The film People–Coral–Mentawai was screened for the first time at Nanyang Technological University (NTU) on 14 Oct 2009. The 20-minute documentary was produced by a small crew of NTU students working under the direction of Prof Isaac Kerlow, currently serving as artist-in-residence at the Earth Observatory of Singapore.

“This project shows that you can make a film with little money and resources that has all the emotional power of a big film,” Prof Kerlow told the audience when the film debuted at NTU’s School of Art, Design and Media.

Kerlow, a pioneer in computer animation who worked nearly a decade for The Walt Disney Company, has been collaborating with EOS scientists on creative projects to increase public understanding of the institute’s work.

People–Coral–Mentawai follows a team of researchers as they gather evidence that led them to predict a very large earthquake is likely to occur off western Sumatra, in the vicinity of Padang, within the next few decades.

Prof Kerlow and two film students accompanied the scientists from EOS, the Indonesian Institute of Science and the California Institute of Technology on an expedition to the Mentawai Islands during the summer of 2008 to record the group’s work.

The researchers were gathering evidence from giant round corals, of a species called Porites, that live in colonies (“microatolls”) surrounding the islands. The corals have flattened heads that grow or die off in response to changes in the level of sea water.

The sea-level exposure of the corals is directly related to the rising or sinking of the islands caused by movements, deep below the ocean, of rocky tectonic plates that make up the crustal surface of Earth. Off the coast of western Sumatra two sets of these plates undergo very complex activity (known as subduction), which makes the area susceptible to strong earthquakes.

When two of the plates converge, one dips below the other. Yet pieces of the massive plates often get interlocked. As the lower plate descends, it drags down part of the upper plate, on which Sumatra and the Mentawai Islands sit. Eventually, after the stress of the tectonic movements builds up over long periods, the interlocked pieces break apart, in a powerful earthquake. That causes the islands to spring back into their original position, and triggers tsunami waves that inundate coastlines and islands.

The corals have annual bands, much like tree rings, that reflect the sea-level changes. The growth patterns enable the scientists to figure out when large earthquakes and tsunamis occurred over past centuries.

In the film, the research team is shown using a power saw to cut away a large slice of a coral specimen. The sample is then labeled and packed aboard a boat to be sent to a laboratory, where the varying sea levels over the years are measured precisely.

From this information, the scientists concluded that a large earthquake struck the western coast of Sumatra about every two centuries for the last 700 years. Each of those big quakes was accompanied by a series of smaller ones. Now, the researchers say, a similar pattern seems underway. They believe several large earthquakes off western Sumatra over the past decade are part of the latest 200-year cycle, which will culminate in a giant earthquake.

Additional evidence for the prediction came from a network of GPS stations installed in western Sumatra and the Mentawai Islands. The machines gather tectonic data that make it possible to calculate the amount of strain that has built up in various sections.

Based on the data, the researchers have concluded that a major break is bound to occur somewhere along a 400-km (250-mile) segment of interlocked plates that lies beneath Mentawai, and the accumulated strain is such that the rupture could generate an earthquake as powerful as magnitude 8.8. That would nearly rival the deadly Indian Ocean earthquake and tsunami of December 2004 (which was magnitude 9.15).

The film includes interviews with residents who experienced recent earthquakes in the area and live today with the knowledge that the next “big one” could happen at any time. One of those featured is Patra Rini Dewi, a 29-year-old Muslim woman who works with a local nonprofit group to educate her neighbours about safety precautions in the event of an earthquake and possible tsunami.

In introducing the film at the NTU screening, Prof Vibeke Sorensen, who chairs the School of Art, Design and Media, told the audience: “We’re very proud of this project. It shows the fundamental role that art plays in understanding nature.”

Prof Kerry Sieh, the director of EOS, appeared with Isaac Kerlow to discuss the collaboration and the artistic ideas that shaped the project. “For a scientist, research is our creativity, our medium of expression,” Prof Sieh said.

Besides educating viewers about the scientific process, he added, the film has a valuable public-service function. “As we carry out our work,” he said, “it’s important for people to understand that this kind of research not only deepens our knowledge of the physical world, but can actually help save lives.”

Under the Artist-in-Residence Programme, another short documentary, on EOS volcano research in the Philippines, is now in the works.