Earth Observatory Blog
It happened at 7:58am (Indonesian time) on 26 December 2004. In a few instants, the equivalent of 370 years of energy use in the United States, or 550 million times the power of the Hiroshima atomic bomb, was released off the west coast of Sumatra. While subducting beneath the Sunda Plate, the Indian Plate produced one of the deadliest natural disasters in recorded history.
A staggering M 9.1 earthquake triggered a devastating tsunami, with waves reaching up to thirty metres (m) high, claiming the lives of more than a quarter million people in fourteen countries.
The quake vibrated the entire planet as much as one centimetre. In Paris, at the Institut de Physique du Globe de Paris (IPGP), marine geophysicist Dr Satish Singh knew he needed to "image the source of the beast" – a phrase that would become the title of this 2005 project proposal. It turns out that Dr Singh was right, the Indian Ocean had many more surprises in store.
On 11 April 2012 at 3:38pm a M 8.6 earthquake occurred in the Wharton Basin, again off the west coast of Sumatra. Despite being the largest intraplate earthquake ever recorded, and causing a massive magnitude-8.2 aftershock, it produced a maximum wave height of only about one metre. Thankfully, this was a strike-slip quake, meaning the Earth’s crust moved horizontally displacing relatively little seawater.
In his quest to decipher the unique events happening in this part of the world, Dr Singh has enlisted several brilliant minds. Dr Helene Carton, a prominent geophysicist, is one of them. She has been a fundamental part of the research since it started, and today her desk reflects her style as a researcher: intense yet organised. She swings back and forth between two computers that display a combination of maps, models and mathematical equations. Many different papers lie around, ready to be consulted.
Post-its, pens, highlighters, rulers and notes complete the scene. Carefully but confidently, she draws several lines on a printed map, incorporating the feedback of the entire team in the design of the route the ship will follow during this expedition.
“What we are doing this time complements what we did in MIRAGE I. We are going to be looking at cross-sections of the area that was mapped last year. Everything is designed to intersect some of the faults and the features found last time.” Dr Carton explains that MIRAGE I focused on acquiring bathymetric images of the areas of interest while during MIRAGE II, the team will be mainly using seismic reflection profiling, a technique that allows them to look as deep as twenty to thirty kilometres below the seafloor.
Equipped with eighteen air-guns, R/V Marion Dufresne is absolutely ready for the mission. Every 50m, the guns will detonate air bubbles that will expand and compress, generating waves that will travel all the way to the bottom of the ocean, bouncing off of the different geological layers within the seafloor. Once they travel back to the surface, they will be detected by a 4.5 kilometre-long streamer, a series of hydrophones following and capturing the wave’s sounds. The data will yield a series of graphic profiles that will illustrate the arrangement of a variety of sediments, and part of the Earth’s crust and mantle.
Five years after the Indian Ocean earthquakes, scientists in the Wharton Basin are still identifying occurrences that were either thought to have been impossible, or that do not happen anywhere else on our planet. Research here, looking at mysterious seismological behaviour deep under the surface of the ocean, resembles a fictional planet more than our own Earth.
The 2012 Indian Ocean earthquakes were unique in both magnitude and location. They ruptured in a complex process along multiple previously unknown faults, which could be a signal that the Indian and Australian plates are breaking up. Some experts even wonder if this could be the birth of a new plate boundary.
One fault, in particular, has caught the team’s attention. Dr Singh said “We imaged a big fault during Mirage I, and we want to see how deep it goes, how it behaves. It is interesting because it’s a very big one and seems to be the most active, it also seems to have ruptured during the 2012 earthquake. In addition to that, we want to see if there are other faults and how they could be interacting with it.”
Putting together an expedition like this is incredibly expensive and complex, let alone two. Yet according to Dr Nugroho Hananto, it is completely worth it. The marine geophysicist was another promising scientist recruited by Dr Singh during one of his research missions in Indonesia. Today he works tirelessly in a mind-blowing choreography to conquer the logistics of deep-sea research, analyse the data coming in from current and previous endeavours, and propose new ways to incorporate the knowledge produced.
The Earth Observatory of Singapore (EOS), the Indonesian Institute of Science (LIPI), the Institut de Physique du Globe de Paris (IPGP), plus a myriad of other collaborators have come together to make it happen. Dr Hananto believes this global interaction only makes the project stronger: “Disseminating information enables us to enhance the science because we can exchange ideas and data, so we can learn from each other. That’s the power of collaboration. We set up protocols that regulate each other’s roles, that’s why we are confident what we are doing is not superficial, it will be long-lasting.”
Thirteen years ago, an earthquake disrupted a tide that still moves to this day. Today, the research vessel Marion Dufresne, the largest of the European fleet, waits at anchor three miles outside Jakarta. She will soon set sail towards the Wharton Basin, carrying curious and bright minds and prepared to conduct ground-breaking science.
Follow the progress of MIRAGE II between 25th September and 20th October 2017 on the EOS blog, and spread the word using #MIRAGEcruise.