Upper-Crustal Seismic Anisotropy in the Cantabrian Mountains (North Spain) from Shear-Wave Splitting and Ambient Noise Interferometry Analysis
Upper-Crustal Seismic Anisotropy in the Cantabrian Mountains (North Spain) from Shear-Wave Splitting and Ambient Noise Interferometry Analysis
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通过剪切波分裂和环境噪声干涉测量分析坎塔布连山脉（西班牙北部）的上地壳地震各向异性
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发表时间：
2020
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通讯作者：
J. Olona
中科院分区：
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作者：
J. Acevedo;G. Fernández‐Viejo;S. Llana;C. López;J. Olona
采用两种独立但互补的方法(a)剪切波分裂法和(b)环境地震噪声干涉测量法研究了坎塔布连山脉（西班牙北部）的地壳上各向异性。为此，我们对两个不同尺度和记录周期的地震台网的地震数据进行了处理和比较。剪切波分裂结果显示，延迟时间在0.06 ~ 0.23 s之间，且快速极化方向在空间上是可变的。我们计算出各向异性层的最大有效厚度约为7.5 km，平均各向异性幅度在4% ~ 8%之间。与此一致的是，我们的环境噪声观测表明，在地壳的前10公里处，各向异性的幅度在4%到9%之间。结果表明，两种方法的快速方向与局部断层方向有明显的相关性，表明各向异性主要受构造控制。在研究区西部，快速极化方向倾向于平行于地壳中的瓦里斯坎构造，而在阿尔卑斯印记较强的东部，许多快速极化方向平行于东西走向的阿尔卑斯构造。
The upper-crustal anisotropy of the Cantabrian Mountains (North Spain) has been investigated using two independent but complementary methodologies: (a) shear-wave splitting and (b) ambient seismic noise interferometry. For this purpose, we have processed and compared seismic data from two networks with different scales and recording periods. The shear-wave splitting results show delay times between 0.06 and 0.23 s and spatially variable fast-polarization directions. We calculate that the anisotropic layer has a maximum effective thickness of around 7.5 km and an average anisotropy magnitude of between 4% and 8%. Consistently, our ambient noise observations point to an anisotropy magnitude between 4% and 9% in the first 10 km of the crust. Our results show a clear correlation between the fast directions from both methods and the orientations of the local faults, suggesting that the anisotropy is mainly controlled by the structures. Furthermore, in the west of the study area, fast-polarization directions tend to align parallel to the Variscan fabric in the crust, whereas to the east, in which the Alpine imprint is stronger, many fast directions are aligned parallel to east–west-oriented Alpine features.