Earthquakes and tsunamis caused by low angle normal faulting in the Banda Sea - Indonesia
Channel: GeoscienceAustralia
Date: 2020-08-05

Presented by Phil R. Cummins.



As the world’s largest archipelagic country in Earth’s most active tectonic region, Indonesia faces a substantial earthquake and tsunami threat. Understanding this threat is a challenge because of the complex tectonic environment, the paucity of observed data and the limited historical record. Here we combine information from recent studies of the geology of Indonesia’s Banda Sea with Global Positioning System observations of crustal motion and an analysis of historical large earthquakes and tsunamis there. We show that past destructive earthquakes were not caused by the supposed megathrust of the Banda outer arc as previously thought but are due to a vast submarine normal fault system recently discovered along the Banda inner arc. Instead of being generated by coseismic seafloor displacement, we find the tsunamis were more likely caused by earthquake-triggered submarine slumping along the fault’s massive scarp, the Weber Deep. This would make the Banda detachment representative not only as a modern analogue for terranes hyper-extended by slab rollback but also for the generation of earthquakes and tsunamis by a submarine extensional fault system. Our findings suggest that low-angle normal faults in the Banda Sea generate large earthquakes, which in turn can generate tsunamis due to earthquake-triggered slumping.

Biography:

Phil R. Cummins received his PhD in Geophysics form U. California Berkeley in 1988 and worked as a postdoctoral and research fellow at the Australian National University (ANU) until 1996, when he moved to the Japan Center for Marine-Earth Science and Technology (JAMSTEC). After leading a geodynamics research unit at JAMSTEC, in 2001 he took up a position leading earthquake and tsunami hazard research at Geoscience Australia (GA). In 2011, he accepted a joint appointment between GA and ANU as Professor of Natural Hazards, where he combines teaching and research in natural hazards at ANU with technical application of earthquake and tsunami science at GA.