LOGISTIC REGRESSION MODEL AND ITS VALIDATION FOR HAZARD MAPPING OF LANDSLIDES TRIGGERED BY YUSHU EARTHQUAKE

At 07: 49(Beijing time)on April 14, 2010,a catastrophic earthquake with Ms 7.1 struck Yushu County,Qinghai Province,China.2036 landslides were interpreted from aerial photographs and remote sensing images,verified by selected field checking.The spatial distribution of the landslides was evidently strongly controlled by the locations of the main surface fault ruptures.The landslides commonly occurred close together.Most of the landslides were small.The landslides were of various types.They were mainly shallow,disrupted landslides,but also included rock falls,deep-seated landslides,liquefied landslides, and compound landslides.The aim of this study was to apply and validate logistic regression model for the Yushu earthquake triggered landslide hazard mapping.The Geographic Information Systems(GIS) and Remote Sensing(RS)technologies were used.A spatial database was developed and analyzed using GIS technology.It includes the landslides and associated controlling parameters which may have influence on the occurrence of landslides..The twelve factors that influence landslide occurrence were created in raster data format base on GIS platform.They include elevation,slope angle,slope aspect,slope curvature,slope position,drainages,lithology,faults,roads,normalized difference vegetation index(NDVI),co-seismic main surface fault-ruptures, and peak ground acceleration(PGA).the coefficients of the evaluation variables were estimated using logistic regression model and were used to calculate the landslide hazard index for the entire study area within a GIS environment.The validation result showed a success rate of 83.21% between the hazard map and the locations of Yushu earthquake triggered landslides.The landslide hazard assessment rank result showed that the"very high hazard"level covers about 4.97% of the total study area but has a number of 766 landslides(37.62% of the total landslides number),which representing good quality of the landslide hazard map.The sequence of the landslide number density percentage descends expeditiously accompany with the hazard level decreasing.