Total Variation Regularization of Geodetically Constrained Block Models in Southwest Taiwan

Abstract

Rapid convergence between the Eurasian plate and the Philippine Sea Plate makes Taiwan one of the most active tectonic regions in the world, and this strain is accommodated on a complex network of thrust and strike‐slip faulting. Here, we use ascending and descending Interferometric Synthetic Aperture Radar (InSAR) data integrated with continuous GPS measurements to monitor interseismic deformation in southwest Taiwan. Geodetic observations show rapid (20–40 mm/year) southwestward motion in the Pingtung plain in south Taiwan and more than 10 mm/year uplift in the southern part of the Western Foothills. We use combined InSAR and CGPS measurements from 2004 to 2010 to constrain a block model of horizontal interseismic crustal deformation. Total variation regularization (TVR) serves as a tool for block model selection to algorithmically assess the block model geometry based on geodetic observations, simultaneously estimating block rotations and fault slip rates on block‐bounding faults. The block model results suggest that the margins of the Western Foothills accommodate most of the interseismic deformation in southwestern Taiwan. Thirty‐five independent blocks are required to explain interseismic crustal deformation with a mean residual velocity of 3.6 mm/year. Based on this horizontal model, we then forward predict vertical displacement and find good consistency between the predicted uplift and the geodetic observations. Our approach shows an efficient and objective way to estimate fault activities and seismic hazards in the interseismic period based on dense geodetic measurements and their uncertainties.

Evidence for Fluid Migration During the 2016 Meinong, Taiwan, Aftershock Sequence

“…We further surmise that the lack of both aftershocks and long‐term seismicity at the location of highest V p / V s (Figure 10) may be due to aseismic creep caused by high pore pressure stabilizing rate‐state frictional sliding (French & Zhu, 2017; Xing et al, 2019). This may also explain how southwestern Taiwan deforms so rapidly without as much seismic energy released as would be expected (Ching et al, 2016; Hu et al, 2007; Huang & Evans, 2019; Wu et al, 2008). If true, seismic hazards may actually be higher around the fringes rather than the center of the high V p / V s anomaly, including where the northern and central aftershock clusters occurred.…”

Mud Diapir or Fault‐Related Fold? On the Development of an Active Mud‐Cored Anticline Offshore Southwestern Taiwan

“…Given the prominent dextral strike‐slip motion along the Chishan‐Youchang fault geodetically (up to ∼30 mm/yr near the coast; Ching et al., 2007; Hu et al., 2007; M.‐H. Huang & Evans, 2019), along with the sharp Yung‐An lineament further to the west (Liu et al., 2004; Figure 13), we propose that these faults in relay may have formed a major strain partitioning fault system running parallel to the deformation front to accommodate the strike‐parallel deformation. To figure out the actual kinematics and seismogenic potential of this major fault system, seafloor geodetic measurements will be the most needed information.…”

Revealing Crustal Deformation and Strain Rate in Taiwan Using InSAR and GNSS

“…This method is done by utilizing GNSS for the long‐wavelength spatial deformation and InSAR for short‐wavelength features. Huang and Evans (2019) estimated crustal deformation in southwest Taiwan between 2005 and 2009 using InSAR‐GNSS combined data and were able to characterize fault slip and locking depth of the major fault system using a total variation regularization approach for southwest Taiwan. However, their work does not include other active deforming regions such as east Taiwan.…”