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Numerical Modeling of Iceberg Capsizing Responsible for Glacial Earthquakes
Author(s) -
Sergeant Amandine,
Yastrebov Vladislav A.,
Mangeney Anne,
Castelnau Olivier,
Montagner JeanPaul,
Stutzmann Eléonore
Publication year - 2018
Publication title -
journal of geophysical research: earth surface
Language(s) - English
Resource type - Journals
eISSN - 2169-9011
pISSN - 2169-9003
DOI - 10.1029/2018jf004768
Subject(s) - iceberg , geology , buoyancy , hydrostatic equilibrium , geodesy , glacier , drag , seismology , ice calving , magnitude (astronomy) , submarine pipeline , mechanics , geophysics , ice sheet , geotechnical engineering , physics , oceanography , geomorphology , pregnancy , lactation , quantum mechanics , astronomy , biology , genetics
The capsizing of icebergs calved from marine‐terminating glaciers generate horizontal forces on the glacier front, producing long‐period seismic signals referred to as glacial earthquakes . These forces can be estimated by broadband seismic inversion, but their interpretation in terms of magnitude and waveform variability is not straightforward. We present a numerical model for fluid drag that can be used to study buoyancy‐driven iceberg capsize dynamics and the generated contact forces on a calving face using the finite‐element approach. We investigate the sensitivity of the force to drag effects, iceberg geometry, calving style, and initial buoyancy. We show that there is no simple relationship between force amplitude and iceberg volume, and similar force magnitudes can be reached for different iceberg sizes. The force history and spectral content varies with the iceberg attributes. The iceberg aspect ratio primarily controls the capsize dynamics, the force shape, and force frequency, whereas the iceberg height has a stronger impact on the force magnitude. Iceberg hydrostatic imbalance generates contact forces with specific frequency peaks that explain the variability in glacial earthquake dominant frequency. For similar icebergs, top‐out and bottom‐out events have significantly different capsize dynamics leading to larger top‐out forces especially for thin icebergs. For realistic iceberg dimensions, we find contact‐force magnitudes that range between 5.6 × 10 11 and 2 × 10 14 kg·m, consistent with seismic observations. This study provides a useful framework for interpreting glacial earthquake sources and estimating the ice mass loss from coupled analysis of seismic signals and modeling results.