CHARACTERISTICS OF LATE QUATERNARY ACTIVITY OF THE FAULT ZONE ON THE SOUTHERN BOUNDARY OF WEIHE DOWN-FAULTED BASIN BELT

The fault zone of the southern boundary of Weihe River begins east from Tongguan and terminates west at Baoji with a total length about 350Km.Its main boundary fractures in-clude the frontal fault zones of Huashan Mt.and Qinling Mt.The history of fault activity and the active characteristics are examined comprehensively according to the geological map(1:50,000).The outstanding new activity of the Huashan Mt.frontal fault zone is revealed.A-long this fault zone and its two sides are distributed the newest fault scarps, base rock frac-tures, loess crevices, landslide and mountain creep, and other deformation and damage relics due to earthquakes.Huashan Mt.frontal zone is most likely the genetic fault zone of 1556 Huaxian earthquake(M=8).#br#Based on the analysis of the two palaeoseismic profiles, it is supposed that the earth-quake recurrence interval is 2000-2500years for Huashan Mt.frontal fault zone, whereas 2000-4000 years for Qinling Mt.fault zone.