Application of Ground Penetrating Radar (GPR) Method for Evaluation of Sediment Structure in Paleotsunami Geopark Development Area, Aceh Besar, Indonesia

Ek Leuntie Cave is a karst cave in Meunasah Lhok, Lhoong District, Aceh Besar Regency. This cave is very rare. It has 12 tsunami layers dating back 7500 years. These layers need to be preserved as a paleotsunami geopark in Aceh. However, there are many challenges to developing public facilities in karst areas, such as sinkholes and landslides. Therefore, this study aims to investigate the potential hazards in the area by using the Ground Penetrating Radar (GPR) method at 700 MHz and 250 MHz frequencies. The GPR method is used because of its ability to image shallow subsurface structures with high resolution. The GPR method was used on 7 survey lines around Ek Leuntie Cave. The resulting radargrams are then processed using GPRPy software to clarify the reflection signal. GPR interpretation at 700 MHz and 250 MHz frequencies produces the same radargram at a very shallow depth, but the boundaries between layers are clearer at 700 MHz. Core data from multiple samples supports GPR interpretation. Based on the core data, the compact layer is located in the sandy soil layer, while the less compact layer is located in the old main road before the tsunami layer and in the bedrock. The less compact layer has potential hazards such as subsidence. The area is located in the west to south of the cave. Based on the GPR radargrams obtained, the investigation area is dominated by clay fill, sandy soil, clayey sand and bedrock. The results of the study are expected to be used as a reference for mitigation in the development of the Ek Leuntie Cave Geopark.