Coulomb stress change is the change in resultant force of shear stress and friction imposed on a receiver fault plane. The resulting stress change is often computed using the Coulomb 3.4 and the postseismic Green’s functions and postseismic components (PSGRN‐PSCMP) programs. Notwithstanding both preferences, both have incomplete optimally oriented failure planes (OOPs) and are inconvenient to resolve Coulomb stress changes on various fault planes placed in varying depths. Here, we present an alternative program termed AutoCoulomb. It leverages the shell command‐line tool to automatically batch‐process Coulomb stress changes on all sorts of receiver fault planes. We first validate the program. We then apply it to the 2020 Mw 7.8 Simeonof Island, Alaska, earthquake, as a case study. Our results show that Coulomb stress changes resolved on fixed receiver faults, using the three programs, are in line with each other. So are those resolved on 3D OOPs using the PSGRN–PSCMP and the AutoCoulomb programs. Nevertheless, Coulomb stress changes on 2D OOPs, generated by the AutoCoulomb program, always outweigh those done by the Coulomb 3.4 program, indicating that 2D OOPs constrained by the latter are not the most optimal. Some nonoptimal 2D OOPs result in the reversal of the signs of Coulomb stress changes, posing a risk of misleading stress shadows with negative Coulomb stress changes. For the case study, the 28 July 2020 Mw 6.1 aftershock received a positive coseismic Coulomb stress change of ∼3.5 bars. In contrast, the compounded coseismic Coulomb stress changes at the hypocenters of the 1946 Mw 8.2, the 1948 Mw 7.2, and the 2020 Mw 7.8 earthquakes are within a range from −1.1 to 0.1 bar, suggesting that coseismic Coulomb stress changes promoted by preceding mainshocks alone are not responsible for these mainshocks. Other factors, such as postseismic viscoelastic relaxation, afterslip, and slow slip, may contribute to promoting their occurrence.

中文翻译：

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AutoCoulomb：计算任意方向接收器故障库仑应力变化的自动可配置程序及其在 2020 Mw 7.8 Simeonof Island, Alaska, Earthquake 中的应用

库仑应力变化是施加在接收器断层面上的剪切应力和摩擦合力的变化。产生的应力变化通常使用库仑 3.4 和震后格林函数和震后分量 (PSGRN-PSCMP) 程序计算。尽管有这两种偏好，但两者都具有不完整的最佳定向故障平面 (OOP)，并且不方便解决位于不同深度的各种故障平面上的库仑应力变化。在这里，我们提出了一个称为 AutoCoulomb 的替代程序。它利用 shell 命令行工具自动批处理各种接收器故障平面上的库仑应力变化。我们首先验证程序。然后，我们将其应用到 2020 Mw 7.8 Simeonof Island, Alaska 地震中作为案例研究。我们的结果表明，使用三个程序在固定接收器故障上解决的库仑应力变化相互一致。使用 PSGRN-PSCMP 和 AutoCoulomb 程序在 3D OOP 上解决的问题也是如此。尽管如此，由 AutoCoulomb 程序生成的 2D OOP 上的库仑应力变化始终大于 Coulomb 3.4 程序所做的那些，表明后者约束的 2D OOP 并不是最佳的。一些非最佳的 2D OOP 会导致库仑应力变化的迹象逆转，从而带来误导性库仑应力变化的应力阴影风险。在案例研究中，2020 年 7 月 28 日发生的 Mw 6.1 余震收到了约 3.5 巴的正同震库仑应力变化。相比之下，复合同震库仑应力在 1946 Mw 8.2、1948 Mw 7.2、2020 年 Mw 7.8 地震在 -1.1 到 0.1 bar 的范围内，这表明仅由先前的主震引起的同震库仑应力变化不是这些主震的原因。其他因素，如震后粘弹性松弛、后滑和慢滑，可能有助于促进它们的发生。