A massive complex of flat, interconnected magma chambers has been discovered by scientists deep beneath Hawaii’s volcanoes that appear to be responsible for a swarm of tiny, unexplained earthquakes felt on the Big Island over the past seven years.
Data collected from seismic stations has been used to trace the structure of these pancake-like chambers, called “thresholds” and have been mapped with “previously unseen accuracy” by researchers, including those at the California Institute of Technology (Caltech) in the United States.
The results, published Thursday in the journal Sciencedemonstrate that these magma chambers, which appear to lie at depths ranging from about 36 to 43 km, are linked to at least two of the island’s active volcanoes – Mauna Loa and KÄ«lauea.
“We were just watching it, and it was just breathtaking, it really was. Since then, I can’t get the picture out of my head,” said study co-author and geophysicist Zachary Ross. The Washington Post.
In the study, scientists assessed data from more than 192,000 small tremors – below magnitude 3.0 – that occurred during the period from 2018 to mid-2022.
The researchers also mapped more than a dozen sills stacked on top of each other, monitored the progression of magma into those sills as it pushed upward through them, and linked it to KÄ activity. “lauea.
But because the study period ended in May 2022, they could not say whether the flow of magma into these chambers led to the November 27 eruption of Mauna Loa – the largest active volcano in the world. planet.
“Before this study, we knew very little about how magma is stored and transported deep beneath Hawai’i. Now we have a high-definition map of an important part of the plumbing system,” said the co -Study author John D Wilding in a statement.
“We know pretty well what the magma is doing in the shallow end of the system above 15km depth, but so far anything below it has only been speculated.” , he said.
The study found that sills tend to be about 300m thick, separated by a distance of about 500m, with the largest of them measuring about 6-7km.
“Volcanic earthquakes are generally characterized by their low magnitude and frequency during magmatic unrest,” said Weiqiang Zhu, another study author.
Using machine learning, the scientists said they could gain “unprecedented ability” to separate signal from noise while analyzing the data to clearly identify earthquakes and their locations to map thresholds.
The technique has helped scientists identify small earthquakes from data that may not be apparent to the human eye on a seismogram.
“It’s analogous to taking a CT [computerized tomography] scanner, the way a doctor can view the inside of a patient’s body. But instead of using controlled sources with X-rays, we use passive sources, which are earthquakes,” Dr Ross explained.
With the help of machine learning, the researchers were able to catalog about 10 times more earthquakes than before and pinpoint their location with a margin of error of less than a kilometer.
“We are excited about recent advances in machine learning, especially deep learning, which help to accurately detect and locate these small seismic signals recorded by dense seismic arrays,” Dr. Zhu added.
However, it is unclear whether sills beneath Hawaii are unique to it or whether such subvolcanic structures are common.
Researchers also don’t know how the movement of magma triggers the tiny earthquakes.
They speculate that injecting a large amount of magma into a space can create a lot of stress that could trigger such earthquake swarms.