16:00 〜 16:15
[MAG37-03] Long-range acoustic measurements of the 2004 submarine eruption near Nightingale Island: Insights from hydrophone triplet array data recorded at IMS station H01W, Cape Leeuwin
キーワード：Submarine eruption, Nightingale Island, IMS, CTBTO
Little is known about active volcanism in the remote regions of the global ocean. Here, we resort to long-range acoustic measurements to study the 2004 eruption at Nightingale Island, Tristan da Cunha. Underwater sound phases associated with the event were recorded at Cape Leeuwin, Western Australia, where a bottom-moored hydrophone array is operated as part of the International Monitoring System (IMS). IMS recordings in combination with local seismic observations suggest that the center of activity is located to the east of Nightingale Island, where a seafloor mapping campaign aboard R/V Maria S Merian (2012MSM20/2) revealed a previously unknown, potentially newly formed stratocone. Signal back azimuth derived from progressive-multi-channel-beamforming differ by more than two degrees from the expected geodesic value, suggesting that low-frequency sound phases may not have traveled along the direct source-receiver path, but were instead reflected off an unnamed seamount located south of Tristan da Cunha. This interpretation is supported by results from transmission loss modeling via the parabolic equation approach, which indicate significant bathymetric obstruction between the volcano and the H01W array in the Southern Ocean. Our study further highlights the potential of the IMS network for the detection and study of future eruptions both at Nightingale Island and elsewhere. Implications for test-ban treaty monitoring and volcano early warning will be discussed.