Yield Estimates for the Six North Korean Nuclear Tests From Teleseismic P Wave Modeling and Intercorrelation of P and Pn Recordings
Yield Estimates for the Six North Korean Nuclear Tests From Teleseismic P Wave Modeling and Intercorrelation of P and Pn Recordings
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DOI：
10.1029/2019jb017418
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发表时间：
2019-05
期刊：
影响因子：
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通讯作者：
D. Voytan;T. Lay;E. Chaves;J. Ohman
中科院分区：
文献类型：
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作者：
D. Voytan;T. Lay;E. Chaves;J. Ohman
使用高频远震 P 波振幅模型以及短周期远震 P 波和区域 Pn 信号的波形均衡来估算朝鲜试验场已宣布的六次地下核试验的当量。每个事件的高频 (>4 Hz) 滤波 P 波位移的第一个周期的平均振幅，根据相对于 2017 年 9 月 3 日事件的台站采样进行调整，使用花岗岩的 Mueller-Murphy 爆炸源模型和 t* = 0.78 ± 0.03 s 的恒定 Q 衰减算子进行建模。产量估计范围为 2.6 至 230 吨。互相关是一种波形均衡程序，可解释事件之间的源函数和深度相位变化，适用于大量滤波（>0.8 Hz）远震 P 和区域 Pn 地震图。通过对两个事件的产量和埋深进行搜索，可以通过多个站点的同步波形均衡来提供最佳参数。根据源地形中的估计位置（假定坡度为 4%），对所有事件使用 430 至 710 m 的指定埋藏深度，并考虑到因风化、岩石分层和损坏区域而导致源区速度降低，得出的产量估计范围为 1.4 至 250 kt。 MDJ 台站 Pn 相的预测谱比与观测谱比的比较表明，这些源模型是合理的。使用互相关 WIC 的首选产量估计，确定了朝鲜试验场的产量校准关系 mbNEIC = 0.9 log10WIC + 4.13。
The yields of the six declared underground nuclear tests at the North Korean test site are estimated using high‐frequency teleseismic P wave amplitude modeling and waveform equalization of short‐period teleseismic P waves and regional Pn signals. Average amplitudes of the first cycle of high‐frequency (>4 Hz) filtered P wave displacements for each event, adjusted for station sampling relative to the 3 September 2017 event, are modeled using Mueller‐Murphy explosion source models for granite and a constant‐Q attenuation operator with t* = 0.78 ± 0.03 s. The yield estimates range from 2.6 to 230 kt. Intercorrelation, a waveform equalization procedure that accounts for source function and depth‐phase variations between events, is applied to large sets of filtered (>0.8 Hz) teleseismic P and regional Pn seismograms. Searching over yield and burial depth for both events gives optimal parameters by simultaneous waveform equalization of multiple stations. Using specified burial depths spanning from 430 to 710 m for all events based on estimated locations in the source topography assuming tunneling with 4% grade, along with allowing for reduction in source region velocity due to weathering, rock layering, and damage zones, gives yield estimates ranging from 1.4 to 250 kt. Comparison of predicted and observed spectral ratios of Pn phases at station MDJ establishes that these source models are reasonable. Using the preferred yield estimates from intercorrelation, WIC, a yield‐calibrated relation of mbNEIC = 0.9 log10WIC + 4.13 is determined for the North Korean test site.