Abstract: This paper briefly reports our newly findings on remains of earthquake surface ruptures along and near the transition segment(between Lizhou and Xichang)of the Anninghe and Zemuhe Fault zones in western Sichuan and analyzes their relations to historically documented large earthquakes.During geological surveys in recent years we find unknown-aged surface ruptures at three sites on and near the transition segment of the Anninghe and Zemuhe Fault zones.Through analyzing both characters of the surface ruptures and their locations in heavily damaged areas of relevant historical earthquakes in the studied region,we distinguish that ruptures at two of the three sites,north of Yangfushan and west of Dapingzi,should be remains of the surface rupture zone of the large 1536 earthquake.The findings of the remains at these two sites suggest not only that the southern portion of the 1536 rupture zone was yielded along the transition segment of the Anninghe and Zemuhe Fault zones,but also that the southernmost end of the 1536 rupture zone would have arrived at or been very close to Xichang.While,ruptures at and near the other site,east of Lijinbao,north of and not far from Xichang,should be remnants of the surface rupture zone of another historical large earthquake occurring in 1850.These remnants further prove that the most northwestern end of the 1850 rupture zone would have arrived somewhere at least several kilometers north of Xichang.It thus can be inferred from the evidence given in this paper that the major fault at and near Xichang was once ruptured by both the 1536 and 1850 earthquakes.Such an inference is compatible with the described phenomena in literal historical records that very heavy destruction and disaster happened in the city of Xichang during both the 1536 and 1850 earthquakes.

Key words: surface rupture remains, large historical earthquakes, Anninghe Fault zone, Zemuhe Fault zone, Sichuan

摘要： 在近些年的野外调查中,我们在安宁河、则木河2断裂带的过渡段(礼州至西昌之间)及其附近的3个场地发现了未知年代的地表破裂。通过分析这些地表破裂的特征以及在本区历史地震重破坏区中的位置,我们认为位于杨福山村以北与大坪子村以西2个场地的破裂应是1536年大地震地表破裂带的遗迹。这不仅反映了1536年大地震破裂带的南段沿安宁河与则木河断裂带的过渡段产生,而且反映了该破裂带的南端很可能到达了或者很接近于西昌。位于西昌略北李金堡村以东的破裂应属于1850年大地震地表破裂带的遗迹,它进一步证明了1850年大地震地表破裂带的西北端可能到达西昌以北至少数千米处。因而,由文中的证据可推断西昌附近的主干活动断裂在1536年和1850年大地震时均发生了破裂。

关键词: 地表破裂遗迹, 历史大地震, 安宁河断裂带, 则木河断裂带, 四川