【作者】 姚琪；

【导师】 杨树锋； 陈汉林； 肖安成；

【作者基本信息】 浙江大学 ， 构造地质学， 2008， 博士

【摘要】 北西向断裂是杭州湾地区最晚形成的断裂,切割了先存的北东、北北东及东西向断裂,其新构造活动特征对区域防震减灾、工程地质环境评价等方面具有重要的意义。孝丰—三门湾断裂和长兴—奉化断裂是该地区具有代表性的两条北西向断裂。本文通过分析这两条断裂的空间发育特征和断裂活动性,对杭州湾地区的北西向断裂的新构造活动特征进行详细研究。通过断裂遥感解译、野外地质调查、断层泥定年分析(热释光、电子自旋共振)和浅层人工地震勘探研究,认为孝丰—三门湾断裂早期为张性断裂,后期转换为左旋走滑断裂,并兼具压性。该断裂在早更新世晚期至中更新世中期有强烈的活动,后期活动有所减弱,在晚更新世仍有活动。沿孝丰—三门湾断裂开挖的4个探槽显示,紧邻孝丰—三门湾断裂的北东走向、东西走向的次级断裂在晚更新世晚期仍有活动,可能受到了孝丰—三门湾断裂晚更新世活动的影响。断层断错地层及断层上覆地层的光释光定年研究显示,这些次级断裂活动时间集中在距今1.65～1.97万年,及4.2～5.12万年间,表明孝丰—三门湾断裂在这两个时间段有所活动。在综合区域地球物理场特征、桐乡凹陷和长河凹陷的人工地震勘探资料的基础上,对长兴—奉化断裂垂向上的构造特征进行了详细研究。认为自侏罗纪至古近纪,长兴—奉化断裂有强烈的活动,控制了中新生代沉积。杭州湾地区的野外地质勘探及浅层人工地震勘探证实,长兴—奉化断裂在晚更新世可能仍有所活动,但断裂活动有北强南弱的趋势。以孝丰—三门湾断裂和北东走向的萧山—球川断裂为例,研究了北西走向断裂与先存断裂之间的相互作用。通过地形地貌分析、定年分析、地球物理勘探分析,认为北西走向的孝丰—三门湾断裂控制了北东走向的萧山—球川断裂活动性分段。结合中国东部其它地区北西向断裂的新构造活动特征,研究了中国东部地区北西向断裂的几何展布、断裂活动性及其与先存断裂的相互作用,总结了中国东部地区北西向断裂的活动特征,提出中国东部的北西向断裂新构造活动具有新生性和成带性,与北东、北北东向断裂的活动具有一定的相关性,且结构面力学性质复杂。更多还原

【Abstract】 The NW-SE trending faults are the latest fault which offset the older faults trending NE-SW, NNE-SSW and E-W in Hangzhou Bay region, China. The neotectonic activity of NW-SE trending faults is important for environment evaluation and earthquake disaster mitigation. The Xiaofeng-Sanmen Fault (XSF) and Changxing-Fenhua Fault (CFF) are the most typical faults in region. The f structural attitude and fault activity of XSF and CFF is investigated for neotectonic activity of NW-SE trending faults in Hangzhou Bay region.Interpretation of remote sensing, geologic survey, dating of fault gouge (Luminescence, Electron spin resonance) and shallow seismic exploration indicate that the XSF was tensional fault in early stage but changed to left-lateral strike-slip fault with squeeze character in later stage. The XSF was intensely active from late stage of Early Pleistocene to middle stage of medio Pleistocene and became weaker later. However, the XSF was still active in Late Pleistocene. There were four trenches excavated along the XSF. The trenches exposed that secondary fault trending NE-SE and E-W were active in late stage of Late Pleistocene. The activity of these subsidiary fractures was influenced by the activity of XSF. According to the Optically stimulated luminescence dating of fault-related sediments and overlying sediments, the activity of these secondary faults could sum up to two periods: 0.0165～0.0197Ma and 0.042～0.0512Ma. The XSF might have two fault movements in these periods.The vertical structural feature of CFF was investigated from geophysical field and artificial seismic exploration. From Jurassic Period to Paleogene Period, the CFF was had intensely fault movements and controlled sedimentary process of Mesozoic Era and Cenozoic Era. The Field geological exploration and Shallow seismic exploration indicates that the CFF was still active in late Pleistocene and the fault activity of north segment was stronger than that of south segment.The interaction between the NW-SE trending fault and pre-exist faults was studied through the case of interaction between the XSF and Xiaoshan-Qiuchuan Fault (XQF) which was a typical NE-SW trending fault and controlled the structural feature in Hangzhou Bay region. Based on the analysis of geomorphy, dating analysis of fault gouge, and geophysical exploration, the XSF controlled the fault activity of XQF.The neotectonic activity of NW-SE trending faults in east China was concluded based on the contrast between the Hangzhou Bay region and the other regions in the east China. The analysis of fault distribution, fault activity and the interaction with the pre-exist faults indicates the characteristic of NW-SE trending faults of east China: palingenesis, banding, pertinence with pre-exist faults and complexity of mechanical property.更多还原