Lots of slow slip earthquakes are believed to be connected to buried water. Until now there was no direct geologic evidence to recommend such a large water tank existed at this specific New Zealand fault.
The Hikurangi plateau is a remnant of a series of epic volcanic eruptions that started 125 million years ago in the Pacific Ocean. A recent seismic survey (red rectangle) led by the University of Texas Institute for Geophysics imaged the plateau as it sinks into New Zealands Hikurangi subduction zone (red line). Credit: Andrew Gase
” We cant yet see deep enough to know exactly the impact on the fault, but we can see that the amount of water thats going down here is actually much higher than regular,” said the studys lead author, Andrew Gase, who did the work as a postdoctoral fellow at the University of Texas Institute for Geophysics (UTIG).
The research was released recently in the journal Science Advances and is based on seismic cruises and scientific ocean drilling led by UTIG researchers.
The Quest for a Deeper Understanding
Gase, who is now a postdoctoral fellow at Western Washington University, is requiring deeper drilling to find where the water winds up so that scientists can figure out whether it affects pressure around the fault– an essential piece of info that could result in more accurate understanding of big earthquakes, he said.
Origins of the Water Reservoir
The site where the scientists discovered the water becomes part of a large volcanic province that formed when a plume of lava the size of the United States breached the Earths surface area in the Pacific Ocean 125 million years back. The occasion was one of the Earths largest recognized volcanic eruptions and rumbled on for several million years.
Gase utilized seismic scans to build a 3D photo of the ancient volcanic plateau in which he saw thick, layered sediments surrounding buried volcanoes. His UTIG collaborators ran laboratory experiments on drill core samples of the volcanic rock and found that water made up almost half of its volume.
The blue-green layer under the yellow line reveals water buried within rocks. Researchers at the University of Texas Institute for Geophysics believe the water could be moistening earthquakes at the nearby Hikurangi subduction zone.
” Normal ocean crust, once it gets to be about 7 or 10 million years of ages need to include much less water,” he said. The ocean crust in the seismic scans was 10 times as old, but it had stayed much wetter.
Gase speculates that the shallow seas where the eruptions occurred wore down a few of the volcanoes into a permeable, broken-up rock that stored water like an aquifer as it was buried. With time, the rock and rock fragments changed into clay, locking in even more water.
The Implications for Earthquake Understanding
The discovery is important since researchers believe that underground water pressure might be a key active ingredient in producing conditions that release tectonic stress through slow slip earthquakes. Instead, the researchers believe the ancient volcanoes and the transformed rocks– now clays– are bring large volumes of water down as theyre swallowed by the fault.
UTIG Director Demian Saffer, a study coauthor and co-chief researcher on the clinical drilling objective, stated the findings suggest that other earthquake faults around the globe could be in comparable situations.
” Its a really clear illustration of the connection between fluids and the design of tectonic fault motion– including earthquake habits,” he stated. “This is something that weve assumed from lab experiments, and is anticipated by some computer system simulations, but there are very few clear field experiments to test this at the scale of a tectonic plate.”
Referral: “Subducting volcaniclastic-rich upper crust supplies fluids for shallow megathrust and sluggish slip” by Andrew C. Gase, Nathan L. Bangs, Demian M. Saffer, Shuoshuo Han, Peter K. Miller, Rebecca E. Bell, Ryuta Arai, Stuart A. Henrys, Shuichi Kodaira, Richard Davy, Laura Frahm and Daniel H. N. Barker, 16 August 2023, Science Advances.DOI: 10.1126/ sciadv.adh0150.
The research study was funded by the U.S. National Science Foundation and science and research study agencies in New Zealand, Japan and the United Kingdom.
A seismic imaging instrument routes behind a research study vessel during a study of New Zealands Hikurangi subduction zone. Led by the University of Texas Institute for Geophysics, the survey found a huge and ancient water reservoir buried miles beneath the seafloor. Credit: University of Texas Institute for Geophysics/Adrien Arnulf
A considerable water tank discovered below the ocean flooring near New Zealand might use insights into the mechanics of slow slip earthquakes and tectonic activity.
Scientists have discovered a seas worth of water locked within the sediment and rock of a lost volcanic plateau thats now deep in the Earths crust. Exposed by a 3D seismic image, the water lies two miles under the ocean floor off the coast of New Zealand, where it might be dampening a significant earthquake fault that deals with the nations North Island.
Slow Slip Earthquakes and Water
The fault is known for producing slow-motion earthquakes, called slow slip events. These can release bottled-up tectonic pressure harmlessly over days and weeks. Researchers would like to know why they occur regularly at some faults than others.
Led by the University of Texas Institute for Geophysics, the survey discovered a vast and ancient water reservoir buried miles below the seafloor. The blue-green layer under the yellow line reveals water buried within rocks. Researchers at the University of Texas Institute for Geophysics believe the water could be dampening earthquakes at the nearby Hikurangi subduction zone. The discovery is important because scientists believe that underground water pressure may be a crucial active ingredient in developing conditions that release tectonic stress through slow slip earthquakes. Rather, the scientists think the ancient volcanoes and the transformed rocks– now clays– are carrying big volumes of water down as theyre swallowed by the fault.
