Mantle seismic anisotropy beneath NE China and implications for the lithospheric delamination hypothesis beneath the southern Great Xing'an range
Mantle seismic anisotropy beneath NE China and implications for the lithospheric delamination hypothesis beneath the southern Great Xing'an range
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DOI：
10.1016/j.epsl.2017.04.030
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发表时间：
2017-08
影响因子：
5.3
通讯作者：
Haichao Chen;F. Niu;M. Obayashi;S. Grand;H. Kawakatsu;Y. Chen;J. Ning;S. Tanaka
中科院分区：
文献类型：
--
作者：
Haichao Chen;F. Niu;M. Obayashi;S. Grand;H. Kawakatsu;Y. Chen;J. Ning;S. Tanaka
我们测量了中国东北部跨大陆 NECESSArray 记录的 SKS 数据中的剪切波分裂，以限制该地区下方的岩石圈变形和岩石圈下流动。我们从 2009 年 1 月 9 日至 2011 年 8 月 31 日期间发生的 125 个宽带站记录的 32 次远震地震中选择了数百个高质量的 SKS/SKKS 波形。这些站覆盖了多种构造地体，包括东部的松辽盆地、长白山山脉和张关才山脉，西部的大兴安岭和西南部的燕山造山带。我们假设每个站都由单个各向异性层覆盖，并采用信噪比 (SNR) 加权多事件叠加方法来估计两个分裂参数（快速偏振方向 和延迟时间 δt），从而为每个站记录的所有 SKS/SKKS 波形提供最佳拟合。总体而言，测得的快偏振方向大致沿NW-SE方向，与绝对板块运动方向有显着差异，但与区域伸展方向大致一致。这表明岩石圈变形可能是观测到的地震各向异性的一般原因。最复杂的各向异性结构出现在大兴安岭南部和松辽盆地西南部的地下。观察到的分裂参数的巨大变化和该区域的地震层析图像与该区域下方正在进行的岩石圈分层一致。
We measured shear wave splitting from SKS data recorded by the transcontinental NECESSArray in NE China to constrain lithosphere deformation and sublithospheric flows beneath the area. We selected several hundreds of high quality SKS/SKKS waveforms from 32 teleseismic earthquakes occurring between 09/01/2009 and 08/31/2011 recorded by 125 broadband stations. These stations cover a variety of tectonic terranes, including the Songliao basin, the Changbaishan mountain range and Zhangguancai range in the east, the Great Xing'an range in the west and the Yanshan orogenic belt in the southwest. We assumed each station is underlaid by a single anisotropic layer and employed a signal-to-noise ratio (SNR) weighted multi-event stacking method to estimate the two splitting parameters (the fast polarization directionφ, and delay time,δt) that gives the best fit to all the SKS/SKKS waveforms recorded at each station. Overall, the measured fast polarization direction lies more or less along the NW–SE direction, which significantly differs from the absolute plate motion direction, but is roughly consistent with the regional extension direction. This suggests that lithosphere deformation is likely the general cause of the observed seismic anisotropy. The most complicated anisotropic structure is observed beneath the southern Great Xing'an range and southwest Songliao basin. The observed large variations in splitting parameters and the seismic tomographic images of the area are consistent with ongoing lithospheric delamination beneath this region.