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Balloon fleet senses earthquakes from stratosphere

Balloon fleet senses earthquakes from stratosphere

A balloon hangs over the mountains, waiting for waves of infrasound generated by an earthquake. Here those waves are approximately visualized by the gray dots. Credit: CNES/Raphael Garcia.

A new study in AGUs Geophysical Survey Letters reports on the first detection of a large, distant earthquake in a network of balloon-bound pressure sensors in the stratosphere. The technique could one day be applied to Venus, whose hot, dense and corrosive atmosphere limits our ability to detect Venus quakes from the planet’s surface. The balloons could also be used in hard-to-reach places on Earth.

Tracking seismic activity on other planets is critical to learning about their internal structures, but unlike on Earth, planetary scientists cannot rely on a global network of ground-based sensors. Instead, they turn to the atmosphere.

When an earthquake strikes, the vibrating ground sends infrasound high into the atmosphere, where the balloons and their instruments wait. The balloons float through the stratosphere several months after launch, passively tracking high-altitude atmospheric patterns. At approximately 11 meters in diameter and 30 kilograms (66 pounds), the balloons can support up to four instruments.

Seismology is relatively new to the stratosphere; the balloons are mostly used for atmospheric science. Previous research has confirmed that these balloon-based sensors can pick up small, local earthquakes, but until now, a multi-balloon network had not detected large earthquakes at great distances.

On December 14, 2021, a magnitude 7.3 earthquake hit the Flores Sea in Indonesia. Within 10 minutes, four of IASE’s Strateole-2 balloons within a radius of 3,000 kilometers (1,860 miles) detected the resulting infrasound, at altitudes of up to 20 kilometers (12 miles). Based on that sensor data, Garcia’s research team was able to accurately calculate the magnitude of the earthquake and several other important parameters about both the earthquake and planetary structure. Their network even allowed them to track the spread of the seismic wave over the surface.

“We’re very, very happy because it wasn’t just a single balloon that detected the earthquake, it was observed on multiple balloons,” said Raphael Garcia, lead author of the new study and a planetary scientist at the Institut Supérieur de l’Aéronatique et de l’Espace of the University of Toulouse.

The study is an important proof-of-concept for applying this seismic monitoring technique to Venus. Although the balloons have only been tested in Earth’s atmosphere, Garcia and his colleagues believe they will also work in Venus’ carbon dioxide-rich atmosphere.

Vivid Venus

In 2021, scientists studying Venus began referring to the next decade as “the decade of Venus,” as three missions to the planet have been accepted for the early 2030s. Venus, Earth’s “sister planet,” intrigues planetary scientists with its unknown internal structure and poorly understood long-term interactions between tectonics and atmosphere that ended up with such a habitable world compared to the nearby Earth. “The story for our interest in Venus is that we don’t know anything about the interior,” Garcia says. “We don’t know how it’s made inside, and on Earth, seismology is one of the best tools to find out.”

As part of the Venus Decade, several teams are working on balloon-based seismic monitoring, but the new study is the first to successfully capture large, natural, multi-balloon earthquakes, Garcia says.

“The quest to detect a major earthquake on stratospheric balloons, it’s kind of competitive,” he says. “But it’s a great game, because in the end we are demonstrating the same concept.” Still, he is pleased that their team achieved this feat. The proposal for balloon-based seismic monitoring on Venus, called Phantom, will be submitted to the New Frontiers NASA missions in conjunction with JPL-NASA and North Carolina State University.

The network’s success also highlights the potential for balloon-based seismic monitoring to complement areas difficult to monitor with a ground-based network, such as the seafloor. The balloons can also be deployed as a quick aid for aftershock monitoring.

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More information:
Raphael F. Garcia et al, Infrasound from large earthquakes recorded on a network of balloons in the stratosphere, Geophysical Survey Letters (2022). DOI: 10.1029/2022GL098844

Provided by American Geophysical Union

Quote: Balloon fleet senses earthquakes in stratosphere (2022, July 28) retrieved July 29, 2022 from https://phys.org/news/2022-07-balloon-fleet-earthquakes-stratosphere.html

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