郯庐断裂带南段重力异常及不同深度的横向构造特征

doi:10.3969/j.issn.0253-4967.2016.02.011

摘要/Abstract

摘要：

为研究郯庐断裂带南段及周边构造的深部特征、空间展布、交切关系，文中利用小波多尺度分析方法对该地区的布格重力场进行场源分离，剖析不同深度下的地壳横向构造；同时采用Parker变密度模型对莫霍面深度进行反演分析。研究表明，郯庐断裂带南段表现为NNE走向的大型重力区域场梯度条带，切割深度达岩石圈地幔，其两侧密度结构及构造特征差异明显。沉积层及上地壳密度结构复杂，郯庐带东支2条断裂形成线性异常纵贯区域；而西支2条断裂线性异常较弱，截切EW向的重力异常体断续延展。中、下地壳密度结构简单，断裂带形成宽缓的低异常条带，反映了白垩纪-古近纪伸展环境下造成的地堑式构造。西支2条主干断裂纵穿合肥市，沿肥东凹陷西缘向S延伸，由于舒城以南的高密度圈闭体遮挡，尖灭于舒城县一带；而肥中、六安-合肥、肥西-韩摆渡EW向的深大断裂交切于西支，未延伸至东支。该区近代小震多发生于断裂构造所对应的重力高、低异常转化带之间，尤其是断裂之间的交会处与郯庐构造带内部，郯庐断裂带南段为历史强震空区段，考虑到断裂带莫霍面陡变及与多条深大断裂交切等深部环境，中强震危险性不容忽视。

关键词: 郯庐断裂带南段, 布格重力异常, 小波多尺度分析, 横向构造, 莫霍面, 地震活动性

Abstract:

To research the faults distribution and deep structures in the southern segment of Tan-Lu fault zone(TLFZ) and its adjacent area, this paper collects the Bouguer gravity data and makes separation by the multi-scale wavelet analysis method to analyze the crustal transverse structure of different depths. Meanwhile Moho interface is inversed by Parker variable density model. Research indicates that the southern segment of TLFZ behaves as a NNE-directed large-scale regional field gravity gradient zone, which separates the west North China-Dabie orogen block and the east Yangtze block, cutting the whole crust and lithosphere mantle. There are quite differences of density structures and tectonic features between both sides of this gradient belt. The sedimentary and upper crustal density structure is complex. The two east branches of TLFZ behave as linear gravity anomalous belt throughout the region, whereas the two west branches of TLFZ continue to extend after truncating the EW-trending gravity anomaly body. The lower crustal density structure is relatively simple. TLFZ behaves as a broad and gentle low abnormal belt, which reflects the Cretaceous-Paleogene extension environment caused graben structure. The two west branches of TLFZ, running through Hefei city, extend southward along the west margin of Feidong depression and pinch out in Shucheng area due to the high density trap occlusions in the south of Shucheng. The Feizhong Fault, Liu'an-Hefei Fault, and Feixi-Hanbaidu Fault intersect the two west branch faults of TLFZ without extending to the east. Recent epicenters are mainly located in conversion zones between the high-density and the low-density anomaly, especially in TLFZ and the junction of the faults, where earthquakes frequently occurred in the upper and middle crust. As strong earthquakes rarely occur in the southern segment of TLFZ, considering its deep feature of abrupt change of the Moho and intersections with many EW-trending faults, the hazard of strong earthquake cannot be ignored.

Key words: the southern segment of Tan-Lu fault zone, Bouguer gravity, multi-scale wavelet analysis, transverse structure, Moho interface, seismic activity

中图分类号:

P315.2

王鑫, 张景发, 姜文亮, 蒋洪波, 田甜, 高敏, 付萍杰. 郯庐断裂带南段重力异常及不同深度的横向构造特征[J]. 地震地质, 2016, 38(2): 370-385.

WANG Xin, ZHANG Jing-fa, JIANG Wen-liang, JIANG Hong-bo, TIAN Tian, GAO Min, FU Ping-jie. TRANSVERSE STRUCTURES FEATURES OF DIFFERENT DEPTHS DERIVED FROM BOUGUER GRAVITY ANOMALIES IN THE SOUTHERN SEGMENT OF TAN-LU FAULT ZONE[J]. SEISMOLOGY AND GEOLOGY, 2016, 38(2): 370-385.

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