For the first time, researchers have identified Earth's largest exposed fault lurking beneath the Banda Sea in eastern Indonesia. As a significant discovery, it explains the mystery of the 7.2 km (4.5 miles) abyss formed deep under the Pacific Ocean.
The researchers have named the biggest exposed fault plane on Earth as "Banda Detachment."
According to the details published in the journal Geology, the mega fault runs through the explosive region known as Ring of Fire where 90 percent of the world's earthquakes and 75 percent of active volcanoes occur.
The research was undertaken by a team of geologists from the Australian National University (ANU) in Canberra and Royal Holloway University of London. They studied maps of the sea floor of the Banda Sea region in the Pacific Ocean before extrapolating with field activity in formulating their hypothesis.
The Weber Deep has been a puzzle for scientists as a massive crack near the Maluku Islands of Indonesia creating the deepest point of Earth's oceans outside the conventional trenches. But there had been no convincing answers as to how it was formed.
Largest Exposed Fault Line
"The abyss has been known for 90 years but until now no one has been able to explain how it got so deep," said lead researcher Jonathan Pownall from ANU.
He said the 7 km-deep abysses beneath the Banda Sea was formed by an extension of what might be Earth's largest-identified exposed fault plane.
On a boat journey in eastern Indonesia in July, Pownall spotted the landforms as surface extensions of the assumed fault line. The lead researcher said he was stunned to see the hypothesized fault plane poking above the waves in front of his eyes.
According to Pownfall, the discovery of the largest fault plane will help in predicting quakes and tsunamis in advance.
Eastward Subduction Rollback
According to the research paper, the effort was to explain the tectonic evolution of the Banda arc in the context of the Australia-Southeast Asia plate collision.
The emergence of a 7.2 km deep forearc in the Weber Deep within the tightly curved Banda arc of eastern Indonesia remained unexplained.
In the new model, researchers argued that a forearc was formed as an extension by eastward subduction rollback in explaining the huge depths at Weber Deep.
They said substantial lithospheric extension in the upper plate was caused by "Banda detachment", which high-resolution bathymetry data has attested as the largest bathymetric expression of any fault in the world's oceans.
During the research expeditions, the team adduced many facts supporting the existence of the massive fault. Chief among them was the presence of rocks at the bottom of the sea bearing straight parallel scars indicating hard cuts.
Simulations of sea floor showed a massive crust bigger than the size of Belgium having been ripped off by a massive crack in the oceanic plates that led to the formation of a depression in the ocean floor.
Professor Gordon Lister of the ANU Research School of Earth Sciences also reiterated that this was the first time the fault has been seen by researchers after assuming it theoretically based on bathymetry data and regional geology.