| Lianfeng and Zhaotong fault zone,which along the eastern side of Xia nshuihe and Xiaojiang Fault Zone,is located in the junction zone between the Daliangshan sub-block and the Southern China block.This zone is an im portant structure intersection area.Many large earthquakes occurred nearby along other faults,while along the Lianfeng and Zhaotong fault zone is prove d that no large earthquake happened more than 1700 years.In recent years,many moderately strong earthquakes have occurred in this zone,causing m ajor disasters,especially the 2014 Ludian MS 6.5 earthquake,causing heavy casualties.At present,the research of fault activity on the Lianfeng and Zhaotong fault zone is still low,which needs further study.In this paper,we use Google Earth,GF-1,GF-2 and other high resolution im age data,30 m resolution A STER DEM data,1:20 million regional geological survey report,historical earthquake records and pr evious research results,to interpret the wide valley surface of the Niulan River,the distribution of Lianfeng and Zhaoto ng Fault zone.Meanwhile cooperati ng with the field survey of Niulan river Valley,the faults activity of Lianfeng and Zhaotong fault zone and geological disasters in seismic damaged areas of major historical earthquake,getting several results as following:(1)Along the Niulan river,there are at least four levels of broad valley surfaces.The age of broad valley developm ent is 2.6-0.585 Ma B.P..It is comparable to the wide valley period of the Xiluodu section of the Jinsha River in altitude and the development ages;(2)According to the deformation of the broad valley surface of the niuan River which cross the fault zone,it is found that the Lianfeng fault and the Zhaotong-Ludian fault is a group of thrusting faults sinc e the Quaternary period,of which the Zhaotong-Ludian fault has the strongest activity since the Quaternary,and the secondly is Lianfeng fault,and the Huize-Yiliang fault has the weakest activity since the Quaternary.(3)lianfeng and Zhaotong fault zone show s distinct linear features in rem ote sensing images,but the activity of fault in this zone is weak since late Pleistocene: the Huize and Yiliang fault is an early-middle Pleistocene active fault,the activity of the SW segments is weake r,and the activ ity of m iddle and Northern segm ents are stronger;Zhaotong-Ludian fault zone incl udes Zhaotong-Ludian fault,Sayuhe fault and Longshu fault.All of those faults are la te Pleistocene active faults.The activity of the Lianfeng fault zone is very weak since late Pleistocene.(4)The NW trending surface raptures caused by the Ludian earthquake in Xiejiayingpan and the back edge of the Wngjipo landslide are tension fissure along the joint sufure of back edge of slope.Those ruptures ar e secondary surface raptures caused by Ludian earthq uake.The NE tre nding surface rupture in Laojun Mountain was a crack formed by mining while not caused by the Ludian Earthquake.(5)The frequent occurrence of strong ear thquakes in this region are m ainly located in the the Zhaotong section of Zhaotong-Ludian fault,intersection area of the Mabian-Yanjin fault and the Lianfeng fau lt,and the north ea st section of the Huize-Yiliang fault.Those earthquakes had caused strong disasters,and the earthquake will induce a lar ge number of landslides,co llapse.The long axis of landslides distribution are cons istent with the extension direction of the seismogenic faults.Compared with other regions with si milar magnitude earthquakes,in this area it could cause more co-seismic landslides.The features of those landslides include larger area,larger earthwork,and larger slip distance.But the level of the landslide is flat.The av erage thickness is small,mostly of those are co llapses,and the la rge landslide is little.Only the ex tremely earthquake area of the great earthquake can induce the large landslide.6)According to the existing large paleo landslides,earthquakes over magnitude 6.5 have been occurred in the NE segment of the Huize-Y iliang fault.The NE segment of the Huize-Yiliang fault has th e ability to occur an earthqu akes which magnitude of 6.5 or above. |
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