Japan Geoscience Union Meeting 2018

Presentation information

[EE] Oral

U (Union) » Union

[U-03] Cryoseismology - a new proxy for detecting surface environmental variations of the Earth -

Thu. May 24, 2018 10:45 AM - 12:15 PM 103 (1F International Conference Hall, Makuhari Messe)

convener:Genti Toyokuni(Research Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku University), Masaki Kanao(National Institute of Polar Research), Seiji Tsuboi(海洋研究開発機構), Chairperson:Toyokuni Genti(東北大学), Tsuboi Seiji, Kanao Masaki

11:20 AM - 11:35 AM

[U03-03] Ambient seismic noise at a Himalayan debris-covered glacier

*Evgeny A. Podolskiy1, Koji Fujita2, Sojiro Sunako2, Akane Tsushima3, Rijan Bhakta Kayastha4 (1.Arctic Research Center, Hokkaido University, 2.Graduate School of Environmental Studies, Nagoya University, 3.Research Institute for Humanity and Nature, Kyoto, Japan, 4.School of Science, Kathmandu University)

Keywords:debris-covered glacier, thermal stress, seismic noise

Seismic data was collected during autumn 2017 at a debris-covered glacier in the Himalayas to provide a wide-scale characterization of its cryo-seismic wavefield. Here, we analyze ambient noise at the glacier and find a strong diurnal variation of seismicity. We show that the air temperature is pacing the intensity of broadband noise (0.1-100 Hz) and that its polarity depends on an existence or a lack of a debris-mantle. Debris-covered area has the highest activity in the afternoon, while debris-free area at night. We consider debris-modulation of thermal stress, leading to near-surface tensile fracture, melt-related rock motion, and wind as the main mechanisms. Debris dampens the diurnal amplitude of the temperature and thus protects the ice from a cyclic mechanical damage, which cracks exposed ice most intensively early in the morning. Together with a well-known thermal insulation effect of debris, such property should protect weathering crust of glaciers from fast degradation.