Juichiro Ashi / Associate Professor / Institute of Environmental Studies
Department of Natural Environmental Studies / / geology of accretionary prism

Career Summary
1991: Post-Doctoral Fellow of JSPS at the Ocean Research Institute, the University of Tokyo
1993: Research Associate at the Geological Institute, the University of Tokyo
2001: Associate Professor at the Ocean Research Institute, the University of Tokyo
2006-present: Associate Professor at Graduate School of Frontier Sciences, the University of Tokyo
Educational Activities
Graduate School: Hadal Environmental Science, Fundamentals of Natural Environmental Studies
Research Activities
1. Studies of fault activities and tectono-sedimentary processes in plate subduction zones
2. Studies of methane hydrates in active tectonic regions
3. Growth process of mud volcanoes and its implications for tectonics and paleoenvironments
4. Origin, migration and venting of fluids in accretionary prisms

Distributions of active faults in the Nankai Trough
Distributions of active faults in the Nankai Trough

1) Ashi, J., Sawada, R., Omura, A. and Ikehara, K. (2014) Accumulation of an earthquake-induced extremely turbid layer in a terminal basin of the Nankai accretionary prism, Earth, Planets and Space, 66:51, doi:10.1186/1880-5981-66-51.
2) Ikehara, K., Irino, T., Usami, K., Jenkins, R., Omura, A. and Ashi, J. (2014) Possible submarine tsunami deposits on the outer shelf of Sendai Bay, Japan resulting from the 2011 earthquake and tsunami off the Pacific coast of Tohoku, Marine Geology 358, 120-127, doi:10.1016/j.margeo.2014.11.004.
3) Tsuji, T., Ashi, J. and Ikeda, Y. (2014) Strike-slip motion of a mega-splay fault system in the Nankai oblique subduction zone, Earth, Planets and Space, 66:120, doi:10.1186/1880-5981-66-120.
4) Ashi, J., Ikehara, K., Kinoshita, M. and KY04-11 and KH-10-3 shipboard scientists (2012) Settling of Earthquake-Induced Turbidity on the Accretionary Prism Slope of the Central Nankai Subduction Zone, Submarine Mass Movements and Their Consequences, Advances in Natural and Technological Hazards Research, Springer, 31, 561-571.
5) Ashi, J., Tokuyama, H. and Taira, A. (2002) Distribution of methane hydrate BSRs and its implication for the prism growth in the Nankai Trough, Marine Geology, 187, 117-191.
6) Ashi, J. and Taira, A. (1993) Thermal structure of the Nankai Accretionary Prism as inferred from the distribution of gas hydrate BSRs: Geological Society of America Special Paper 273, 137-149.
Other Activities
Geological Society of Japan
Seismological Society of Japan
American Geophysical Union
Future Plan
Fluids in subduction zones play important roles in deformation, thermal structure and material cycle. We have studied subsurface and surface expressions of fluid/gas migration such as methane hydrate, cold seep, and mud volcano in order to determine the relationships between behavior of fluids/gases and the growth of an accretionary prism. Our group attempts to discover more dynamic processes using in-situ monitoring, high-resolution surveys and pinpoint sampling at deep-sea.
Messages to Students
The deep-sea floor is very active and closely linked to our lives beyond what might imagine. Our group has several remote-sensing instruments, sampling and observation at deep-sea. You are welcome to join us in studying the active processes of subduction zones for revealing earthquakes, tsunamis and natural resources.