Reconstruction of Retrogressive Landslides Using Integrated Technique of Geoelectric Resistivity and Borehole Logging in Sumampir, Purbalingga Regency, Central Java

Abstract The landslide occurred in Sumampir of Purbalingga Regency has reached 120 m length and 50 width. This is suspected to be a retrogressive landslide, which was manned by associated with the cliffs Brangkal River. interpreted as progressive development river bank failures, continues enlarge dimensions measured currently. main active steep scarp along 60 height up 8 m, several transverse tensile cracks were found between above crown. These have caused partial subsidence on side village road that crosses it. In order determine existence slip surface developed since first formed until last one, an integrated technique geoelectric resistivity borehole logging been applied. then used reconstruct progression retrogressively towards top. results analyses indicated there are four stages formation. located at 80 south road, defined initial landslide. second 40 from possible former damaged prior road. third distance 15 considered bridge collapse. fourth causing concrete slab moved south. average depth about m. confirmed using data, obtaining relatively hard weathered claystone layers 6-8