Fore-arc Java-Sumatra extends from southwest of Sumatra to the northeast of java, consisting of various Prism accretions and basins (Fig.1). Geological conditions of Fore-arc Java-Sumatra we can mirror the geological structure and stratigraphy of the basins the area thrive on. Fore-arc Java-Sumatra formed by convergence of the Indo- Australian plate and the Asian Plate during the middle Eocene to late Oligocene, followed by the latest charging transgressive marine and open sediments on the Fore-arc east java and Fluvial-lacustrine sediments developed in NW Java and Sumatra. Geological conditions of Fore-arc in western Indonesia recorded from Aceh basin, with a long (> 200 km) and narrow (< 50 km). Bounded by the West Andaman Fault, a trench-linked strike-slip fault obliquely crossing the northward extension of the Great Sumatran Fault. Research from Atsushi using the seismic method mention that the deposits in the basin are thickest along the boundary fault between the basin and the Outer-arc high, and gradually thin with increasing distance from the faults. And then followed by The Simeulue Basin extends over 260 km in NW-SE direction and 100 km in SW-NE direction, part of a classic example of subduction, Convergence system along the Sunda Arc becomes increasingly oblique from south to north resulting in large-scale, dextral strike-slip fault systems within the fore-arc basins and on Sumatra (Malod and Kemal, 1996; Sieh and Natawidjaja, 2000). The geological conditions of the next West of Fore-arc Java-Sumatra basin can be learned from Nias, Mentawai and Southwest Java. Nias and Mentawai basins accordance in the deliberations of the Matson and Moore (1992) with primarily concerned to seismic stratigraphy and not with geology structure discusses about important roles to the Batee Fault, a featured primarily defined by mapping on the Sumatra mainland, and to a flexure, which can be identified with the Mentawai fault zone which marks the rear margin of the trench- slope break. Due to the geological structure of the Mentawai Islands were quite significantly shows that the marine Oligocene graben fill (Fig.2) at that basin. Basin Southwest of Java had a complicated post-rift Neogene tectonic history, resulting in the Eocene Bayah formation and the Eocene Ciletuh formation, with features of deltaic deposits indicates basin development of syn-rift stage of fore-arc. Figure 1. Tectonic setting of Sumatra Darman and Sidi (2000) modification Figure 2. Sedimentary basins of Sumatra •Awang Harun Satyana modification Page 1 Geology Of Forearc Java Sumatra David Hamonangan