Observation of surface seismic activity changes of an Alpine glacier during a glacier‐dammed lake outburst

Abstract

[1] During the 2004 outburst flood of Gornersee, Switzerland, we observed surface microseismic activity (so-called icequakes) near the glacier-dammed lake on Gornergletscher. Using surface waves, we located near-surface tensile fracturing events by inverting time delays using a quasi-Newton scheme. We located 8520 near-surface events with uncertainties of less than 10 m. Seismic activity increased during the lake drainage, and the icequake epicenters migrated downglacier. Furthermore, we identified events whose fault plane orientations are nearly perpendicular to the local pattern of surface crevassing. These observations can be explained by the rotation of principal strains at the glacier surface deduced from local ice flow measurement which occurred during the flotation of the ice dam at the onset of the lake drainage. In general, we suggest that our technique is a useful tool to locate large data sets of microseismic events and can be used to monitor the temporal evolution of fracture processes and their dependence on glacier flow and glacier hydrology.Citation: Roux, P.-F., F. Walter, P. Riesen, S. Sugiyama, and M. Funk (2010), Observation of surface seismic activity changes of an Alpine glacier during a glacier-dammed lake outburst,

Tidal bending and strand cracks at the Kamb Ice Stream grounding line, West Antarctica

“…The sounds were common at some times of the day and absent at others, which we inferred to be associated with the tide. These qualitative observations are very similar to those made by Robin (1958). In contrast to the situation at KIS, we observed few strand cracks on the north and south sides of the Whillans Ice Stream (WIS) grounding line when working there during the same field seasons, and never heard propagation events in the WIS grounding zone.…”

“…Swithinbank, 1955;Robin, 1958). Since those early investigations, grounding zones (transitions from fully grounded to fully floating ice) have been recognized as critical boundaries in understanding change in the ice-sheet/ice-shelf system (Mercer, 1978;Thomas and others, 1979;Schoof and Hewitt, 2013).…”

Ice tectonic deformation during the rapid in situ drainage of a supraglacial lake on the Greenland Ice Sheet

“…The inability to identify individual events prevents the location of seismicity using standard methods (e.g. Walter et al, 2008;Roux et al, 2010). Whilst Jones et al (2013) demonstrate that a technique based on amplitudes may be used to locate such seismicity, the application of this method is beyond the scope of this study.…”

Towards monitoring the englacial fracture state using virtual-reflector seismology

“…However, as shown, for example, by Neave & Savage (1970), Roux et al (2010), Mikesell et al (2012) and Walter et al (2015), shallow icequakes characterized by a dominant Rayleigh wave are numerous and generally spatially varying as a function of time. These shallow icequakes do not need to be distributed such that the generated Rayleigh waves illuminate the region of interest uniformly from all angles: provided their distribution ensures that no large angles are left without energy flux, application of VRS is possible.…”

“…Additionally, variable icequake source locations both in space and time (e.g. Roux et al 2010) complicate the retrieval of stable virtual-source responses.…”