Journal of Open Technologies in Geophysics

Seismic Refraction Modeling Using Time-Terms Inversion Based on Linear Programming: A Study on Synthetic Data

Asido Saputra Sigalingging — 2026-06-25

Seismic refraction is a geophysical method widely used to model the distribution of subsurface velocity. The main challenge of this method is the instability of the inversion that often arises due to noise and inaccuracies in determining the first arrival time (first arrival picking). In general, the inversion is carried out using the Least-Squares method, which tends to be unstable under non-ideal data conditions. To overcome this, this study develops a Time-Terms Inversion (TTI) approach utilizing Linear Programming. The linear formulation of TTI allows the inversion process to be expressed as an optimization problem with a clearly defined objective function, so that the resulting solution is more stable and resistant to data errors. Numerical tests on synthetic data show that this approach can reduce the influence of picking errors while maintaining the accuracy of the velocity model. These results show that the combination of TTI and Linear Programming is effective for seismic refraction modeling under synthetic data conditions affected by noise and picking inaccuracies.

Application of HVSR Method for Evaluating Seismicall-Induced Slope Instability Potential in Sukorejo Village, Pugung District, Tanggamus Regency, Indonesia

Erianti Sihombing — 2026-06-28

This study investigates HVSR parameters, predominant frequency (Fo), amplification factor (Ao), shear strain, and seismic vulnerability index (Kg) to evaluate their relation to local geology, morphology, and earthquake-induced landslide potential in the hilly region of Tanggamus. The results show that areas with high amplification values (>12), particularly in the F3–E3 to D5 zones, experience significant strengthening of seismic waves within the upper soil layers. These zones also exhibit low predominant frequencies (2–8 Hz), indicating thick sedimentary deposits with strong impedance contrast that tend to resonate at low frequencies, especially on long slopes and inter-hill valleys. Increased shear strain values (>0.15) suggest soft, unconsolidated, and water-saturated soils that are easily deformed during seismic shaking, increasing their susceptibility to failure. The seismic vulnerability index (Kg) reaches its highest levels (>1200) in the same areas, reflecting the combined effect of thick sediments, strong amplification, and low-frequency resonance. Geological analysis shows that highly vulnerable zones correspond to the Hulusimpang Formation (Tomh), characterized by weak sedimentary materials, while more stable regions underlain by the Gunungkasih Complex (Pzg) display lower HVSR parameter values. Overall, the F3–E3–D5 zone is classified as the most susceptible to earthquake-triggered landslides, the D3–F4–H3 zone as moderate

Geoelectric Mapping for Subsurface Bedrock Identification Implications for Construction Planning at ITERA

M. Rafif Pascaloa — 2026-06-29

Sustainable infrastructure development in educational institution areas requires accurate subsurface characteristics, particularly in identifying the presence of hard rock layers for building foundations. One of the effective and non-destructive geophysical methods for this requirement is the electrical resistivity method. Therefore, geoelectric mapping measurements were carried out along two lines to identify the hard layers within the ITERA campus area. The configuration used in the mapping measurement was the Wenner-Schlumberger configuration, which is well-known for providing a balanced lateral and vertical resolution. These geoelectric measurements had minimum and maximum AB/2 values of 2 and 192 meters, respectively, to obtain an optimal imaging depth coverage. The processed geoelectric mapping data shows variations in subsurface resistivity, which is strongly suspected to be tuffaceous sandstone with high resistivity values (). This distribution of the hard layer is expected to serve as supporting data and recommendations for future physical construction planning and development within the ITERA campus environment.

Application of Geoelectric Method for Groundwater Exploration: Comparative Study of Wenner-Alpha and Wenner-Schlumberger Configurations in Way Manak, Tanggamus

Rosy Reuni Nainggolan — 2026-06-30

Groundwater is an important resource that needs to be managed sustainably, especially in areas with high dependence on groundwater such as Way Manak Village, Tanggamus Regency. This study aims to identify and map the distribution of aquifer layers in the Hulusimpang Formation using the Wenner-Alpha and Wenner-Schlumberger geoelectric resistivity configurations. Data acquisition was carried out on two intersecting lines of 235 meters with a distance between electrodes of 5 meters, and one vertical sounding point (VES). Data were processed using RES2DINV and IPI2Win software with a final RMS error value of 1.22–6.6%. The modeling results indicate a low resistivity zone (±8–22 Ωm) at a depth of 1–19 m which is interpreted as a shallow aquifer layer, associated with the tuffaceous sandstone and sandy tuff lithology of the Hulusimpang Formation. The Wenner-Schlumberger configuration shows better penetration capability and depth resolution than Wenner-Alpha, making it more effective in detecting vertical and lateral resistivity variations. Overall, the combination of these two configurations provides a more comprehensive picture of subsurface hydrogeology, and the results can be used as a reference in planning groundwater resource management in the research area.

Identification of Soil Characteristics in Pugung District, Tanggamus Using the HVSR Method

Joseph Alexander Butarbutar — 2026-06-30