Nanyang Technological University (NTU Singapore) scientists at the Earth Observatory of Singapore (EOS) will be leading an international team to the Wharton Basin in the Indian Ocean to investigate the cause of the largest intraplate earthquake ever recorded in an ocean.
The magnitude-8.6 earthquake which occurred on 11 April 2012 off the west coast of Sumatra is referred to by seismologists as the 2012 Great Earthquake.
This month-long expedition involving French and Indonesian partners aims to fully understand the anatomy of the rupture patterns and faults of this intraplate earthquake.
Relatively rare, an intraplate earthquake occurs in the interior of a tectonic plate (or massive irregular solid rock slabs), whereas the more common interplate earthquake occurs at the boundary between two tectonic plates.
The study seeks to also find out if the recent large earthquakes at the Wharton Basin is heralding the start of a new fault line, which happens only once every few million years.
Officially known as The MIRAGE (Marine Investigation of the Rupture Anatomy of the 2012 Great Earthquake) Expedition, it will be conducted on board the French research vessel R/V Marion Dufresne owned by the Institut Paul Emile Victor (IPEV).
The expedition is joined by France’s Institut de Physique du Globe de Paris (IPGP) and the Indonesian Institute of Sciences (LIPI).
The 110-metre oceanographic vessel will depart Colombo, Sri Lanka, on 1 July 2016 and make its way to the Wharton Basin located in the northeast quarter of the Indian Ocean.
The international scientific team consists of more than 20 scientists and students from all three research institutes, in addition to the crew on board the R/V Marion Dufresne.
Professor Paul Tapponnier, a world-renowned earthquake expert from NTU’s EOS and one of the main scientists in the project, said, “Just this year alone, the west coast of Sumatra has seen two large earthquakes with magnitudes measuring 6.6 and 7.8. They are so strong that the tremors are felt even in Singapore, where there is no known tectonic activity.
“With the Asian region a hotbed of tectonic activity, it is important for us to research and discover which earthquakes can lead to tsunamis and why, which can better prepare scientists and policymakers about the natural disasters that communities will be facing.”
The team’s expedition to the Wharton Basin follows an earlier one in June last year to the Mentawai Gap, west of the city of Padang in Sumatra.
The expedition mapped out the section of the seabed that has not seen an earthquake in the last 200 years but is expected to rupture imminently, as adjoining sections along the same fault have already ruptured.
The data will allow scientists to get a better understanding of the targeted section of the 200-kilometre-long Mentawai Gap that is expected to lead to one or more major earthquakes.
Named the Mentawai Gap — Tsunami Earthquake Risk Assessment (MEGA-TERA), it was conducted on board the Schmidt Ocean Institute’s research vessel Falkor. in June last year.
During the month-long voyage, the team of international scientists obtained 17,597 square km of high-resolution bathymetry along with 2,665 km of seismic reflection profiling.
The seabed imagery and data from Mentawai Gap will be compared to the Wharton Basin where the Great Earthquake happened, so as to analyse the differences between intraplate and interplate earthquakes and to see if there are any causal link between the two.
Professor Satish Singh, a visiting professor at EOS and a marine geophysicist from IPGP in France, will be leading this voyage.
“One of the biggest mysteries of the plate tectonics is ‘why and how a plate deforms away from the plate boundaries and produces giant earthquakes” said Prof Singh, who has been on over 26 ocean expeditions to understand underwater earthquakes.
“Like the last expedition, we will be using advanced deep-sea mapping technologies to study the seafloor at depths of 5,000 metres or more, so as to see if we can detect any discernible patterns or scars of previous earthquakes in the area, will give us a more accurate history of past earthquakes in the Wharton Basin.”
Dr Nugroho Hananto is co-leading of the expedition from Research Centre for Geotechnology from LIPI.
All information and data obtained from the Indian ocean expeditions, such as the high-resolution maps of the ocean seabed, are shared publicly with other scientists and research organisations around the world.
Source: Press Release