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Published February 29, 2008 | Published
Journal Article Open

Geomorphology of the southernmost Longitudinal Valley fault: Implications for evolution of the active suture of eastern Taiwan

Abstract

In order to understand fully the deformational patterns of the Longitudinal Valley fault system, a major structure along the eastern suture of Taiwan, we mapped geomorphic features near the southern end of the Longitudinal Valley, where many well-developed fluvial landforms record deformation along multiple strands of the fault. Our analysis shows that the Longitudinal Valley fault there comprises two major strands. The Luyeh strand, on the west, has predominantly reverse motion. The Peinan strand, on the east, has a significant left-lateral component. Between the two strands, late Quaternary fluvial sediments and surfaces exhibit progressive deformation. The Luyeh strand dies out to the north, where it steps to the east and joins the Peinan strand to become the main strand of the reverse sinistral Longitudinal Valley fault. To the south, the Luyeh strand becomes an E-W striking monocline. This suggests that the reverse motion on the Longitudinal Valley system decreases drastically at that point. The Longitudinal Valley fault system is therefore likely to terminate abruptly there and does not seem to connect to any existing structure further to the south. This abrupt structural change suggests that the development of the Longitudinal Valley suture occurs through discrete structural "jumps," rather than by a continuous northward maturation.

Additional Information

© 2008 American Geophysical Union. Received 16 October 2006; revised 3 September 2007; accepted 26 October 2007; published 29 February 2008. We greatly appreciate the assistance of Y.-C. Chen and T. Watanuki in the field. We have benefited significantly from the information collected by and the stimulating discussions with the students of two bi-national field classes of the National Taiwan University and Caltech, held in the Peinanshan area in 2001 and 2005. We are also grateful for valuable discussions with H.-T. Chu, J.-C. Lee, W.-T. Liang, D. V. Wiltschko, Y.-M. Wu, and S.-B. Yu. Our mapping was facilitated by J. Giberson, manager of the Caltech's GIS laboratory. The 5-m DEM was generously provided by the Central Geological Survey, MOEA, Taiwan. Radiocarbon dating by M. Kashgarian in the Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, is greatly appreciated. The comments and suggestions of E. Kirby and two anonymous reviewers greatly helped us improve this manuscript. Our project in Taiwan was supported by NSF grant EAR-0208505 and by the Gordon and Betty Moore Foundation. This is Caltech Tectonics Observatory Contribution #28.

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August 22, 2023
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