The mb : Ms (⁠mb vs. Ms⁠) relationship is an important criterion for screening explosions from earthquakes and has been widely adopted in seismological monitoring by the Comprehensive Nuclear‐Test‐Ban Treaty Organization. In general, the earthquakes have larger Ms than the underground explosions with equivalent mb⁠. However, it has been reported that this recognition criterion failed to identify some explosions at the North Korea nuclear test site. In this study, we investigate the potential effects of secondary source components, including the compensated linear vector dipole (CLVD) and double‐couple (DC) sources, on mb and Ms magnitude measurements and the physical mechanism of the mb : Ms recognition criterion by calculating synthetic seismograms. The results show an apparent critical body‐wave magnitude of 5 when using the mb : Ms method to discriminate North Korean underground nuclear explosions. The Ms measurements decrease as the CLVD components increase, whereas the effects from the DC source can be neglected. Small events, such as the first five North Korean nuclear tests, generate weak CLVD components, leading to the failure of mb : Ms‐based discrimination, whereas the last event, with a larger magnitude, caused extensive damage and hence can be successfully discriminated. In addition, the large difference between the source spectrum of explosions and those of earthquakes might be another important factor in the successful mb : Ms‐based discrimination of the sixth North Korean nuclear test.

中文翻译：

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地下核爆炸次要来源对mb的影响：Ms判据及其对朝鲜核试验的歧视意义

mb：Ms（⁠mbvs.Ms⁠）关系是筛选地震爆炸的重要标准，并已被《全面禁止核试验条约》组织广泛用于地震监测。通常，地震的Ms大于等效于mb的地下爆炸的Ms。但是，据报道，这种识别标准未能识别出朝鲜核试验场发生的一些爆炸。在这项研究中，我们调查了次级源分量（包括补偿线性矢量偶极子（CLVD）和双耦合（DC）源）对mb和Ms幅度测量以及mb：Ms识别标准的物理机制的潜在影响。计算合成地震图。结果显示，使用mb时的明显体波临界值为5：区分朝鲜地下核爆炸的方法。Ms测量值随着CLVD分量的增加而减小，而来自直流电源的影响可以忽略不计。小事件，例如前五次朝鲜核试验，产生的CLVD分量很弱，导致基于mb：Ms的歧视失败，而最后一次事件的规模更大，造成了广泛的破坏，因此可以成功地区分。此外，爆炸和地震的震源谱之间的巨大差异可能是成功取得mb的另一个重要因素：对朝鲜第六次核试验的基于质谱的判别。小事件，例如前五次朝鲜核试验，产生的CLVD分量很弱，导致基于mb：Ms的歧视失败，而最后一次事件的规模更大，造成了广泛的破坏，因此可以成功地区分。此外，爆炸和地震的震源谱之间的巨大差异可能是成功取得mb的另一个重要因素：对朝鲜第六次核试验的基于质谱的判别。小事件，例如前五次朝鲜核试验，产生的CLVD分量很弱，导致基于mb：Ms的歧视失败，而最后一次事件的规模更大，造成了广泛的破坏，因此可以成功地区分。此外，爆炸和地震的震源谱之间的巨大差异可能是成功取得mb的另一个重要因素：对朝鲜第六次核试验的基于质谱的判别。