A Midsummer Flights Dream: Detecting Earthquakes from Solar Balloons

Leo Martire (NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA) – leo.martire@jpl.nasa.gov
Siddharth Krishnamoorthy (NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA)
Attila Komjathy (NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA)
Daniel Bowman (Sandia National Laboratories, Albuquerque, NM)
Michael T. Pauken (NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA)
Jamey Jacob (Oklahoma State University, Stillwater, OK)
Brian Elbing (Oklahoma State University, Stillwater, OK)
Emalee Hough (Oklahoma State University, Stillwater, OK)
Zach Yap (Oklahoma State University, Stillwater, OK)
Molly Lammes (Oklahoma State University, Stillwater, OK)
Hannah Linzy (Oklahoma State University, Stillwater, OK)
Zachary Morrison (Oklahoma State University, Stillwater, OK)
Taylor Swaim (Oklahoma State University, Stillwater, OK)
Alexis Vance (Oklahoma State University, Stillwater, OK)
Payton Miles Simmons (Oklahoma State University, Stillwater, OK)
James A. Cutts (NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA)

NASA Jet Propulsion Laboratory
California Institute of Technology
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Pasadena, CA 91109

Popular version of paper ‘3aPA8 – A Midsummer Flights’ Dream: Balloon-borne infrasound-based aerial seismology
Presented Wednesday morning, December 01, 2021
181st ASA Meeting, Acoustics in Focus

Earthquakes cause the Earth’s surface to act as a giant speaker producing extremely low frequency sound in the atmosphere, called infrasound, similar to how striking a drum produces audible sound. Because sound attenuation is weak at these low frequencies, infrasound propagates very efficiently in the Earth’s atmosphere, and can be recorded at distances up to hundreds of kilometers.

As a result, pressure sensors carried by high-altitude balloons can record the direct infrasound induced by earthquakes. Our balloons carry two pressure sensors to help detect and characterize the so-called seismic infrasound. The study of infrasound is a viable proxy for measuring the motion of the ground: indeed, computer simulations and previous balloon experiments have shown that the infrasound signal retains information about the earthquake that generated it.

Drone footage of a solar-heated balloon carrying two infrasound sensors over Oklahoma, just after take-off. Notice how the lower instrument is being reeled down to increase sensor separation.

The interior of Venus, Earth’s sister planet, remains a mystery as of today. Unlike Mars, the surface of which has been explored by numerous landers and rovers, the surface of Venus is particularly inhospitable: atmospheric pressure is 92 times that on Earth, and the temperature can exceed 475 degrees Celsius. This makes direct ground motion measurements particularly challenging. However, balloons flying in the Venusian cloud layer would encounter much more temperate conditions (~0 degree Celsius and Earth’s sea level atmospheric pressure), and could therefore survive long enough to make significant records of venusquake-induced infrasound.

On July 22, 2019, Brissaud et al. conducted the first ever experiment to detect the infrasonic signature of a magnitude 4.2 earthquake in California from a high-altitude balloon. During the summer of 2021, NASA’s Jet Propulsion Laboratory (JPL), Oklahoma State University (OSU), and Sandia National Laboratories (SNL) collaborated to increase the number of detections by launching infrasound sensors over the seismically-active plains of Oklahoma. The team used an innovative solar hot air balloon design to reduce the cost and complexity that comes with traditional helium balloons.

Launching an infrasound solar-heated balloon from Oklahoma State University’s Unmanned Aircraft Flight Station (Glencoe, OK)

Over the course of 68 days, 39 balloons were launched in hope of capturing the seismo-acoustic signal of some of the 743 Oklahoma earthquakes. Covering an average distance of 325 km per day and floating at an average altitude of 20 km above sea level, the balloons passed close to 126 weak earthquakes, with a maximum magnitude of 2.8. We are now analyzing this large dataset, which is potentially filled with infrasound signatures of earthquakes, thunderstorms, and several human-caused signals such as chemical explosions and wind farms.

This flight campaign allowed the team to optimize the design of balloon instrumentation for the detection of geophysical events on Earth, and hopefully on Venus in the future.

© 2021. All rights reserved. A portion of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.

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