Derivation of Elastic Parameters from Integrated Seismic Refraction Tomography and Multichannel Analysis of Surface Waves (MASW) for Geotechnical Site Characterization at APT Pranoto Airport, Samarinda, East Kalimantan

Abstract

APT Pranoto Samarinda Airport is a transportation infrastructure facility that has experienced subsidence in the taxiway area, indicating potential issues related to subsurface conditions. This study aims to determine the distribution of dynamic elastic parameters, estimate the approximate groundwater table position, and evaluate the brittleness of subsurface materials via seismic refraction tomography (SRT) and multichannel analysis of surface waves (MASW). The derived parameters include Young’s modulus, bulk modulus, shear modulus, and Poisson’s ratio. The brittleness index was used to evaluate material brittleness, while the /  ratio was used to estimate the approximate groundwater table position. The interpreted dynamic elastic parameters were qualitatively compared with lithological information and standard penetration test (SPT) data obtained from nearby soil borings to support the interpretation of subsurface conditions. The results indicate that shallow layers exhibit relatively lower Young’s, shear, and bulk modulus values than deeper layers. In contrast, deeper layers exhibit higher elastic parameter values, while the brittleness index indicates a transition from relatively ductile shallow materials to more brittle materials at greater depths. The /  distribution suggests an approximate groundwater table at depths of 2.5–3 m. Relatively high Poisson’s ratio values in some zones may reflect pore-fluid influence on the elastic response of the subsurface materials. However, it should be noted that Poisson’s ratio alone is insufficient to establish groundwater saturation. At depths greater than 15 m, higher elastic parameter values generally correspond to higher nearby SPT values. However, these dynamic elastic parameters should not be interpreted as direct measures of geotechnical soil stiffness. These subsurface characteristics may help explain the deformation susceptibility of the taxiway area; however, the specific cause and depth interval responsible for the observed subsidence cannot be determined from the present data alone.