台灣地震地研究－台灣西南部活斷層研究─臺灣西南部活動斷層活動性近斷層監測之研究
Date Issued
2004
Date
2004
Author(s)
DOI
922116M002004
Abstract
Four campaigns of GPS measurements have been conducted by the Central
Geological Survey since 1995 to investigate the fault surface activity and crustal
deformation patterns in southwestern Taiwan. GPS surveys provide the velocity field
of the Pingtung-Kaohsiung area in SW Taiwan, in the transition zone from collision to
subduction. Station velocities decrease from 42.2 mm/yr in the west to 55.5 mm/yr in
the east along azimuths from 247 o to 273 o . In the central and western study area, GPS
stations move nearly toward the west. In the Pingtung-Kaohsiung coastal area, the
velocity vectors show a counter-clockwise deviation toward the SW, which we
explain in terms of lateral extrusion. The transtensional deformation and along-strike
southward increase in extensional deformation in southwest Taiwan result from low
lateral confining conditions related to the Manila subduction zone as a free boundary
or/and the presence of the Peikang High indenter. The GPS vectors indicate that the
Chishan Fault is dominated by right-lateral motion with a surface fault slip rate of ~7
mm/yr in a N50 o W direction. The Kaoping Fault bounded in the west side of Pingtung
plain is dominated by left-lateral motion with a surface fault slip rate of ~4-8 mm/yr
in a N-S direction. The significant right-lateral component of motion of ~24-30 mm/yr
can be accommodated along the active structures west of the Chishan Fault, between
the coast and the deformation front. The right-lateral and left-lateral structures
facilitate the southwestward extrusion. The major Chaochou Fault is a high-angle
reverse fault with left-lateral movement. Based on our GPS study, the velocity
gradients across this fault are not significant, suggesting that the Chaochou Fault is
locked near the surface.
Publisher
臺北市：國立臺灣大學地質科學系暨研究所
Type
report
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