Institution: | Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Silver Street, Cambridge CB3 9EW;Geodetic Institute, Gamlehave Alle 22, DK-2920 Charlottenlund, Denmark;NTNF/NORSAR, PO Box 51, N-2007 Kjeller, Norway;British Geological Survey, Murchison House, West Mains Road, Edinburg EH9 3LA |