Generation of Infrasound Waves at Sites of Underground Mine Collapses. Issue 12 (26th June 2018)

• Record Type: Journal Article
• Authors: Che, Il‐Young; Kim, Geunyoung; Kim, Youngchai; Kim, Kwangsu
• Is Part Of: Geophysical research letters. Volume 45:Issue 12(2018)
• Page Start: 5977
• Page End: 5984
• Publication Date: 2018-06-26
• Subjects: infrasound -- underground mine -- collapse; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2018GL078187
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: In 2015 and 2016, collapse‐induced earthquakes, accompanied by surface subsidence, occurred at two underground mines in South Korea and were followed by impulsive infrasound signals that were detectable at distances greater than 200 km. To explain the infrasound generation caused by the collapses, we hypothesize that excess pressure was released by the rapid outflow of an underground air mass into the atmosphere caused by the sudden implosion of earth into the underground space. We tested this idea with a physical model that assumes a displaced air volume as a monopole source with reduced pressure. The estimated volumes of the two collapses were ~1.7 × 10 5 and ~7.3 × 10 5 m 3, respectively, which agrees with the collapse volumes inferred from surface subsidence data. The infrasound generation model we used is applicable to the monitoring of other catastrophic failures within manmade or natural subsurface cavities. Plain Language Summary: Infrasound, a low‐frequency atmospheric acoustic wave, was observed following accidental underground mine collapses in South Korea. Examination of the observations showed that underground air abruptly flowed out of the mines. The size of the collapses was inferred based on an infrasound generation model. The results imply that it may be possible to identify failures of large underground spaces, such as manmade tunnels or naturally formed caves, from infrasound. Key Points: Underground mine collapses generate distinct infrasound as well as seismic waves The sudden release of an underground air volume may be an origin of infrasound Infrasound can be an indicator of catastrophic failures of underground spaces