ABSTRACT
Three basic geomorphic units, which have developed in response to the climate changes during the last glaciation, are recognized along the northern piedmont of the ENE-trending Liulengshan Range from airphoto interpretation and field observation. These three units are the inter-stadial fluvial fan (S3) about 23–53 ka old, the maximum-glacial fluvial fan (S2) about 10–23 ka old and the post-glacial fluvial fan (S1) about 0–10 ka old, respectively. Five fluvial terraces (T0-T4) have also developed owing to the climatic temperature flucturation on thousand-years scale. These geomorphic units and fluvial terraces are chronometrically dated by thermoluminescence dating method. Striped geomorphic mapping shows a natural segmentation in offset geomorphology along the north Liulengshan fault. A set of quantitative data on faulting age, vertical throw and slip rate are obtained from longdistance topographic profile levellings across the offset geomorphic units or fluvial terraces. The average Holocene vertical slip rates of the north Liulengshan fault are in the range of 0.43–0.55 mm/a. Late Quaternary irregular faulting is demonstrated by temporal and spatial ebbing-and-flowing variation in vertical slip rate. The period of 1.56–7.6 ka BP is the main phase of intensely vertical faulting along the northern piedmont of Liulengshan Range. Paleoseismic data show that its surface-rupturing earthquake recurrence interval reaches 5,000–6,000 years. The coseismic vertical throw for the latest one reaches (3.4±0.3) m, and its elapse time has reached 6,000–7,200 years on the Huajialing-Xiejiayao segment, which indicates that the north Liulengshan fault is now in the risk of surface-rupturing earthquake occurrence.
