The Use of Poisson's Ratio and HVSR Analysis for Clustering Liquefaction Hazard Potential (Case Study: Mandalika Special Economic Zone Buffer Zone)

Liquefaction is a geotechnical phenomenon resulting from decreased strength and stability of water-saturated soil due to vibrations or dynamic loads caused by earthquakes. This phenomenon can potentially cause substantial damage to infrastructure and buildings and threaten the safety of humans. The area has never experienced liquefaction, but the Mandalika is a special economic zone (SEZ) that faces directly onto the earthquake source Megatrust of the Indian Ocean, which has the potential to cause an earthquake of 9.0 Mw. The surrounding villages, namely Kuta, Mertak, Sukadana, and Sengkol, support this area. The rapid development of this area as a tourism and infrastructure destination has resulted in the need to understand and mitigate the risk of liquefaction that could impact the safety and sustainability of development in the area. This study aims to cluster the liquefaction potential of the Madalika area and its surroundings based on Poisson's ratio data supported by the results of horizontal to vertical spectrum ratio (HVSR) analysis and groundwater depth data. Microseismic data were measured at around 60 points spread throughout the research area. Poisson's ratio was calculated from the primary and secondary wave velocities of ground profiling microseismic data and groundwater level data measured in dug wells owned by residents. The value of the Poisson's ratio in the study area is about 0.1 to 0.5. Observing high or low Poisson's ratio values can help determine the potential for liquefaction moments caused by vibration and estimate the level of liquefaction risk in the Mandalika area. Poisson's ratio data was supported with data on sediment thickness, about (4 – 129) meters, (1 – 5) meters of groundwater level, and (64 – 918) ms-1 of Vs-30 to determine class potential liquefaction. The ranking or class liquefaction is based on factors influencing a row occupied by Kuta Village, Sengkol Village, Sukadana Village, and Mertak Village.