A structural model for the Java Margin Subduction Zone, Indonesia, from multi-channel and wide-angle seismic data

Abstract

The plate margin offshore Java and the Lesser Sunda islands are located in the eastern portion of the Sunda plate margin, which starts from Burma in the northwest to the Banda arc in the southeast. Different geological configurations in the Sunda plate margin vary enormously from the west to the east due to the variations in sediment supply and the different nature of the oceanic plates along the convergent plate boundary. The Sunda arc hosts earthquakes spanning from moderate magnitude ones to some of the largest earthquakes on Earth. In order to understand the current tectonic structure, the oceanic crust relief, and the temporal evolution of the large volume accretionary mass of the eastern Java and Lesser Sunda margins, we use MCS streamer data and OBS data collected by BGR and GEOMAR to image the plate interface reflection, the upper plate tectonic structure, and velocity attributes of the convergent plates. In this study, we incorporate an innovative seismic processing approach called the Non-Rigid Matching technique applied to the reflection tomography and the pre-stack depth migration and retrieve the structural image of the forearc wedge and the geometry of the plate interface. The depth migrated seismic sections and the bathymetry reveal different scales and shapes of the oceanic relief. By comparing the observed subducting seamount location with the 1994 tsunami earthquake epicentre, the co-seismic slip model, and the aftershock focal mechanisms, we conclude that the seamount acts as an earthquake barrier in the 1994 rupture's propagation process and is weakly coupled in the inter-seismic period before the co-seismic rupture