Abstract:The integrity of paleoseismic events on active fault is an important basis for recognizing activity behavior and evaluating its future strong earthquake risk. Interpreting the microtopographic features of active faults based on high-resolution imagery can complement with paleoseismic trenching methods, jointly constructing a complete earthquake recurrence model. This paper takes the Linze Fault on the northern margin of Yumushan in the middle of the Hexi Corridor as the research object, generate high-precision topographic and geomorphological data based on unmanned aerial vehicles and photogrammetric methods, through detailed interpretation of the offset geomorphology of active faults, then measure 90 set of single or multiple cumulative vertical offset on linear fault scarps saved on alluvial-proluvial fan along the fault zone, and get the curve of cumulative offset probability density(COPD) to obtain its vertical offset clustering characteristics. A total of 6 peak accumulated offset were identified along the fault, which were 0.5、0.9、1.5、2.1、2.7、3.3 meters, respectively, revealing that the Linze fault may have experienced at least six palaeoseismic events with magnitude ranging from Ms6.6 to 7.0 since Late Pleistocene. Thus, we compared and analyzed the integrity of paleoseismic events revealed by previous studies using paleoseismic trenching methods. Referring to the dating results of paleoseismic events determined by trenching, the latest seismic event occurred 2.1-2.5 ka ago. Based on the above analysis, the Linze fault conform to the characteristic seismic recurrence pattern, and its tectonic activity continuously compresses and expands towards both sides of the fault and interior of the basin. Comprehensive analysis of recurrence pattern and elapsed time, the latest seismic event of the Linze fault is close to its recurrence interval, indicating a high risk of strong earthquakes.
