| Summary: | 博士 === 國立中央大學 === 地球物理研究所 === 92 === This study will be focused on the analysis of regional mesoscopic
structural framework as well as the analysis of active faults in central and
southern Taiwan. Three areas were chosen for structure analysis in order to
decipher their geometrical characteristics and sequential developments by
an integrated interpretation using seismic , well log, and field-geology data.
Three areas include (1) in the vicinity of the Chelungpu Fault in the Taichung
area, (2) east margins of the Peikang High, and (3) south of the Peikang High
in Tainan and Kaohsiung areas. Several balanced and palinspatic-restored
sections are constrained by seismic data. Analysis on drill cores recovered
from the 1999 Chi-Chi earthquake rupture (i.e, the Chelungpu Fault) in
central Taiwan, shows that the Chelungpu Fault consists of several major
shear zones and their mechanical boundaries coincide with the lithological
boundaries of stratigraphic sequence. According to the analysis on palinspatic
sections using top of Cholan Formation as a datum plane, it shows that there
is a displacement along the fault plane of about 13.7 kilometers, at least, for
the Chelungpu Fault.
At the eastern edge of the Peikang High, geometrical irregularity of the
basement high and the discontinuity of the tectonic trend in the north-south
direction are the most important factors that control the geological
development for each compartment. The Peikang High is plunged both
southward and northward to form the Meishan Ridge. The east-west striking
Meishan Ridge is bounded by the Tsaoling Fault system to the north and
Meishan Fault to the south. The thin skin thrusting was retarded by the ridge 129
and resulted in the emergence of Chiuchungkeng Fault to form a low angle
thrust. The Tsoling Fault system is an important inverted fault. This inverted
fault shows reverse features in shallow part while in deeper part it remains
normal fault features. Data revealed that the southern part of Chelungpu
Fault nappe disappears near the Tsoling Fault. The Meishan Fault is also an
important inverted fault. The B Fault and the Meishan Fault are composed
of one boundary fault in the southern side of Peikang High. The Meishan
fault is not directly connected to the B Fault while a relay ramp is verified
as a transitional accommodation zone. The Meishan Fault is interpreted to
have extended to the Minshung tonship. The Chaiyi graben is determined as
a thoroughly inverted graben by the restoration method. The Chaiyi graben is
judged to have occurred prior to the deposition of the Nanchuang Formation.
On the coastal plain and transitional zone between offshore and land in
Kaohsiung and Tainan, the Tsochen Fault is an important NW-SE trending
tear fault in southwestern Taiwan. Napalin Anticline and Hsinhua Fault
located at the southern side of Tsochen Fault appear as backthrusts and
composed as the triangle zone near the Longchuan structure. Nearshore area
near Erzenchi is characterized by fault-bend fold in a reverse direction. The
foreland deposits of the Gutinkeng Formation is dominated by thick, low
density mudstone which is very suitable for the development of triangle zone
in the middle and deep part of subsurface. If the deformation front is defined
as the appearance of buried frontal low angle thrust or the inverted faults, this
study has proved that the position of deformation front has been extended
westward some 10-15 kilometers from the junction between foothill and
coastal plain, and the zone of front also extended to the offshore of Kaoshung
and Tainan areas.
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