SDPlate Tectonics and Crustal Deformation
Around the Japanese Islands
MANABU HASHIMOTO
Geographical Survey Institute, Tsukuba, Ibaraki, Japan
DAVID D. JACKSON
Department ofEarth and Space Sciences, University of California, Los Angeles
Journal of Geophysical Research, Vol.98, No.B9, P.16149-16166, 1993
We analyze over a century of geodetic data
to study crustal deformation and plate motion
around the Japanese Islands, using the block-fault
model for crustal deformation developed by
Matsu'ura et al. (1986). In this model, crustal
deformation corresponds to the sum of relative
movement among designated blocks and displacement
due to dislocations along the locked parts
of designated faults. We model the area including
the Japanese Islands with 19 crustal blocks
and 104 faults based on the distribution of
active faults and seismicity. Three kinds of
data are used; rates of change of angles and
lengths, and average velocities of very long
baseline interferometry stations. With the
inversion of these geodetic data we obtain
block motions and average slip rates of faults.
This geodetic model predicts that the Pacific
plate moves N69 +- 2W at about 80 +- 3 mm/yr
relative to the Eurasian plate which is much
lower than that predicted in geologic models.
Substantial aseismic slip occurs on the subduction
boundaries. The block containing the lzu Peninsula
may be separated from the rigid part of the
Philippine Sea plate. The faults on the coast
of Japan Sea and the western part of the Median
Tectonic Line have slip rates exceeding 4 mm/yr,
while the Fossa Magna does not play an important
role in the tectonics of the central Japan.
The geodetic model requires the division of
northeastern Japan, contrary to the hypothesis
that northeastern Japan is a part of the North
American plate. Owing to rapid convergence,
the seismic risk in the Nankai trough may be
larger than that of the Tokai gap. _ΆκΦίι
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