A study of zoning liquefaction in prone areas using fuzzy models: Abarkuh city, Yazd Province

Catastrophic earthquakes and their consequences have led to specific attention to liquefaction effects during recent years. Within areas with a higher groundwater level, seismic vibration occurring due to an earthquake can decrease the cohesiveness and strength of water-richsand soils and turn them suddenly into liquid materials. Such a process of changing solid materials to liquid ones under seismic effects is called “liquefaction”. Liquefied saturated soils may deform with little shear resistance.This can cause extensive damages to urbanand rural buildings and other structures such as coastal foundations, sea rigs, water resources, wateror gas pipelines, and power pylons. Some parts of Abarkuh county is under liquefaction risk due to morphotectonic conditions and active fault systems, such as the main Dehshir-Baft fault and its accessory branches, young Quaternary deposits with especial geological conditions and existence of extensive undergroundwater. Due to the lack of studies on the liquefaction risk and the significance of preventingany consequent life losses or financial damages in AbarkuhCounty, we try to study the major factors of triggering liquefaction, investigating the areas with higher risk factors.We also make some suggestionsas to reduce probable losses. To evaluate the major factors that affect liquefaction, G.I.S software, and, to determine the high risk areas, a fuzzy logic model are used. After making fuzzy layers to increase the sensitivity of liquefaction zonation mapping, threeGama phases of 0.7, 0.8, and 0.9are used. By comparing different Gama effects, we have decided to execute Gama 0.9 level due to its higher resolution and better coverage on liquefaction zonation. The result of this modeling indicates the location of a 100 km2 area within a high risk factormainly in NE, E and SE parts of the county. The area of moderate risk with about 65 km2 is located in SE and near the central of the county.