The thickness of the liquefable layer can be the factor inducing liquefaction hazard, apart from seismicity. Several studies have been conducted to predict the possibility of the liquefable layer based on the filed sampling. However, a detailed investigation of the subsurface interpretation has not been defined, in particular the thickness estimation of the liquefable layer. This study is carried out in south Cilacap area where potential liquefaction is exists due to the earthquake history data and near surface condition. The aim of this study is to investigate the physical properties and thickness distribution using GGMplus gravity data and resistivity data. This research is conducted by spectrum analysis of gravity model and 2D resistivity model . This study’s main results is by performing the residual gravity anomaly with the associated SRTM/DEM data to define the subsurface physical distribution and structural orientation of the area. Residual gravity anomaly is also separated through the low pass filter in order to have robust interpretation. The residual anomaly indicates that the area has identical structural pattern with geological and SRTM map. The results show a pattern of high gravity index in the northeast area of ​​the study having range of 70 – 115 MGal gravity index, associated with the volcanic breccia, and a low gravity profile with less than 65 in the southwest, associated with the alluvial and water table dominated distribution. The thickness of Alluvial is determined by resistivity model with H1 at a range of 3 meters and H2 at a range of 4 m. This research is included in the potential liquefaction category with the potential for a large earthquake.

The Humpa Leu East (HLE) prospect is one of the newly discovered porphyry Cu‐Au prospects in the Hu'u district, Sumbawa Island, Indonesia. The HLE prospect was formed by calc‐alkaline magmatic activity in an active continental margin setting. The prospect is typical calc‐alkaline porphyry Cu‐Au mineralization related to multiphase diorite and quartz diorite porphyry intrusions, which are hosted by andesitic crystalline tuff, volcanic breccia, and andesite lava. Hydrothermal alteration recognized at the surface includes potassic, propylitic, advanced argillic, intermediate argillic, and argillic alteration. Two styles of Cu‐Au mineralization were identified in the HLE prospect, that is, quartz‐sulfide veins and sulfide dissemination, formed in the early, intermediate, and late stages. The early stage is associated with M (magnetite ± bornite ± chalcopyrite), A (quartz + magnetite), and AB (quartz + magnetite + chalcopyrite ± pyrite) veins. These veins were mainly formed in the potassic alteration zone. The intermediate stage is characterized by B (quartz + chalcopyrite + pyrite) and C (chalcopyrite ± pyrite) veins and mainly associated with the chlorite‐sericite and sericite alteration zones. The late stage is mainly associated with D (calcite + gypsum + quartz + pyrite ± chalcopyrite ± sphalerite ± galena) veins with sericite‐chlorite alteration halo. Petrography and electron microprobe analyses indicate that calcite mainly replaced Ca‐rich plagioclase. Fluid inclusion petrography and Raman spectroscopy revealed that monophase vapor inclusions, as well as two‐phase (V + L) and multiphase (V + S + L) fluid inclusions contain CO2 gas. The potassic alteration with significant amounts of calcite is indicative of CO2‐rich fluids, which is uncommon in other porphyry Cu‐Au deposits. On the basis of textural and fluid inclusion analyses, calcite formed by a reaction between Ca‐rich plagioclase and CO2‐rich hydrothermal fluids. The CO2 in the hydrothermal fluids of the HLE prospect was likely derived from the magma.