Expectations for international MARGINS' collaborations from the point of view of an "active margin" country Gaku KIMURA The University of Tokyo iFREE JAMSTEC

One Day Suddenly! 2004 Sumatra Tsunami 1944 Tonankai Earthquake Mie Prefecture

Top 12 since 20C 1906 Equador 1923 Kamchatka 1938 Banda 1950 Tibet 1952 Kamchatka 1957 Alaska 1960 Chile 1963 Kuril 1964 Alaska 1965 Rat Alaska 2004 Sumatra 2005 N.Sumatra Nankai Trough: Longest Historical Record

Ide et al., 2007

Obana & Kodaira, 2009

国土地理院／世界最稠密 GPS 南海トラフ Recent Great Discoveries Obara, Science 2002, Ito et al., Science 2007, Ide et al., Nature 2007 Plate boundary depth contour Rupture Area Deep Low Frequency Tremor Deep ultra-low Frequency Tremor Slow slip Shallow ultra Low Frequency Tremor

Soon: Direct observation within fault zone bore hole Recent Great Discoveries : far field observation Deep LFT Shallow LFT Chikyu

Moore et al., 2009

Splay Fault Oceanic Crust Decollement 3D Nankai accretionary wedge Moore et al., 2007, 2009

The splay Fault from the bottom

Many landslides around active portion of the splay fault

Horizontal slice at -2910m Clear deformation of young (<0.5My) slope sediments

南海トラフ海底地形・断面図 フィリピン海プレート Splay Fault 10cm X-ray CT Drilling Result of the splay fault Kinoshita, Tobin et al., 2009

1944 Tonankai! Disturbed mud is a key

Analyzed by Yamaguchi et al.

Conclusion 1.Nankai Trough SEIZE is a quite successful on- going international collaboration through individual PIs, IODP frame, Margins program and others. 2.International collaboration is strongly expected from “active margin” countries because natural geo-hazard issues are so serious and urgent. 3.A new frame of international MARGINs is expected in each country.