EAPS Department Lecture Series - Peter Kelerman (Columbia/LDEO)
A viscous mechanism for earthquakes and icequakes
Following from work by Kelemen & Hirth Nature 2007 (and Whitehead & Gans 1975) on a viscous mechanism for intermediate depth earthquakes in the mantle, Christine McCarthy, David Goldsby, Rob Skarbek and I have been investigating a viscous shear heating mechanism for repeating, intraglacial icequakes. Fine grained layers in glacial ice contain abundant dust particles, suggesting grain size pinning. Grain size dependent rheology renders these layers weaker than the surrounding ice. Under some circumstances, such weak layers focus viscous deformation and shear heating, leading to “viscous icequakes”. We can select parameters that match the period of repeating earthquakes observed on the Whillans Ice Stream, and other periodic intra- or sub-glacial earthquakes worldwide. It is interesting to contemplate similar instabilities in the lower crust and mantle lithosphere, involving compositionally weak layers within a stronger matrix.
About this Series
Weekly talks given by leading thinkers in the areas of geology, geophysics, geobiology, geochemistry, atmospheric science, oceanography, climatology, and planetary science. Lectures take place on Wednesdays from 3:45pm in MIT Building 54 room 915, unless otherwise noted.