1. Department of Civil and Earth Resources EngineeringKyoto University C1‐1‐111 Kyotodaigaku‐Katsura Nishikyo‐ku Kyoto 606‐8501 Japan
2. Department of Geoscience and PetroleumNorwegian University of Science and Technology S.P. Andersens veg 15a NO‐7491 Trondheim Norway