Crustal anisotropy in southwest Ireland from analysis of controlled source shear-wave data
Crustal anisotropy in southwest Ireland from analysis of controlled source shear-wave data
复制标题
DOI：
10.1016/j.tecto.2009.04.029
复制
发表时间：
2009-09
期刊：
影响因子：
2.9
通讯作者：
P. Readman;F. Hauser;B. O'reilly;V. Do
中科院分区：
文献类型：
--
作者：
P. Readman;F. Hauser;B. O'reilly;V. Do
本文利用可控震源地震实验中记录在爱尔兰西南部的三分量剪切波（S波）资料的走时分析结果，研究了地壳各向异性的大小。所使用的数据是从三分量短周期台站的20次在线拍摄中记录的，这些台站沿两个平行剖面沿着以约1公里的间距部署。使用在地球表面附近（Sg）和从莫霍面（SmS）反射的地震相位，对记录在垂直、径向和横向地震仪组件上的垂直和水平极化S波之间的走时差进行了分析。两个相位的分量之间的走时差基本上在±0.2 s的范围内，这是测量的不确定性，没有观察到随炮点接收器偏移的相干变化。还根据上地壳和下地壳各向异性程度不同的一维S波速度模型计算了合成S波地震图。Sg和SmS相位的走时差从这些合成地震记录中提取，证实对于在上地壳或下地壳中具有1-2%的可能对称性的各向异性，应导致横向和径向以及横向和垂直分量之间的走时差随源-接收器偏移的可观察变化。研究表明，地壳各向异性并没有显着的贡献显着的各向异性最近推导出的SKS和SKKS测量在爱尔兰，因此，证实居住在亚地壳和更深的地幔水平。
Results from a travel-time analysis of three-component shear-wave (S-wave) data recorded in southwest Ireland during a controlled source seismic experiment have been used to investigate the magnitude of crustal anisotropy. The data used were recorded from 20 in-line shots on three-component short-period stations deployed at approximately 1-km spacing along two parallel profiles. Analysis of the travel-time differences between vertically and horizontally polarised S-waves recorded on vertical, radial and transverse seismometer components was undertaken using seismic phases travelling near the Earth's surface (Sg) and reflected from the Moho (SmS). Travel-time differences between the components for both phases scatter largely within the range ±0.2 s, which is about the uncertainty in the measurements, with no observed coherent variation with shot-receiver offset. Synthetic S-wave seismograms were also computed from 1-D S-wave velocity models with varying degrees of anisotropy in the upper and in the lower crusts. Travel-time differences of Sgand SmS phases picked from these synthetic seismograms confirm that for anisotropies with probable symmetries of magnitude 1–2% in either the upper or lower crust should result in an observable variation of the travel-time differences between the transverse and radial, and transverse and vertical components with source–receiver offset. The study shows that crustal anisotropy does not contribute significantly to the marked anisotropy recently deduced from SKS and SKKS measurements in Ireland, which is therefore confirmed to reside at sub-crustal and deeper mantle levels.