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中国大陆下扬子及邻区地壳结构基本特征:深地震测深研究综述
引用本文:白志明,吴庆举,徐涛,王晓.中国大陆下扬子及邻区地壳结构基本特征:深地震测深研究综述[J].中国地震研究,2016,30(3):298-315.
作者姓名:白志明  吴庆举  徐涛  王晓
作者单位:中国科学院地质与地球物理研究所岩石圈演化国家重点实验室,北京 100029;中国地震局地球物理研究所,北京 100081;中国科学院地质与地球物理研究所岩石圈演化国家重点实验室,北京 100029;中国科学院青藏高原地球科学卓越创新中心,北京 100101;中国科学院地质与地球物理研究所岩石圈演化国家重点实验室,北京 100029;中国科学院大学,北京 100049
摘    要:The Deep Seismic Sounding( DSS) projects carried out from the 1970 s in the lower Yangtze region and its neighboring area were reviewed in this paper,then the basic wave group features of those wide angle reflection / refraction record sections,and of the crustal structure are summarized. It shows that there were in total five clear wave groups on the record sections,which include the first arrival Pg,the reflection P1 from the bottom interface of the upper crust,the reflection P3 from the bottom interface of the middle crust,the strong reflection Pm from the Moho boundary,and the refraction Pn from uppermost mantle. In general,these phases are easily consistently traced and compared,despite some first arrivals being delayed or arriving earlier than normal due to the shallow sedimentary cover or bedrocks. In particular,in the Dabie Mountain region the seismic events of a few gathered shots always have weak reflection energy,are twisted,or exhibit disorganized waveforms, which could be attributed to the disruption variations of reflection depth,the broken Moho,and the discontinuity of the reflection boundary within crust. The regional crustal structures are composed of the upper,middle and lower crust,of which the middle and lower layers can be divided into two weak reflection ones. The crustal thickness of the North China and Yangtze platform are 30km- 36 km,and the Moho exhibits a flat geometry despite some local uplifts. The average pressure velocity in lower crust beneath this two tectonic area is 6. 7 ± 0. 3km / s. Nevertheless,beneath the Dabieshan area the crustal thickness is 32km- 41 km,the Moho bends down sharply andtakes an abrupt 4km- 7km dislocation in the vertical direction. The average pressure velocity in the lower crust beneath the Dabieshan area is 6. 8 ± 0. 2km / s.

关 键 词:深地震测深  波组特征  地壳结构特征  安徽及邻区
收稿时间:2016/1/29 0:00:00

Basic features of the Crustal Structure in the Lower Yangtze and its Neighboring Area in the Chinese Mainland: Review of Deep Seismic Sounding Research
Bai Zhiming,Wu Qingju,Xu Tao and Wang Xiao.Basic features of the Crustal Structure in the Lower Yangtze and its Neighboring Area in the Chinese Mainland: Review of Deep Seismic Sounding Research[J].Earthquake Research in China,2016,30(3):298-315.
Authors:Bai Zhiming  Wu Qingju  Xu Tao and Wang Xiao
Affiliation:State Key Laboratory of Lithosphere Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;Institute of Geophysics, China Earthquake Administration, Beijing 100081, China;State Key Laboratory of Lithosphere Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101, China;State Key Laboratory of Lithosphere Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;University of Chinese Academy of Sciences, Beijing 100049, China
Abstract:The Deep Seismic Sounding ( DSS) projects carried out from the 1970s in the lower Yangtze region and its neighboring area were reviewed in this paper, then the basic wave group features of those wide angle reflection / refraction record sections, and of the crustal structure are summarized. It shows that there were in total five clear wave groups on the record sections, which include the first arrival Pg, the reflection P1 from the bottom interface of the upper crust, the reflection P3 from the bottom interface of the middle crust, the strong reflection Pm from the Moho boundary, and the refraction Pn from uppermost mantle. In general, these phases are easily consistently traced and compared, despite some first arrivals being delayed or arriving earlier than normal due to the shallow sedimentary cover or bedrocks. In particular, in the Dabieshan region the seismic events of a few gathered shots always have weak reflection energy, are twisted, or exhibit disorganized waveforms, which could be attributed to the disruption variations of reflection depth, the broken Moho, and the discontinuity of the reflection boundary within crust. The regional crustal structures are composed of the upper, middle and lower crust, of which the middle and lower layers can be divided into two weak reflection ones because of the clear seismic events on the record sections. The crustal thickness of the North China and Yangtze platform are 30-36km, and the Moho exhibits a flat geometry despite some local uplifts. The average pressure velocity in lower crust beneath this two tectonic area is 6.7 ± 0.3km / s. Nevertheless, beneath the Dabieshan area the crustal thickness is 32-41km, the Moho bends down sharply and takes an abrupt 4-7km dislocation in the vertical direction. The average pressure velocity in the lower crust beneath the Dabieshan area is 6.8 ± 0.2km / s.
Keywords:Deep seismic sounding projects  Wave group feature  Crustal structure feature  Anhui  Province and its neighboring area
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