The seismic signature of glacier outburst floods (Invited)
Abstract
Glacier outburst floods discharge large volumes of water from ice-dammed lakes, moraine-dammed lakes, subglacial cavities, or other reservoirs of liquid water. Breaching of moraine- or ice-dammed lakes represent significant hazards for communities adjacent to mountainous regions and a better understanding of the phenomena is warranted. Identifying a unique seismic signature may aid in development of an early warning system and provide the ability to 'remotely' detect when areas are undergoing flooding. We focus efforts on examining seismic data from two distinct regions in Alaska. First, we recorded an outburst flood from a glacier-dammed lake adjacent to Mendenhall Glacier near Juneau, using an array of short- and broadband-period seismometers installed in ice boreholes. We manually pick icequakes and then use the template waveforms in a waveform matching technique that allows us to identify missed events during very active or otherwise noisy time periods. Second, we observe glacier-related seismicity at the Alaska Volcano Observatory network installed on the flanks of Mt Spurr, a relatively active Aleutian arc volcano 130 km west of Anchorage. The activity is plausibly a repeat of a glacier outburst flood that occurred during 1992. During the 1992 flood, an outburst flood exited from beneath a glacier that flows down the southern slope of Mt. Spurr. In both cases, the observed seismicity indicates long, emergent periods (hours to days) of continuous high frequency energy (>10 Hz) at stations closest to the outlet, during vigorous flooding. Secondly, after flooding peaks, distinct short-duration (seconds) icequake events are observed, likely due to collapse of subglacial drainages. No distinct precursors appear in the seismic record, though this may be due to aseismic small-scale failures or ice floatation that lead to the breach.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.C54B..03W
- Keywords:
-
- 0774 CRYOSPHERE Dynamics;
- 7299 SEISMOLOGY General or miscellaneous;
- 0700 CRYOSPHERE;
- 0776 CRYOSPHERE Glaciology