Glacial Seismology
Photo Mosaic of the 'Loose Tooth' rift system on the Amery Ice Shelf, East Antarctica. One of the field sites where we have been deploying GPS and seismometers.
Swarms of ice quakes correlate with rift propagation.
Seismometer vault at station A on iceberg C16, October, 2003.
Two basic avenues of research into origins and implications of glacial seismicity have been underway since about 2003. In the first avenue, Jeremy Bassis and colleagues from Scripps Institution of Oceanography (Helen Fricker) and University of Tasmania (Richard Coleman), Australia, have been involved in efforts to detect ice-shelf rifting (on the Amery Ice Shelf) using a portable seismometer array placed near the tip of a large fracture in the ice shelf (see image on the right). In the second avenue, our group has collaborated with seismologists from Northwestern University (Emile Okal) and New Mexico Tech (Richard Aster) to investigate the source mechanism of non-volcanic tremor (NVT) emanating from large tabular icebergs in the Antarctic. We are anticipating future work to continue with the help of the University College Dublin seismology group.
Harmonic Tremor from Icebergs
You can read about our research on iceberg harmonic tremor here (PDF).
See and hear iceberg tremor here (YouTube video).
Seismometer deployment on iceberg C16, Ross Sea, Antarctica, during 2003 field campaign. Seismometers at sites A, B, C, and D on the iceberg, and seismometers on Ross Island's Erebus Volcano Observatory, received tremor signals generated by iceberg-on-iceberg collisions between C16 and B15A.
Seismograms (a, b, e, f) and spectrograms (c, d) from measurements made at station B on iceberg C16. The aseismic eye is used to locate the source of the tremor and to determine its causal mechanism.
Ice Shelf Rifting Studies
Rifts, large fractures that penetrate the entire ice thickness, are precursors to iceberg calving events. These fractures can extend up to hundreds of kilometers and propagate for decades before becoming the detachment boundary of icebergs. Little is known about the forces and mechanisms that lead to rift initiation and propagation - partly because we have very few measurements against which hypotheses can be tested. To address this, we've been working with an international team of scientists to deploy global positioning system receivers (GPS) and seismometers around the tip of a propagating rift on the Amery Ice Shelf, East Antarctica. The field work has been done in conjunction with a program monitoring rift propagation using satellite imagery.
You can read about our research on ice-shelf rifting here (PDF), and here (PDF).
