Construction of regional and local seismic anisotropic structures from wide-angle seismic data: crustal deformation in the southeast of China |
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| Authors: | Z Zhang J Teng J Badal E Liu |
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| Institution: | (1) State Key Laboratory of Lithosphere Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China;(2) Physics of the Earth, Sciences B, University of Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza, Spain;(3) Formerly British Geological Survey, West Mains Road, Edinburgh, EH9 3LA, UK;(4) Present address: ExxonMobil URC, Houston, TX, USA |
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| Abstract: | We present a method to obtain spatial distributions of seismic anisotropy associated with regional stress and local faulting
in the crust from wide-angle seismic data. The method contains three steps. The first step consists of obtaining radial- and
transverse-component seismic sections using a pre-stack depth migration algorithm from the S-wave velocity model determined
by conventional interpretation of picked intra-crustal seismic events. In the second step, we compute time delays between
split shear-waves and polarizations of fast split shear-waves by minimizing the transverse-component seismic energy. The time
delay and polarization in each layer are derived using a layer-stripping method. The final step is to estimate the average
splitting parameters along the whole profile. Thus, the average time delay and polarization can be regarded as caused by the
effects owing to regional structure and stress fields, whereas the residual values of the splitting parameters are considered
to be related to local structures and local faulting. Our method allows us to construct multi-layer anisotropic images, which
may later be interpreted in terms of intra-layer coupling/decoupling or deformation. We present results from a set of three-component
seismic data acquired by a controlled source experiment in the southeast region of China. The results demonstrate that the
average polarizations and time delays are consistent with the direction and strength of the stress field, and their lateral
variations related to local anisotropy match the spatial distribution of surface faulting crossing the acquisition seismic
profile. |
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| Keywords: | The Yangtze block The Cathaysia block Wide-angle seismic data Seismic anisotropy Regional stress Local faulting |
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