IN HARMS WAY: TECTONIC HAZARDS OF THE EASTERN SUNDA ARC REGION, INDONESIA

Detailed field studies and tectonic hazard modeling of the eastern Sunda Arc of Indonesia reveal several strong earthquake source regions and explosive volcanoes that threaten one of the most densely populated and rapidly developing regions on the planet. Plate boundary reorganization in the region partitions strain to many newly developing structures throughout the arc-trench system, including the Flores and Wetar backarc thrust systems, the newly recognized Roti-Semau transcurrent fault system, and volcanoes, such as Tambora. These nascent plate boundary segments develop as a function of increased coupling of the underthrust Australian continental margin with the eastern Sunda Arc, which has shifted the site of convergence from the Timor Trough to the Banda Sea region.

New GPS studies of the transition from subduction to collision demonstrate that even though the majority of convergence between the Asian and Australian plates is taken-up along the backarc thrust system, there is still 20 mm/yr of convergence between Timor and Darwin, Australia. If this motion is from loading along the Timor Trough thrust front, then this region may pose a significant threat of a mega-thrust earthquake and associated tsunami. Studies of uplifted coral terraces in the region show evidence of co-seismic uplift and provide a record of some of the most recent mega-thrust events. An inexpensive and simple early warning system linked to strong motion sensors is proposed for the densely populated coastal regions of Java and other islands throughout the eastern Sunda Arc.