Fault importance index (FII) as earthquake source criteria for seismic zonation: case study of India

Abstract

The organizations in different countries involved in seismic zoning modify the maps in response to various seismic events. The predictive ground motion is used in the analyses which may not be estimated using a single attenuation relation, because it is established on theoretical basis not with the actual ones and hence always errors are included in the analysis. However, the impact of faults is not considered in many of such seismic zoning efforts in several countries. An earthquake is generally triggered along the fault line; magnitude of generated earthquake depends on many factors, mainly the fault characteristics. Hence, the fault is the basic source of seismic activity and its presence and importance directly influences the seismic status of a region. In the present study a new term “fault importance index (FII)” is proposed which is a numeric value estimated from fault characteristics. The FII value for each of linear feature is calculated and relation is derived between the FII with earthquake intensity. The generated polynomial equations relate the past intensity spread with FII. The seismic risk zone map is then generated on the basis of FII. The developed seismic risk map has been compared to few earlier seismic maps and it can be used for design of buildings especially near the earthquake source.