HR: 1330h
AN: T12C-0473    [PDF]
TI: Active Structure Evolutions Deduced from Geomorphic and Geodetic Evidence, from Hsinchu to Taoyuan, Northwestern Taiwan
AU: * Chen, Y
EM: ygchen@ccms.ntu.edu.tw
AF: Inst. of Geosciences, NTU, No. 1, Sec. 4th, Roosevelt Rd., Taipei, 106 Taiwan
AU: Wang, Y
EM: piin1979@pchome.com.tw
AF: Inst. of Geosciences, NTU, No. 1, Sec. 4th, Roosevelt Rd., Taipei, 106 Taiwan
AU: Hou, C
EM: hcs@linx.moeacgs.gov.tw
AF: Inst. of Geosciences, NTU, No. 1, Sec. 4th, Roosevelt Rd., Taipei, 106 Taiwan
AU: Hou, C
EM: hcs@linx.moeacgs.gov.tw
AF: Central Geological Survey, 2, lane 109, Hua-Hsin St., Chung-Ho, Taipei, 235 Taiwan
AU: Chen, W
EM: wenshan@ntu.edu.tw
AF: Inst. of Geosciences, NTU, No. 1, Sec. 4th, Roosevelt Rd., Taipei, 106 Taiwan
AB: As we know, Taiwan fault-and-thrust belt is built up by the arc-continent collision that is related to polarity flipping of subduction. The flipping boundary, delineated from Hsinchu to Hualien, divides the mountain belt into northern as well as southern part. Looking at the current tectonic configuration surrounding Taiwan, the northern one corresponds to the Ryukyu arc-trench system and has recently been influenced by back-arc rifting of Okinawa Trough (OT), which reactivated during Quaternary. As a consequence, the stress currently executing in northern Taiwan must be different from the southern Taiwan, manifesting to different neotectonic features. It is governed by the extensional stress transferred from OT. Basins, such as Taipei and Ilan, are the evidence to confirm this point. Along the western Taiwan located to the south of Taipei basin is the Taoyuan-Hsinchu area, where the landscape is still characterized by those previously produced under compression. In Taoyuan, two subparallel blind fault-related folds with axes trending NNE were developed due to the reactivation of preexisting normal fault system in continental margin. The entire system remained active until later than 30 ka. To the Hsinchu, the neotectonics is characterized by another two duplex systems (each one is composed of a thrust and its related anticline). The structural orientation is similar to of the Taoyuan. There are two main drainages, i,e.,Touchien and Fengshan rivers, flow across and separate Taoyuan and Hsinchu. Evident linear scarps and lineations have been developed aside oblique to the above-mentioned orientations of compression structures but roughly following the flowing direction. We interpret that they are generated by wrench fault systems tearing apart the original structures to accommodate the recently adjusted stress field. As recognized by the relevant geomorphic evidence, they are suggested as strike-slip faults with possibly normal dip-slip component. The newly accomplished dataset derived from geodetic network shows that except for the Hsincheng fault nearly no detectable contraction occurs across the major structures in the study area. The most surprising phenomenon is that the Fengshan river geodetically plays a major boundary. The northern crust (Taoyuan) is moving due east relatively to the southern crust (Hsinchu) in a rate of ca. 2 cm/yr. This represents that the Fengshan river is currently a right-lateral strike-slip fault, confirming the former strike-slip suggested by geomorphic features. To probe the other details, more stations and precise measurements are needed in the future.
DE: 1206 Crustal movements--interplate (8155)
DE: 7221 Paleoseismology
DE: 8000 STRUCTURAL GEOLOGY (New field, replaces single entry 8165)
DE: 8123 Dynamics, seismotectonics
SC: Tectonophysics [T]
MN: 2003 Fall Meeting