Structure-controlled seismic anisotropy along the Karadere–Düzce branch of the North Anatolian Fault revealed by shear-wave splitting tomography
Structure-controlled seismic anisotropy along the Karadere–Düzce branch of the North Anatolian Fault revealed by shear-wave splitting tomography
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DOI：
10.1016/j.epsl.2014.01.046
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发表时间：
2014-04
影响因子：
5.3
通讯作者：
Zefeng Li;Haijiang Zhang;Zhigang Peng
中科院分区：
文献类型：
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作者：
Zefeng Li;Haijiang Zhang;Zhigang Peng
我们使用Zhang等人（2007）开发的三维（3D）剪切波分裂（SWS）层析成像方法来绘制土耳其西部北安纳托利亚断层（NAF）卡拉德雷-迪兹杰分支地壳各向异性的空间分布。输入数据包含 1999 年 Mw 7.4 伊兹米特地震和 Mw 7.1 Düzce 地震 7856 次余震的 20 751 个 SWS 延迟时间测量值。结果表明，沿着 NAF 的 Karadere-Düzce 分支有一个连续的带状高度各向异性带，一般宽约 3 公里，深约 5 公里。沿着卡拉德雷段观察到的各向异性的不对称模式与伊兹米特破裂单侧向东传播的不对称损害是一致的。在伊兹米特断裂带末端附近发现了另一个强各向异性区域，靠近随后迪兹杰地震中断裂的断层段的倾斜方向。这些结果与前人研究推断的浅层断裂带各向异性基本一致。虽然各向异性通常在深度和/或断层带外部变弱，但我们还确定了几个深达 10 公里的高度各向异性区域，主要在 Almacik 地块内。这些孤立的各向异性区域可以通过具有不同矿物排列的单个侵入火成岩体来解释。总体而言，NAF 卡拉德雷-迪兹杰分支上地壳的地震各向异性受到构造控制。
We use a three-dimensional (3D) shear-wave splitting (SWS) tomography method developed by Zhang et al.(2007) to map the spatial distribution of crustal anisotropy in the Karadere–Düzce branch of the North Anatolian Fault (NAF) in western Turkey. The input data consists of 20 751 measurements of the SWS delay times from 7856 aftershocks of the 1999 Mw 7.4 İzmit and Mw 7.1 Düzce earthquakes. The results show a continuous belt-like highly anisotropic zone along the Karadere-Düzce branch of NAF, generally∼ 3 km wide and down to∼ 5 km deep. The observed asymmetric pattern of anisotropy along the Karadere segment is qualitatively consistent with asymmetric damages from the unilateral eastward propagation of the İzmit rupture. Another strong anisotropy region was found near the end of the İzmit rupture zone, close to the dipping direction of the fault segment that ruptured during the subsequent Düzce earthquake. These results are generally consistent with the shallow fault-zone anisotropy inferred from previous studies. While the anisotropy generally becomes weaker at depth and/or outside the fault zone, we also identify several highly anisotropic regions as deep as∼ 10 km, primarily within the Almacik block. These isolated anisotropy regions could be explained by individual intrusive igneous rock bodies with different mineral alignment. Overall, seismic anisotropy in upper crust of the Karadere-Düzce branch of the NAF is structurally controlled.