Topographic classification of North Eastern Region of India using geospatial technique and following seismic code provisions

The availability of high-resolution digital elevation models (DEM) and advancements in geospatial techniques enable a more accurate measure of slope position classes and classification of landforms using algorithms like topographic position index (TPI). In this study, TPI-based slope position classes are used for the identification of major relief features like ridges, and these are embedded with DEM-derived terrain slope to perform the topographic amplification-based classification of the North Eastern Region (NER) of India, according to the present European (Eurocode-8) and Italian seismic codes using GIS tools. They are classified into four topographic classes: T1, T2, T3, and T4. The relation of geological units, seismic site classification map, and land use land cover (LULC) classes with identified topographic classes for the study region are analyzed. The results reveal that similar to 25% of the study area is a potentially high amplification zone (T4 class; amplification factor of 1.4 as per Eurocode-8), primarily associated with dense and light vegetation type land cover. The Indian seismic recording station sites and the epicenters of past earthquake events in the region are classified based on the obtained topographic classification map. Approximately, 47% of earthquake events of large magnitudes and 30% of strong motion network (SMN) station sites are in localities with potential topographic effects. The human settlements are predominantly found in places identified with no or minimal amplification zone (T1 class; amplification factor of 1). The presented topographic classification map of NER can assist the decision-makers and authorities to identify potentially high amplification areas considering seismic hazards and making choices for future infrastructural development.