Shyu, J. Bruce H. and Sieh, Kerry and Avouac, Jean-Philippe and Chen, Wen-Shan and Chen, Yue-Gau (2006) Millennial slip rate of the Longitudinal Valley fault from river terraces: Implications for convergence across the active suture of eastern Taiwan. Journal of Geophysical Research B, 111 (B8). Art. No. B08403. ISSN 0148-0227. http://resolver.caltech.edu/CaltechAUTHORS:20101116-152223235
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The Longitudinal Valley fault is a key element in the active tectonics of Taiwan. It is the principal structure accommodating convergence across one of the two active sutures of the Taiwan orogeny. To understand more precisely its role in the suturing process, we analyzed fluvial terraces along the Hsiukuluan River, which cuts across the Coastal Range in eastern Taiwan in the fault's hanging wall block. This allowed us to determine both its subsurface geometry and its long-term slip rate. The uplift pattern of the terraces is consistent with a fault-bend fold model. Our analysis yields a listric geometry, with dips decreasing downdip from about 50° to about 30° in the shallowest 2.5 km. The Holocene rate of dip slip of the fault is about 22.7 mm/yr. This rate is less than the 40 mm/yr rate of shortening across the Longitudinal Valley derived from GPS measurements. The discrepancy may reflect an actual difference in millennial and decadal rates of convergence. An alternative explanation is that the discrepancy is accommodated by a combination of slip on the Central Range fault and subsidence of the Longitudinal Valley floor. The shallow, listric geometry of the Longitudinal Valley fault at the Hsiukuluan River valley differs markedly from the deep listric geometry illuminated by earthquake hypocenters near Chihshang, 45 km to the south. We hypothesize that this fundamental along-strike difference in geometry of the fault is a manifestation of the northward maturation of the suturing of the Luzon volcanic arc to the Central Range continental sliver.
|Additional Information:||© 2006 American Geophysical Union. Received 29 July 2005; revised 10 March 2006; accepted 14 April 2006; published 12 August 2006. We are grateful for valuable discussions with H.-H. Chen, H.-T. Chu, M.-L. Hsieh, J.-C. Lee, W.-T. Liang, M.-S. Lin, R.-J. Rau, C.P. Stark, and S.-B. Yu. We were fortunate to have the significant help of our friends and students from the National Taiwan University, especially C.-H. Chen,Y.-C. Chen, L.-H. Chung, C. Huang, S.-H. Huang, P.-N. Li, T. Watanuki, Y.Wang, B.C.-C. Yang, and I.-C. Yen, for the heavy and arduous field works of this research. Radiocarbon dating by M. Kashgarian in the Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, is crucial for this research. Y.-J. Hsu and Y.-M. Wu generously provided us with their GPS and seismicity data along with valuable comments. The comments and suggestions of S. Toda, J. Townend, and an anonymous reviewer greatly helped us improve this manuscript. Our project in Taiwan was supported by NSF grant EAR-0208505 and partly by project 92EC2A380204 of the Central Geological Survey, MOEA, Taiwan. This research was also supported in part by the Gordon and Betty Moore Foundation through the Tectonics Observatory at Caltech. This is contribution 13 of Caltech Tectonics Observatory.|
|Group:||Caltech Tectonics Observatory, Caltech Tectonics Observatory. Taiwan Tectonics and Seismicity|
|Subject Keywords:||Taiwan; river terraces; Longitudinal Valley fault; neotectonics; suture|
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|Official Citation:||Shyu, J. B. H., K. Sieh, J.-P. Avouac, W.-S. Chen, and Y.-G. Chen (2006), Millennial slip rate of the Longitudinal Valley fault from river terraces: Implications for convergence across the active suture of eastern Taiwan, J. Geophys. Res., 111, B08403, doi:10.1029/2005JB003971|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||17 Nov 2010 19:14|
|Last Modified:||26 Dec 2012 12:38|
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