四川盆地南缘筠连-长宁地震区扎子坳断层探测及活动性初步研究

Detecting Fault and Activity Studies of Zhazi’ao Fault in Junlian-Changning Earthquake Zone in the Southern Margin of Sichuan Basin

通过地震活动性调查、地表地震地质调查、浅层地震勘探、高密度电法勘探及探槽剖面分析等多种手段对扎子坳断层进行综合研究,结果发现,扎子坳断层发育于古生代二叠系砂岩和中生代三叠系灰岩、砂岩地层中,属逆断层,断层总体呈NNE向展布,长约15 km,破碎带影响宽度一般小于20 m,断层规模较小。结合浅层地球物理勘探和探槽剖面分析结果初步推测,扎子坳断层不具备晚更世晚期活动性,为2017-01-28筠连4.9级地震的发震构造。

This paper uses various methods such as seismicity,surface seismic geological survey,shallow seismic exploration,high-density electrical method exploration and trench excavation to investigate the Zhazi’ao fault.Through investigation,the Zhazi’ao fault is developed in the Paleozoic Permian sandstone and Mesozoic Triassic limestone and sandstone formations.It is a reverse fault.The fault is generally NNE-oriented and the length is about 15 km.The width of the fracture zone is generally less than 20 m,and the fault scale is small.Combined with shallow geophysical exploration and trenching profiles,it is preliminarily presumed that the Zhazi’ao fault does present late Pliocene fault activity,and is the seismogenic structure of the Junlian M4.9 earthquake on January 28,2017.