Name : FUKAO, Yoshio
Position : Professor
Division/Center : Ocean Hemisphere Research Center
Research Area : Seismology
RESEARCH
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
phenomenon.
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.
PUBLICATIONS
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.