| Summary: | 碩士 === 國立成功大學 === 地球科學系碩博士班 === 94 === 261 campaign-mode GPS observations and 6 continuously recording GPS data collected from the southern Taiwan GPS Network between 1995 and 2005 were adopted to reveal the crustal deformation in the southern Taiwan. We discuss the crustal deformation from Coastal Range to the Central Range, the strain rate pattern of the Central Range and the curvature-induced flexural extension in the western Taiwan foreland basin. GPS velocity field was estimated relative to the continuous GPS station S01R on the Penghu islands. GPS velocities for the stations from Coastal Range to Longitudinal Valley varied from 59.42 mm/yr to 83.28 mm/yr in azimuths ranging from 280.00° to 323.30°. GPS velocities for the stations from south of the Central Range to Hengchun Peninsula varied from 25.37 mm/yr to 61.80 mm/yr in azimuths ranging from 263.30° to 293.63°. The Hengchun Peninsula to southern Central Range, strain rate estimated from GPS velocities, is 0.01 – 1.8 μstrain/yr. From south to middle Coastal Range, the strain rate is 0.9 – 1.7 μstrain/yr. On the Hengchun Peninsula and Central Range areas, strain rate field from south to north shows significant ENE-WSW, E-W and ENE-WSW extension. In the southern Central Range, strain rate field from east to west is 0.19 µstrain/yr, 0.36 µstrain/yr and 0.02 µstrain/yr, respectively. In the central part of Penghu islands, strain rate field from south to north shows significant NNE-SSW to ESE-WNW extension. In the western side of Taiwan Strait, the strain rate estimated from GPS velocities is 0.004 - 0.009 μstrain/yr. In the eastern side of Taiwan Strait, the strain rate is 0.018 - 0.121 μstrain/yr. In the central part of Penghu islands, strain rate field from south to north shows significant convergence.
The velocity field of southern Taiwan was divided by Peikang High where Taitung is the boundary. Clockwise and counterclockwise rotations appears in the north and south of Taitung, respectively. Due to the lateral extrusion of southern Taiwan, the GPS velocity tends to accelerate in Kaoshung-Pingtung area. The principal strain rates from southern to northern Central Range shows significant extension. The extensional mechanism is due to the rapid exhumation where resulted from the collision between Philippine Sea Plate and Eurasian Plate. Over the twin flanks of Central Range, the extensional strain rate in east-west direction increased with the height of the range, and the top of the mountain also has the maximum extensional strain rate. This appearance was produced by simultaneous exhumation and mountain collapse. Taiwan Strait is still in a stable tectonic environment and Penghu islands are currently experiencing curvature-induced flexural extension resulting from the loading of Taiwan orogen.
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