Forearcs are the most dynamic tectonic environment on the Earth, being characterized mainly by the largest earthquakes as well as deformation along the convergence plate boundary. We have integrated marine geophysical and geological database. The offshore studies have been applying a combination between conventional geophysical surveys (single and multichannel seismic) as well as relatively new technologies of SeaMARC II and GLORIA seafloor mapping system. The geological studies including field studies of subareal portion of the accretionary wedge of Sawu Island and uplifted portion of forearc basement (Sumba Ridge) of Sumba Island. The forearc region between West Sumba-West Timor is one of the unique features probably from all over the forearc region in the world. The region has a unique tectonic setting includes the transition from conventional (Andean Type) of Indian Ocean subduction along the east Sunda Trench in the west to arc-continent collision along the Timor Trough in the east. This forearc region has been studied both on land and offshore intensively during the last ten years. However, several major problems remain unresolved: (1). What are the structural styles along the transitional forearc region; (2). What is the nature of basement of Lombok forearc basin west of Sumba island; (3). What is the origin of Sumba; (4). How does the continental crust (Sumba Ridge) behave during the initiation of collision; (5). What is the nature of Sawu Basin? (6). Where is the eastern extension (north of Sawu or west Timor) of the Sumba Ridge?