GEOTECHNICAL PARAMETER ANALYSIS OF LANDSLIDE-PRONE AREAS USING MASW AND SEISMIC REFRACTION

Abstract

National transportation routes in the Seulawah region frequently experience damage due to external factors, particularly intense rainfall and seismic activity associated with the Seulimum fault. These impacts often trigger geohazards such as landslides, subsidence, and road deformation, which are strongly related to weak subsurface geotechnical conditions. This study aims to characterize the geotechnical properties of subsurface materials along the Seulawah route by integrating seismic refraction and Multichannel Analysis of Surface Waves (MASW) methods. Data acquisition was conducted using PASI 16S24-N instruments at two survey locations, with two seismic refraction lines and two MASW lines at each site, and a geophone spacing of 2 meters. Data processing was performed using Seisimager and PlotRefa software to generate compressional wave velocity (Vp) and shear wave velocity (Vs) models. The results indicate that the upper layer, at a depth of approximately 8–11 m, is characterized by low Vp (295–1000 m/s) and Vs (112–350 m/s) values, low density (1.73–1.86 g/cm³), and low bearing capacity (1.94–4.87), suggesting soft and unstable materials. In contrast, the second layer exhibits significantly higher geomechanical properties, with Vp reaching 2411 m/s, Vs up to 897 m/s, density ranging from 2.14 to 2.92 g/cm³, and bearing capacity of 26.23, indicating dense volcanic materials such as tuff or breccia. These findings demonstrate a clear transition from weak surface layers to more competent subsurface formations and confirm that the integration of seismic refraction and MASW methods provides an effective approach for detailed geotechnical characterization in landslide-prone areas.