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2008年汶川M_S8.0地震在龙门山中段的彭灌断裂带产生的地表破裂,是该地震产生的第二大地表破裂带。综合应用地质、钻井以及二维、三维地震数据,利用横贯前山带的多条人工地震反射剖面,对彭灌断裂带产生同震破裂的断层进行准确识别和解释。研究表明,龙门山中段的彭灌断裂带是一套由3条主要断层和次级广泛发育的断裂组合构成,浅层表现为叠瓦构造样式,断裂之间发育小型双重构造。汶川M_S8.0地震在彭灌断裂带产生的地表破裂是由该断裂带前缘③号主断层活动产生的。彭灌断裂整体看上陡下缓,为轴面多次转折形成断坪一断坡式组合样式。分析认为彭灌断裂初步形成于晚三叠世末期,晚侏罗世之后大规模逆冲推覆,新生代继续活动,是多期次继承性断层。根据浅表地质主要断裂构造以及同震地表破裂特征,龙门山中段彭灌断裂带沿走向可分为白鹿和汉旺两个次级构造段。对龙门山中段彭灌断裂带的浅、表构造特征进行研究,可为进一步认识前山带主要断裂构造带提供一定的依据和约束。
The surface rupture caused by the 2008 Wenchuan M_S8.0 earthquake in the Peng-Guan fault zone in the middle of the Longmen Shan area is the second largest surface rupture zone produced by the earthquake. Based on the comprehensive application of geological, drilling and two-dimensional and three-dimensional seismic data, a series of artificial seismic reflection profiles across the anterior mountains are used to accurately identify and interpret the coseismic ruptures in the Pengzheng fault zone. The study shows that the Peng-Guan fault zone in the middle part of the Longmen Shan area is composed of a combination of three major faults and secondary extensively developed faults. The shallow layer shows the shoal-tile structure pattern and the small double structure develops between the faults. The surface rupture caused by the Wenchuan M_S8.0 earthquake in the Peng-Guan fault zone is caused by the activity of the main fault ③ in the front of the fault zone. As a whole, the Pengchong fault appears to be steep and gentle, forming multiple fault-slope combination patterns for the axial plane. According to the analysis, the Peng-Gushui fault formed initially in the late Triassic, and was thrust back in large scale after Late Jurassic. The Cenozoic continues to be a multi-stage successional fault. According to the main epicenter faults and the features of coseismic surface rupture, the Peng-Guan fault zone along the middle Longmen Shan can be divided into two secondary structural sections, namely Bailu and Hanwang. Studying the shallow and epicenospheric tectonic features of the Peng-Guan fault zone in the middle part of Longmenshan can provide some basis and constraint for further understanding of the main fault zone of the former mountain belt.