1. Postgraduate Student, Dept. of Earth Sciences, Univ. of Gothenburg, BOX-460, SE-405 30 Gothenburg, Sweden (corresponding author).
2. Postgraduate Student, Dept. of Land and Water Resources Engineering, Royal Institute of Technology (KTH), SE-100 44 Stockholm, Sweden.
3. Senior Lecturer, Dept. of Earth Sciences, Univ. of Gothenburg, BOX-460, SE-405 30 Gothenburg, Sweden.