addition, the implemented bootstrap method implicitly accounts for modeling errors affecting every station and phase differently. A local 1D velocity model extracted from a full 3D velocity model yields more consistent results than other models applied previously. For all velocity models and combinations of input data tested, a shift in location of 1 km to the south is observed for the test event compared to the public catalog. A full moment tensor computed employing the local 1D velocity model features negative isotropic components and may be interpreted as normal fault and collapse at reservoir level.

中文翻译：

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荷兰格罗宁根气田的烃诱发地震概率矩张量反演，第1部分：测试

自1991年以来，已经观测到诱发地震，并将其与格罗宁根气田的天然气生产联系起来。记录的波形很复杂，部分是由储层上覆的Zechstein盐层造成的，部分是由自由表面的混响，内部倍数，界面转换，导波和储层下方的潜水波产生的。因此，选择用于矩张量反转的极性或幅度是有问题的，而相位识别可能会采用全波形技术来规避。尽管矩张量已成为分析地震震源的基本工具，但其不确定性却鲜有报道。我们介绍了一种概率矩张量估计的方法，并基于格罗宁根（Groningen）场中的单个事件演示了其用法，专注于输入数据和反演参数的详细测试，以得出良好的规则，用于记录格罗宁根（Groningen）字段中事件的矩张量。除了力矩张量，还提供事件位置。与矩张量同时估计的震源通常对地壳结构的不确定性不太敏感，这与格罗宁根油田的应用有关，因为迄今为止，将地震与特定断层联系起来的任务受到地震位置分辨率的限制。由于采用了概率方法，因此可以映射参数折衷，不确定性和模糊性。此外，已实施的引导程序方法隐式考虑了影响每个站点和相位的建模误差。从完整3D速度模型中提取的局部1D速度模型比以前应用的其他模型产生更一致的结果。对于所有速度模型和测试的输入数据组合，与公共目录相比，测试事件向南偏移1公里。采用局部一维速度模型计算的全力矩张量具有负的各向同性分量，并且可以解释为正常断层和储层水平的崩塌。