## 1 Introduction  
Natural gas has an important role among energy sources from the point of being eco-friendly and cost effective. The liquefaction of natural gas makes it possible to transport larger quantities of gas [1]. Floating storage and regasification units (FSRU) have recently become a preferred strategic solution for transporting liquefied natural gas (LNG) between offshore terminals. As a result, the number of FSRU terminals built on marine sediments, which are unsuitable foundation soils, is increasing day by day in many parts of the world. Instabilities FSRU terminals can cause environmental pollution and economic consequences [2]. Therefore, the resilience of these terminals has crucial importance in terms of environmental safety. Marine sediments are generally unfavorable foundation soils due to their susceptibility to liquefaction and low-bearing capacity. To increase the shear strength and prevent liquefaction, the marine sediments require improvement before construction. Some approaches have been developed to reduce the liquefaction problem. Deep soil mixing, jet grouting, dynamic compaction, lime stabilization, vibro-compaction, and ground freezing techniques can be employed to decrease the liquefaction potential [3]. Among the ground improvement techniques, jet grouting is one of the most commonly used. There are several previous studies about the application of the jet grout method and the evaluation of their performance [4; 5; 6; 7; 8; 9; 10; 11; 12]. The main subjects of the previous studies about jet grouting are the design of the columns [13; 14; 15; 16; 17], the mixture of grouting material [18; 19; 20], the injection methods [21; 22; 23; 24], and the quality controls of the columns [25; 26; 27]. [PERSON] et al. [28]have numerically demonstrated that using jet-grouted micro piles significantly reduces the risk of liquefaction in clean sands. However, most of these studies were conducted in a terrestrial environment. The application of jet grouting, particularly in the submerged sandy layers in ocean engineering, has emerged in the last decades [12]. [PERSON] et al. [29] discussed the improvement of the foundation ground that will settle on the seabed of a plaza planned to be built in Doha Port, Qatar by the jet grouting method. [PERSON] et al. [29] specified that non-destructive geophysical measurements are frequently used in controlling the quality of jet columns besides mechanical and observational control techniques. [PERSON] et al. [30] evaluated the applicability of the surface wave method for identifying the jet grout columns produced in heterogeneous soils. The researchers found that the selection of lateral sampling range in surface wave testing has importance because no apparent difference was determined between the survey line along the reinforced and un-grouted ground when the spacing between the jet columns is less than the minimum wavelength. On such an occasion, [PERSON] et al. [30] suggested that the total shear wave velocity of the jet-grouted ground should be measured with the multi-channel analysis of the surface wave (MASW) method, regardless of the location of the survey line. According to [PERSON] et al. [28], the MASW method is a good tool for quantifying ground improvement. To estimate the diameter of the produced jet columns, [PERSON] et al. [31] suggest a method based on the integration of standard cross-hole and downhole seismic measurements. Nevertheless, this approach is applicable in the terrestrial environment. In the literature, a quality control approach based on geophysical measurement before and after jet column construction in offshore environments has not been encountered. The quality control of jet grout columns is carried out conventionally by performing offshore drillings. On 6 February 2023, a series of earthquakes struck Turkiye, with the largest earthquake measuring 7.8 on the Richter scale. The earthquakes caused widespread damage, including liquefaction of soil in some areas.