3-D Velocity Structure of the Middle and Upper Crust in the Yunnan Region,China |
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| Authors: | Zhengqin He Tailan Ye Wei Su |
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| Institution: | (1) Institute of Geophysics, China Earthquake Administration, Beijing, 100081, China |
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| Abstract: | Using short-period (1–18 s) surface wave data recorded by 23 stations of the Yunnan Digital Seismic Network of China we determined
phase velocities of the fundamental Rayleigh wave along 209 paths by the two-station narrowband filtering and cross-correlation
method, followed by an inversion for phase velocity distributions at various periods using the Ditmar-Yanovskaya method. We
then obtained a 3-D S-wave velocity structure of the middle and upper crust in the Yunnan region using the genetic algorithm.
The results show strong lateral variation of phase velocity in the region. The short-period phase velocity variation is closely
related to thickness variation of sedimentary layer in the shallow crust. Within the depth range of 26–30 km, the S-wave velocity
in the Sichuan-Yunnan rhombic block is lower than in the surrounding areas. Most large earthquakes of M > 6.0 in Yunnan occurred
in the transition zones between low and high velocities. |
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| Keywords: | The yunnan region phase velocity of rayleigh waves tomographic imaging middle and upper crust 3-D velocity structure |
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