CAJ | 학술논문

长兴-奉化断裂是斜跨杭州湾地区的一条新生代北西向断裂,改造了该地区印支运动以来北东向为主的构造格局,对区域矿产资源开发、油气勘探有着重要意义.由于该断裂在航磁异常图上表现不明显,地表行迹不连续,且极易与早期断裂的次级断裂混淆,因此该断裂的存在及其几何展布一直有所争议.本文结合杭州湾地区的TM遥感图像解译、布格重力异常场、以及人工地震勘探资料,分析长兴-奉化断裂的几何展布及中新生代活动特征,提出长兴-奉化断裂西起长兴煤山,经桐乡、海宁、余姚、宁波,向东南延伸入海,而非前人据航磁异常提出的自长兴向奉化地区延伸.TM遥感影像解译表明该断裂是由一系列新生的北西向小断裂呈右阶斜列、平行或断续出现所构成,断错了先存的北东向、东西向构造.人工地震资料显示自白垩纪至古近纪,长兴-奉化断裂均有活动,参与控制了杭州湾地区白垩纪-古近纪陆相盆地的沉积.该断裂在地表和剖面上表现为右旋张扭,是中国东部地区北西向断裂系统带的一部分.
장흥-봉화단렬시사과항주만지구적일조신생대북서향단렬,개조료해지구인지운동이래북동향위주적구조격국,대구역광산자원개발、유기감탐유착중요의의.유우해단렬재항자이상도상표현불명현,지표행적불련속,차겁역여조기단렬적차급단렬혼효,인차해단렬적존재급기궤하전포일직유소쟁의.본문결합항주만지구적TM요감도상해역、포격중력이상장、이급인공지진감탐자료,분석장흥-봉화단렬적궤하전포급중신생대활동특정,제출장흥-봉화단렬서기장흥매산,경동향、해저、여요、저파,향동남연신입해,이비전인거항자이상제출적자장흥향봉화지구연신.TM요감영상해역표명해단렬시유일계렬신생적북서향소단렬정우계사렬、평행혹단속출현소구성,단착료선존적북동향、동서향구조.인공지진자료현시자백성기지고근기,장흥-봉화단렬균유활동,삼여공제료항주만지구백성기-고근기륙상분지적침적.해단렬재지표화부면상표현위우선장뉴,시중국동부지구북서향단렬계통대적일부분.
The Changxing-Fenghua fault (CFF) is a regional fault trending in NW-SE, which diagonally goes across the Hangzhou Bay region. The CFF changed the NE-SW trending tectonic frameworks which were formed in the Indosinian movement. The CFF plays an important role for the development of mineral resources and oil resources. It consists of a series of NW-SE-trending faults which are discontinuous, parallel to each other or dextral en-echelon array. Secondary NW-SE-trending faults of NE-SW- or E-W-trending deep preexisting faults are easily misdeemed from the CFF. Therefore, the distribution, even the determination of the CFF are challenged in recent decades. We analyzed the distribution and activity of the CFF in the Mesozoic and Cenozoic according to the TM remote sensing image, aeromagnetic anomaly map, Bouguer gravitational anomaly map and artificial seismic profiles of the Tongxiang-Pinghu depression, Changhe depression and Ningbo basin. The TM remote sensing image indicates the new NW-SE-trending fractures assemble in Shangyu city, the northern part of Simin Shan and the Ningbo city. And the difference from the previous understanding is that the NW-SE-trending fractures around Fenghua city are only secondary fractures of preexisting deep faults. Although inconspicuous in the aeromagnetic anomaly map and discontinuous on the ground surface, the CFF is a remarkable boundary of positive and negative abnormality on the Bouguer anomaly map. The fracture distribution and the Bouguer anomaly map suggest the CFF starts in Chang-xing County and expends southeastwardly to the East China Sea. The CFF spreads as en-echelon fractures and passes by the Tongxiang, Haining, Yuyao and Ningbo cities, rather than the Fenghua city as people suspected from the aeromagnetic anomaly map before. Artificial seismic exploration showed that the CFF controlled the deposition process and rebuilt the structures of continental basins from the Cretaceous to Eogene. The CFF cut across old structures with dextral horizontal displacement on the ground surface and strata as a normal fault on the artificial seismic profile. Therefore, the CFF is a tenso-shear fault and belongs to the NW-trending active fault zones of the eastern Chinese continent in the Mesozoic and Cenozoic.