The interesting point of this article, which has been presented at INDONESIAN PETROLEUM ASSOCIATION 35th Annual Convention and Exhibition May 2011 is that the deep seismic reflection data acquired by Western Geco and CGGVeritas have provide new information for understanding the evolution Sumatran forearc basins.
This is an abstract of a talk presented at American Geophysical Union, Fall Meeting 2011. Active deformation along the western margin of the present day Mentawai forearc basin appeared as anticlinal ridges. Beneath the anticlinal ridges, the deformation zone exhibits (1) main backthrust, as the upward continuation of the Mentawai Backthrust in forearc basin, (2) seaward verging imbricated thrusts developed in the accretionary wedge and (3) the landward verging thrust developed in the forearc basin. The landward verging Mentawai Backthrust zone and together with the Frontal Thrusts, formed the doubly vergent active tectonics in the Sumatra subduction system.
This article notes the structural features in the Mentawai forearc that can be interpreted as products of compression of the accretionary wedge and forearc basin sediments. Compressional phases since the Late Miocene initiated (a) the landward vergent foldthrust belt in the Mentawai Fault Zone (MFZ), (b) reactivation of seaward vergent imbricated thrusts in the retro-accretionary wedge, and (c) uplift of the accretionary wedge and some parts of the forearc basin. The authors interpret that the northwest part of the accretionary wedge underwent higher compression and tilting. The compression of the forearc is suggested to be controlled by the combination of the geometry and position of the continental backstop, and the subducting bathymetric high in the oceanic plate.