Joint tomographic inversion of first-arrival and reflection traveltimes for recovering 2-D seismic velocity structure with an irregular free surface  

作　　者：XinYan Zhang ZhiMing Bai Tao Xu Rui Gao QiuSheng Li Jue Hou José Badal 

机构地区：[1]Key Laboratory of Deep-Earth Dynamics of Ministry of Land and Resources,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China [2]State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China [3]CAS Center for Excellence in Tibetan Plateau Earth Sciences,Beijing 100101,China [4]School of Earth Science and Engineering,Sun Yat-sen University,Guangzhou 510275,China [5]Institute of Geophysics,China Earthquake Administration,Beijing 100081,China [6]Physics of the Earth,Sciences B,University of Zaragoza,Spain

出　　处：《Earth and Planetary Physics》2018年第3期220-230,共11页地球与行星物理（英文版）

基　　金：financial support for this work contributed by the National Key Research and Development Program of China(grant nos.2016YFC0600302,2016YFC0600101 and 2016YFC0600201);the National Natural Science Foundation of China(grants 41604075,41430213,41574092 and 41474068)

摘　　要：Irregular surface flattening,which is based on a boundary conforming grid and the transformation between curvilinear and Cartesian coordinate systems,is a mathematical method that can elegantly handle irregular surfaces,but has been limited to obtaining first arrivals only.By combining a multistage scheme with the fast-sweeping method(FSM,the method to obtain first-arrival traveltime in curvilinear coordinates),the reflected waves from a crustal interface can be traced in a topographic model,in which the reflected wavefront is obtained by reinitializing traveltimes in the interface for upwind branches.A local triangulation is applied to make a connection between velocity and interface nodes.Then a joint inversion of first-arrival and reflection traveltimes for imaging seismic velocity structures in complex terrains is presented.Numerical examples all perform well with different seismic velocity models.The increasing topographic complexity and even use of a high curvature reflector in these models demonstrate the reliability,accuracy and robustness of the new working scheme;checkerboard testing illustrates the method's high resolution.Noise tolerance testing indicates the method's ability to yield practical traveltime tomography.Further development of the multistage scheme will allow other later arrivals to be traced and used in the traveltime inversion.Irregular surface flattening,which is based on a boundary conforming grid and the transformation between curvilinear and Cartesian coordinate systems,is a mathematical method that can elegantly handle irregular surfaces,but has been limited to obtaining first arrivals only.By combining a multistage scheme with the fast-sweeping method(FSM,the method to obtain first-arrival traveltime in curvilinear coordinates),the reflected waves from a crustal interface can be traced in a topographic model,in which the reflected wavefront is obtained by reinitializing traveltimes in the interface for upwind branches.A local triangulation is applied to make a connection between velocity and interface nodes.Then a joint inversion of first-arrival and reflection traveltimes for imaging seismic velocity structures in complex terrains is presented.Numerical examples all perform well with different seismic velocity models.The increasing topographic complexity and even use of a high curvature reflector in these models demonstrate the reliability,accuracy and robustness of the new working scheme;checkerboard testing illustrates the method's high resolution.Noise tolerance testing indicates the method's ability to yield practical traveltime tomography.Further development of the multistage scheme will allow other later arrivals to be traced and used in the traveltime inversion.

关 键 词：IRREGULAR surface FLATTENING boundary conforming grid MULTISTAGE scheme TRAVELTIME TOMOGRAPHY 

分 类 号：P35[天文地球—空间物理学]