1. Takayuki Nagata and Taku Nonomura were with the Graduate School of Engineering, Tohoku University, Sendai, Miyagi, Japan
2. Institute of Fluid Science, Tohoku University, Sendai, Miyagi, Japan
3. School of Engineering, Tohoku University, Sendai, Miyagi, Japan
4. Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan