Mesoscale seismic hazard zonation in the Central Seismic Gap of the Himalaya by GIS-based analysis of ground motion, site and earthquake-induced effects

The paper describes the mesoscale seismic hazard zonation study carried out in the Central Seismic Gap of the Himalaya by integration of ground motion, site and earthquake-induced effects using GIS technique. Three indices, namely (i) earthquake hazard index, (ii) liquefaction susceptibility index and (iii) landslide susceptibility index were estimated for comprehensive seismic hazard zonation mapping in this area. The earthquake hazard index was estimated by integration of data such as lithology, faults, soil, landforms, Gutenberg–Richter parameter (b value), predominant frequency, amplification factor and peak horizontal acceleration using the analytical hierarchy process (AHP) method. Similarly, geology and topographic parameters were integrated using the AHP method to estimate the Liquefaction Susceptibility Index. A multivariate statistical technique was used to estimate the Landslide Susceptibility Index. The three indices were combined to prepare mesoscale seismic hazard zonation map of the area which was classified into low, moderate, and high seismic hazard zones. Validation of the mesoscale seismic hazard zonation map was done using the isoseismal data of past earthquakes. High seismic hazard zones are found in the foothills and Siwalik region of the Himalaya, which consist of alluvial sand and unconsolidated sediments, whereas moderate zones are identified partially in the foothills, Siwalik and the Lesser Himalaya. This map will be useful for earthquake hazard mitigation in the NW Himalaya.