Stress drop, while difficult to measure reliably and at scale, is a key source parameter for understanding the earthquake rupture process and its relationship to strong ground motion. Here, we use a P‐wave spectral decomposition approach, designed for large and densely sampled datasets, to measure earthquake stress drop in the region surrounding the 2019 Ridgecrest, California, earthquake sequence. With more than 11,000 measurements of earthquake stress drop in the 20‐yr time period from 2000 through 2019, this dataset provides an opportunity to understand how coseismic stress changes and how other geophysical factors relate to the distribution of stress drop and its evolution in space and time. We observe a mild but persistent deviation from self‐similar scaling, with larger events having systematically higher stress drops, though this trend depends on the assumption of an omega‐square source spectral model. Earthquake stress drop increases with hypocentral depth in this study region, and the Ridgecrest aftershocks tend to have higher stress drops than the pre‐event seismicity. This is in part due to their deeper hypocenters. Coherent spatial patterns of stress drop in the aftershock sequence correlate with the slip distribution of the M 7.1 mainshock, whose northwest rupture tip terminated in a long‐lived zone of enervated stress drop. Although physical interpretation of these results is complicated by the trade‐offs between the timing, depth, and location of these earthquakes, the observations provide new insight into the physics of the earthquake source in an area of renewed seismic activity in southern California.

中文翻译：

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2019年加利福尼亚里奇克莱斯特地震序列的应力降和震源尺度

应力下降虽然难以可靠地进行大规模测量，但却是了解地震破裂过程及其与强地面运动的关系的关键参数。在这里，我们使用专为大型且密集采样的数据集设计的P波频谱分解方法来测量加利福尼亚州2019 Ridgecrest地震序列周围区域的地震应力下降。从2000年到2019年的20年时间内，地震应力下降的测量值超过11,000次，该数据集提供了一个机会，可以了解同震应力如何变化以及其他地球物理因素如何与应力下降的分布及其在空间和空间中的演化有关。时间。我们观察到与自相似缩放有轻微但持续的偏差，较大的事件会系统地产生较高的应力下降，尽管这种趋势取决于欧米茄方波谱模型的假设。在该研究区域中，地震应力下降随震源深度的增加而增加，并且Ridgecrest余震的应力下降往往比事前地震活动性更高。部分原因是由于它们的震源更深。余震序列中应力降的连贯空间模式与M 7.1主震的滑动分布有关，后者的西北破裂尖端终止于长效应力降区域。尽管对这些结果的物理解释由于这些地震的时间，深度和位置之间的权衡而变得复杂，但这些观察结果为加利福尼亚南部重新发生地震活动的地区的震源物理学提供了新的见识。