Seismologists distinguish underground nuclear explosions from more commonly occurring earthquakes using moment tensor inversion, high‐frequency P/S amplitude ratios, mb:Ms comparisons, and P‐pP differential travel times. These methods are generally successful for large seismic events (⁠M>3–4⁠) well recorded at regional‐to‐teleseismic distances (⁠>150 km⁠); however, it is unclear whether they can be modified to work for small events (⁠M<3⁠) well recorded only at local distances (⁠<150 km⁠). Here, we evaluate a recently proposed, local‐distance seismic source discriminant—the difference between local magnitude (⁠ML⁠) and coda duration magnitude (⁠MC⁠)—using seismograms of earthquakes and buried, single‐fired chemical explosions recorded in three regions of the western United States. The quantity ML–MC was previously found to be sensitive to source depth, effectively discriminating mine blasts, induced earthquakes, and very shallow tectonic earthquakes from deeper crustal earthquakes. In this study, we report the first evaluation of ML–MC as a depth discriminant using data from buried, single‐fired explosions that, unlike the seismic sources studied earlier, are good analogs for underground nuclear explosions. We find that even when using generic, uncalibrated methods of assigning magnitudes, ML–MC separates single‐fired explosions and earthquakes. The area under the receiver operating characteristic curve is 0.92 for 19 explosions and 14 earthquakes in Washington, 0.90 for 22 explosions and 90 earthquakes in Wyoming, and 0.99 for three explosions and 149 earthquakes in Nevada. ML:MC comparisons have the potential to enhance discrimination based on high‐frequency P/S amplitudes ratios—which perform less well at local than regional distances—because the two metrics have complementary sensitivities.

中文翻译：

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从局部震级（ML）和尾气持续时间震级（MC）的比较中区分美国西部局部地震（<150 km）的小地震和地下单发化学爆炸

地震学家使用矩张量反演，高频P / S振幅比，mb：Ms比较和P-pP差动传播时间来区分地下核爆炸与更常见的地震。这些方法通常适用于在区域到远程地震距离（⁠> 150km⁠）上记录良好的大型地震事件（⁠M> 3-4）。但是，尚不清楚是否可以修改它们以仅在本地距离（⁠<150km⁠）上记录良好的小事件（M <3⁠）工作。在这里，我们使用记录在三个区域中的地震和地下单发化学爆炸的地震图，评估了最近提出的局部距离地震源判别式-局部震级（⁠ML⁠）和尾声持续时间震级（⁠MC⁠）之间的差异。美国西部的地区。以前发现ML-MC数量对震源深度敏感，可以有效地区分地雷爆炸，诱发地震和较浅的地壳地震与较深的地壳地震。在这项研究中，我们报告了使用埋藏式单发爆炸的数据对ML-MC作为深度判别式的首次评估，该数据与之前研究的地震源不同，是地下核爆炸的良好类似物。我们发现，即使使用通用的，未经校准的量级分配方法，ML-MC也可以将单发爆炸和地震分开。接收器工作特性曲线下的面积在华盛顿州的19次爆炸和14次地震中为0.92，在怀俄明州的22次爆炸和90次地震中为0.90，在内华达州三次爆炸和149次地震中为0.99。ML：