Seismologists welcome quiet world
Silenced human activity may allow scientists a unique chance to study earthquakes
Seismologists are examining a potential perk of social distancing: the Earth is quieter.
Highways aren’t reverberating with the sound of commuters. Stadiums aren’t shaking from foot-stomping chants. Bars aren’t blaring live music.
Such facets of daily life cause background noise that seismologists must sift through. But as the new coronavirus pandemic forces people to stay home, some cities might find it easier to detect small, local earthquakes, which could further researchers’ understanding of these movements and of fault zones more broadly.
And while there’s not activity to observe in Houston, which Rice University professor and seismologist Alan Levander said is among “the seismically safest places to be in the United States,” around the world some 30 to 40 seismologists are looking for new data in their suddenly silent communities.
“All of this is very theoretical for now,” said Thomas Lecocq, a geologist and seismologist with the Royal Observatory of Belgium. “But if you come back in six months, people from all around the world will have good examples to show you.”
Where he lives in Brussels, the amplitude of humancaused vibrations has dropped 33 percent during the daytime. These daylight hours during the week are now similar to prepandemic daylight hours on the weekends.
Variation in noise is common. Before the COVID-19 pandemic, nights had always been quieter than days with
some evenings, say in the middle of the week, being especially quiet. On the rare occasion when it snows in Brussels, the city comes to a halt and the noise drops to a level similar to what the city is experiencing now.
But the snowstorms don’t last as long.
“Now, it’s continuous,” Lecocq said.
Seismologist Rob Porritt, a research science and engineering associate at the University of Texas Institute for Geophysics, examined
three Texas seismographs for a similar silence. The first two, one on the UT campus in Irving where some necessary activity continues and the second next to an Irving fire station, did not see a noticeable drop in humancaused noise.
The third seismograph, located in the small city of Kenedy in the Eagle Ford Shale, saw a decrease, though Porritt couldn’t say if that was caused by fewer people working on their ranches, a drop in energyrelated activity or other factors.
Academic studies have linked Texas earthquakes
to hydraulic fracturing activity and the disposal of oilfield wastewater.
Porritt said seismographs in Texas tend to be in rural areas that are already less noisy; so the newfound silence won’t be as noticeable. But in cities located on major fault zones, such as the San Andreas Fault in California, seismographs could find activity that might have been missed among the noise. He said small local earthquakes have a high frequency, similar to noise created by humans, whereas larger earthquakes have a lower frequency.
“In an earthquake prone area to have the city be suddenly silent, the data quality will improve a lot,” said Levander with Rice University.
He said Houston, and the entire Gulf Coast, contains fault zones. But the faults slip very, very slowly. Meaning an earthquake is extremely unlikely.
So Houstonians will have to find other ways to appreciate the silence. Maybe those living along Loop 610 will finally enjoy their balconies. If the heat doesn’t get to them first.