Abstract: Various earthquake rupture phenomena along the Zemuhe fault were found through field investigation and the age of them was studied by means of lichen measurement, which proves that the surface rupture zone occurred along the Zemuhe fault with a length of at least 90 kilometers during the 1850 earthquake, the maximum horizontal displacement is 7 meters and the maximum vertical displacement is 5.8 meters. The earthquake faulting caused all kinds of geomorphic and geological features, including fault scarps, fault gullies, offset streams and fans, sag ponds, earthquake wedges, landslides and talus etc. According to the scale and the displacement of the earthquake fault along with historical record, it is suggested that the magnitude of the 1850 earthquake should be 8 and the epicentre should be sited at Daqingliangzi, south of Xichang.

Key words: Sichuan, Xichang earthquake, Surface ruptures, Earthquake fault

摘要： 本文对则木河断裂带上各种地震地表破裂现象作了调查和时代方面的研究,结果表明,1850年西昌地震在西昌北的李金堡至宁南的松新间形成了长达90km的地震形变带。地震位错的最大水平位移为7m,垂直位移一般为0.5～2m,对地震形变带中的各种变形遗迹和地震地表破裂特征的研究表明,则木河断裂是这次地震的发震构造,震中位于大箐梁子一带,震中烈度达Ⅹ～Ⅺ。地震破裂的力学性质为左旋扭张,与则木河断裂晚第四纪以来的活动一致。地震破裂具有向南突出发展的不对称特点。

关键词: 四川, 西昌地震, 地表破裂, 地震断层