TECTONIC STUDIES AND EARTHQUAKE RISK BASED ON TECTONIC MORPHOLOGY STUDIES IN SAVEH RECTANGLE

The Saveh area is located in the south foreland basin of the central Alborz (Alavi, 1996). Based on geological divisions of Iran, it consists of two zones, including Central Iran and the Urmia-Dokhtar Zone (Berberian and King, 1981), so that the assumed range is located in northwestern Iran and part of the Urmia-Dokhtar volcanic belt passes fromits south (Berberian, 2014, 1976). Both zones, including structural-sedimentary and seismic zones, are important landforms of the Iran Plateau, consequently, this zone is a unique region. In this region, active and seismic faults form the boundary between the tectonic subsidence and the mountains of the region along the east-west to the northwest-southeast direction. The occurrence of destructive earthquakes in the past centuries, especially in the past few decades, indicates the seismicity and seismic potential of the faults in this area. Therefore, identifying and investigating faults in the area and assessing the seismic and morphological potential of the area, so using some of the geomorphic indices such as; Hypsometric Integral (Hi), Elongation Ratio (Re), Basin Shape (Bs), Drainage Asymmetry Factor (AF), Valley-to-Depth Width (Vf), Valley Floor Width-to-Height Ratio (Vc), Valley Cross-Section Ratio (V), Stream Length-Gradient Index (SL) Mountain Front Sinuosity (Smf), it is highly significant. The way forward of this study, entails seismic sources, identification and estimation of seismic parameters and involvement of historical earthquakes in analyses. Seismic variables are then estimated using Gutenberg-Richter and Kiko-Sellovel methods as well as Zmap program and attributed to seismic sources. The mentioned seismicity data were analyzed and calculated in order to provide the seismic acceleration map in Saveh area in EZ-Frisk software environment. The probabilistic method was used in order to estimate the maximum values of the ground-level movement parameters. Based on these studies, were prepared the active tectonic zoning map in the study area and acceleration earthquake map in the near-zero-period (PGA) for the return period of 475, 975, and 2475 years by using probabilistic method. Regarding these maps, the maximum acceleration is approximately 0.94 g and is related to the earthquake with a return period of 2475 years. For a return period of 975 years, the maximum acceleration values are nearly 0.69 g. In the return period of 475 years, the maximum earthquake acceleration is about 0.49 g, which they have a good compatible with the basins that demonstrate high activity.

Keywords:

Probabilistic method , Seismic acceleration map , EZ-Frisk software , Seismic parameters , Morphological