Assessment of Liquefaction Potentials of the Soils of the World’s one of the Greatest Tourist Attractions for Upcoming High Magnitude Earthquake. Fethiye/Türkiye

Earthquake induced soil liquefaction first gained importance after the 1964 Alaskan and Niigata Earthquakes. Soil liquefaction is responsible with severe effects due to the decrease in strength and stiffness of the soils underlying the engineering structures following the increase in pore water pressure. Therefore, studies based on the assessment of the liquefaction potentials of the soils have always been significant and in great interest by the researchers. Assessment of the liquefaction potentials of the soils are especially significant for the cities with high population. Fethiye is one of those cities particularly during summers due to high tourist influx (177.569 people in winters, over 1 million people in summers). Fethiye, where is known to be hit by an earthquake with moment magnitude 7.1 in 1957, is estimated to be hit by such an upcoming earthquake in the following years according to the Gutenberg-Richter magnitude-frequency relationship. This paper discusses the liquefaction susceptibilities of the Quaternary deposits within the Fethiye basin calculated according to the simplified procedure. Soil samples from 256 almost evenly distributed boreholes drilled within the microzonation projects within the study area have been used in the calculation of liquefaction susceptibilities of the soils. Calculated factor of safety values have been converted to the liquefaction potential index values to understand the liquefaction hazard. Liquefaction hazard in the region varies from very low to very high (LPI=0 Very Low, 0<LPI≤5 Low, 5<LPI≤15 High, LPI>15 Very High) in the region. According to the analyses, liquefaction potentials of the soils increase towards the coastal margin of the basin where groundwater level gets shallower. Moreover, it has been seen that the clayey soils are not liquefiable according to the Chinese criteria and the liquefiable soils within the study area are mainly sands and silty sands. As it is moved towards the Eastern inland margin, gravel amount increases, groundwater level deepens and liquefaction susceptibilities of the soils decrease. Thus, new urbanization plans must mainly be held in these low susceptible regions, and if it is inevitable not to construct buildings within the liquefiable zone, the essential soil improvement actions must be held to eliminate undesired destructions.

Keywords: Liquefaction, Liquefaction Potential Index, Fethiye, Tourist Attraction, Hazard Mapping.