Name : SENO,  Tetsuzo
            Position : Professor
            Division/Center : Division of Geodynamics
            Research Area : Tectonics and dynamics
            homepage : http://www.eri.u-tokyo.ac.jp/seno/
 
 
 
 

Research:

       I investigate three major subjects: plate motion determination in the western Pacific-east Asian region, intraplate stresses in
       continental plates and arcs, global sea level change related to mantle convection.

       On the plate motion determination, I had determined the Philippine Sea(PH), Eurasia (EU) and Pacific plate (PA) motions using slip
       vectors of interplate earthquakes and NUVEL-1 PA-EU motion data. In 1996, I included two more plates, the Okhotsk (OK) and
       North American plates (NA) in the inversion scheme and proved that OK exists as an independent plate from NA. In 1998, I
       separated the Amurian plate (AM) from EU, and determined the motions of all the 6 plates in the Asian region simultaneously.

       On the intraplate stresses in the overriding plates, I have derived a general rule relating the forearc's stress and the slab stress in its
       upper portion and the ridge push. That is, if the slab is in down-dip tension(compression), the forearc stress is compression
       (tension). Taking into account the differential stress variation across the arc (more tension in the backarc than in the forearc), I can
       explain the backarc stresses in most of the arcs. However, there are a few exceptions which do not obey this rule; they are the
       Marianas, Kyushu and the Aegean. I explained these arcs' stresses by lateral flow beneath the upper plate, which might originate
       from the upwelling from the deep mantle.

       I investigate the global sea level in relation to the history of the mantle convection. They are divided into two parts: secular variation
       due to the change in mode of mantle convectin, and cyclic variation due to the breakup and closing of the supercontinent, i.e. due to
       Wilson cycles. For the secular variation of mantle convection, I propose a sequence of the stagnant plate, buoyant slab convection and
       plate tectonics. Two periods of emergence of the continental area during 2.8-2.1 Ga and 1.0-0 Ga is expected from this sequence.
       From the Wilson cycles, I calculate CO2 variation, which is consistent with the enviromental variation for the last WIlson cycle since
       0.6 Ga.

Publications

Seno, T., Syntheses of the regional stress fields of the Japanese islands, The Island Arc, 8, 66--79, 1999.

Seno, T., Why the Philippine Sea plate moves as it does, J. Geol. Soc. Phil., 55, 105--117, 2000.

Seno, T., The Sept. 21, 1999 Chi-Chi earthquake in Taiwan: implications for tsunami earthquakes, Terr. Atmos. Ocean, 11, 701--708, 2000.

Seno, T., K. Otsuki, and C.-N. Yang, The 1999 Chi-Chi, Taiwan earthquake: A subduction zone earthquake on land , Bull. Earthq. Res. Inst., 75, 57--77, 2000.