Joint land-sea seismic survey and research on the deep structures of the Bohai Sea areas
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Joint land-sea seismic survey and research on the deep structures of the Bohai Sea areas HAO Tianyao1*, YOU Qingyu1, LIU Lihua1, LV Chuanchuan1, XU Ya1, LI Zhiwei2, ZHAO Chunlei1, ZHENG Yanpeng3, LIU Chenguang3, HAN Guozhong3 1
Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan 430077, China 3 The First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China 2 Wuhan
Received 10 May 2013; accepted 5 August 2013 ©The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2013
Abstract This paper presents the survey and research work of two land-sea profiles in the Bohai Sea, China, carried out in 2010–2011, including the seismic sources on land and in the sea, the ocean bottom seismographs (OBS) and their recovery, the coupling of OBS and the environment noise in sea area, the data quality of OBSs, and the result of data analysis. We focused on the investigation of crustal structures revealed by the two NE\EW-trending joint land-sea profiles. In combination with the Pn-velocity distribution and gravitymagnetic inversion results in the North China Craton, we propose that the undulation of the Moho interface in the Bohai and surrounding areas is not strong, and the lithospheric thinning is mainly caused by the thinning of its mantle part. The research result indicates that obvious lateral variations of Moho depth and seismic velocity appear nearby all the large-scale faults in Bohai Sea, and there is evidence of underplating and reforming of the lower crust by mantle material in the Bohai area. However, geophysical evidence does not appear to support the “mantle plume” or “delamination” model for the North China Craton destruction. The crustal structure of the Bohai Sea revealed “a relatively normal crust and obviously thinned mantle lid”, local velocity anomalies and instability phenomena in the crust. These features may represent a combined effect of North China-Yangtze collision at an early stage and the remote action of Pacific plate subduction at a late stage. Key words: seismic survey profiles, velocity anomaly, crustal structure, lithospheric thinning, Bohai Sea Citation: Hao Tianyao, You Qingyu, Liu Lihua, Lv Chuanchuan, Xu Ya, Li Zhiwei, Zhao Chunlei, Zheng Yanpeng, Liu Chenguang, Han Guozhong. 2013. Joint land-sea seismic survey and research on the deep structures of the Bohai Sea areas. Acta Oceanologica Sinica, 32(12): 13–24, doi: 10.1007/s13131-013-0383-4
1 Introduction The North China Craton (NCC) is presently the only place in the world where the intensive destruction of thick Archaean lithosphere has been confirmed, and is considered by scientists as the “best example of the destruction of ancient lithospheric mantle”. Therefore, research on the process and mechanism of its destruction becomes currently a frontal issue of geoscience. The study of its deep structure, especially the crustal structure, is important for understanding the destruction process and
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