High‐resolution imaging of lithospheric structures in northeastern Tibet by full waveform inversion of teleseismic body waves
High‐resolution imaging of lithospheric structures in northeastern Tibet by full waveform inversion of teleseismic body waves
复制标题
远震体波全波形反演对藏东北部岩石圈结构高分辨率成像
DOI：
10.1111/1755-6724.13942
复制
发表时间：
2019
期刊：
影响因子：
--
通讯作者：
R. Gao
中科院分区：
文献类型：
--
作者：
Yi Wang;R. Gao
西藏东北部是青藏高原向欧亚大陆内部扩张的复杂活动锋区，位于青藏高原、鄂尔多斯地块和阿拉善地块的交汇地带。鉴于藏东北地区特殊的构造背景，该地区的地震研究对建立高原动力学模型和区域地质解释具有重要意义。但由于数据采集条件和传统成像技术的限制，以往的反演结果仍存在明显差异，导致对该地区演化的地质解释存在争议。更确定性的地质解释，西藏东北部通常需要更高的分辨率比目前的图像速度结构的三维图像。为了获得精细分辨的层析成像图像，我们进行了全波形反演（FWI）的宽带地震体波记录的密集临时样带和相邻的地震台站部署在西藏东北部。将一维地球模型中的全球波传播方法与区域域中的三维谱元方法相结合，采用混合方法模拟了宽波段的地球电磁波场。用伴随状态法计算了最小二乘波形失配函数在区域域上对弹性扰动的灵敏度核。利用这些波形灵敏度核，采用迭代FWI算法反演区域台站记录的宽带体波数据，得到构造模型。根据所获得的FWI构造模型和前人的研究成果，对青藏高原东北部的岩石圈变形和高原生长机制有了较全面的认识。
As the complex active frontal part of Tibetan Plateau expanding toward the Eurasia interiors, northeastern Tibet (NE Tibet) is located in the converging region where the Tibetan Plateau, the Ordos Block and the Alashan Block intersect. In view of the special tectonic setting of NE Tibet, a seismic study in this region is of great importance for establishing a plateau dynamics model and regional geological interpretation. However, due to the limitations of data acquisition conditions and traditional imaging techniques, there are still significant differences between previous inversion results, leading to controversial geological interpretations of the evolution in this region. More deterministic geological interpretations of NE Tibet usually require 3D images of velocity structures with a higher resolution than in current images. In order to obtain finely resolved tomographic images, we performed Full Waveform Inversion (FWI) on broad-band teleseismic body wave records collected by dense temporary transect and adjacent seismological stations deployed in NE Tibet. A hybrid method which couples a global wave propagation method in a 1D Earth model with a 3D spectral-element method in a regional domain was used to model broad-band teleseismic wavefields. The sensitivity kernels of the least square waveform misfit function with respect to elastic perturbations in the regional domain were computed with the adjoint state method. By using these waveform sensitivity kernels, an iterative FWI algorithm was used to invert broadband body waveform data recorded by regional stations to obtain the structural model. A thorough view of lithospheric deformation and mechanism of plateau growth in NE Tibet is provided based on the obtained FWI structural model and previous studies.