Institution: | Department of Geophysics, University of Oslo, Box 1022, Blindern, 0315 Oslo, Norway. E-mail:;Norwegian Water Resources and Energy Administration, Box 5091, Majorstua, 0301 Oslo, Norway. E-mail:;Department of Geophysics, University of Oslo, Box 1022, Blindern, 0315 Oslo, Norway. E-mail: |