Receiver Functions of Seismic Waves in Layered Anisotropic Media: Application to the Estimate of Seismic Anisotropy
Receiver Functions of Seismic Waves in Layered Anisotropic Media: Application to the Estimate of Seismic Anisotropy
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DOI：
10.1785/0120080130
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发表时间：
2008-12
影响因子：
3
通讯作者：
M. Nagaya;H. Oda;Hirokazu Akazawa;M. Ishise
中科院分区：
文献类型：
--
作者：
M. Nagaya;H. Oda;Hirokazu Akazawa;M. Ishise
摘要本文研究了地震各向异性对P波接收函数的影响，计算了P波入射到六边形对称多层各向异性结构上的合成地震图。受各向异性影响的接收函数的主要特征是：（1）地震能量在径向和横向接收函数上的出现;（2）接收函数上的P -到- S（Ps）转换波形随射线后方位角的增加而发生系统性变化;另一个重要的影响是剪切波分裂的PS转换波和其他后期阶段混响的S波。通过使用合成接收函数的数值实验，我们证明了波形互相关分析适用于分裂接收函数上的Ps相位来估计层结构的地震各向异性。利用Ps相位的优点是（1）它们在接收器函数上比在地震图上更清楚地出现，（2）它们告诉我们地震射线路径沿着的什么地方是各向异性的。剪切波分裂的真实的分析是执行莫霍面产生的Ps相位，在日本西南部的中国区的6个地震台站的接收功能上确定。分裂Ps相位的两个到达之间的时间延迟估计为0.2-0.7秒，并且快到达分量的极化方向是从北-南到东北-西南。这一结果与最近的剪切波分裂测量结果以及中国地区地壳地震和活动断层走向的线性震中分布趋势一致。
Abstract We investigate the effect of seismic anisotropy on P -wave receiver functions, calculating synthetic seismograms for P -wave incidence on multilayered anisotropic structure with hexagonal symmetry. The main characteristics of the receiver functions affected by the anisotropy are summarized as (1) appearance of seismic energy on radial and transverse receiver functions, (2) systematic change of P -to- S ( Ps ) converted waveforms on receiver functions as ray back-azimuth increases, and (3) reversal of the Ps -phase polarity on the radial receiver function in a range of the back azimuth. Another important influence is shear-wave splitting of the Ps -converted waves and other later phases reverberated as S wave. By numerical experiments using synthetic receiver functions, we demonstrate that the waveform cross-correlation analysis is applicable to splitting Ps phases on receiver functions to estimate the seismic anisotropy of layer structure. Advantages to utilizing the Ps phases are (1) they appear more clearly on receiver functions than on seismograms and (2) they inform us about what place along the seismic ray path is anisotropic. Real analysis of shear-wave splitting is executed to the Moho-generated Ps phases that are identified on receiver functions at six seismic stations in the Chugoku district, southwest Japan. The time lags between the two arrivals of the split Ps phases are estimated at 0.2–0.7 sec, and the polarization directions of the fast arrival components are from north–south to northeast–southwest. This result is consistent with recent results of shear-wave splitting measurements and the trend of linear epicenter distributions of crustal earthquakes and active fault strikes in the Chugoku district.