IDENTIFICATION SLIP SURFACE USING RESISTIVITY AND VLF-R MODE IN GOA KISKENDO YOGYAKARTA INDONESIA

Abstract

In the tourism area of Goa Kiskendo, Jatimulyo Village, district Girimulyo of Kulonprogo,
Yogyakarta province which is quite popular for naturally cave tourist destination. In November 2017, there
was a landslide that broke the transportation route to the Goa Kiskendo, Yogyakarta-Central Java province
tourism area. Based on the Center of Volcanology for Disaster and Geological Mitigation map of soil
movement in Girimulyo district, Jatimulyo Village is in the medium to high-risk movement zone. To anticipate
aftershocks of a landslide in the same area, it is necessary to map areas that are potentially landslide occurs.
For mapping, this area, the geophysical surveys using resistivity method with dipole-dipole configuration and
electromagnetic very low frequency (VLF) resistivity mode were conducted in Goa Kiskendo area to identify
the slip surface based on the contrast resistivity value. From the results of resistivity data processing, and 3D
visualization it is obtained a contrast of different resistance values consist of two layers. The first layer, which
is in the range of 10 Ωm-79 Ωm, is identified as soil and the second layer, which is in the range of 0,15 Ωm10 Ωm is interpreted as water saturated limestone. Water saturated limestone is identified as the slip surface or
bedrock in the depth of 3 m – 25 m, and the soil movement when the landslide occurs, the materials will move
from the north to southeastward.