Moment Tensor Inversion for Nuclear Explosions: What Can We Learn from the 6 January and 9 September 2016 Nuclear Tests, North Korea?
Moment Tensor Inversion for Nuclear Explosions: What Can We Learn from the 6 January and 9 September 2016 Nuclear Tests, North Korea?
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DOI：
10.1785/0220160139
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发表时间：
2017-03
影响因子：
3.3
通讯作者：
S. Cesca;S. Heimann;M. Kriegerowski;J. Saul;T. Dahm
中科院分区：
文献类型：
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作者：
S. Cesca;S. Heimann;M. Kriegerowski;J. Saul;T. Dahm
2016年1月和9月，朝鲜民主主义人民共和国进行了两次核爆炸。震中位于2006年、2009年和2013年之前的爆炸附近。我们对2016年的地震事件进行了地震学分析，结合了区域距离的全波形分析和远震距离的地震阵列波束分析。我们估计最相关的源参数，如源深度、矩释放和全矩张量（MT）。最佳的MT解决方案可以分解为与爆炸直接相关的各向同性震源和一个额外的偏差项，可能是由于与地形和/或地下设施特征的近源相互作用。我们还进行了精确的分辨率测试，以评估源参数的不确定性和权衡。这一分析揭示了以往浅层爆炸源研究中震源参数不一致的问题。真实MT的分辨率受到强源参数权衡的阻碍，因此可以找到广泛的拟合MT解，从主要的正各向同性项到主要的负垂直补偿线性矢量偶极子。真正的机制可以通过在远震距离上对地震阵列的首次运动极性进行额外建模来区分。对2016年爆炸与早期核试验的比较评估记录了相似的垂直波形，但2016年爆炸的振幅显著增加，这证明2016年9月9日是朝鲜有史以来进行的最大核爆炸，震级为4.9级，浅层深度不到2公里，尽管没有证据表明发生了核聚变爆炸。对横向分量波形的建模表明，2009年、2013年和2016年震源的双偶分量的大小和方向是可变的。
ABSTRACT Two nuclear explosions were carried out by the Democratic People’s Republic of North Korea in January and September 2016. Epicenters were located close to those of the 2006, 2009, and 2013 previous explosions. We perform a seismological analysis of the 2016 events combining the analysis of full waveforms at regional distances and seismic array beams at teleseismic distances. We estimate the most relevant source parameters, such as source depth, moment release, and full moment tensor (MT). The best MT solution can be decomposed into an isotropic source, directly related with the explosion and an additional deviatoric term, likely due to near‐source interactions with topographic and/or underground facilities features. We additionally perform an accurate resolution test to assess source parameters uncertainties and trade‐offs. This analysis sheds light on source parameters inconsistencies among studies on previous shallow explosive sources. The resolution of the true MT is hindered by strong source parameters trade‐offs, so that a broad range of well‐fitting MT solutions can be found, spanning from a dominant positive isotropic term to a dominant negative vertical compensated linear vector dipole. The true mechanism can be discriminated by additionally modeling first‐motion polarities at seismic arrays at teleseismic distances. A comparative assessment of the 2016 explosion with earlier nuclear tests documents similar vertical waveforms but a significant increase of amplitude for the 2016 explosions, which proves that the 9 September 2016 was the largest nuclear explosion ever performed in North Korea with a magnitude M w 4.9 and a shallow depth of less than 2 km, although there are no proofs of a fusion explosion. Modeling transversal component waveforms suggests variable size and orientation of the double‐couple components of the 2009, 2013, and 2016 sources.