Detection of Fracture Induced Anisotropy in Temperate Glaciers Using Georadar
Abstract
Transverse waves through a medium containing preferentially oriented inclusions travel at different speeds depending on their polarization relative to the inclusions. Using the Alford rotation seismologists can determine the bulk orientation of the voids when analyzing elastic shear wave data. Observations spanning 4 field seasons show subvertically oriented planar fractures in the Bench Glacier in the Chugach Mountains, AK. If these are caused by the stress field, the fractures should be preferentially oriented. In 2007 and 2008 we designed surveys to test the azimuthal orientation of the fractures. We collected three polarizations; xx- configuration (transverse magnetic), yy-configuration (transverse electric) and cross-polarized. Each polarization was collected in five directions ranging from 0 to 90 degrees relative to the glacial axis. Preliminary results show an azimuthally dependent velocity. By applying the Alford rotation to georadar data we hope to determine the voids do have a preferential orientation. This will yield new insight into the formation and distribution and content of englacial voids and provide complementary information to multi- azimuthal velocity surveys acquired previously.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFMNS43A1178N
- Keywords:
-
- 0689 Wave propagation (2487;
- 3285;
- 4275;
- 4455;
- 6934);
- 0720 Glaciers;
- 0776 Glaciology (1621;
- 1827;
- 1863);
- 0794 Instruments and techniques