## 3 Geotechnical Site Investigations and Liquefaction Analysis  
A comprehensive site investigation program was conducted by Sebat Co. [45] to determine the geotechnical characteristics of the foundation ground on which an FSRU terminal was planned to be constructed. A total of 10 offshore boreholes with depths ranging from 24 m to 49 m were drilled and several samples were collected for the laboratory testing. The location of the boreholes is given in Figure 5. The depth of the boreholes, the thickness of the lithologic units, and some characteristics of these units such as the Normalized Standard Penetration Test (SPT-N) and Rock Quality Designation (RQD) are summarized in Table 1. In the drillings of DS-5, DS-6, DS-7, DS-8, and DS-9, a mud layer with a thickness varying between 0.8 m and 1.6 m was observed. A loose sand level lies beneath the mud layer and its thickness ranges from 1.30 m to 4.30 m, and its SPT-N values were determined as 3-7. Following the loose sand, the moderately dense sand layer is situated with a thickness change between 1.8 m and 8.2 m. Considering the SPT-N values, the loose and moderately dense sand layers can be classified as ZE-type (loose sand and V\({}_{\text{s30}}\) < 180 m/s) and ZD-type (moderately dense sand and V\({}_{\text{s30}}\) = 180-360 m/s) soils, respectively, according to Turkiye Building Earthquake Regulation [46]. The normalized SPT value of this layer ranged between 8 and 41 with an average of 18. The jointed sandstone layer begins right after the sand layer and all drillings have been finished in this unit. Figure 4: Active fault map of the project area (modified after [44]). Figure 5: The locations of the boreholes on the site plan of the FSRU terminal [45]. In the study, a total of 26 grain-sized distribution analyses were performed. Some of the grain-sized distribution curves and liquefiable soil boundaries defined by [PERSON] [47] are presented in Figure 6. The samples mainly consist of fine sand-sized grains with a small amount of silt, clay, and gravel. The samples presented in Figure 6 exhibited fines that were plotted partially outside the range of liquefiable soils. However, soils with similar grain-sized distributions have been interpreted to have liquefied in the past [48; 49]. [PERSON] [50] described the liquefiable soils as having a fines content (<0.005 mm) lower than 15% and a liquid limit lower than 35%. In the study area, the fines content of the seabed sediments is smaller than 10% and they are non-plastic. Consequently, the seabed sediments in this study are identified as liquefiable soils. The liquefaction phenomenon is a serious problem for the FSRU terminal due to the project site being located in a seismically active area and sandy layers being prone to liquefaction. Therefore, the factor of safety against liquefaction (FSL), the liquefaction potential index, and the liquefaction severity index were calculated for the project site in this study. In liquefaction analysis, the peak ground acceleration for the study site is designated as 1.05 g (for a 2475-year return period). The FSL for the project site was determined following the method suggested by [PERSON] et al. [51]. FSL is the ratio of the resistance force of the soil against liquefaction (cyclic resistance ratio, CRR) and the cyclic stress caused by an earthquake (cyclic stress ratio, CSR). The magnitude scaling factor was assumed as 1 considering the magnitude of the expected earthquake in the study area. The SPT blow counts were normalized by employing energy ratio correction (E\({}_{\rm r}\) = 60%) [52], overburden correction factor (C\({}_{\rm N}\)) [53], borehole diameter, rod length, and sampler correction factors [51]. Liquefaction analyses by using Equations (1)-(3) show that the FSL of the project site varies between 0.04 and 0.29. A conventionally liquefaction-resistant site is considered to be one for which FSL \(\geq\) 1.2 for a 475-year ground motion using the NCEER procedure [54].