Fifteen years of surface deformation in Western Taiwan: Insight from SAR interferometry

- InSAR reveals crustal deformation in western Taiwan during 1995-2001 and 2005-2008.
- Seasonal deformation analysis shows the potential to distinguish tectonic and hydrologic deformation.
- The long-term steady state deformation highlights the tectonic escape in southwestern Taiwan, whereas uplift along Western Foothills.
- Significant land subsidence appears along coastal areas in western and southwestern Taiwan, and most of the land subsidence areas also experience higher (> 1 cm) seasonal variation.

Geodetically measured surface displacements are produced by a combination of underlying deformation processes acting at different spatial and temporal scales. A complete history of surface measurements in an area can help discriminate contributions from tectonic, hydrologic, and anthropogenic processes. In this study, we use Synthetic Aperture Radar (SAR) images of the active mountain front and adjacent coastal plain of southwestern Taiwan to generate time series of surface deformation from 1995 to 2001 and from 2005 to 2008 based on the InSAR small baseline method. The InSAR measurements agree well with LOS motions estimated from continuous GPS measurements of 3D displacements between 2006 and 2008. A significant range increase in line of sight (LOS) is dominated by land subsidence in the coastal area of western and southwestern Taiwan. Subsidence rates vary with annual periods and are highly correlated with seasonal precipitation, which are likely associated with groundwater recharge and withdrawal. The long-term deformation is dominated by long-term tectonic loading in SW Taiwan during the interseismic period of the earthquake cycle, including elastic strain along or continuous creep on the active faults. Our results show the ability of InSAR to reveal spatiotemporal crustal deformation in western Taiwan with high spatial resolution and accuracy, which is potentially important for evaluating seismic hazards.