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Geometry-preserving full-waveform tomography and its application in the Longmen Shan area
作者姓名:Xingpeng DONG  Dinghui YANG  Hejun ZHU  Yun CHEN
作者单位:Institute of Geology;Department of Mathematical Sciences;Department of Geosciences;State Key Laboratory ofLithospheric Evolution
基金项目:supported by the National Key R&D Program of China(Grant No.2017YFC1500301);the National Natural Science Foundation of China(Grant Nos.U1839206,42004077)。
摘    要:Classic L2-norm-based waveform tomography is often plagued by insurmountable cycle skipping problems;as a result,the iterative inversion falls into local minima,yielding erroneous images.According to the optimal transportation theory,we adopt a novel geometry-preserving misfit function based on the quadratic Wasserstein metric(W2-norm),which improves the stability and convexity of the inverse problem.Numerical experiments illustrate that W2-norm-based full-waveform tomography has a larger convergence radius and a faster convergence rate than the L2-norm and can effectively mitigate cycle skipping issues.We apply this method to the Longmen Shan area and obtain a reliable lithospheric velocity model.Our tomographic results indicate that the crystalline crust underlying the Sichuan Basin wedges into the crustal interior of the Tibetan Plateau,and the mid-lower crust of the eastern Tibetan Plateau is characterized by low shear-wave velocities,indicating that ductile crustal flow and strong interactions between terranes jointly dominate the uplift behavior of the Longmen Shan.Furthermore,we find that large earthquakes(e.g.,the Wenchuan and Lushan events)occur not only at the junction between high-and low-velocity regions but also in the transition zone from positive to negative radial anisotropy.These findings improve our understanding of the mechanism responsible for large earthquakes in this region.

关 键 词:Optimal  transportation  Geometry-preserving  properties  Cycle  skipping  problem  Longmen  Shan  Lower  crustal  flow  model
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