Application Of Newmark Models For Assessment Of Earthquake-triggered Landslides

The April 20,2013 Sichuan Lushan Mw6.6 earthquake and the Sichuan Wenchuan Mw7.9 earthquake in May 12,2008 were the two strong earthquakes occurred on the Longmen mountain tectonic belt.A large number of landslides have been induced by these two earthquakes,resulting in huge casualties and loss of property.It is of great significance to explore an effective method of evaluating the risk of earthquake landslides for the prevention and reduction of earthquake landslides.Based on the Newmark method,the earthquake landslide hazard assessment of Lushan earthquake and Wenchuan earthquake has been carried out respectively.The following results have been achieved:(1)By applying the Newmark model and statistical analysis models(LR and SVM),this study carried out the landslide hazard assessment of Lushan earthquake.In the Newmark model,we used the landslide point density(LND),the average gradient(Mean-slope)and the mean peak ground acceleration(Mean-PGA)to group the lithology and get critical acceleration(ac)map.The Newmark displacement map and the probability map of the slope instability were obtained by combining the ac map and PGA map.(2)In the statistical analysis model of LR and SVM,7040 samples(4540 landslide sites and 2500 random non-landslide sites)were randomly divided into the training set(5000 samples)and validation set(2040 samples).Based on the relationship between landslide distribution and influence factors,we selected critical acceleration(ac)of intermediate output data Newmark model,topographic relief,PGA,distance to river as the independent variables for LR and SVM.Finally,the ROC curves for three landslide hazard models were drawn and the AUC values were calculated.The landslide hazard maps produced by LR shows similar result as that obtained by applying SVM and the AUC values indicate that these two models combined with ac data perform highly better than the Newmark model.(3)This paper studies the landslide hazard assessment and slope-failure function using two Newmark displacement models regressed by the site station records and global station records respectively.Taking the 2008 Wenchuan earthquake as an example,based on the topographic and geological data of the study area,we got factor-of-safety map and critical acceleration(ac)map.Using two Newmark simplified models regressed by site station records and global station records,two Newmark displacement maps were obtained by combining the ac map and PGA map.(4)Based on actual landslides inventory of the Wenchuan earthquake,we constructed the probability curves of two Newmark models relating predicted displacement to probability of slope-failure.The result shows that the ability to predict landslide occurrence of two Newmark simplified model are overall consistent,the assessment results can better reflect the macroscopic distribution characteristics of coseismic landslides,most predicted landslide cells are distributed in the two sides of Beichuan-Yingxiu fault,especially Pengguan complex rock mass in hanging wall.The parameters of two probability curves based on two Newmark models have changed slightly,which indicates that the criteria for probability curve established by different Newmark model is different.In this study based on the Newmark method,the earthquake landslide hazard assessment of Lushan earthquake and Wenchuan earthquake has been carried out respectively.On the one hand,according to the Newmark model and two statistical analysis methods(LR and SVM)integrating with the output results of Newmark method,we conducted the landslide hazard assessment of Lushan earthquake and found a more effective method of landslide hazard assessment.On the other hand,the slope-failure curve of Wenchuan earthquake can provide reference for subsequent regional earthquake landslide rapid emergency assessment and seismic landslide hazard analysis.