Skip to main content
U.S. flag

An official website of the United States government

Calving seismicity from iceberg-sea surface interactions

January 1, 2012

Iceberg calving is known to release substantial seismic energy, but little is known about the specific mechanisms that produce calving icequakes. At Yahtse Glacier, a tidewater glacier on the Gulf of Alaska, we draw upon a local network of seismometers and focus on 80 hours of concurrent, direct observation of the terminus to show that calving is the dominant source of seismicity. To elucidate seismogenic mechanisms, we synchronized video and seismograms to reveal that the majority of seismic energy is produced during iceberg interactions with the sea surface. Icequake peak amplitudes coincide with the emergence of high velocity jets of water and ice from the fjord after the complete submergence of falling icebergs below sea level. These icequakes have dominant frequencies between 1 and 3 Hz. Detachment of an iceberg from the terminus produces comparatively weak seismic waves at frequencies between 5 and 20 Hz. Our observations allow us to suggest that the most powerful sources of calving icequakes at Yahtse Glacier include iceberg-sea surface impact, deceleration under the influence of drag and buoyancy, and cavitation. Numerical simulations of seismogenesis during iceberg-sea surface interactions support our observational evidence. Our new understanding of iceberg-sea surface interactions allows us to reattribute the sources of calving seismicity identified in earlier studies and offer guidance for the future use of seismology in monitoring iceberg calving.

Publication Year 2012
Title Calving seismicity from iceberg-sea surface interactions
DOI 10.1029/2012JF002513
Authors T.C. Bartholomaus, C.F. Larsen, Shad O'Neel, M.E. West
Publication Type Article
Publication Subtype Journal Article
Series Title Journal of Geophysical Research F: Earth Surface
Index ID 70045534
Record Source USGS Publications Warehouse
USGS Organization Alaska Science Center Water