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胶东半岛地处华北平原东北部沿海地区,北东向断裂带异常发育,该区不仅是华北震区中、强地震活动的频发区,又是中-新生代地壳构造活动的大陆边缘带.中国东部最大规模的郯庐断裂带纵贯胶东半岛西部,苏鲁超高压变质带位于该半岛南侧,彰显其地理位置重要而特殊.为深入认识我国近海与海陆过渡带地壳结构特征及其深部动力学背景等基础科学问题,2013年在胶东半岛东部实施了海陆联合探测项目.本文对布设的北西向宽角反射/折射探测剖面进行了计算处理,获取了该测线的地壳精细结构及其构造特征.结果表明:胶东半岛地壳结构复杂,该区基底埋深较浅,地表速度偏高,地壳速度结构呈现东西迥异的非均匀性特征,具有横向分层、纵向分块的典型特性.作为郯庐断裂带重要组成部分的牟平—即墨断裂带是胶东半岛上非常重要的断裂带,该断裂带东西两侧的地壳结构特征差异非常明显,断裂带东侧速度偏低,而西侧速度偏高,地壳各分层界面形态在该断裂带两侧起伏变化明显,地壳结构整体上呈现南东浅北西较深的结构特征.总体来看,胶东半岛不同区段呈现出的结构差异与该区大地构造单元的划分基本相符,在界面起伏变化明显的区域与地表穿过的断裂带遥相呼应.作为华北板块和扬子块体相互碰撞的边缘地带,胶东半岛复杂的深部结构特征与西太平洋板块对其的俯冲挤压有着密切的关联,该研究对了解本区地壳构造变化的深部动力学背景有着重要的研究意义.
The Jiaodong Peninsula is located in the northeastern coastal plain of the North China Plain with an exceptionally developed NE-trending fault zone. The area is not only a frequent area with strong and moderate seismic activity in the North China earthquake area, but also a continental marginal zone of the Meso-Cenozoic crustal tectonic activity. The largest Tancheng-Lujian fault belt in eastern China runs through the western part of the Jiaodong Peninsula, and the Sulu UHP metamorphic belt is located on the south side of the peninsula, highlighting its importance and uniqueness. In order to understand deeply the crustal structure and its deep dynamics Background and other basic scientific issues, the joint land-sea exploration project was implemented in the eastern part of Jiaodong Peninsula in 2013. In this paper, the Northwest wide-angle reflection / refraction detection profile was calculated and obtained, and the crustal fine structure and its tectonic characteristics The results show that the crustal structure of Jiaodong Peninsula is complex, the depth of the basement is shallow and the surface velocity is high, and the velocity structure of the crust shows heterogeneous features with different features, with the characteristics of horizontal stratification and vertical partitioning. The Muping-Jimo fault zone, an important part of the fault zone, is a very important fault zone in the Jiaodong Peninsula. The crust on both east and west of the fault zone The differences of the structural features are obvious. The eastern side of the fault zone is low in velocity and the west side is high in velocity. The morphology of the stratified interfaces in the crust changes obviously on both sides of the fault zone. The crustal structure shows a deep south-east shallow northwest structure In general, the structural differences in different sections of Jiaodong Peninsula are basically in accordance with the division of tectonic units in this area, and echoes with the fault zones penetrating through the surface in regions with obvious changes of interface.As a key component of North China Plate and Yangtze Block The complex deep structural features of the Jiaodong Peninsula are closely related to the subduction and extrusion of the western Pacific plate in the marginal areas where collisions occur. This study is of great significance for understanding the deep dynamic background of crustal structural changes in this area.