The July 2019 Mw 6.4 and 7.1 Ridgecrest earthquakes triggered numerous aftershocks, including clusters of off‐fault aftershocks in an extensional stepover of the Garlock fault, near the town of Olancha, and near Panamint Valley. The locations of the off‐fault aftershocks are consistent with the stress‐similarity model of triggering, which hypothesizes that aftershocks preferentially occur in areas where the mainshock static stress change tensor is similar in orientation to the background stress tensor. The background stress field is determined from the inversion of earthquake focal mechanisms, with the spatial resolution adapted to the local density of earthquakes. The mainshock static stress change is computed using finite‐source models for the Mw 6.4 foreshock and Mw 7.1 mainshock. I quantify the similarity between these two stress fields using the tensor dot product of the normalized deviatoric stress tensors. The off‐fault aftershocks in the Garlock stepover and the Olancha area fall within lobes of positive stress similarity, whereas the aftershocks near Panamint Valley are partially within a lobe. The cluster in the Garlock fault stepover and the smaller of two clusters near Olancha occur in regions of locally anomalous background stress that results in higher stress similarity. I compute the spatial density of M≥2.0 aftershocks and find that the aftershock density increases as a function of stress similarity, with a factor of ∼15 difference between high stress‐similarity and low stress‐similarity areas. This result is robust with respect to the choice of mainshock model and the uncertainty of the background stress field. The aftershock density varies substantially inside the high stress‐similarity lobes, however, indicating that other variable background conditions, such as material properties, temperature, and fluid pressure, may also be playing a role. Specifically, temperature and fluid pressure conditions might help explain the low rate of aftershocks in the Coso geothermal field.

中文翻译：

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里奇克莱斯特6.4级和7.1级地震余震的应力相似触发模型

2019年7月的里奇克莱斯特6.4级和7.1级地震引发了无数余震，包括在奥兰查镇附近和Panamint山谷附近的加洛克断层延伸段中形成的断层余震群。断层余震的位置与触发的应力相似模型一致，该模型假设余震优先发生在主震静应力变化张量与背景应力张量方向相似的区域。背景应力场是根据地震震源机制的反演确定的，其空间分辨率适合于地震的局部密度。主震静应力变化是使用Mw 6.4前震和Mw 7.1主震的有限源模型计算的。我使用归一化偏应力张量的张量点积来量化这两个应力场之间的相似性。加洛克（Garlock）阶跃和奥兰查（Olancha）地区的断层余震属于正应力相似波瓣，而帕纳明特山谷（Panamint Valley）附近的余震部分位于波瓣内。Garlock断层阶跃中的团簇和Olancha附近的两个团簇中的较小者出现在局部异常背景应力的区域中，从而导致更高的应力相似性。我计算了M≥2.0余震的空间密度，发现余震密度随应力相似度的增加而增加，高应力相似度区域与低应力相似度区域之间的差异约为15。对于主冲击模型的选择和背景应力场的不确定性，该结果是可靠的。余震密度在高应力相似性凸角内显着变化，但是，这表明其他可变的背景条件（例如材料特性，温度和流体压力）也可能起作用。具体来说，温度和流体压力条件可能有助于解释科索（Coso）地热田中余震发生率低的原因。