STUDY OF SUBSURFACE CONDITIONS OF SOUTHERN CROSS ROAD USING THE WENNER-SCHLUMBERGER METHOD FOR DISASTER MITIGATION

Abstract

A study using the geophysical resistivity method, as a part of a disaster mitigation attempt, has been carried out in the Southern Cross Road (JLS), in the area of Gedangan District Malang Regency, East Java. The study was conducted to investigate the geological disaster potentials, such as fractures, land discontinuities, and ground movements, which exist along the road, that now is a popular route amongst tourists and travelers. The research was conducted using the Wenner-Schlumberger configuration, where a distance of 20 m between adjacent sounding points was chosen. The data obtained were processed by the inversion method to obtain 2D subsurface resistivity cross-sectional features. From five locations surveyed, various low resistivity values, ranging from 2.5 to 30 Ωm, were obtained, which indicate the presence of seawater intrusion or underground water flows that fill the subsurface cavities. Limestone discontinuities were also observed, indicated by resistivity values ranging from 25 to 70 Ωm, which were suspected as an indication of faults. High resistivity (150-700 Ωm) zones, where there is no limestone present significantly, were also detected at some points, which indicate the embankment of the road construction materials. The overall study also confirms that the resistivity method, especially with the Wenner-Schlumberger configuration, is useful for identifying the geological disaster potentials, which, in turn, will be useful in conducting the risk analysis for the Southern Cross Road or similar roads.