SPACE — Scientists have discovered a huge reservoir of water hidden deep beneath the seabed off the coast of New Zealand. This is thought to explain why the region experienced slow-motion earthquakes.
According to the researchers, ocean-sized water is locked in volcanic rock that formed 120 million to 125 million years ago during the early Cretaceous. At that time, a mass of lava the size of the United States broke through the earth’s crust and solidified into a vast plateau.
A thick layer of sediment had covered the rocks and buried the remains of the explosives to a depth of 3 kilometers beneath the seabed of the Pacific Ocean.
Researchers mapped fault lines along the east coast of New Zealand’s North Island and found that these ancient rocks were abnormally wet, with water content of almost half the volume of cores drilled from the seabed.
“Normal ocean crust, once it is about seven or 10 million years old, should contain less water,” said the study’s lead author, Andrew Gase, a marine geophysicist and seismologist at the University of Texas Geophysical Institute (UTIG).
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The shallow sea surrounding the ancient volcanic plateau is thought to have eroded the rocks into a porous honeycomb. It absorbs water and stores it like an aquifer.
“These waterlogged areas slowly changed over thousands of years, absorbing more water as rocks were ground into clay and buried,” the researchers wrote.
The researchers discovered this underwater reservoir 15 km from the Hikurangi fault, or subduction zone, where the Pacific tectonic plate dives under the Australian plate and into the Earth’s mantle. Friction between these plates results in unusually slow-motion earthquakes that can last for months and cause almost no damage to the Earth’s surface.
Also known as events slow slipthese earthquakes only occurred in a few places around the world, including the Pacific Northwest, Japan, Mexico and New Zealand.
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According to researchers, events slow slip often associated with buried water deposits. When one tectonic plate slides under another tectonic plate, the water contained in the rock can create a high pressure condition that slows the process and prevents the sudden shift from occurring.
According to research published August 16 in the journal Science Advances, the newly discovered water reservoir is a boon because it makes slow-motion earthquakes harmless. They occur every one or two years on the Hikurangi fault.
“This is something we hypothesized from laboratory experiments and predicted by some computer simulations, but there have been few clear field experiments to test it at the plate tectonic scale,” said study co-author Demian Saffer. He is director of UTIG and a professor in the Department of Earth and Planetary Sciences.
The researchers used seismic scanning to create 3D images of the underwater region and locate the reservoir. But to determine how far it extends into the Earth’s crust and determine its effect on the pressure around the fault, they had to drill deep into the seabed.
2023-10-16 12:40:00
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