This story is one where I feel like I was part of the experiment. 

In July 2019, after attending a star party in Joshua Tree, I spent the Fourth of July holiday with dear friends in Los Angeles. On the morning of July 4, the house we were in, poised ever so delicately on the side of a rather steep hill, started to shake, rattle, and roll. I called out, “Earthquake!”, and for about thirty seconds we all kind of went, “Huh, this is lasting a while.” And then, in proper L.A. fashion, we went back to getting ready for brunch. 

That magnitude 6.4 earthquake was part of a chain of quakes that would include a 7.1 trembler on July 6, which I didn’t feel because I was on the Transformers ride at Universal. While this earthquake is just a side note on a pleasant summer trip for me, for folks closer to the epicenter in Ridgecrest, CA, these quakes meant a lot of clean up and a fair amount of repair work; and for scientists at Caltech and the Jet Propulsion Laboratory, these quakes meant a chance to test balloon-carried earthquake detectors they hope to send to Venus. 

While we normally detect quakes by how they literally shake the ground, this airborne sensor instead looks for slight changes in air pressure. On July 22, with their sensors at altitudes between 11-15 miles, they successfully detected low-frequency sound waves caused by aftershocks. This high altitude (well above commercial air traffic and in the land of weather balloons) makes observing earthquakes needlessly complicated, but on Venus, this exact same technique will allow scientists to study Venus quakes without melting their detectors – a factor that makes all the complications more than worth it.

More Information

NASA JPL press release

“The First Detection of an Earthquake From a Balloon Using Its Acoustic Signature,” Quentin Brissaud et al., 2021 May 20, Geophysical Research Letters