Geoelectrical Delineation of Inactive Fault Paths for Foundation Design at IKN Sepaku

Abstract

This study delineated inactive fault paths in the Sepaku tourism area of Indonesia's new capital city, East Kalimantan, and translated the subsurface evidence into geotechnical design parameters. Two-dimensional geoelectrical resistivity surveys were conducted along two traverses of approximately 1,197 and 1,105 m, validated against outcrop and borehole observations, and converted into design values by reproducible closed-form methods. Resistivity ranged from 1.1 to 81.3 Ω·m, distinguishing weathered zones, bedding, and a fault zone of several discrete traces. Flexible pavement under a 400 kN reference load settled 9.5 mm, below the 20 mm serviceability threshold. A bored pile 0.8 m in diameter and 20 m deep gave an allowable capacity of 2,589 kN. An engineering buffer of 52.4 m was derived by summing the half-width of the fault-trace resistivity anomaly, a resolution allowance, and the extent of the imposed stress field. These values were site-specific and required validation before wider application.