Source scaling of Pn and Lg spectra and their ratios from explosions in central Asia: Implications for the identification of small seismic events at regional distances
Source scaling of Pn and Lg spectra and their ratios from explosions in central Asia: Implications for the identification of small seismic events at regional distances
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DOI：
10.1029/2001jb000509
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发表时间：
2002-07
影响因子：
--
通讯作者：
Jiakang Xie
中科院分区：
文献类型：
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作者：
Jiakang Xie
[1]利用中亚地区mb = 6.6的核爆炸和几次mb ≤ 3.7的化学爆炸的多站Pn和Lg谱记录，反演震源地震矩（M0）、拐角频率（fc）和路径变量Q模型。一个修改的Mueller-Murphy源模型很好地拟合了核爆炸，并合理地拟合了化学爆炸，尽管来自化学爆炸的Pn被事件变量光谱波动所复杂化。新的源谱标度是针对地下爆炸导出的，范围在3.7 ~ 6.6毫巴之间;它们保留了以前标度的特征，例如：（1）PnM 0大于LgM 0，（2）fc和M0之间的四分之一根标度，（3）Pnfc比Lgfc高1.4倍。缩放的一个必要的和重要的后果是，Pn/Lg的频谱比迅速增长之间的fc的Pn和Lg的中间频率范围。由于fc的规模与事件的大小，这个频率范围转移更高的较小的事件。这种大小依赖性直接证实了从上述爆炸观察到的Pn/Lg比。这一点也可以通过在WMQ站使用许多mb-106和mb-105苏联爆炸观测到的Pn/Lg比值得到证实。提出了一个程序，然后占的Pn/Lg比值的大小依赖性的爆炸识别。
[1] Multiple station recordings of Pn and Lg spectra from an mb = 6.6 nuclear explosion and several mb ≤ 3.7 chemical explosions in central Asia are used to invert for source seismic moments (M0), corner frequencies (fc), and path-variable Q models. A modified Mueller-Murphy source model fits the nuclear explosion well and fits the chemical explosions reasonably well, although Pn from chemical explosions are complicated by event-variable spectral fluctuations. New source spectral scalings are derived for underground explosions in a wide mb range between ∼3.7 and 6.6; they preserve features of the previous scalings, such as (1) larger PnM0 than LgM0, (2) quarter-root scaling between fc and M0, and (3) higher Pnfc than Lgfc by factors of ∼4. A necessary and important consequence of the scalings is that the Pn/Lg spectral ratio grows rapidly in an intermediate frequency range between the fc of Pn and Lg. Since fc scales with event size, this frequency range shifts higher for smaller events. This magnitude dependence is directly confirmed using observed Pn/Lg ratios from the above explosions. It is also confirmed using Pn/Lg ratios observed at station WMQ using many mb ∼ 6 and mb ∼ 5 Soviet explosions. A procedure is proposed to account for then magnitude dependence of Pn/Lg ratios in the explosion identification.