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通过对“4.20”芦山地震构造破裂及变形特征的分析研究,阐明触发M=7.0级强烈地震的构造因素是NE向大川-双石断裂的逆断兼右旋走滑错动,断层面最大逆断-右旋滑动量达到1.51m。震中位置应在地震断裂通过的双石-太平区段而非震害严重的龙门乡。造成龙门乡震害异常的主要因素是该盆地较厚的第四系强烈的场地效应及建筑物结构强度不足。此次地震是龙门山断裂带地壳构造应力调整、地壳岩体应力-形变过程进入累进性发展阶段的必然结果。地壳破裂扩展方向具有向龙门山中央断裂发展的趋势。
Through the analysis and study of the structural rupture and deformation of the “4.20” Lushan earthquake, it is clarified that the structural factor triggering the M = 7.0 strong earthquake is the reverse and right-lateral strike-slip dislocation of the NE-Dakuan-Shuangshi fault with the largest fault plane Inverted - right-handed sliding amount of 1.51m. The location of the epicenter should be at the Shimen-Taiping section where the earthquake ruptured rather than at the ghost town of Longmen. The main reason causing the anomalous earthquake damage in Longmen Township is that the thick Quaternary system in the basin has strong site effects and the structural strength of buildings is not sufficient. The earthquake is the inevitable result of crustal tectonic stress adjustment and the stress-strain process of the crustal rock mass entering a progressive stage of development in the Longmen Shan fault zone. The direction of crustal expansion has the tendency to develop toward the central Longmenshan fault.