open access

https://hdl.handle.net/2115/86649

Ocean-Bottom Seismology of Glacial Earthquakes : The Concept, Lessons Learned, and Mind the Sediments

英語

2021-09

Seismological Society America

Seismological research letters

92(5)

2850-2865

About 70% of Earth's surface is covered by ocean, for which seismic observations are challenging. Seafloor seismology overcame this fundamental difficulty and radically transformed the earth sciences, as it expanded the coverage of seismic networks and revealed otherwise inaccessible features. At the same time, there has been a recent increase in the number of studies on cryoseismology. These have yielded multiple discoveries but are limited primarily to land and ice-surface receivers. Near ice calving fronts, such surface stations are noisy, primarily due to crevassing and wind, are hazardous to maintain, and can be lost due to iceberg calving. To circumvent these issues, we have applied ocean-bottom seismology to the calving front of a tidewater glacier in northwest Greenland. We present details of this experiment, and describe the technical challenges, noise analysis, and examples of recorded data. This includes tide-modulated seismicity with thousands of icequakes per day and the first near-source (similar to 200-640 m) underwater record of a major kilometer-scale calving event in Greenland, which generated a glacial earthquake that was detectable similar to 420 km away. We also identified a decrease in bottom-water temperature, presumably due to modified water stratification driven by extreme Greenland glacial melting, at the end of July 2019. Importantly, we identify glacial sediments as the key reason for the anomalously long (similar to 9.7 hr) delay in the sensor release from the fjord seafloor. Our study demonstrates a methodology to undertake innovative, interdisciplinary, near-source studies on glacier basal sliding, calving, and marine-mammal vocalizations.

学術雑誌論文

Accepted Manuscript

0895-0695