Seismic Anisotropy from SKS Splitting beneath Northeastern Tibet
Seismic Anisotropy from SKS Splitting beneath Northeastern Tibet
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DOI：
10.1785/0120130054
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发表时间：
2013-12
影响因子：
3
通讯作者：
T. Eken;F. Tilmann;J. Mechie;Wenjin Zhao;R. Kind;H. Su;G. Xue;M. Karplus
中科院分区：
文献类型：
--
作者：
T. Eken;F. Tilmann;J. Mechie;Wenjin Zhao;R. Kind;H. Su;G. Xue;M. Karplus
青藏高原东北部边界具有2km的地形落差和地壳厚度的快速变化。地表构造以昆仑走向为主？滑动断裂系统和邻近的昆仑隐伏逆冲断层。目前研究的主要目的是绘制该地区沿着INDEPTH IV线性阵列的地震各向异性参数的横向变化图，以研究地壳和地幔结构背景下地表和内部变形之间的联系。为了实现这一目标，我们进行了最小？横向？基于能量的SKS分裂测量，使用INDEPTH IV阵列的23个站，部署在西藏东北边缘。平均快极化方向和分裂时间延迟的平均堆叠失配面的所有分析的事件在每个站。快速方向与主要主动罢工的罢工协议？滑动断层和走向？滑动震源机制，但不与化石结构，如金沙缝合线，意味着各向异性记录岩石圈岩石组构形成的岩石圈内最近的变形，而不是代表冻结？在各向异性或剪切软流圈由于绝对板块运动。分布在整个北方高原的大分裂延迟表明，变形分布，而不是集中在狭窄的剪切带与昆仑罢工？滑动断层因此，朝向柴达木的分裂延迟的下降是那里变形程度低得多的自然结果。
The northeastern boundary of the Tibetan high plateau is marked by a 2 km topographic drop and a coincident rapid change in crustal thickness. Surface tectonics are dominated by the Kunlun strike?slip fault system and adjacent Kunlun concealed thrust. The main objective of the current study is to map lateral variations of seismic anisotropy parameters in this region along the linear INDEPTH IV array in order to investigate the link between surface and internal deformation in the context of crust and mantle structure. To achieve this aim, we performed Minimum?Transverse?Energy based SKS splitting measurements using 23 stations of the INDEPTH IV array deployed across the northeastern margin of Tibet. Average fast polarization directions and splitting time delays are obtained by averaging stacked misfit surfaces of all analyzed events at each station. The agreement of fast directions with the strikes of major active strike?slip faults and strike?slip focal mechanisms, but not with fossil structures such as the Jinsha suture, implies that the anisotropy records lithospheric petrofabric formed by recent deformation within the lithosphere rather than representing frozen?in anisotropy or shear within the asthenosphere due to absolute plate motion. The distribution of large splitting delays throughout the northern plateau suggests that deformation is distributed rather than focused onto narrow shear zones associated with the Kunlun strike?slip faults. The drop in splitting delays toward the Qaidam is then a natural consequence of the much lower degree of deformation there.