Earthquakes in the Fort Worth basin (FWB) have been induced by the disposal of recovered wastewater associated with extraction of unconventional gas since 2008. Four of the larger felt earthquakes, each on different faults, prompted deployment of local distance seismic stations and recordings from these four sequences are used to estimate the kinematic source characteristics. Source spectra and the associated source parameters, including corner frequency, seismic moment, and stress drop, are estimated using a modified generalized inversion technique (GIT). As an assessment of the validity of the modified GIT approach, corner frequencies and stress drops from the GIT are compared to estimates using the traditional empirical Green’s function (EGF) method for 14 target events. For these events, corner‐frequency residuals (GIT−EGF) have a mean of −0.31 Hz, with a standard deviation of 1.30 Hz. We find consistent mean stress drops using the GIT and EGF methods, 9.56 and 11.50 MPa, respectively, for the common set of target events. The GIT mean stress drop for all 79 earthquakes is 5.33 MPa, similar to estimates for global intraplate earthquakes (1–10 MPa) as well as other estimates for induced earthquakes near the study area (1.7–9.5 MPa). Stress drops exhibit no spatial or temporal correlations or depth dependency. In addition, there are no time or space correlations between estimated FWB stress drops and modeled pore‐pressure perturbations. We conclude that induced earthquakes in the FWB occurring on normal faults in the crystalline basement release pre‐existing tectonic stresses and that stress drops on the four sequences targeted in this study do not directly reflect perturbations in pore‐fluid pressure on the fault.

中文翻译：

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德克萨斯州沃思堡盆地诱发地震事件的应力降估计

自 2008 年以来，沃斯堡盆地 (FWB) 的地震是由与非常规天然气开采相关的回收废水的处理引起的。四次较大的有感地震，每一次都发生在不同的断层上，促使部署本地距离地震台站并记录这些地震四个序列用于估计运动学源特征。源谱和相关的源参数，包括角频率、地震矩和应力降，是使用改进的广义反演技术 (GIT) 估计的。作为对修改 GIT 方法有效性的评估，将 GIT 的角频率和应力降与使用传统经验格林函数 (EGF) 方法对 14 个目标事件的估计进行比较。对于这些事件，转角频率残差（GIT-EGF）的平均值为-0。31 Hz，标准偏差为 1.30 Hz。对于常见的一组目标事件，我们发现使用 GIT 和 EGF 方法的一致平均应力降分别为 9.56 和 11.50 MPa。所有 79 次地震的 GIT 平均应力降为 5.33 MPa，类似于全球板内地震的估计值 (1-10 MPa) 以及研究区附近诱发地震的其他估计值 (1.7-9.5 MPa)。应力下降不表现出空间或时间相关性或深度依赖性。此外，估计的 FWB 应力降与模拟的孔隙压力扰动之间没有时间或空间相关性。