Name : MORITA,  Yuichi
            Position : Associate Professor
            Division/Center : Ocean Hemisphere Research Center
            Research Area : Seismology, Seismometry
 
 
 
 

       My main research interest is seismological structure of the Earth's mantle and core inferred from the seismic body waves. Even at
       present, we do not have enough seismic data for revealing the detailed structure deep inside of the Earth. So, I devote myself to carry
       out seismic observations in the global scale. I participated in the Ocean Hemisphere Network Project whose target is to reveal the
       geophysical structure deep inside of the Earth from the data acquired in the project. We constructed seismic observatories in the
       Northeastern Pacific region which is characterized by the slab subduction zone. From the results of the seismic tomography, the
       subducting slab may be stagnant there. In order to examine the detailed structure around there, I begun to install temporally four
       broadband seismometers in China under the collaboration with the China Seismological Bureau. Using data acquired here, I will
       analyze t he velocity structure around 660km discontinuity beneath China and will discuss on the dynamics of the slab subduction.

       In addition to the above work, I am also interested in the seismometry. In order to carry out the seismic observation mentioned above,
       we need specialized instruments. In fact, the instruments which we can purchase now is not suitable for the circumstances in
       developing countries, where they have unstable electricity, less accessibility for transportation and inconvenience for
       telecommunication. So, we developed the new type of the recording system which has much portability and lower power consumption.
       And I am recently interested in the new type of seismometers. Among them, I now concentrate on the digital feedback broadband
       seismometer, which has many advantages in its usage but is not realized yet. I started project to design the digital feedback
       seismometer, estimate its feasibility and produce it. New kinds of instruments for seismic observation will enable us to get new kinds
       of data which we could not do. Therefore, the study on the development of new kinds of instruments is also important in the field of
       geophysics.

Publications:

Yamamoto, M., H. Kawakatsu, S. Kaneshima, T. Mori, T. Tutui, Y. Sudo, and Y. Morita, Detection of a crack-like conduit beneath the active crater at Aso volcano, Japan, Geophys. Res. Lett., 26, 3677--3680, 1999.

M. Kikuchi, Y. Yamanaka, K. Abe and Y. Morita, Source rupture process of the Papua New Guinea earthquake of July 17, 1998 inferred from teleseismic body waves, Earth Planets Space, 51, 1319--1324, 1999.

Yamamoto, M., H. Kawakatsu, S. Kaneshima, T. Iidaka, J. Oikawa, S. Watada, Y. Morita, M. Yoshikawa, T. Hashimoto, and M. Nakabo, ASOBOI97: Aso Seismic Observation with Broadband Instruments in 1997, Bull. Earthq. Res. Inst., 74, 267--285, 1999.