Mapping shallow heterogeneity with teleseismic P to Rg scattered waves
Mapping shallow heterogeneity with teleseismic P to Rg scattered waves
复制标题
利用远震 P 到 Rg 散射波绘制浅层非均质性
DOI：
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发表时间：
1996
期刊：
影响因子：
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通讯作者：
Hal Mendoza
中科院分区：
文献类型：
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作者：
J. Revenaugh;Hal Mendoza
本文利用南加州地震台网的9000多条短周期P波尾波记录，绘制了P波到Rg波散射强度和散射Rg波群速度的横向变化图。基于Revenaugh（1995 a）的结果，我们使用散射强度和地形粗糙度的相关性作为模型拟合的指标，以估计0和3 Hz之间的五个频带上的群速度色散。Rg群速度显示正常色散，从0到0.6 Hz频率的2.7 ± 0.3 km/sec降低到2.0到3.0 Hz频段的2.2 ± 0.4 km/sec。横向不均匀性是通过假设Rg速度是局部地形粗糙度的函数来引入的。网格搜索/迁移分析得出"平滑"和"粗糙"地形的群速度分别为2.2和2.85公里/秒，区分"平滑"和"粗糙"地形的当地标准差的阈值为150米。散射强度图近似于整个南加州的地形粗糙度，这意味着南极P波尾波持续时间和相对振幅水平强烈依赖于近地表（<3 km）地质。
Over 9000 records of teleseismic P-wave coda from the Southern California Seismic Network are used to map lateral variations in P to Rg scattering strength and the group velocity of scattered Rg. Building on the results of Revenaugh (1995a), we use the correlation of scattering strength and topographic roughness as an indicator of model fit to estimate group-velocity dispersion over five frequency bands between 0 and 3 Hz. Rg group velocity displays normal dispersion, decreasing from 2.7 ± 0.3 km/sec for frequencies between 0 and 0.6 Hz to a low of 2.2 ± 0.4 km/sec for the 2.0 to 3.0 Hz band. Lateral heterogeneity is introduced by assuming Rg velocity is a function of local topographic roughness. Grid-search/migration analysis yields group velocities of 2.2 and 2.85 km/sec for “smooth” and “rough” terrain, respectively, and a 150-m threshold for the local standard deviation of topography distinguishing “smooth” from “rough”. The map of scattering strength approximates topographic roughness throughout southern California, implying that teleseismic P-wave coda duration and relative amplitude level depend strongly on near-surface (<3 km) geology.