Linking Interseismic Crustal Deformation to Long-Term Rock Denudation and Surface Processing in Taiwan

Abstract:

Plate convergence at more than 80 mm/yr and high annual precipitation make Taiwan one of the most active tectonic regions in the world with high erosion rate. Decadal suspended-sediment erosion rates were previously shown to be correlated with cumulative scalar seismic moment, but a link between sediment transport and interseismic fault activity and crustal deformation remains unknown. In this study, we use ascending and descending Interferometric Synthetic Aperture Radar (InSAR) data to reveal interseismic crustal deformation in Taiwan. We combine InSAR and GPS measurements in 2006-2010 time period and from prior to the 1999 M_w 7.6 Chi-Chi earthquake as interseismic crustal deformation, and use block models to interpret interseismic geodetic measurements. We use the total variation regularization (TVR) algorithm to determine the number of faults and slip along the block-bounding faults needed to explain the interseismic geodetic measurements. We find 20-40 mm/yr interseismic slip rates on predominated thrust faults in eastern and southwestern Taiwan, whereas faults have less than 20 mm/yr slip rates in northwestern Taiwan. Higher interseismic slip and uplift rates in eastern Taiwan agree with long-term denudation rate as well as decadal erosion rate, and both modern and Holocene river erosion rates show higher correlation with interseismic fault slip than with topographic relief, stream power, or decadal seismic moment release. Our results imply that although large earthquakes could enhance sediment transport in a short period of time, higher interseismic slip rates lead to uplift and greater erosion in a longer time scale.