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 w...

Full description

Saved in:
Bibliographic Details
Published in:Tectonophysics 2009-12, Vol.479 (1), p.4-18
Main Authors: Hsu, Ya-Ju, Yu, Shui-Beih, Simons, Mark, Kuo, Long-Chen, Chen, Horng-Yue
Format: Article
Language:English
Subjects:
Earthquake focal mechanism
GPS
Seismicity
Strain rate
Taiwan
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary: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.
ISSN:0040-1951
1879-3266
DOI:10.1016/j.tecto.2008.11.016