Wide-angle and multi-channel seismic surveys in Zhongsha waters
Wide-angle and multi-channel seismic surveys in Zhongsha waters
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DOI：
10.6038/cjg2020n0259
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发表时间：
2020-04-01
影响因子：
1.4
通讯作者：
Wang Qiang
中科院分区：
文献类型：
--
作者：
Li YuHan;Huang HaiBo;Wang Qiang
中沙海域（环礁）由于滩礁分布广泛，长期以来一直是南海地震勘探的空白区。为揭示该地区的地壳结构和地层构造特征，全面描述南海大陆边缘新生代的伸展过程，首次在中沙环礁及其邻区进行了1条OBS 2017 - 2广角地震剖面和4条多道地震剖面的观测。对海底地震仪（OBS）数据进行了格式转换、位置重定位等处理，识别了地壳深部的震相，并利用正演模拟方法模拟了地壳结构。通过对多道地震剖面的地层和构造解释，建立了6套沉积地层。OBS 2017 - 2的数据处理表明，数据质量很高，深震震相清晰，在环礁上延伸更长，达到100多公里。中沙环礁以陆壳略薄为特征，厚度约25 km。多道地震资料显示，环礁内沉积层较薄。除位于环礁西南部的排洪-梅溪断裂外，环礁内基本上没有发生过构造-岩浆活动。中沙环礁坡脚附近有广泛的岩浆侵入体和火山活动。中沙环礁的上地壳减薄和沉积特征表明，该地区可能经历了强烈的暴露剥蚀过程。近年来，中沙海域大角度多道地震勘探的开展，填补了南海地区地质、地球物理研究的空白，为了解该海域的构造-沉积演化提供了重要资料。
Due to the wide-spread shoals and reefs, Zhongsha waters (atoll) has long been a blank area for seismic exploration in the South China Sea. To reveal the crustal structures and the stratigraphic-tectonic characteristics of this area, and to comprehensively depict the Cenozoic extension process of the continental margins in the South China Sea, we carried out one wide-angle seismic profile OBS2017-2 and four multi-channel seismic profiles in the Zhongsha Atoll and its adjacent areas for the first time. The Ocean Bottom Seismometer (OBS) data was processed by format conversion, position relocation, etc. The seismic phases from deep crust were identified and used to simulate the crustal structures by forward modeling approach. Six sets of sedimentary strata were established based on the stratigraphic and tectonic interpretation of the multi-channel seismic profiles. The data processing of the OBS2017-2 shows that the data quality is very high, the deep seismic phases are clear and extend longer on the atoll, reaching over 100 km. The Zhongsha Atoll is characterized by slightly-thinned continental crust, with thickness of about 25 km. Sedimentary layers in the atoll are relatively thin as shown in the multi-channel seismic data. Basically, there is few tectonic-magmatic activities exist within the atoll except for a basement-cutting fault that named Paihong-Meixi Fault in the southwest of the atoll. Extensive magmatic intrusions and volcanoes exist only around the slope toe of the Zhongsha Atoll. The thinned upper crust and the sedimentary characteristics in the Zhongsha Atoll indicate that this area may have experienced strong processes of exposure and denudation. The recent wide-angle and multi-channel seismic surveys in the Zhongsha waters have filled in the blank of geological/ geophysical research in the South China Sea, providing important data for understanding the tectonic-sedimentary evolution in this area.