Coseismic landslide susceptibility assessment using geographic information system

Abstract

Indonesia is one of the most earthquake prone countries in the world. More than 14,000 earthquakes of magnitude greater than 5 occurred in Indonesia between 1897 and 2009. Earthquakes are a major cause of slope instability eventually triggering coseismic landslides, which cost 1.5 million US$/ year in Java: one of the most densely islands in Indonesia. This paper aims to assess coseismic landslide susceptibility using Geographic Information System (GIS) on the western flank of Baturagung Escarpment, 8 km southeast of the Yogyakarta City, a data sparse area. Therefore, we have used a probabilistic seismic hazard analysis to calculate the peak ground accelerations, while the coseismic landslide susceptibility analysis was done by the scoring method in the GIS adopted from Mora and Vahrson model (Costa Rica), which is well adopted for data sparse areas. The west flank of Baturagung Escarpment is dominated by moderate level of coseismic landslide with an average Coseismic Landslide Susceptibility Level (CLSL) of 33–162. The upper slope of Baturagung Escarpment, which consists of Semilir Formation has the CLSL of 163–512, corresponding to medium level CLSL (Mora and Vahrson model). The low level CLSL is mainly located on the foot slopes of Baturagung Escarpment, while the alluvial and colluvial plains located along the Opak River have very low CLSL (0–6). Based on the mapped landslide occurrence, the landslides tend to occur in the zone of moderate CLSL and they are distributed along the border between moderate and low coseismic landslide zone, meaning that the change on local condition could be playing an important role in triggering coseismic landslide.