16:00 〜 16:15
[MTT45-03] A single-station seismo-acoustic data analysis on the January 15, 2022 eruption of Hunga Tonga-Hunga Ha’apai vocano
キーワード：火山噴火、空振、地震波
A large shallow-sea eruption occurred at Hunga Tonga-Hunga Ha’apai volcano (hereafter noted Hunga volcano) on January 15, 2022. The eruption was extremely explosive and generated waves in the atmosphere, ocean, and solid earth, that propagated all over the earth. In general, the global seismic networks can capture large, very-long-period (<0.02 Hz) signals generated by large explosions but are not able to resolve the detailed sequence toward and after the main events. Infrasound can propagate further due to the low attenuation in the atmosphere. However, in most cases of remote eruption observations, only one station at a good location captured waveforms sufficiently clear to extract the detailed sequence, while other stations in the global network exhibited diffusive signals. Not necessarily with remote observations, it frequently occurs that an eruption is recorded only by a single station. Analyzing the seismo-acoustic data of the single station is effective for understanding the eruption sequence.
The seismic station closest to the Hunga volcano was MSVF in Fiji, 754 km to the west. The data were downloaded from IRIS. Although the station had no infrasound array or sensor, a micro-barometer recorded pressure changes at 1 Hz, collocated with the broadband seismometers. We applied single-station seismo-acoustic data analysis methods to identify infrasonic and seismic signals from this station. First, we evaluated the seismometers’ responses to infrasound as functions of frequency below 0.16 Hz. Then, we compared the power ratios of the seismometers to the pressure sensor with the response functions. In the high-frequency ranges (> 1Hz), we investigated the power ratio of the surface seismometer to the borehole seismometer. As a result, we successfully extracted the temporal variation of the seismic wave and infrasound powers during the January 15 eruption in a broad range (0.006-10 Hz). The result will provide quantitative information about the types and intensity changes of the activity. It demonstrates the ability of this station for monitoring volcanoes in Tonga, which will be useful for future volcano monitoring in the area.
The seismic station closest to the Hunga volcano was MSVF in Fiji, 754 km to the west. The data were downloaded from IRIS. Although the station had no infrasound array or sensor, a micro-barometer recorded pressure changes at 1 Hz, collocated with the broadband seismometers. We applied single-station seismo-acoustic data analysis methods to identify infrasonic and seismic signals from this station. First, we evaluated the seismometers’ responses to infrasound as functions of frequency below 0.16 Hz. Then, we compared the power ratios of the seismometers to the pressure sensor with the response functions. In the high-frequency ranges (> 1Hz), we investigated the power ratio of the surface seismometer to the borehole seismometer. As a result, we successfully extracted the temporal variation of the seismic wave and infrasound powers during the January 15 eruption in a broad range (0.006-10 Hz). The result will provide quantitative information about the types and intensity changes of the activity. It demonstrates the ability of this station for monitoring volcanoes in Tonga, which will be useful for future volcano monitoring in the area.