Models for Area Seismic Source Definition and Parameterization for Georgia and the Surrounding Region

Models of area seismic source (ASSs) are the basic and most important inputs required for Probabilistic Seismic Hazard Analysis (PSHA), because on them mainly depends the reliability of the final results of seismic hazard assessment. Determinations of these models include the delineation of ASSs and their parameterization. In practical applications, when clear procedures for constructing ASSs do not exist, this leads to large variations in the computed hazard.In the Caucasus, where active faults are clearly defined and parameterized, and seismicity is relatively well documented, a method of ASS delineation is used, which was developed by us. The procedure for constructing ASSs is based on the delineation, along the active fault, of an area with a certain width. The width of the ASS is dependent from fault plane dip and width, from the thickness of seismically active layers and from geometrical sizes earthquake source. ASSs asymmetry relative to the axial line of the fault is a characteristic feature of these construction. On the basis of these method, ASSs were delineated for Georgia and the surrounding region.Each ASS is expressed by a set of parameters that will represent the basic input for seismic hazard assessment. Mmax assessments were implemented on the basis of three seismological and two geological methods. The magnitude-frequency distribution b parameter was calculated for 16 generalized tectonic units, for which seismic statistics were quite complete, and the a parameter was determined for each ASS. A study of the depth distribution of earthquakes showed that seismicity in this region is mainly shallow.