NEWLY FOUND SURFACE RUPTURE REMAINS OF LARGE HISTORICAL EARTHQUAKES ON AND NEAR THE TRANSITION SEGMENT OF THE ANNINGHE AND ZEMUHE FAULT ZONES,WESTERN SICHUAN,CHINA

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.