Seismic scattering and absorption parameters in the W-Bohemia/Vogtland region from elastic and acoustic radiative transfer theory
Seismic scattering and absorption parameters in the W-Bohemia/Vogtland region from elastic and acoustic radiative transfer theory
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DOI：
10.1093/gji/ggv393
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发表时间：
2015-12
影响因子：
2.8
通讯作者：
P. Gaebler;T. Eulenfeld;U. Wegler
中科院分区：
文献类型：
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作者：
P. Gaebler;T. Eulenfeld;U. Wegler
S U-M-M-A-R-Y估计了捷德交界处W-Bohemia/Vogtland震群震区下方地壳结构随频率变化的地震散射和本征衰减参数。用弹性和声辐射传输理论模拟了合成地震记录包络。通过将这些合成包络与来自2008年10月W-Bohemia/Vogtland震群的14个浅层局部地震的观测记录包络进行拟合，确定了散射和吸收参数。这两种不同的模拟方法对估计的地壳参数产生了相似的结果，并显示了传输平均自由程和本征吸收路径长度的相似的频率依赖关系。这两种方法都表明，在所研究的震中距离范围和3至24赫兹的频段内，W-Bohemia/Vogtland地区的本征衰减占主导地位，而散射衰减占主导地位。地震记录包络的弹性模拟表明，需要前向散射来解释数据，然而，前向散射的程度是不可解析的。与声学模拟结果相比，弹性情况下的参数估计误差较小。输运平均自由程的频率衰减表明，随机介质可用近乎指数的自相关函数来描述。随机介质的涨落强度和关联长度不能独立估计，但只能计算与介质的输运平均自由程有关的参数的组合。此外，我们的弹性模拟表明，使用我们的数值方法，不可能求出随机介质的平均自由程的值。
S U M M A R Y In this study, frequency-dependent seismic scattering and intrinsic attenuation parameters for the crustal structure beneath the W-Bohemia/Vogtland swarm earthquake region close to the border of Czech Republic and Germany are estimated. Synthetic seismogram envelopes are modelled using elastic and acoustic radiative transfer theory. Scattering and absorption parameters are determined by fitting these synthetic envelopes to observed seismogram envelopes from 14 shallow local events from the October 2008 W-Bohemia/Vogtland earthquake swarm. The two different simulation approaches yield similar results for the estimated crustal parameters and show a comparable frequency dependence of both transport mean free path and intrinsic absorption path length. Both methods suggest that intrinsic attenuation is dominant over scattering attenuation in the W-Bohemia/Vogtland region for the investigated epicentral distance range and frequency bands from 3 to 24 Hz. Elastic simulations of seismogram envelopes suggest that forward scattering is required to explain the data, however, the degree of forward scattering is not resolvable. Errors in the parameter estimation are smaller in the elastic case compared to results from the acoustic simulations. The frequency decay of the transport mean free path suggests a random medium described by a nearly exponential autocorrelation function. The fluctuation strength and correlation length of the random medium cannot be estimated independently, but only a combination of the parameters related to the transport mean free path of the medium can be computed. Furthermore, our elastic simulations show, that using our numerical method, it is not possible to resolve the value of the mean free path of the random medium.