Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published December 10, 2009 | public
Journal Article

Interseismic crustal deformation in the Taiwan plate boundary zone revealed by GPS observations, seismicity, and earthquake focal mechanisms


We use GPS-derived surface velocities, seismicity, as well as estimates of earthquake focal mechanisms from the time period before the 1999 Chi-Chi earthquake to evaluate spatial variations of surface strain rate and crustal stress regime in the Taiwan plate boundary zone. We estimate strain rates with a new but simple approach that solves for surface velocity on a rectangular grid while accounting for the distance between observations and each grid node and the impact of a spatially variable density of observations. This approach provides stable and interpretable strain-rate estimates. In addition, we perform a stress tensor inversion using earthquake focal mechanisms determined by P waves first-motion polarities. Our estimates of the principal orientations of two-dimensional surface strain rate tensor generally agree with the inferred orientations of the stress axes. This agreement suggests that a large scale variation of stress orientations from the surface to the base of the crust is insignificant and the predicted faulting style is consistent with stress buildup during the interseismic loading. We find that the geometric configuration of the Chinese continental margin alone cannot fully explain the distribution of maximum contraction and compressive axes in Taiwan. Distribution of seismicity and focal mechanisms before and after the Chi-Chi mainshock suggest that the maximum principal stress axis is vertically-oriented in the Central Range; in contrast to the horizontal maximum principal stress axis in western Taiwan and the Longitudinal Valley. Extension in the Central Range reflects the consequence of exhumation and crustal thickening.

Additional Information

© 2008 Elsevier B.V. Received 29 May 2008; revised 11 November 2008; accepted 18 November 2008. Available online 3 December 2008. We are grateful to many colleagues at the Institute of Earth Sciences, Academia Sinica who have participated in collecting GPS data. The generous provision of continuous GPS data by Ministry of the Interior, National Cheng-Kung University, National Chiao-Tung University and IGS community is greatly appreciated. We thank the editor, Dr. D. Brown, Dr. J. Malavieille and an anonymous reviewer for their constructive comments, Y. M. Wu kindly provides earthquake focal mechanisms, J.-P. Avouac and W. T. Liang provide valuable suggestions. Several figures were created using GMT written by Wessel and Smith. This study is supported by the Institute of Earth Sciences, Academia Sinica, the National Science Council of the Republic of China grant NSC 95-2119-M-001-064- MY3 and NSC 95-2745-M-001-005, the National Science Foundation grant EAR-0537625 to Caltech, and the Gordon and Betty Moore Foundation. This is a contribution of the Institute of Earth Sciences, Academia Sinica, IESAS1287, Caltech Seismological Laboratory contribution number 10004, and Caltech Tectonics Observatory number 84.

Additional details

August 21, 2023
October 19, 2023