The Identification of Krakatoa Tsunami Deposits Based on Comparison of Geological and Electrical Resistivity Tomography Method, in Kunjir, South Lampung

Abstract

Abstract The research location is located in Kunjir Village, Rajabasa District, South Lampung. This village is an area that was affected by the tsunami waves due to the eruption of Mount Krakatau in 1883 and the village worst affected by the Krakatoa tsunami on 22 December 2018 in Lampung. This research was conducted to determine tsunami deposits using geoelectrical methods which are correlated with stratigraphic observations and thin section petrographic analysis on river walls in the study area. The geoelectrical method used is Electrical Resistivity Tomography (ERT). The ERT survey was carried out on 1 line located near the river. The purpose of the ERT survey is to determine tsunami deposits. Based on geological observations, it is suspected that there is a tsunami deposit in the form of a layer of sand mixed with pyroclastic and pumice rocks. Based on thin section petrographic analysis, it tends to show a pattern of changes in composition upward following changes in grain size. Based on the pseudo-section of the result of Electrical Resistivity Tomography processing, it is suspected that tsunami deposits were found in sandstone with a resistivity value of 17 - 100 Ωm.