Sub Zoning of Earthquake Risk in Sabzevar City by Using GIS

Sabzevar is one of the ancient cities of Khorasan Razavi province that now is the second most populous city of province, after Mashhad city. During previous decades, Sabzevar city has had a rapid physical growth that has resulted in significant constructions without safety in terms of natural disasters such as earthquake. Construction is performed just for responses to short term accommodation demands. Developing the town towards north has occupied the hazardous geological and geo-morphological features such as faults Neogene hills, earthquake centers, steep slopes, new alluvial fans and sediments of Quaternary. In this study, the most important factors which accelerate the risk in case of earthquake occurrences were identified. Then some data layers such as distance from fault, topographic slope, structural slope, lithology, land use, population and building density, oldness of building and distance from historic earthquake centers were constructed in GIS. Weighting of effective factors was determined based on AHP method and subsequently the map of earthquake hazard zonation was prepared in 5 classes of very high, high, intermediate, low and very low risk. The map of earthquake hazard zonation reveals that in case of earthquake, 11 km2 of the town will be in very high risk zone, 37 km2 will be in high risk zone, 49 km2 will be in intermediate risk zone, 60 km2 will be in low risk zone 59 km2 will in very low risk zone.