Study On Yushu Earthquake Landslides Of Qinhai Province, China

Earthquake-induced landslide has got people’s attention because of itsenormoushazard, and gradually become a new hotspot in the field of seismicgeology.Current studiesathome and abroad focus on aspects of characteristics anddynamic mechanism. The study about palaeo-earthquakelandslides is seldom,especially studying age and intensity of ancient earthquake bypalaeo-earthquakelandslides, which is still needed to be further researched.The2010Yushu earthquake with Ms7.1triggered a series of secondarygeological hazards. Itsummarizes different type, distribution and characteristics of2010Yushu earthquake landslides and palaeo-earthquakelandslides found alongYushu active fault,discuss the coupling relationship about palaeo-earthquakelandslidesand ancient earthquake by chronological analysis and obtain the followingpreliminary conclusions（1）On the basis of field survey in Yushu, combined with Quickbird remotesensing image data and aerial photo interpretation method by visual interpretation,there are542landslides.Based on the above, the major characteristicsand spatialdistribution of landslides, which includeslide,collapseand debris flow, are presented inthis paper. Among them the paper focuses on character of earthquake collapse whichis much more than others.And according to type of material,the earthquakecollapseare classified into three types, which are debris fall, debris flow and rock fall,and the paper analysis each developmental characteristic and condition.（2）The result shows the earthquake landslide mainly distributes in the area oflength of about95km and along both sides of the fault rupture in a wide2km range.As well as, the spatial distribution of earthquake landslides has well correspond withco-seismic surface rupture sections, distances of seismogenic fault and macroscopicepicenter location. ItreflectsYushu strike-slip fault control typical disaster. The paperalso presents the intact form of non-tectonic rupture and summarizes it mainly cracksin middle side and press-shear in both sides, and the width and height of rupture is decreasing from middle to both sides.Moreover, in view of close relationship amongthe distribution of landslides triggered by earthquake and earthquake surface ruptureand damage degree of the meizoseismal area, the author proposedearthquake-inducedlandslide can quickly locate the macroscopic epicenter andcontributes to further earthquake intensity evaluation of the meizoseismal area, whichprovides theoretical basis and guiding significance for earthquake relief work andfuture geology hazard risk assessment.（3）At same time, the author discovered13palaeo-earthquake landslides basedon the field geological survey. The research shows the palaeo-earthquakelandslides aslarge scale mainly distribute along with active fault in wide5km range, which isintensity controlled byYushu active fault. As well as, according to analysis of thecharacteristics of landslide surface morphology,scale and formation age and thesuperimposition relationship between ancient landslides and the surrounding stratum,palaeo-earthquake has features of large number, in-situ recurrence,multi periods ofactivities.（4）The author collected14C dating sample further from main scarp of severaltypical palaeo-earthquake landslides, AMS14C dating results indicate they mainlyformed in the mid-to late Holocene, and focus on5periods, respectively are6560±30cal.aB.P,4370-3330cal.aB.P,2960-2280cal.aB.P,1300-1270cal.aB.P and790-400cal.aB.P,which has a good corresponding relationship with paleoseismic eventsperiods revelation by digging trenches. Further by comparing with the scale of allpalaeo-earthquake landslides, speculated that the biggestpaleo-earthquake on Yushufault zonestruck between4370cal.aB.P to2280cal.aB.P and between790cal.aB.P to400cal.aB.P,which the magnitude are greater than Yushu Ms7.1earthquake in2010.Finally the study demonstrates relatively uniform age of massivepalaeo-earthquake landslides can indicate the paleoseismic events occurrence timeand has important significance to add and recovery paleo-seismic event catalogue.