Infrasonic observations of the June 2009 Sarychev Peak eruption, Kuril Islands: Implications for infrasonic monitoring of remote explosive volcanism

Abstract

Sarychev Peak (SP), located on Ostrov Matua, Kurils, erupted explosively during 11–16 June 2009. Whereas remote seismic stations did not record the eruption, we report atmospheric infrasound (acoustic wave ~ 0.01–20 Hz) observations of the eruption at seven infrasound arrays located at ranges of ~ 640–6400 km from SP. The infrasound arrays consist of stations of the International Monitoring System global infrasound network and additional stations operated by the Korea Institute of Geoscience and Mineral Resources. Signals at the three closest recording stations IS44 (643 km, Petropavlovsk-Kamchatskiy, Kamchatka Krai, Russia), IS45 (1690 km, Ussuriysk, Russia), and IS30 (1774 km, Isumi, Japan) represent a detailed record of the explosion chronology that correlates well with an eruption chronology based on satellite data (TERRA, NOAA, MTSAT). The eruption chronology inferred from infrasound data has a higher temporal resolution than that obtained with satellite data. Atmosphere-corrected infrasonic source locations determined from backazimuth cross-bearings of first-arrivals have a mean centroid ~ 15 km from the true location of SP. Scatter in source locations of up to ~ 100 km result from currently unresolved details of atmospheric propagation and source complexity. We observe systematic time-variations in trace-velocity, backazimuth deviation, and signal frequency content at IS44. Preliminary investigation of atmospheric propagation from SP to IS44 indicates that these variations can be attributed to solar tide variability in the thermosphere. It is well known that additional information about active volcanic processes can be learned by deploying infrasonic sensors with seismometers at erupting volcanoes. This study further highlights the significant potential of infrasound arrays for monitoring volcanic regions such as the Kurils that have only sparse seismic network coverage.