龙门山南段构造变形及应力序列

2008年5月12日的汶川大地震表明龙门山断裂带仍然是一个构造活动带,为达到防震减灾的目的,对龙门山进行深入研究显得非常必要。作者通过龙门山南段的怀远和雅安两条实测构造地质剖面,应用传统的构造解析法,结合构造带的分带讨论思想,对野外实测的褶皱、节理和断层等构造变形要素进行综合分析,确定出各构造带的变形和应力序列。中央断裂带构造变形次数达10次以上,其中以NW-SE向逆冲最多,部分为左旋逆冲或右旋逆冲。滑覆体构造变形序列达5次左右。前山断裂带的构造变形序列较少,约5次以上。

Analysis of Structural Deformation and Stress Sequences in the Southern Segment of the Longmen Mountains

The Longmen Mountains thrust belt is located in the western margin of Sichuan Basin in China and the collision belt between the Yangtze plate and Songpan-Ganzi fold belt. The northern end of which connects with the EW-trending Qi-Qin-Kun tectonic belt and the southern end connects with the Kang-Dian NS-trending tectonic belt. The thrust belt is one of the most important earthquake zones of China and where many huge earthquakes occurred in history. 26 destructive earthquakes and more than 20 earthquakes which are over 6 magnitude have taken place since 1169 in all. The M=8.0 Wenchuan earthquake,which occurred on May 12,2008,showed that the Longmen Mountains thrust belt is still an active tectonic zone. An in-depth study on the Longmen Mountains is necessary in order to achieve the purpose of earthquake prevention and disaster reduction. The traditional structural analysis,which combined with the thought of the structural belt,is applied in this paper. The sequences of deformation and stress are obtained on the basis of the deformation analysis in the southern segment of the Longmen Mountains. There are more than 10 times of structural deformation in the central fault of the southern segment of the Longmen Mountains. The times of northwestern thrusting is more than others and there are also some left-lateral and right-lateral movements. There are 5 times of structural deformation in the sliding nappes. The times of structural deformation in the front fault of the Longmen Mountains is,less than the central fault,about five.