There has been an unexplained swarm of small earthquakes on the Big Island since the eruption of Klauea.
The magma chambers of at least two of the island's active volcanoes are recharged by the pancake-like chambers. The Caltech scientists were able to use data from the island's seismology stations to map out the structure of the sills using a machine-learning method.
The researchers were able to watch the progress of the magma as it pushed through the sills and link it to Klauea's activity. The team doesn't know if they can spot the magma flow that led to the November 27 eruption of Mauna Loa, but they intend to look at that next.
We didn't know a lot about how magma is stored and transported. A high-definition map of an important part of the plumbing system was published in the journal Science.
This is the first time scientists have been able to see a magma structure in person. "We know what the magma is doing in the shallow part of the system, but until now, everything below that has just been the subject of speculation," Wilding says.
There were more than 192,000 small temblors that occurred over a 3.5 year period, and the team was able to map out more than a dozen of them. The biggest is about 6 kilometers. The sills are between 300 and 500 meters in thickness and separated by a distance.
According to the Science paper, volcanic earthquakes are characterized by their small magnitude and frequent occurrence.
Recent advances in machine learning, particularly deep learning, which are helping to accurately detect and locate these small seismic signals recorded by dense seismic networks are exciting. Seismologists can use machine learning to analyze large archives, identify patterns in small earthquakes, and gain insight into underlying structures and physical mechanisms.
The senior authors on the paper were Wilding and Zhu, as well as Jackson and Ross.
The team didn't have to place a single piece of hardware to do the study because they used data from the United States Geological Survey. The machine-learning algorithm developed in Ross's lab gave them an unprecedented ability to separate signal from noise in order to identify earthquakes and their locations.
The way a doctor can see the inside of a patient's body is similar to taking a computed tomographic Scan. Instead of using controlled sources, we use passive sources.
The team was able to locate their locations with a margin of error of less than a kilometer, and previous locations were determined with error margins of a few kilometers. Using a training dataset of millions of previously identified earthquakes, a deep-learning method was used to spot earthquake signals.
Even with small earthquakes, the program finds patterns that distinguish them from background noise. A four-year-long earthquake swarm near Cahuilla, California, was revealed by Ross using the technique.
The sills are thought to be between 36 and 43 kilometers deep. The deepest humans have ever been drilled is over 12 kilometers. At a phase boundary, the rock of the same chemical composition transitions from one group above to another.
Jackson realized that the transitions occurring in this rock coupled to magma injections could host chemical reactions and processes that stress or weaken the rock.
Jackson says that the transition of spinel to plagioclase may be happening through diffuse migration, entrapment, and crystallization of magma.
Transient weakening can be caused by chemical reactions and coupled deformation. Grain sizes in the sill complex would be constantly changed by current magma injections. The process could exploit variations in strength to create and sustain seismogenic features.
Researchers don't know if the sills beneath the Big Island are unique to Hawai'i or not. Hawai'i is the best monitored island in the world, with dozens of seismic stations giving us a glimpse into what's happening beneath the surface. How many other places is this happening? It's wilding.
It is not clear how the tiny earthquakes are triggered. The mechanisms of earthquakes are not understood. The injection of a lot of magma into a space could cause a lot of stress.
John D. Wilding wrote about the magmatic web beneath Hawai'i. There is a science.ade5755
Journal information: Science
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