Volcano Opto‐Acoustics: Mapping the Infrasound Wavefield at Yasur Volcano (Vanuatu). Issue 8 (21st April 2023)

• Record Type: Journal Article
• Authors: Johnson, J. B.; Boyer, T.; Watson, L. M.; Anderson, J. F.
• Is Part Of: Geophysical research letters. Volume 50:Issue 8(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-04-21
• Subjects: infrasound -- open‐vent volcano -- image processing -- volcano monitoring -- computer vision -- lava lake; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2022GL102029
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: We explore the capabilities of volcano opto‐acoustics, a promising technique for measuring explosion and infrasound resonance phenomena at open‐vent volcanoes. Joint visual and infrasound study at Yasur Volcano (Vanuatu) demonstrate that even consumer‐grade cameras are capable of recording infrasound with high fidelity. Passage of infrasonic waves, ranging from as low as 5 Pa to hundreds of Pa, from both explosions and persistent tremor, pressurizes and depressurizes ambient plumes inducing visible vaporization and condensation respectively. Optical tracking of these pressure wavefields can be used to identify spectral characteristics, which vary within Yasur's two deep craters and are distinct for explosion and tremor sources. Wavefield maps can illuminate the propagation of blasts as well as the dynamics of persistent infrasonic tremor associated with standing waves in the craters. We propose that opto‐acoustic monitoring is useful for extraction of near‐vent infrasound signal and for tracking volcanic unrest from a remote distance. Plain Language Summary: Open‐vent volcanoes often have lava lakes or vents where magma is exposed at the bottom of a crater. These volcanoes degas continuously and explode intermittently producing sounds that are low frequency in nature, often below the threshold of human hearing. Such infrasounds are used by volcano scientists to monitor eruptive behavior over time and estimate eruption style and intensity. This current study uses data from Yasur Volcano (Vanuatu) to demonstrate that it is possible to measure infrasound robustly and accurately using cameras, rather than infrasonic microphones. We observe that infrasonic pressure waves induce detectable changes in the clouds or volcanic plume and we process the video imagery to extract infrasound records from remote vantage points. This is an emerging field we call volcano opto‐acoustics and it has potential utility for volcano monitoring at other open‐vent volcanoes worldwide. Key Points: Time series pixel brightness data from cameras show a strong correlation with co‐located infrasound records Video image processing can be used to extract the spatial infrasound wavefield produced at open‐vent volcanoes Radiation of sound waves, existence of standing waves, and crater acoustic response may be investigated with volcano opto‐acoustics