Activity On Kangxian-Wudu Fault Zone And Its’ Seismic Hazard Assessment

Kangxian-Wudu fault zone located in the western end of the Qinling Mountainsacross the north-south tectonic zone in the northern section of tectonics in WestQinling nearly east-west trending tectonic belt with the Wudu arc tectonic system ofcomposite parts belonging to the Qinling orogenic belt and the eastern edge of theintersection of the Qinghai-Tibet Plateau area. It is one of the regional active faults inthe southeast of Gansu province. Because fault activity in this region is relatively in aweak point, therefore this article will focus on the activity of this fault zone, and bvalue analysis of seismic hazard. According to air satellite images interpretation andfield seismic geological investigation on this fault, we have obtained results are asfollows:(1) Make clear of geometry and spatial distribution of this fault zone. Bounded byMadigou and Shenjiayuan area, this fault zone can be divided into threesegmentations. They are West (F1), Middle (F2) and East (F3) segment separately.Trending-NW West segment turn to NEE, then compound with Middle segment;Middle segment is almost EW trending, divided into the north branch fault and southbranch fault, where the north branch of the fault trending NEE, the south branch faulttrending NWW to Shenjiayuan differentiated by NNE-trending secondary faults andEast segment. East segment is nearly EW trending.(2) Identify the activity of the fault segment. The west fault segment in the earlyQuaternary activity characteristics show of compressional thrust; the middle faultsegment in the Late Pleistocene–Holocene indicates intense activity of the mainleft-lateral strike-slip, both the thrust movement; Late Pleistocene period activity ofthe east fault segment based compressional thrust movement, both sinistral strike-slipmovement component.(3) Gain plentiful geological phenomena along the fault zone. These landforms aremainly left lateral displacement of water systems and ridges, fault facet, faultescarpment, saddle, fault waterfall, ground fissures, bedrock collapse, landslide, faultSprings, trench and fault scarps, etc.. Especially in the Ganquan area, we found thatthe characteristics of Holocene activity are relatively strong.(4) Acquire the Middle and East segmentations of the horizontal slip rate. SinceLate Pleistocene, the slip rate of Middle segment increases from west to east. Since Holocene, slip rate of Middle segment is also increased from west to east. Since thelate Pleistocene slip rate of the fault zone from west to east is increased.(5) Understand fully of the tectonic conversion relationship from NW trending toEW trending in Kangxian-Wudu fault zone. Since the Late Quaternary, the NWtrending structure is still inheritance extrusion thrust movement-based, with theregional tectonic stress field changes in the East segment gradually converted to nearEW tectonic horizontal movement to dominate both the thrust movement component.(6) Analysis obtained Wudu-Kangxian fault zone may have paleo-earthquakeevents at least five times, but only one time, that is1730±111a BP. we can makesure.(7) The b-values of each segment of Kangxian-Wudu fault zone are different.Some differences in the middle segment of b-value is generally low, belonging to thehigh stress accumulation region, which shows that this region belongs to the seismichazard zone, if the region is an earthquake where is likely to lead to the breakdown ofthe middle segment, in the region have occurred to the possibility of earthquakesaround Magnitude seven.