A series of four chemical explosions were detonated in a deep borehole within the Yucca Flat Dry Alluvium Geology (DAG) at the Nevada National Security Site between 2018 and 2019. The two larger chemical explosions of 50 tons (DAG‐2) and 10 tons (DAG‐4) TNT equivalent yield triggered energetic aftershock sequences numbering 1392 and 347 microearthquakes, respectively, within the first 10 days. No significant aftershock activity was observed for the two smaller 1‐ton explosions (DAG‐1 and DAG‐3). We used a back‐projection method based on travel‐time migration and stacking of signal‐to‐noise ratio traces to detect, associate and locate aftershocks from a subset of 22‐geophones within a larger 2  2 km seismic array surrounding the borehole. The aftershocks located within 300 m of the borehole and the depths were above the working points of 300 and 50 m depths of DAG‐2 and DAG‐4, respectively, ruling out triggering slip on geologic faults or disturbances beneath neighboring collapse craters. DAG‐2 and DAG‐4 aftershocks decayed at similar rates, with power‐law exponents of p = 1.48 and p = 1.49, respectively. These decay rates are comparable to aftershocks sequences triggered by earthquakes and historical nuclear explosions at Yucca Flat. A smooth power‐law aftershock decay within the first 10 days suggests a triggering mechanism from explosion generated stress relaxation due to the diffusion of high gas pressures in the cavity and radial fractures. A more random and episodic aftershock rate would be expected due to cavity collapse or falling rubble in chimney formation.

中文翻译：

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利用反投影法初步分析源物理实验爆炸触发的微地震

在2018年至2019年之间，在内华达国家安全站点的丝兰平板干冲积地质（DAG）内的一个深孔中，发生了一系列的四次化学爆炸。两次较大的化学爆炸分别为50吨（DAG-2）和10吨（ DAG-4）TNT等效产量在头10天内分别触发了编号分别为1392和347微地震的高余震序列。对于两个较小的1吨级爆炸（DAG-1和DAG-3），未观察到明显的余震活动。我们使用了基于行进时间迁移和信噪比迹线叠加的反投影方法，以检测，关联和定位较大的2部22部检波器中的余震。  围绕井眼的2 km地震阵列。位于井眼300 m之内的余震深度分别在DAG-2和DAG-4深度分别为300和50 m的工作点之上，排除了在邻近断陷坑下方的地质断层或扰动引起的滑动。DAG-2和DAG-4余震以相似的速率衰减，幂律指数为p  = 1.48和p 分别为1.49。这些衰减率可与由丝兰地带地震和历史核爆炸引发的余震序列相媲美。在开始的10天内，平稳的幂律余震衰减表明，由于高气压在型腔中的扩散和径向裂缝，爆炸产生的应力松弛引起了触发机制。由于空腔坍塌或烟囱形成中的碎石掉落，预计会有更大的随机余震发生率。