沂沭断裂带莱州湾海域重力场特征

Gravity Field Characteristics of Yishu Fault Zone in Laizhou Bay

沂沭断裂带是郯庐断裂带的山东段,该断裂带不仅规模大,而且活动性强,具有"两堑夹一垒"的构造格架。利用实测1:20万海底高精度重力测量数据对沂沭断裂带莱州湾海域重力场特征进行了研究,采用欧拉反褶积、纹理分析等边界识别方法对数据进行处理解释,旨在对研究区进行构造格架的细化。根据重力场特征,推断断裂22条,以NE-NNE向和近EW向为主,推断沂沭断裂带4条主干断裂在莱州湾呈NNE向近平行舒缓波状展布;初步划分了3个三级构造单元,5个四级构造单元,12个五级构造单元;推断昌邑-大店断裂以西重力高反映了基底凸起,重力低主要反映了中、新生代凹陷,断裂以东重力高主要反映了早前寒武纪变质岩分布,重力低主要反映了中生代花岗岩体分布。

Yishu fracture zone is the Shandong section of Tanlu fracture zone. The fracture is not only large in scale, but also strongly active, which has the tectonic framework of "two grabens with one base". Based on the 1:200 000 seabed high-precision gravity survey data, the characteristics of gravity field in Laizhou Bay of Yishu fault zone were studied. The data were processed and interpreted by Euler deconvolution and texture analysis for equal boundary recognition in order to refine the tectonic framework of the study area. According to the characteristics of gravity field, 22 faults are inferred, and the main faults are NE-NNE and near EW faults. The four main faults of Yishu fault zone are distributed in Laizhou Bay, in NNE-trending, paralleling, soothing and undulated. The tectonic units are initially divided into three third level, five forth level,and twelve fifth level of tectonic units. It is inferred that on the west side of the Changyi-Dadian fault the high gravity reflects the basal uplift, and the low gravity mainly reflects the Mesozoic-Cenozoic depression;while on the east side of the fault the high gravity mainly reflects the distribution of the Early Precambrian metamorphic rocks, and the low gravity mainly reflects the distribution of the Mesozoic sequence rocks.