High‐Precision Relocation With the Burial Depths of the North Korean Underground Nuclear Explosions by Combining Pn and Pg Differential Traveltimes
High‐Precision Relocation With the Burial Depths of the North Korean Underground Nuclear Explosions by Combining Pn and Pg Differential Traveltimes
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DOI：
10.1029/2020jb020745
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发表时间：
2021-06
期刊：
影响因子：
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通讯作者：
G. Yang;L. Zhao;X. Xie;L. Zhang;Z. Yao
中科院分区：
文献类型：
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作者：
G. Yang;L. Zhao;X. Xie;L. Zhang;Z. Yao
在地震核监测中，准确的震源深度是可靠估计爆炸当量的重要前提。相对定位方法经常用于此目的。然而，基于区域Pn波的常规方法通常不能对震源深度给出令人满意的约束，这主要是由于埋藏深度和震源时间之间的强烈权衡。本研究探索了一种高精度的相对定位方法，通过使用下行起飞Pn波和水平起飞Pg波的差分走时来同时确定相对震中和震源高程。Pg波和Pn波的属性，包括波形之间的一致性，差分走时测量的可靠性，以及它们对震中和深度变化的敏感性，进行了研究。通过联合应用这两种类型的波形数据，所提出的方法显着增强了对源深度变化的约束。该方法应用于从中国、韩国和日本收集的区域地震数据，以确定朝鲜六次地下核爆炸的相对震中、起源时间和相对埋深。震源深度然后用于提供埋深校正，以估计爆炸当量。2006年10月、2009年5月、2013年2月、2016年1月、2016年9月和2017年9月引爆的六次朝鲜核爆炸的深度分别确定为330、540、506、468、521和570米，经埋深校正后的当量分别为1.6、5.7、13.4、分别为12.6、21.7和225.7 kt。
In seismic nuclear monitoring, an accurate source depth is an important prerequisite for reliably estimating the explosive yield. Relative location methods are often used for this purpose. However, the conventional method based on regional Pn waves usually fails to give satisfactory constraints on the source depth, mainly due to the strong trade‐off between the burial depth and origin time. This study explores a high‐precision relative location method to simultaneously determine the relative epicenter and source elevation by using differential traveltimes from both downward‐takeoff Pn waves and horizontal‐takeoff Pg waves. The properties of both Pg and Pn waves, including the consistency between waveforms, the reliability of differential traveltime measurements, and their sensitivities to epicenter and depth variations, are investigated. By jointly applying both types of waveform data, the proposed method significantly enhances the constraint on the source depth variation. This method is applied to regional seismic data collected from China, South Korea, and Japan to determine the relative epicenters, origin times and relative burial depths of six North Korean underground nuclear explosions. The source depths are then used to provide burial‐depth corrections to estimate the explosive yields. The depths of the six North Korean nuclear explosions detonated on October 2006, May 2009, February 2013, January 2016, September 2016, and September 2017 are determined to be 330, 540, 506, 468, 521, and 570 m, respectively, and their yields after burial depth corrections are 1.6, 5.7, 13.4, 12.6, 21.7, and 225.7 kt, respectively.