Name : FUKAO,  Yoshio
            Position : Professor
            Division/Center : Ocean Hemisphere Research Center
            Research Area : Seismology


1.Seismological study of the Earth's structure:
       We have recently found a general tendency that subducted slabs are trapped in Bullen's transition region in a depth range from 400 to
       about 1000km. We are now analyzing waveform data from the OHP (Ocean Hemisphere network Project) and other global networks
       to resolve the fine seismic wave structure of Bullen's transition region.
2.Study of continuous excitation of Earth's free oscillations:
       Our group has for the first time found the evidence of continuous excitation of Earth's free oscillations from records of the OHP
       network and then proved its real existence based on independent data set. We are seeking for an excitation source for this surprising
3.Seismic detection of enigmatic submarine events:
       We have analyzed water-acoustic waves and water-sediment-coupled seismic waves recorded by OBS (Ocean bottom
       Seismometer) cable arrays to detect a series of small volcanic eartquakes associated with the tsunami earthquake with a CLVD
       mechanism and the swarm activities right beneath the outer-arc high of the Japan trench, respectively. We have started a systematic
       search for enigmatic submarine phenomena.
4.Seismological study of crustal fluid:
       We have analyzed monotone oscillation phenomena characteristic to the crustal system of solid and fluid, including the free oscillation
       phenomena of magma liquid in a volcanic conduit and of water column in a well-aquifer system. We are now attempting to obtain more
       examples of strange phenomena in the crust containing fluids in it.
5.Gravimetric study of the central Andes:
       We have completed gravity measurements in whole Peru and compilation of Peruvian gravity data to obtain a detailed gravity map of
       whole Peru. Based on this huge data set, we are now studing the crustal structure beneath the central Andes.


Kumagai, H., Y. Fukao, S. Watanabe and Y. Baba, A self-organized model of earthquakes with constant stress drops and the b-value of 1, Geophys. Res. Lett., 26, 2817--2820, 1999.

Fukao, Y., M. Kono, A. Yamamoto, M. Saito, K. Nawa, A. Giesecke, and C. Perales, Gravity measurements and data reduction for Bouguer anomaly map of Peru, Bull. Earthq. Res. Inst., 74, 161--266, 1999.

Nishida, K., N. Kobayashi and Y. Fukao, Resonant oscillations between the solid Earth and the atmosphere, Science, 287, 2244--2246, 2000.

Fujita, E., Y. Fukao and K. Kanjo, Strain offsets with monotonous damped oscillations during the 1986 Izu-Oshima Volcano eruption, J. Geophys. Res., 105, 443--462, 2000.

Widiyantoro, S., A. Gorvatov, B.L.N. Kennet and Y. Fukao, Improving global shear-wave travel-time tomography using three dimensional ray tracing and iterative inversion, Geophys. J. Int., 141, 747--758, 2000.

Gorbatov, A., S. Widiyantoro, Y. Fukao, and E. Gordeev, Signature of remnant slabs in the North Pacific from P-wave tomography, Geophys. J. Int., 142, 27--36, 2000.

Kunugi, T., Y. Fukao and M. Ohno, Underdamped responses of a well to nearby swarm earthquakes, J. Geophys. Res., 105, 7805--7818, 2000.

Nawa, K., N. Suda, Y. Fukao, T. Sato, Y. Tamura, K. Shibuya, H. McQueen, H. Virtanen and J. Kaariainen, Incessant excitation of the Earth's free oscillations: global comparison of superconducting gravimeter records, Phys. Earth Planet. Inter., 120, 289--297, 2000.

Sugioka, H., Y. Fukao, T. Kanazawa and K. Kanjo, Volcanic events associated with an enigmatic submarine earthquake, Geophys. J. Int., 142, 361--370, 2000.

Nakatani, M., S. Kaneshima and Y. Fukao, Size-dependent microearthquake initiation inferred from high-gain and low-noise observations at Nikko district, Japan, J. Geophys. Res., 105, 28095-28109, 2000.