摘要:
通过重磁资料系统处理、研究、解释,确认滨海断裂带珠江口段的存在,且是一条规模巨大特征明显的断裂带,深度在30km以上,呈NEE向展布,是由滨岸断裂带和滨海断裂带界限的高重力地质块体带,重力、航磁梯度带或灰度带图像反映清楚。在浅部,它与NW和NE向断裂互有切割,不过,NW向断裂切割滨海断裂带和NE向断裂带的频度更高,图像更清晰。在10km以深,NE、NW向断裂基本上消失,阻截在滨海断裂带内,某些资料认为,NE向莲花山断裂带往西南入海(本区)转为NEE走向,从重磁资料分析,这些NEE走向断裂其实是滨海断裂带的一部分。莲花山断裂带进入本区后,仍以NE45°左右方向,经深圳、香港,至万山群岛被滨海断裂带截断,图像清楚,不存在NE向转NEE向现象。滨海断裂带是一条活动性较强的断裂带,在珠江口段,强势不改,它与NW、NE向断裂交汇并相互切割,具备5级以上地震构造条件,尤其是与形成时代新、活动性较强的NW向断裂交切部位(如镇海湾、广海湾、崖门、澳门、担杆列岛地区)。但是,NW向断裂在本区较浅,不如粤闽、粤桂交界地区深(≥ 30km),所以本研究区(段)地震强度应低于后者。
Abstract:
Based on processing, analyzing and interpreting the gravimetry and magnetometry data, it is confirmed that the segment of the coastal fracture zone in the Pearl River mouth is existent, it is a great fracture zone with large scale, depth over 30 km, obvious characteristics, and development in NEE direction. And it is a geologic block zone with high gravity, bounded by the sea coast fracture zone and the littoral fracture zone, and image of the gradient zone and grey degree zone of the gravimetry and the aeromagnetometry also showed that clearly. In the shallow part, it was intersected by NW and NE faults, but the NW faults intersected the littoral fracture zone and the NE fracture zone more frequently and clearly. However,in the deep layer with the depth over 10 km, the NE and NW fractures disappeared on the whole. According to some reference materials it is considered that the Lianhuashan fault belt in the NE direction extended to SW and went down to the sea in the research area, then the trend changed to the NEE direction, and the gravimetry and magnetometry data indicated that these faults in the NEE direction were a part of the coastal fracture zone actually. But entering the researeh area, the Lianhuashan fault belt extended still in the direction about N 45W, then went through Shenzhen and Hongkong. However,it was intersected by the coastal fracture zone at the Wanshan Islands. The image showed that quite clearly, but could not find the change of the trend from NE to NEE.The coastal fracture zone had high activity,intersected with the NW and NE faults in the Pearl River mouth segment,and there was seismotectonic condition of M ≥ 5 in the places where the fractures dissected mutually, especially in the places where the coastal fracture intersected with the NW faults which devel-oped later and of high activity (such as Zhenhai Bay,Guanghai Bay, Yamen, Macao, and Dangan Chain Island area). But in the research area,the NW fault is shallower than in the border lands of Guangdong-Fujian Provinces and Guangdong-Guangxi Provinces (where h≥ 30 km), therefore in this area the earthquake strength should be lower accordingly.
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