Geologists have uncovered for the first time the decades-old mystery of the Banda Detachment fault, probably the largest exposed fault on Earth, formed when one tectonic plate slipped under another into the Earth's mantle. There are fears that the fault could soon trigger a mega-thrust earthquake if it slips suddenly.
New Atlas reports that the region recorded a cataclysmic magnitude 9.9 earthquake in 1692. The mega-thrust earthquake generated a 15-meter (49-foot) tsunami and aftershocks that continued for nine years. Although subsequent quakes have been less powerful, some researchers fear that enough strain has accumulated in the Banda subduction zone since 1692 to generate another catastrophe similar to the 1629 event.
Earthquakes and volcanoes usually occur at fault zones where tectonic plates meet and one plate slips beneath the other or where the edges of the plates rub violently against each other.
The Banda Detachment is a massive 60,000-square-kilometer tear, part of the deadly Ring of Fire in eastern Indonesia, just north of Australia. The 60,000-square-mile fault plane forms a 7.2-kilometer (4.4-mile) deep chasm -- the Weber Deep -- in the floor of the Banda Sea, according to researchers at the Australian National University (ANU).
The Weber Deep, near the Indonesian Maluku Islands, is believed to be the deepest point in the Earth's oceans not part of a trench.Researchers from the Australian National University observed hundreds of straight parallel scars on the rocks on the floor of the Banda Sea that showed the Weber Deep was formed when a part of the crust, bigger than Belgium or Tasmania, was ripped apart by a 120-kilometer extension along the detachment fault.
"The discovery will help explain how one of the Earth's deepest sea areas became so deep," lead researcher Dr. Jonathan Pownall said, according to a release by ANU.
According to professor Gordon Lister, from the ANU Research School of Earth Sciences and co-author of the study published in the journal Geology, researchers had for decades hypothesized the existence of the Banda Detachment based on previous data obtained from studies of the geology of the region.
But now, for the first time, researchers from ANU and the Royal Holloway University of London are documenting its existence through direct observation and studying its features in detail using high-resolution maps of the sea floor.
"We had made a good argument for the existence of this fault we named the Banda Detachment based on the bathymetry data and on knowledge of the regional geology."
Pownall said that he noticed the surface extensions of the undersea fault line while on a boat journey to eastern Indonesia.
"I was stunned to see the hypothesized fault plane, this time not on a computer screen, but poking above the waves," he said.
"The Banda Detachment and Weber Deep may be among the largest of their kind in the modern Earth."The discovery of the Banda Detachment could lead to a major breakthrough in earthquake and tsunami prediction for the region, the experts said. The discovery of the fault has also raised fresh concerns about the risks of a massive mega-thrust earthquake in the region. According to geologists, if the fault slips suddenly, it could easily trigger one of the largest and most devastating earthquake and tsunami events in recorded history.
Pownall said that his team was working to gather more information about the fault, believed to be the largest exposed fault on Earth. The study, according to the researchers, could help other researchers assess the danger of future mega-thrust earthquake and tsunami events similar to the 1692 9.2-magnitude event that caused a 15-meter (49-foot) tsunami and aftershocks that persisted for nine years after the initial quake.
"Our research found that a 7 km-deep abyss beneath the Banda Sea off eastern Indonesia was formed by extension along what might be Earth's largest-identified exposed fault plane," Pownall said. "In a region of extreme tsunami risk, knowledge of major faults such as the Banda Detachment, which could make big earthquakes when they slip, is fundamental to being able to properly assess tectonic hazards."
"...knowledge of major faults, such as the Banda Detachment, which could make big earthquakes when they slip, is fundamental to being able to properly assess tectonic hazards."
The Banda Detachment fault runs through the deadly Ring of Fire, the most active fault line in the world that girds the Pacific Ocean basin, stretching from New Zealand to the east coast of Asia, Canada, and the U.S., and as far as the southern tip of South America (see diagram above).