The floating lab, Joides Resolution, heads for Indonesian waters Abby Kenigsberg and IODP-JRSO

It was one of the biggest and deadliest tsunamis in recorded history. The Boxing Day tsunami of 2004 killed a quarter of million people with waves reaching 15 metres.

Now, a drilling expedition under way in the Indian Ocean hopes to uncover the secrets of large underwater earthquakes that can trigger such tsunamis.

A multinational team on board the research vessel Joides Resolution, a “floating laboratory”, is about to collect sediment samples from 1.5 kilometres beneath the ocean floor.


“We want to find out more about how specific sediments control the size and type of earthquakes in this kind of environment,” says Lisa McNeill of the University of Southampton.

The team will focus on the Sunda subduction zone, where the Indo-Australian plate goes beneath the Sunda plate. The fault that forms between them is where many large-scale earthquakes have , including the one that caused the Boxing Day tsunami.

The team is drilling some 4900 metres below the sea surface, on a section of the seabed that lies to the west of Indonesia, before the Indo-Australian plate reaches the subduction zone.

They will take samples of the sediment and rock that was scraped off from the downgoing tectonic plate.

One of the primary questions they hope to answer is whether the pressures and temperatures experienced at depth here lead to the unusual properties of this subduction zone fault, and if that in turn leads to larger and more powerful earthquakes.

Sediments tend to become denser at high temperatures and pressures, and eventually turn into rock. In some cases though, fluids become trapped and the sedimentary materials are then weakened.

“We think the former is dominating here, and that the strengthening of the material leads to the earthquake rupture taking place at shallower depths within the subduction zone than normal,” says McNeill. “If the materials are stronger at shallower depths and over a wider area of the subduction zone, this can make the earthquake rupture wider, causing a larger magnitude earthquake.”

“We can’t predict earthquakes, but we can learn more about what happens below the Earth’s surface, why rocks break and cause earthquakes that ultimately trigger tsunamis,” says Brandon Dugan of the Colorado School of Mines.

As well as analysing what the sediments are made of, the team will identify fossils to tell when and where the sediments formed, and work out how they deform at the high pressures and temperatures deeper down in the subduction zone.

In addition to finding out what they call the “recipe for disaster”, they hope to learn about Earth’s past climate and the history of the Himalayas.

The expedition is part of the International Ocean Discovery Program and runs until 6 October. You can request to watch it live.

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