Deep Earth forces reveal where the next megaquake may strike in Southeast Asia
Caption: A major breakthrough in earthquake science reveals how deep slab pull beneath Java controls where great seismic events occur along the Sunda megathrust.
A new Monash University study has identified how powerful forces deep within the Earth are shaping the risk of destructive “mega-earthquakes” along one of the world’s most dangerous plate boundaries, the Sunda megathrust.
Using advanced 3D supercomputer simulations, researchers have shown that the deep subducting slab beneath Java creates strong mantle flows and stress that push further north into Sumatra and the Andaman region, priming those areas for the world’s most powerful earthquakes.
The Sunda megathrust has already produced some of the deadliest events in modern history, including the 2004 Mw 9.3 Sumatra–Andaman earthquake and tsunami.
Yet until now, it has remained unclear why the worst earthquakes consistently occur along the northern segment, where the subducting slab is actually younger and shorter, and normally expected to be weaker.
Lead author Dr Thyagarajulu Gollapalli, from the School of Earth, Atmosphere and Environment at Monash University, said the research overturns long-held assumptions about how seismic hazards build up at convergent margins.
“We found that the enormous pull of the deep Java slab acts like a giant anchor, dragging the surrounding plate and increasing stress hundreds of kilometres away,” Dr Gollapalli said.
“This deep forcing explains why northern Sumatra experiences the greatest compression and the most powerful earthquakes, even though the local slab there is too weak on its own.”
The research also reveals that Java’s southern megathrust may act as a seismic ‘barrier’, where high normal stress pushes the plates tightly together — potentially reducing the likelihood of giant ruptures in that region.
Senior author Professor Fabio Capitanio, also from the School of Earth, Atmosphere and Environment, said the work provides a crucial new lens for forecasting seismic hazard.
“This is the first time we have been able to connect the deep engine of subduction to the exact locations where great earthquakes nucleate,” Professor Capitanio said.
“Our models show that what happens 600 kilometres beneath Java can determine where catastrophic events strike at the surface, and where they do not.”
The authors say their findings will help refine future seismic risk models in Southeast Asia, home to more than 300 million people living within range of the Sunda megathrust.
The study “Bridging the gap between subduction dynamics and the long-term strength of the Sunda megathrust” is now available in Nature Communications.
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