UDSimulation
of Temporal Variation in Coulomb Failure
Functions in the Source Region of the Hyogo-ken
Nanbu Earthquake
Simulation of Temporal Variation
in Coulomb Failure Functions in the Source
Region of the Hyogo-ken Nanbu Earthquake
Manabu
HASHIMOTO
Research Center for Earthquake Prediction,
Disaster Prevention Research Institute,
Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
Journal of Seismological
Society of Japan, Vol.50, Supplement, P.229-249,
1998
We synthesize temporal variation in Coulomb
Failure Functions (CFF) for the mechanism similar
to
the 1995 Hyogo-ken Nanbu earthquake taking
both interseismic stress loading and coseismic
changes due to large events into account. A
block-fault model derived from the inversion
of triangulation and trilateration data during
100 years by HASHIMOTO and JACKSON (1993) is
adopted as the model for interseismic loading.
Temporal changes in CFF is calculated as a
sum of secular changes for back slip of block
boundary faults in their model during arbitrary
period since 1855 and coseismic changes due
to large events which occurred during the corresponding
period with simple pure elastic dislocation
model. Among the several factors which affect
CFF change in the source region of the 1995
Hyogo-ken Nanbu earthquake, increasing back
slip of faults along the Nankai trough, which
may represent strengthening of coupling, decreases
CFF for right-lateral strike-slip mechanism
on NE-SW trending vertical faults by 0.2 MPa/100yr
at (34.6N, 135.04E and 10 km deep). Back slip
along the Arima-Takatsuki Tectonic Line and
Rokko fault system increase CFF most (1.6 MPa/100yr), though
the calculated point is closely located to
the edge of modeled block-boundary fault.
These calculations seem contradictory to the
hypothesis that strengthening of coupling between
the subducting Philippine Sea plate and the
Japanese islands induces the activity of large
inland events. Loading of locked part due to
stable sliding of deeper part of block boundary
faults may play a main role for the accumulation
of stress. Among large events, the 1946 Nankaido
earthquake may have caused eminently large
increase in CFF (0.1 MPa) near the epicenter
of the Hyogo-ken Nanbu earthquake. The 1944
Tonankai earthquake may have increased CFF
by about 0.01 MPa, but the 1927 Tango earthquake
decreased it by 0.02 MPa. Other events may
not have larger effect than 0.01 MPa. Summing
up these contributions, our results suggest
that the CFF for the Hyogo-ken Nanbu earthquake
increased larger than 2 MPa since 1855.
Key words: Stress
changes. Coulomb failure function, Hyogo-ken
Nanbu earthquake, Back-Slip model, Dislocation
model.
_ΆκΦίι
|
