‘Bored’ Seismologists Find a New Hobby: Tracking Silence

May 26, 2020by Anna Kuchment, The Dallas Morning News (TNS)
Southern Methodist University geophysicist Stephen Arrowsmith with a seismogram projection showing measurements taken from the basement of SMU's Henroy Building, where he does his seismology studies, on May 13, 2020, in Dallas. (Tom Fox/Dallas Morning News/TNS)

DALLAS — If you’ve been noticing more birds chirping and more frogs singing, it’s probably not your imagination.

Noise created by humans, such as car and truck traffic, quieted by about 30% between late March, when Gov. Greg Abbott closed schools and restaurants across Texas, and early May, according to a new analysis by researchers at Southern Methodist University.

“There was quite a big change in some areas,” said Stephen Arrowsmith, a seismologist at SMU, who took on the project with a class of undergraduate and graduate students this spring.

Arrowsmith and his students looked at data from a dozen seismometers across North Texas, including in Irving, Dallas, Farmers Branch, Richardson and Fort Worth. Seismometers are used to detect earthquakes, but they are sensitive to just about everything that makes the ground vibrate, such as strong winds, ocean waves, passing trains, construction and traffic.

Each instrument contains a small weight on a spring. As the earth moves, the weight remains in place, allowing the seismometer to measure the amount of movement relative to the weight.

Scientists usually avoid placing seismometers in cities, because the racket of human activity makes earthquake signals hard to detect. But North Texas is an exception.

Scientists at SMU and at the University of Texas at Austin’s Bureau of Economic Geology placed seismometers in the Dallas-Fort Worth area after Texas experienced a surge of small to moderate-sized quakes beginning in 2013. The stations are now part of the state-wide TexNet seismic monitoring program. Researchers linked the North Texas quakes, which peaked in 2015 before dying down, to oil and gas activity.

Arrowsmith and his students saw a range of noise reductions at the various stations. The biggest changes, perhaps not surprisingly, occurred on college campuses. At the University of Texas at Dallas’ campus in Richardson, a TexNet seismic station registered students’ comings and goings as classes started and ended each weekday.

“After the shutdown, that totally disappears, and the background noise goes way down,” said Arrowsmith.

Stations in Irving also registered significant noise reductions, mostly likely due to fewer cars and trucks on the roads, he said.

A seismic station at a firehouse near Farmers Branch, though, registered no change in noise levels, presumably because first responders have remained active throughout the pandemic.

“Each station is telling you about quite local things that are going on near that station,” Arrowsmith said. “So you need a good network of stations to fully understand what the effect of the shutdown is on a city as a whole.”

The idea of using seismometers to track urban noise gained popularity in March when Belgian seismologist Thomas Lecocq posted some of his urban noise data from Brussels on Twitter.

Lecocq, of the Royal Observatory of Belgium, received such an overwhelming response from scientists that he launched the group “Lockdown Seismology” on the Slack communications platform. “It’s where bored seismologists around the world are collaborating,” Arrowsmith joked.

Lecocq wrote in an email to The Dallas Morning News that he wanted to document the noise levels to show how small changes in personal behavior can make an international impact.

Cities have seen a wide range of noise reductions, ranging from 20% to 90%, Lecocq said. Dallas has seen among the smaller reductions, said Arrowsmith, which he attributes to stricter lockdown measures in Europe.

He’s working to correlate noise levels with mobility data from companies that use cellphone signals to track how far people travel and how much they interact with one another.

Now that Texas has loosened restrictions and businesses have started to reopen, noise levels have crept up but have not yet reached pre-shutdown levels, Arrowsmith said.

He hopes his findings will contribute to a growing list of creative ways in which researchers are using seismometers. In his spring forensic seismology course Arrowsmith teaches students how seismic stations can help investigators solve crimes like terrorist bombings, aid scientists in tracking nuclear tests in countries like North Korea, or assist inspectors in investigating accidents like space shuttle explosions and chemical plant blasts.

Recently, researchers have begun using seismic stations to track storms over the ocean, because large crashing waves register on the instruments, too.

Even in Dallas, Arrowsmith said, seismometers clearly register sounds from the Atlantic Ocean.

One potential application of his research is to better understand the shallow layers of Earth beneath cities. “That could be useful in places where there’s a real seismic hazard like San Francisco or Los Angeles,” he said, “where just knowing what that shallow structure is tells you a lot about how it would respond in a big earthquake.”

———

©2020 The Dallas Morning News

Distributed by Tribune Content Agency, LLC.

In The News

Vote by Mail Has a Long History in Florida, but in 2020 It’s a Coronavirus Salvation and Battleground
2020 Elections
Vote by Mail Has a Long History in Florida, but in 2020 It’s a Coronavirus Salvation and Battleground

Voting by mail, a centerpiece of elections in Florida for almost 20 years, is being hailed in 2020 as a life-saving necessity amid the coronavirus pandemic and attacked by President Donald Trump and his supporters as “fraud.” Elections supervisors can begin sending out mail-in ballots on... Read More

Census to Start Door-Knocking After Pandemic Pause
Census
Census to Start Door-Knocking After Pandemic Pause

WASHINGTON — The Census Bureau will plan a “final push” outreach effort this month to encourage many communities that haven’t responded to the census to do so, the agency said Wednesday during an update of plans amid a coronavirus pandemic that continues to spike in pockets... Read More

Democrats Rebuke White House Over Possibly Directing Virus Aid Away from Public Schools
Education
Democrats Rebuke White House Over Possibly Directing Virus Aid Away from Public Schools

WASHINGTON — President Donald Trump’s apparent proposal that future coronavirus aid for schools be tied to students, rather than school districts, has drawn rebukes from key Democrats. “He wants to increase funding in CARES four for education, but he’s looking at potentially redirecting that to make... Read More

US Coronavirus Cases Top 3 million as Multiple States Face Alarming Resurgence
Health
US Coronavirus Cases Top 3 million as Multiple States Face Alarming Resurgence

The United States has reached another grim milestone in the coronavirus pandemic, with the number of confirmed infections surging past 3 million on Wednesday. The official tally, compiled by Johns Hopkins University, is almost twice as high as the second hardest-hit country, Brazil, and represents nearly... Read More

Supreme Court Rules Job Discrimination Laws Don’t Protect Church-School Teachers
Employment
Supreme Court Rules Job Discrimination Laws Don’t Protect Church-School Teachers

WASHINGTON — The Supreme Court on Wednesday banned teachers who work at church-run schools from filing discrimination lawsuits against their employers, ruling that the Constitution’s protection for religious liberty exempts church schools from state and federal anti-discrimination laws. The justices, by a 7-2 vote, shielded two... Read More

Biden to Call for Moderate Approach to Reviving US Economy
2020 Elections
Biden to Call for Moderate Approach to Reviving US Economy

WASHINGTON — Joe Biden will call for a moderate approach toward reviving the U.S. economy if elected president that includes spurring manufacturing and encouraging innovation, shelving for now the more ambitious proposals pushed by progressive Democrats, people familiar with his plans said. The Democratic nominee plans... Read More

News From The Well
scroll top