[M-IS08] 南大洋・南極氷床が駆動する全球気候変動

[MIS08-P06] Hierarchical clustering applied to icequakes observed at Langhovde Glacier in East Antarctica

*箕輪 昌紘¹、Podolskiy Evgeny²、近藤 研^3,1、杉山 慎¹ (1.北海道大学・低温科学研究所、2.北海道大学・北極域研究センター、3.北海道大学大学院環境科学院)

キーワード：氷河、氷震、南極

Glacier often generates similar icequakes due to their common seismogenesis. Therefore, finding clusters of icequakes is critical to investigate the mechanisms of ice fracturing and glacier dynamics. We monitored icequakes near the ice-shelf front of Langhovde Glacier in East Antarctica in the summer of 2017/18 and up the grounding line of the glacier in the summer of 2021/22. The hierarchical clustering method was applied to the seismic records, which is based on the correlation coefficient among the icequakes. Seven and six clusters were generated for the seismic records in 2017/18 and 2021/22, respectively. For example, in 2017/18, clusters 1 and 2, with a center frequency of around 10 Hz, coincided with the lowering tide when the horizontal speed of the glacier increased. Clusters 3 and 4, with center frequency ranges from 20 to 50 Hz, coincided with the rising tide when the ice shelf lifted in pace with the tide. Other clusters 5-7, dominated by frequencies higher than 100 Hz, showed a relation with meteorological records. When air temperature dropped below zero, the frequencies of clusters 5 and 7 increased up to 200 events/hour. Noise generation due to high wind speed is expected to cause cluster 6. In the presentation, we will discuss the clustering method, temporal variation of the clustered events and their possible mechanisms.