17:15 〜 18:45
[MIS10-P08] Long-term monitoring of icequakes on the grounding zone of Langhovde Glacier, East Antarctica
キーワード：接地線、氷震、南極氷床
The dynamics of glaciers on the grounding zone control the mass change of the Antarctic ice sheet and have to be better understood1). Glacier emits discrete seismic signals when it fractures and slides over the bedrock2). Therefore, passive icequake monitoring can provide an opportunity to study glacier dynamics. In 2021, we started comprehensive geophysical monitoring of the dynamics on the grounding zone of Langhovde Glacier, East Antarctica. Two borehole seismometers were installed into the glacier at depths of 4 m and 200 m, where the thickness of the glacier was 551 m. We used Lennartz LE-3/BH(s) MkⅢ seismometer with DATA-CUBE3 Type 2 recorder sampling at 50 Hz. The system was powered by a 12 V 110 Ah battery and a 24 W solar panel. The direction, pitch and roll of the seismometer were also measured by a magnetometer and tilt sensor (HMR3300) three to four times per day. Figure 1 shows number of icequakes, amplitude and tremor of the observed signals of the deeper borehole seismometer between 25 December 2021 and 2 February 2024. The number of icequakes shows diurnal, weekly, and seasonal variations. For example, we observed about twice more frequent seismic events during Austral summer than winter (Fig. 1). At the lower frequencies between 0.1 and 1 Hz, the seismic tremor increased between January and June in 2022 and 2023 (Fig. 1), likely due to ocean waves exciting the glacier when sea-ice concentration was low. We are going to further investigate the diurnal to seasonal variations in the icequakes of Langhovde Glacier to understand its dynamics, by also using GNSS and other seismometers deployed on the glacier surface during a field campaign in the austral summer of 2021/2022 and 2023/2024.