Title: Importance of identification of source zones in seismic hazard analysis

Abstract

Development of seismotectonic map of the study area is a first step while attempting seismic hazard analysis. It consists of finding past earthquakes within a defined seismotectonic province along with the information on seismic sources in the region. Information on past earthquakes can be gathered from various database and gives more or less a complete picture of known earthquakes within a user defined region. Information on seismic sources is very critical. It is primarily due to the fact that while the development of seismic sources is a continuous process depending upon the tectonic setting and governing dynamics of the region. However, studies targeting to identification of seismic sources in a region happens for specific purpose that too confined to specific regions. As a result, although information about past earthquake is available, knowledge of seismic sources responsible for generating such events is incomplete majority of times. This can be understood from the fact that numerous seismic hazard studies exist with earthquake events present in locations of no seismic source. Overcoming this limitation of partial knowledge of linear seismic sources, numerous studies attempted seismic hazard studies based on identification of zones/ aerial seismic sources. However, it has been observed that identification of such zones are mostly based on either visual identification or taking variation of parameters such as rupture characteristics, geology, topography etc. into account. In such case, whether the seismic activity in each identified zone is uniform or not is not checked. Present manuscript will present a broader overview of factors considered in identification of source zones for seismic hazard studies and their effect on the findings of such seismic hazard studies. Further, rational methods which are in practice in seismology to identify regions of uniform seismicity will be discussed in detail. Identification of appropriate source zones will also have effect of relative use of selected attenuation relations since the range of distance of each identified source zone from the site of interest will change. How this affect can be taken into account while determining relative weights of selected attenuation relations, will also be discuss in this manuscript.