Three-dimensional velocity images in Yunnan and its neighboring district |
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| Authors: | Rui-Feng Liu Pei-Shan Chen and Qiang Li |
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| Institution: | (1) Institute of Geophysics, State Seismological Bureau, 100081 Beijing, China |
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| Abstract: | Using the techniques of seismic tomography three-dimensional velocity images at crust and upper mantle in Yunnan province
and its adjacent region have been successfully reconstructed. The results of image are: (1) The image of the velocity in the
upper crust is closely related to the well-known geological structure of the surface, the Kangdian earth axis is a distinct
high velocity area, and a high velocity rock stratum, which appoaching the surface of the earth, has been formed. (2) There
is a low-velocity layer between 26°–31°N and 100°–104°E in deep crust, the depth of Moho discontinuity in Sichuan bass in
is less than 50 km. (3) The results of seismological tomography not only reveal the lateral heterogeneity in the researched
region, but also find approximately the strike of Honghe fault from the image at bottom of crust, and the velocity in both
side of the fault are different obviously. (4) There is a low-velocity column within 25 km to 110 km in Tengchong region,
which may be occured by upward moving of the basalt in the mantle. (5) In studied area, the thickness of the crust in west
part is thicker than in southeast part. (6) From the image at bottom of the crust we can find that earthquakes with magnitude
greater than 5 occurred in big velocity gradient zones, especially in transition zone between high and low velocity. There
are a few earthquake in the low-velocity area. (7) We can see from Figure 6 that there still clearly exists lateral heterogeneity
at 450 depth.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 61–67, 1993. |
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| Keywords: | seismic tomography lateral heterogeneity Yunnan and its neighboring district the images of velocity |
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