“4·20”芦山地震的构造破裂与发震断层

摘要

This article studies the tectonic rupture and deformation characteristics of the Lushan earthquake (Ms 7.0) occurred in Sichuan on April 20,2013 and clarifies that the factor which causes 7.0 Ms earthquake is the reverse faulting and right-lateral strike-slip movement of the NE trending Dachuan-Shuangshi fault.The biggest displacement on the fault plane reaches 1.51 m.The epicenter is not in Longmen Country with serious seismic hazards,but in the Shuangshi-Taiping area where the seismic fault goes through.The main factor caused earthquake disasters anomalously in Longmen Country is the strong site effect of the relatively thick Quaternary in this basin and the strength of the buildings is insufficient.The earthquake is an inevitable result due to the crustal stress adjustment and the stress-deformation of crustal rock mass developing in the progressive stage of the Longmenshan Fault Zone.The trends of the crustal rupture propagation direction develop toward the Longmenshan central fault.%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1.51 m.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.