Jakarta –
Researchers in New Zealand have found interesting factors that can influence the scale earthquake The next destructive thing is in the Hikurangi subduction zone, the fossils of tiny marine organisms that lived tens of millions of years ago.
The Hikurangi Subduction Zone is New Zealand’s largest plate boundary fault, extending off the east coast of the North Island, where two plates meet. This is where the Pacific Plate plunges under the Australian Plate.
This region can produce large earthquakes, with events of magnitude greater than 8 predicted. A deeper investigation of the area is needed to accurately predict earthquakes, but its location and depth offshore make it difficult to study.
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In the latest study, a research team led by Dr. Carolyn Boulton of Te Herenga Waka-Victoria University in Wellington investigates the rocky cliffs of the Hungaroa fault, which lies on the edge of the Hikurangi subduction zone.
Layers of limestone, mudstone and siltstone on the cliffs near Tora, about 35km southeast of Martinborough, provide a good indication of what is happening in the offshore subduction zone. Rocks such as those on the cliffs settled on the ocean floor between 35 and 65 million years ago.
A big piece of the puzzle
Researchers found large amounts of calcite in these rocks. Calcite is a common carbonate mineral which, in this case, originates from ancient unicellular marine organisms, mainly foraminifera, such as plankton.
Calcite deposited by small, long-dead marine organisms can affect how two large tectonic plates interact mechanically.
If the calcite dissolves in large enough quantities, it can weaken the fault, allowing two tectonic plates to slide easily without triggering a real earthquake on the surface.
But if they don’t dissolve, the fault lines can become blocked and store energy that can eventually be released earthquake the greater one.
“Calcite dissolves more quickly when it is highly stressed and when it is colder,” says Dr. Carolyn Boulton, lead author of the study, cited by Interesting Engineering.
“It dissolves more easily at low temperatures, such as room temperature. But it becomes more difficult to dissolve as the temperature rises, let’s say much deeper into the Earth,” he continued.
In subduction zones, temperatures rise more slowly than on land by just 10 degrees Celsius per km. So the faults are very sensitive to what calcite, the shell of old dead marine organisms, does.
“The calcite number and behavior of these organisms is a big piece of the puzzle of how big it is earthquake the next, “he said.
The Hikurangi subduction zone still holds many mysteries that scientists need to unravel. It is still unclear how calcite actually plays a role in the real world. And unfortunately, it is difficult to inspect the actual subduction zone without complicated drilling equipment.
“What we really want to know is: Are there any slow slip events out there that we haven’t detected yet? Are the rocks moving without an earthquake or are they really stuck? This will help tell us what might happen in the next earthquake.” ‘Boulton said.
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(rn / afr)
