Monitoring and Detecting Transient Deformation in Western Taiwan Using Dense GPS Arrays and the Network Strain Filter

摘要

We compute the time-dependent horizontal transient deformation field of western Taiwan from 2006 to 2016 using time series data from 196 continuous GPS stations. Spatially and temporally coherent transient signals are identified by analyzing data from the entire geodetic networks simultaneously using the Network Strain Filter developed by Ohtani et al. [2010]. The filter separates spatially coherent transient deformation from steady secular rates, seasonal variations, and site-specific noise. In the eleven-year time span, six transient deformation patterns are observed. Comparison with calculated postseimsic displacements following known earthquakes with similar fault geometries suggest that three of the transients are the result of postseismic afterslip and/or viscoelastic mantle flow in response to the 1999 Chi-Chi earthquake, the 2010 Jiashian earthquake and the 2013 Nantou earthquake series, respectively. Two identified island-wide transient events in 2012 and 2016 are not associated with large earthquakes and the mechanisms behind the deformation are still not clear. A localized transient event in southwestern Taiwan occurs near the source area of the 2010 Jiashian earthquake and precedes the earthquake by four years. Our results suggest that transient crustal deformation is prevalent in Taiwan in the form of postseismic and other aseismic events. Future work incorporating the vertical component of GPS time series and expanding the study area to the whole island will allow for a more complete view and understanding of the transient deformation field of Taiwan.