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2013年4月20日在四川芦山县境内发生了一次M_S 7.0级地震。芦山地震发生在青藏高原东缘龙门山南段,地震区没有产生明显的地表破裂带。本文以横穿地震区的青衣江中游河段为研究对象,通过河流阶地对比与精细测量,得出其阶地序列与阶地纵剖面图,揭示出褶皱变形是龙门山构造带南段芦山震区的主要变形样式,断裂晚第四纪以来活动性不明显,T_4、T_3、T_2、T_1阶地形成以来的最大抬升量分别为64.7m、61.6m、20.2m、6.8m。GPS同震垂直位移与阶地变形特征相一致,推断此次地震的震源破裂位移主要以褶皱隆起的形式表现出来,并在远离震中的局部地区有小幅下降。芦山地震发震构造符合断裂扩展褶皱模型。
On April 20, 2013, an M_S 7.0 earthquake occurred in Lushan County, Sichuan Province. The Lushan earthquake occurred on the southern Longmen Shan, the eastern margin of the Qinghai-Tibet Plateau, with no apparent surface rupture zone in the earthquake zone. In this paper, the section of the middle reaches of the Qingyi River crossing the earthquake area is taken as the research object. By comparing and finely measuring the terraces of the rivers, the terrains and terraces of the Qingyi River are obtained. It is revealed that the fold deformation is the Lushan earthquake area in the southern segment of the Longmen Shan tectonic belt Since the Quaternary, the maximum uplift of T_4, T_3, T_2 and T_1 terraces was 64.7m, 61.6m, 20.2m and 6.8m respectively. The GPS coseismic vertical displacements are consistent with terrace deformation characteristics. It is inferred that the focal rupture displacements of the earthquake mainly appear in the form of folds and uplift and slightly decrease in some areas away from the epicenter. Seismogenic structure of Lushan earthquake accords with the model of fracture extension fold.