Publications

Northwest Sumatra forearc is characterized by oblique to hyper-oblique subduction of Indo-Australian plate beneath Asia-Eurasian plate. The accumulated strain is partitioned into two major directions, perpendicular and parallel to the trench. Trench perpendicular strain is mainly taken by the subducting thrust with the creation of fold and thrust system in the accretionary wedge, while trench parallel strain is mostly taken up by the Sumatra Fault Zone (SFZ) cutting along the Sumatra mainland. The residual strain resulted from those two major structures is likely accommodated in the zone in the accretionary wedge between the deformation front and the SFZ. We use two deep seismic profiles perpendicular to the deformation front acquired by WesternGeco, which were coincided with wide angle seismic refraction profiles and 28 seismic profiles provided by TGS – Nopec to study the seismogenesis and neotectonics of Northwest Sumatra forearc. Our results indicate two major structural features in the forearc: 1) the West-Andaman Faults (WAF), which have been interpreted as strike-slip faults, are near surface expression of deep rooted backthrust, which demarcate the accritionary wedge sediments and continental crust. 2) Strike slip fault located close to Sumatra platform, which seems to offset the top of pre-Neogene basement and in some places offset the seafloor. Both backthrust and strike slip faults are segmented into active and non active segment and controls the evolution and deformations of the Northwest Sumatra forearc. A large transpressional ridge known as Tuba Ridge might be formed by right lateral movement of the strike slip fault located close to Sumatra shelf in concert with eastern branch of WAF. Deformations along the forearc basin are mainly controlled by compressions and are characterized by 1) anticline with normal faulting and 2) anticline associated with mud volcanism. Different styles of anticlines are controlled by the rapid sedimentary loading, pore pressure, tectonics loading and faulting during the evolution of the basin.