Comparison of Information Value Method and Analytical Hierarchy Process in the Earthquake-Induced Landslides Hazard Zonation (A Case Study)

Although many studies have been done on the landslide hazard zonation, landslide caused by the earthquake has received less attention. Analysis of features of landslides caused by the earthquake and their distribution is very important in recognizing landslide-prone areas for future earthquakes. The purpose of this study is to identify the effective factors and zonation of landslides caused by the earthquake through information value and Analytical Hierarchy Process (AHP) methods in the area near the epicenter of the Manjil earthquake with an area of 309.30 km. In this study, landslide hazard zonation caused by earthquake was performed by using bivariate regression (information value) and AHP, and the efficiency of these two methods were studied and compared. Hence, according to the landslides location, comparative studies and the results of other researchers, seven factors including Arias intensity, internal friction, cohesion, slope angle, aspect, direction, elevation and terrain rough, have been identified as the most important factors in the landslides caused by Manjil earthquake. Then, these factors were prepared in a Geographical Information System (GIS). All information and data for the initial analysis were imported into GIS, and zonation maps of the landslide caused by the earthquake were prepared with regard to the above-mentioned methods. For this purpose, in the information value method, the inventory map has been initially integrated with the maps of effective factors in the landslides occurrence. After calculating the weight of each subclass of factors and finally adding the results of the previous stage in the information layer table in the Arc GIS, landslide hazard zonation map was obtained by this method. Through using the expert opinions and the tables used in the AHP method, the effective criteria and sub-criteria in the occurrence of landslide caused by earthquakes in the study area were compared. Afterward, the results of these comparisons were placed in Expert Choice software, and the relative weights of each criteria and sub-criteria was obtained. Then, the obtained final weights were added to the effective factors information layer table. Finally, hazard zonation map of landslide caused by earthquake in the study area was obtained by this method. According to the results of AHP method, Arias intensity and terrain rough factors had highest and lowest impact on the landslide occurrence. The greatest impact for sub-criteria 10–11.54 is related to the Arias intensity, and minimum impact is related to the smooth sub-criteria of terrain rough factor. Further, according to the zonation maps obtained by these two methods, the models obtained from AHP and the information methods, high risk and very high risk zones have respectively constituted 73 and 52 percent of the region. After reviewing the efficiency of procedures employed in this study by using two quality sum (QS) and precision (P) indicators, the results showed that bivariate regression model is more appropriate than AHP method and its results are more consistent with reality.