Arizona’s deserts might not be situated on a tectonic plate boundary where geographical activity can cause earthquakes, but that doesn’t make the state immune from the disturbance of tremors.
It has been 139 years since Arizona’s strongest recorded earthquake on the Pitaycachi fault struck in 1887. The 7.5 magnitude event, known as the Sonoran Earthquake, took place near the southeastern Arizona-Mexico border.
Since then, more have been felt in more recent years across the state. Flagstaff experienced a trio of earthquakes in the early 1900s, and the Prescott and Chino Valley area was hit with a magnitude 5 earthquake in 1976. Flashing forward to 2015, the Phoenix valley felt a magnitude 4.1 earthquake that hit Black Canyon City.
So if earthquakes aren’t a consistent threat to the state, why focus so many resources on studying them? The short answer: Not only will it happen again in Arizona, but infamous fault lines such as the San Andreas Fault exist not too far from the state’s western boundary.
In the School of Earth and Space Exploration at Arizona State University, several faculty members and their teams are working on various projects that hope to inform not only scientists, but also those who work in industries such as oil and gas, about tectonic activity around the world, especially in the Southwest.
Ramon Arrowsmith, the school’s interim director and professor, has been studying earthquake geology, paleoseismology and geomorphology of fault zones and has been publishing about their history of activity and hazards for over 35 years. Despite the historically low occurrence of earthquakes in the state compared with other places in the country, Arrowsmith emphasizes how important it is to study these potential situations on a more local level.
“They do happen, and we need to be able to explain them. There’s more and more infrastructure everywhere, and so therefore, earthquakes that used to not matter, matter more now,” Arrowsmith said. “There’s nuclear power plants and dams, now also semiconductor plants. We need to have expertise locally to understand what some of these hazards are and have an informed understanding locally.”
Alongside Assistant Research Professor Chelsea Scott, Arrowsmith is the co-founder and co-principal investigator of the OpenTopography project, the largest collection of freely available high resolution topography data. Within Arizona, Arrowsmith has also previously researched the seismic hazard facing Palo Verde Generating Station, a nearby nuclear power plant.
“I worked some on the seismic hazard at the generating station, which is a big source of power for Arizona Public Service, sitting 50 miles west of Phoenix,” he said. “One of the biggest hazards to Palo Verde is the earthquakes on the San Andreas Fault — even though they’re farther away — because the sources are bigger and the recurrence rate of those earthquakes is more frequent.”
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Location of the 7.4 magnitude earthquake in Ternate, Indonesia, that ASU’s seismometer detected April 1.
Image courtesy of Earthquakes@ASU
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The seismometer can pick up seismic activity from across the world. This graph represents the 7.4 Earthquake in Ternate, Indonesia, taken April 1 at 3:48 p.m. Arizona time.
Image courtesy of Earthquakes@ASU
He brings this research into the class he teaches on field geology, where geoscience students learn about geologic records of earthquakes. The skills these students gain are in high demand, with the U.S. Bureau of Labor Statistics predicting a 3% growth in jobs for geoscientists by 2034.
“I talk about hazards and the value of what they’re learning. Arizona doesn’t have a lot of hazard implications, some for flooding, but in California there’s a lot of earthquake hazard work,” Arrowsmith said.
“Right now I have two former master’s students who work at the Utah Geological Survey, and they work on the active fault mapping problem. A former PhD student leads the earthquake hazards and monitoring program for the Arizona Geological Survey.”
Beyond Arrowsmith’s class, the school helps oversee the university’s seismometer located on the Tempe campus. Despite its location, the seismometer can collect data from all over the world, recording even the smallest hints of an earthquake. It recently picked up an earthquake in Indonesia, just shy of 8,000 miles away.
“Earthquakes are a global problem,” Arrowsmith said. “… I’ve spent a lot of time working in central Asia, and I went to Indonesia because those are places where we could get access to the record of recent big earthquakes and understand how they work, and then bring that knowledge back home.”
New age of data accessibility
A global lens is key to better understand the geological processes surrounding earthquakes.
Professor Ed Garnero and his team are working on ADEPT, the first-of-its-kind database that stores international logs on earthquakes.
“Our group initiated a project to collect every freely available seismogram on the planet. You would think there must be some agency that already does that, and there isn’t,” Garnero said.
Because data collection and government agencies from around the world have different protocols, a lot of information such as seismic data remains private. This in turn can make it more difficult for researchers to cross-reference international seismograms for earthquakes and their histories in different regions.
The ADEPT website collects data from centers across the world for individual seismic events and plots them in different graphs for anyone to view.
“The whole other side of seismology is understanding earthquakes and earthquake processes. Those are societally really important. You would want all of the data, you would want to understand Earth as a medium better,” Garnero said. “… That’s what we’ve been doing in seismology; we’ve been half-seeing.
“The more information you have, the more that the energy samples the whole medium, the more we might get the imaging right. So then we know more about how the waves travel, the more we might be able to describe earthquakes with greater accuracy and so on.”
This project has helped Garnero form an international community, collaborating with teams such as tomographers in Zurich, Switzerland. Through this experience, the team has collected a significant amount of data and will be releasing a book that will serve as an encyclopedia of seismic data.
“We’re writing this book to help train students and also help them to train machines and artificial intelligence. We have all this great data, so let’s have some fun with it,” he said.
For Garnero, ASU serves as a hub for some of the best minds in the field.
“In geophysics and seismology, I think the most successful programs do have a critical mass of researchers. We have a bunch of faculty who have expertise on what we would call interiors research, that allows us to attract the best graduate students, and all of us are super collaborative with people around the planet,” Garnero said. “We’re a top program for interiors research because of the critical mass of faculty who are doing high-impact science.”