The discovery, located two miles under the sea off the coast of New Zealand, may provide answers to the mysterious phenomenon of slow-motion earthquakes known as slow-slip events.
This gigantic reservoir was discovered by 3D seismic images and lies beneath the North Island of New Zealand.Near a major seismic fault known for slow slip events.
Unlike typical earthquakes that release tectonic stress quickly, these slow slip events release stress gradually, over days or weeks.
Although its destructive nature is less, The reasons for the frequent occurrence of these slow earthquakes on some faults remain elusive. So it's hard to explain.
Large water tank
Many of these slow-slip events, also known as “quiet earthquakes,” were believed to occur Associated with buried water. However, the amount of water impoundment on this particular fault near New Zealand is unprecedented.
“We still can't see deep enough to know exactly the effect of the fault, but we can see that the amount of water falling here is actually higher than normal,” he explained. Dr. Andrew CaseLead author of the study.
Ocean Drilling
The survey is based on seismic vessels and scientific drilling at sea Led by a team at the University of Texas Institute for Geophysics (UTIG).
Dr. Case, currently a postdoctoral fellow at Western Washington University. That calls for deeper drilling to find out where the water ends up, so researchers can determine if it's affecting the pressure around the fault.. This is important data that can lead to a more accurate understanding of large earthquakes, he said.
An ancient volcanic landscape
The reservoir site is a monument A volcanic eruption occurred about 125 million years ago., almost the size of the United States. This event was one of the most important volcanic eruptions in Earth's history and lasted for millions of years.
Used by Dr. Case Seismic scanners To reconstruct a 3D representation of this ancient volcanic landscape, Finding thick layers of sediment around dormant volcanoes. Subsequent laboratory tests on volcanic rock samples It turns out that almost 50% of the rock's volume is water.
Influence of ground water stress
According to Dr. Case, Normal oceanic crust around 7 to 10 million years ago must have had a significantly lower water content. However, the crust identified in these scans is a century old but significantly more hydrated.
Experts believe that the early shallow seas where these eruptions occurred eroded some of the volcanoes into porous structures capable of holding water. For thousands of years, These pieces turn into clay and further bind water.
This idea is important because it is widely believed that groundwater pressure It plays an important role in creating favorable conditions for slow earthquakes.
Saturated sediments
Typically, this occurs when water-saturated sediments are buried next to a fault, confining groundwater. however, The composition of New Zealand fault sediments differs from this standard.
Instead, the researchers propose that ancient volcanic remnants and their transformation into clay pushed significant amounts of water down.
OBJECTIVE RESULTS OF THE STUDY
Emphasizing the broad implications of this discovery, UTIG Director, Demian Suffersuggested that Seismic faults around the world may share similarities with this scenario.
“This is a very clear example of the connection between fluids and the style of movement of tectonic faults, including earthquake behavior,” Chaffer said.
This is something we have hypothesized from laboratory experiments and some computer simulations predict, but there are very few clear field experiments to test this at the scale of a tectonic plate.
The research was funded by the US National Science Foundation and research institutions in New Zealand, Japan and the UK.
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