The application of geophysical methods is widely used for the assessment of subsurface geological features, including the determination of potential groundwater aquifers, understanding of stratigraphy sequences, and structural analysis. The demand for groundwater exploration is on the rise, encompassing needs for domestic, industrial, and agricultural purposes. However, unsuccessful groundwater exploration has occurred owing to a lack of comprehensive subsurface information. Groundwater, as an alternative water source, remains largely unexplored within the Penang Island. In relation to this, a thorough study on the geophysics and geology should be carried out. It is certainly not as simple as just digging a well to draw water. Current technologies widely used for groundwater exploration include geophysical methods, remote sensing, Geographic Information System (GIS), hydrogeological, and machine learning. Therefore, geophysical methods were applied to obtain subsurface information to determine and classify the materials using selected geophysical properties. Geophysical methods, particularly Electrical Resistivity Tomography (ERT) is a non-invasive technique that allows for accurate identification of aquifer boundaries, saturated zones, and is cost-effective. This research aims to assess the subsurface features and evaluate the delineation of potential groundwater zones using 2-D electrical resistivity imaging and serves as a preliminary guide for identifying suitable locations for groundwater exploration in Universiti Sains Malaysia, Penang Island, Malaysia. Eight resistivity survey lines (LR01-LR08) are conducted within the research area. The 2-D resistivity imaging survey was conducted using Pole-dipole array for LR02, LR03, LR04, LR06, LR07, and LR08 while Wenner Schlumberger array for LR01 and LR03 with 5 m minimum electrode spacing. The Wenner-Schlumberger array was chosen due to site constraints in placing the remote electrodes within the study area. The research area’s geology is characterised by an underlying igneous rock, featuring a centrally positioned granitic range that extends in a north-south direction, accompanied by low-lying elevations ranging between 5 metres and 20 metres above sea level. For this research, an automated multi-electrode resistivity meter, the ABEM Terrameter SAS 4000 system is employed. The resistivity values underwent an inversion process using RES2DINV software to generate the electrical resistivity topography model. The resistivity profiles are cross plotted using Surfer 8 and Sketchup software to obtain the overview of resistivity anomalies continuity between the resistivity profiles. The results showed the resistivity values ranged from 1 Ωm to 20,000 Ωm. Subsurface materials were categorised into four types based on their resistivity value ranges: Water-saturated zones (1 Ωm to 300 Ωm), weathered material (301 to 1,000 Ωm), weathered bedrock (1,001 to 4,500 Ωm), and fresh bedrock (> 5,000 Ωm). Several faults and anomalies are interpreted as potential water-saturated zones for groundwater drilling purposes. They are the continuation of water-containing zones between LR02, LR05, and LR08 profiles. These zones are proposed as a suitable potential location for drilling for groundwater. This outcome could contribute to establishing a one-stop centre for hardrock groundwater resources and developing sustainable guidelines for their management in the granitic region of Malaysia.

2-D resistivity imaging method is widely used to delineate fault zones. The fault referred as a rock fractures or discontinuity in rock volume due to relative displacement caused by the earth movement. In this study, 2-D resistivity imaging survey conducted in Iejue, Aceh Besar locality with the aim to delineate the Seulimeum fault system for this locality. Two survey lines L1 and L2, with a total length of 1200 m each, conducted across the suspected fault using ABEM SAS4000 system with Pole-dipole array and 10 m minimum electrodes spacing. 2-D resistivity imaging profile shows the exploration depth of >320 m with resistivity range of 1-1800 Ωm. The contrast in resistivity values for both lines L1 and L2 indicates the suspected fault at distance of 550-600 m and 500-550 m respectively. Correlation of 2-D resistivity imaging analyses with a geological map of the area shows that the fault is trending in the NW-SE direction with fault lineament approaching the resistivity result. Two distinct resistivity zones identified for each survey line; a saturated zone starting at distance of 600 m toward the end of the line and high resistivity zone at distance of 0 m to 550 m. This saturated zone interpreted as a ground fluid, while the high resistivity zone represents as existing alluvium, sandstones, and volcanic sediments.

Exploration geophysics is widely used to map the subsurface characteristics of a region, to understand the underlying rock structures and spatial distribution of rock units. 2-D resistivity and seismic refraction methods were conducted in Sungai Batu locality with objective to identify and map the sediment deposit with correlation of borehole record. 2-D resistivity data was acquire using ABEM SAS4000 system with Pole-dipole array and 2.5 m minimum electrode spacing while for seismic refraction ABEM MK8 seismograph was used to record the seismic data and 5 kg sledgehammer used as a seismic source with geophones interval of 5 m spacing. The inversion model of 2-D resistivity result shows that, the resistivity values 500 Ωm as the hard layer for this study area. The seismic result indicates that the velocity values 3600 m/s interpreted as the hard layer in this locality.