三峡九湾溪断裂带断层泥的特征及分段研究

在分析研究前人资料的基础上,结合野外实际工作和室内研究,从三峡九湾溪断裂带内各段断层泥的特征研究分析出发,探讨了九湾溪断裂带的分段性,结果发现:九湾溪断裂带存在明显的分段性,中段和南段地震活动频度和强度大,应变强度高,断层活动以粘滑为主,其分维值在2.2～2.6之间,石英碎砾表面发育各种撞击揳入现象、线状擦痕等显微构造;北段地震活动频度和强度较小,应变强度弱,断层活动以稳滑为主,兼具粘滑,其分维值在2.4～2.8之间,石英颗粒多为磨圆球砾,其刻蚀形貌以裂而不破现象为代表;中段是九湾溪断裂带最有可能发生诱发地震的地段和我们的重点监测地段。

THE CHARACTERISTICS AND STUDY ON SEGMENTATION OF FAULT GOUGES FROM THE JIUWANXI FAULT ZONE

In this paper we present the characteristics of fault gouges from the Jiuwanxi fault zone , such as the compositions and structures of clay minerals, magnetic structures , geochemistry, especially the quantitative observation of the microstructural features and the surface textures of quartz grains of fault gouges from this fault zone by means of scanning electron microscopy (SEM) . The segmentation of this fault zone has been further studied based on fractal theory. The results show that the Jiuwanxi fault zone displays a clear segmentation in its geometry, activity and structure. The middle and southern segments of this fault zone display a high seismologic activation frequency and intensity and high strain strength, and their fractal dimensions of fault gouges ranging from 2. 2-2. 6,which suggest that the activity of fault here is essentially characterized by sticky slip ; the northern segment of this fault zone with a fractal dimension of fault gouges from 2. 4-2. 8 suggests that the activity of fault here is characterized by steady creeping slip with some sticky slip; and the middle segment of this fault zone is the most probable place for generating induced earthquakes and is the major segment to be seriously monitored.