Ancaman kerusakan bangunan dan infrasruktur lainnya disebabkan oleh adanya zona lemah di bawah permukaan yang dapat menyebabkan bencana alam, seperti likuifaksi, khususnya di pesisir pantai, yang dicirikan memiliki muka air tanah dangkal, tingkat kepadatan lapisan tanah sangat lepas dan geologi daerah terdiri dari batu pasir dan endapan aluvium. Penelitian ini bertujuan untuk menentukan nilai hambatan jenis (resistivitas) dan hambatan konus dari zona lemah di Desa Sekotong Barat, Kecamatan Sekotong Kabupaten Lombok Barat dan bagaimana hubungan empiris nilai resistivitas dengan hambatan konus. Penelitian ini dilakukan menggunakan metode geolistrik konfigurasi Wenner dengan jumlah 6 lintasan dan panjang setiap lintasan 200 meter dan juga menggunakan uji sondir pada 3 titik. Berdasarkan hasil interpretasi data diperoleh litologi batuan di daerah penelitian terdiri dari lapisan pasir jenuh air, lempung lanauan, lempung pasiran dan pasir padat. Hasil inversi data geolistrik menunjukkan keberadaan zona lemah membentang pada seluruh daerah penelitian kecuali pada lintasan 3 dan lintasan 4 yang ditafsirkan tidak berbahaya bagi bangunan diatasnya karena tersusun oleh zona kuat. Diperoleh zona lemah dengan nilai resistivitas kurang dari 10 yang diidentifikasi sebagai lapisan pasir jenuh air dan lempung lanauan dan dibuktikan pula dengan hasil uji sondir memiliki nilai hambatan konus kurang dari 20 kg/cm2. Resistivitas dan hambatan konus berbanding lurus dan hubungan empiris yang dihasilkan berupa grafik polinomial orde tiga dengan koefisien determinasi.0,804

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.

The application of geophysical methods for the characterization of geomorphologic subsurface features has become very popular in recent years. Convential geophysical applications on undifferentiated and weathered slopes have been less effective. Multichannel analysis of surface waves (MASW) is a new hope for the solution of the problem. MASW methods was used to the first step in order to reconstruct the ancient eruption of Mount Samalas. MASW was applied to the remnants of ancient volcanic sediment on Lombok Island to determine the physical and physical characteristics of seismic subsurface features. This paper is also discussion the application's capabilities of the MASW method on undifferentiated and weathered volcanic deposits on the slope area and classified them. The results of the research show that MASW technique is powerful in characterizing and delineating the stratum of the layers of undifferentiated and weathered volcanic precipitation areas. MASW is able to predict subsurface structures, especially for shallow and thin layers and presenting site class information for internal structure (vertical resolution). Based on S wave velocity structure, undifferentiated and weathered volcanic layer, genes are classified into site class C, D, and E. In the future, this method will completed with combination of other geophysical method and parameters variation (frequency and spaces) for isopach mapping of volcanic sediment and then analysis of ancient volcanic eruption dynamics.

Abstrak. Dinamika fluida akan mempengaruhi sifat fisis dari fluida yang ada di bawah permukaan. Apabila terjadi intrusi, maka resistivitas batuan bawah permukaan akan berkurang. Sebaliknya, apabila air mengalir dari darat ke laut pada musim penghujan, maka resistivitasnya akan semakin bertambah. Penelitian ini bertujuan untuk mengetahui volume dinamika fluida dalam selang waktu 6 bulan di kawasan Mandalika. Pulau Lombok. Akuisisi data menggunakan metode geolistrik resistivitas konfigurasi dipole-dipole, sebanyak 37 lintasan. Pengukuran pertama dilakukan pada Maret 2022 dan pengukuran kedua dilakukan pada Agustus 2022 Dengan volume total dari selang waktu 6 bulan yaitu 336.000.000 , perubahan resistivitas bernilai positif memiliki volume sebesar 86.980.000 , volume perubahan resistivitas bernilai negatif sebesar 22.700.000 m3 dan resistivitas bernilai konstan memiliki volume sebesar 276.600.000 m3.

Fault activities was detected during periods of 2016 to 2018 which presented by land subsidence in East Lombok and Central Lombok regencies during this period. In order to find out the impact of the earthquake which occurred from July to August 2018, time lapse microgravity anomaly before and after earthquake was compared, i.e. time lapse microgravity anomaly 2016 to 2018 period and 2018 to 2019 period. Measurements were carried out at about 80 points which distributed in both of regencies. Time lapse microgravity anomalies periods of 2016 and 2018 show positive values at all measurement points and deformation analysis revealed that subsidence occurred at all study areas. The results of the time lapse microgravity anomaly data processing between the periods of 2018 to 2019 show the opposite one. The results of data analysis and processing of time lapse microgravity anomaly during period 2016 to 2019 shows the deformation process on the surface before the earthquake Lombok and it was stopped due to the events of the Lombok Earthquake in 2018. The earthquake that generated by the thrust fault mechanism causing elevation change of the research area in Central Lombok Regency and East Lombok, an event of uplifting occurred.