The acoustic and gravity waves created by quakes can be used to constrain the seismic source mechanism and the planetary interior, as well as to infer the capability of quakes to produce tsunamis (Astafyeva, 2019). These atmospheric waves are also critical to infer the internal structure of planets with dense and hot atmospheres, like Venus, for which the surface deployment of a seismometer is very challenging (Garcia et al., 2005;Stevenson et al., 2015). These signals were first inferred from their induced variations of electron content in the ionosphere and atmospheric airglow emissions by remote sensing methods (Hines, 1960;Lognonné et al., 2006). Then, in situ measurements based on satellite drag variations were described (Garcia et al., 2013(Garcia et al., , 2014. Quake signal observations from pressure sensors on board balloons have been studied recently in order to validate mission concepts for future Venus exploration Garcia et al., 2020;Krishnamoorthy et al., 2019). However an observation of a natural quake event with a realistic geometry was still missing to fully validate the observational concept and the amplitude scaling laws. After a first detection of a local quake of small magnitude by a pressure sensor on a stratospheric balloon (Brissaud et al., 2021), we present here the first detection of a quake by a network of pressure sensors in the stratosphere on board Strateole-2 balloons.
Seismology on Venus has long eluded planetary scientists due to extreme temperature and pressure conditions on its surface, which most electronics cannot withstand for mission durations required for ground-based seismic studies. We show that infrasonic (low-frequency) pressure fluctuations, generated as a result of ground motion, produced by an artificial seismic source known as a seismic hammer, and recorded using sensitive microbarometers deployed on a tethered balloon, are able to replicate the frequency content of ground motion. We also show that weak, artificial seismic activity thus produced may be geolocated by using multiple airborne barometers. The success of this technique paves the way for balloon-based aeroseismology, leading to a potentially revolutionary method to perform seismic studies from a remote airborne station on the earth and solar system objects with substantial atmospheres such as Venus and Titan.
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