A Study on Coseismic Deformation near Fault Zone in Western Taiwan（Ⅱ）
Date Issued
2003
Date
2003
Author(s)
DOI
912211E002048
Abstract
During the 1999 Chi-Chi
earthquake, the movement of the
Chelungpu fault caused large
deformation of the surface of the
earth, and destruction of buildings
nearly along the Chelungpu fault
trace. Trench excavations of the
monoclinal structure were taken, and
provide a good chance to study the
deformation features and
mechanisms of the natural
monoclinal folds. This study includes
two parts: the kinematic modeling
and continua numerical simulation.
In the first part, for the purpose of
understanding the deformation of
monoclinal folds induced by faulting
events, the numerical modeling is
done by choosing trishear
kinematical model which firstly
suggested by Erslev (1991). In the
inverse analysis of monoclinal folds
of Shijia trench profile in Nantou, the
results are: (1) the ramp angle of
blind fault is about 30°, and (2) the
depth of fault tip now is about 7.4m
beneath the hanging wall surface, and
(3) there are at least two more
faulting events beside Chi-Chi
earthquake, and the rigid body
motion of hanging wall along the
fault plane are about 5, 2, 0.5 meters
individually from young to old events.
In the second part, in order to
understanding the rationality of
trishear kinematical model, the
numerical simulation of the process
of fault propagation is taken by
running FLAC (continua numerical
software) and the fault is simulated
by using interface. The results are: (1)
there is a triangular shear zone
observed in front of the fault tip, and
(2) the displacement vectors of
particles rotate and decrease from
hanging wall to footwall. The results
are in agreement with the
assumptions of trishear model. But,
according to the numerical
simulation, the parameters of trishear
model do not keep constant in the
process of fault propagation ,which
should be considered when
kinematical modeling is taken.
Otherwise, fault propagation is a
process of stable fracture propagation.
If the force for basement uplift does
not increase continuously, the
propagation of fault plan will stop.
Publisher
臺北市：國立臺灣大學土木工程學系暨研究所
Type
report
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