High-frequency seismic wave propagation within the heterogeneous crust: effects of seismic scattering and intrinsic attenuation on ground motion modelling
High-frequency seismic wave propagation within the heterogeneous crust: effects of seismic scattering and intrinsic attenuation on ground motion modelling
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DOI：
10.1093/gji/ggx269
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发表时间：
2017-09
影响因子：
2.8
通讯作者：
S. Takemura;Manabu Kobayashi;K. Yoshimoto
中科院分区：
文献类型：
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作者：
S. Takemura;Manabu Kobayashi;K. Yoshimoto
为了建立高频（bbb1hz）地震波传播的实际模型，我们利用观测到的日本西南Chugoku地区中小地壳地震的高净速度地震图，分析了P波和S波的视辐射模式和衰减。通过对比观测和模拟地震记录，我们估计了地壳小尺度速度非均质性和P波和S波固有衰减的实用参数集（QP.int−1和QS.int−1）。采用一维地壳速度结构模型，外加三维小尺度速度非均质性和本征衰减，采用有限差分法对地震波传播进行了数值模拟。估计的地壳小尺度速度非均质性具有指数型功率谱密度函数的随机特征，相关长度为1 km，均方根值为0.03。QP.int−1和QS.int−1的估计值范围分别为10−2.6 ~ 10−2.0和10−2.8 ~ 10−2.4，表明QP.int−1 > QS.int−1高频（> 1hz）。固有衰减大于散射衰减，这是由小尺度速度非均质性引起的。本研究获得的地壳参数可用于利用三维非均质结构模型进行物理模拟，以评估中地壳地震的峰值地面速度和尾包线。
S U M M A R Y For practical modelling of high-frequency (>1 Hz) seismic wave propagation, we analysed the apparent radiation patterns and attenuations of P and S waves using observed Hi-net velocity seismograms for small-to-moderate crustal earthquakes in the Chugoku region, southwestern Japan. By comparing observed and simulated seismograms, we estimated practical parameter sets of crustal small-scale velocity heterogeneity and intrinsic attenuations of P and S waves (QP.int−1 and QS.int−1). Numerical simulations of seismic wave propagation were conducted via the finite-difference method using a 1-D crustal velocity structure model with additional 3-D small-scale velocity heterogeneity and intrinsic attenuation. The estimated crustal small-scale velocity heterogeneity is stochastically characterized by an exponential-type power spectral density function with correlation length of 1 km and root-mean-square value of 0.03. Estimated QP.int−1 and QS.int−1 values range from 10−2.6 to 10−2.0 and 10−2.8 to 10−2.4, respectively, indicating QP.int−1 > QS.int−1 for high frequencies (>1 Hz). Intrinsic attenuation dominates over scattering attenuation, which is caused by small-scale velocity heterogeneity. The crustal parameters obtained in this study are useful for evaluating peak ground velocities and coda envelopes for moderate crustal earthquakes via physical-based simulations using a 3-D heterogeneous structure model.