Three-dimensional crustal velocity structure of P-wave in East China from wide-angle reflection and refraction surveys |
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Authors: | ZhiXin Zhao JiRen Xu |
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Institution: | (1) Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 100037, China |
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Abstract: | The 3-D crustal structure of P-wave velocity in East China is studied based on the data obtained by wide-angle seismic reflection
and refraction surveys. The results suggest that a deep Moho discontinuity exists in the western zone of the study region,
being 35–48 thick. High-velocity structure zones exist in the upper crust shallower than 20 km beneath the Sulu and Dabie
regions. The cause of high-velocity zones is attributable to high-pressure metamorphic (HPM) and ultra-high-pressure metamorphic
(UHPM) terranes with high velocity and density exhuming up to the upper crust in the Sulu and Dabie orogenies. Anomalous zones
of low velocity are in the lower crust, about 30 km beneath the Sulu and Dabie regions. The Moho discontinuity is as deep
as 38 km beneath the Dabie region, deeper than those in the surrounding areas. The Moho discontinuity beneath the Sulu orogenic
region is also a little deeper than those in its vicinity, being about 32 km. The deep Moho discontinuity zone implies that
the low crustal velocity structure zone is in that region. The low-velocity characteristics in the lower crust are probably
related to the remnant crustal root of the old mountains due to the orogeny in the Sulu and Dabie regions. The high-velocity
anomalous zones in the upper crust and low-velocity anomalous zones in the lower crust beneath the Sulu region are all located
northeast of the northern segment of the Tan-Lu fault. However, the high- and low-velocity anomalous zones beneath the Dabie
region are located southwest of the southern segment of the Tan-Lu fault. Such a distribution of the velocity-anomalous zones
looks to be attributable a left lateral slip motion along the Tan-Lu fault. The distribution pattern of the velocity-anomalous
zones may show some evidence for the left strike-slip motion regime of the Tan-Lu fault.
Supported partly by National Natural Science Foundation of China (Grant No. 40674026) and National Special Science Foundation
of China (Grant No. 200811037) |
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Keywords: | Crustal velocity structure Dabie-Sulu orogen Moho discontinuity left lateral strike-slip motion wide-angle reflection and refraction survey |
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