Muographic monitoring of hydrogeomorphic changes induced by post-eruptive lahars and erosion of Sakurajima volcano

Oláh, László and Tanaka, Hiroyuki K.M. and Hamar, Gergő (2021) Muographic monitoring of hydrogeomorphic changes induced by post-eruptive lahars and erosion of Sakurajima volcano. SCIENTIFIC REPORTS, 11. No. 17729. ISSN 2045-2322

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Abstract

Post-eruptive destabilization of volcanic edifices by gravity driven debris flows or erosion can catastrophically impact the landscapes, economies and human societies surrounding active volcanoes. In this work, we propose cosmic-ray muon imaging (muography) as a tool for the remote monitoring of hydrogeomorphic responses to volcano landscape disturbances. We conducted the muographic monitoring of Sakurajima volcano, Kyushu, Japan and measured continuous post-eruptive activity with over 30 lahars per year. The sensitive surface area of the Multi-Wire-Proportional-Chamber-based Muography Observation System was upgraded to 7.67 m 2 ; this made it possible for the density of tephra within the crater region to be measured in 40 days. We observed the muon flux decrease from 10 to 40% through the different regions of the crater from September 2019 to October 2020 due to the continuous deposition of tephra fallouts. In spite of the long-term mass increase, significant mass decreases were also observed after the onsets of rain-triggered lahars that induced the erosion of sedimented tephra. The first muographic observation of these post-eruptive phenomena demonstrate that this passive imaging technique has the potential to contribute to the assessment of indirect volcanic hazards

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