The ongoing modernization of the Taiwan semi-dynamic datum based on the surface horizontal deformation model using GNSS data from 2000 to 2016

Abstract

A semi-dynamic geodetic datum, composed of a static geodetic datum and a surface deformation model, is proposed in this study to maintain the accuracy of geodetic datum in Taiwan. A concept to construct the surface deformation model is also suggested to accommodate the characteristics of temporal variation of the velocity field and coseismic displacements caused by earthquakes in Taiwan. In this study, we proposed a surface deformation model, containing a secular velocity grid model during 2000–2016 and a coseismic displacement grid model of the 2016 ML 6.6 Meinong earthquake, as an example to examine its adaptability in Taiwan. The secular velocity field relative to the station KMNM from 2000 to 2016 was first evaluated in this study using data from 380 continuous GNSS stations in Taiwan. Integrating 672 campaign-mode GNSS velocities from 2002 to 2016, a secular velocity grid model was constructed using the Kriging interpolation method. The high-precision coseismic displacements of the 2016 Meinong earthquake calculated using the IGS ultra-rapid orbit were also evidenced. The coseismic displacement grid model for all Taiwan for this event was built using the kinematic dislocation model to prevent contamination from nontectonic sources. Another 1341 independent GNSS control points surveyed in 2013 and 2016 were adopted to validate the reliability of the surface deformation model. After correction by the deformation model, 1219 points (91%) matched the criterion at the urban region of cadastral surveying in Taiwan (< 6 cm). The Electronic Global Navigation Satellite System (e-GNSS) in Taiwan is suggested to be integrated with the geodetic semi-dynamic datum to improve the precision of e-GNSS and to monitor the accuracy of the surface deformation model in the Taiwan semi-dynamic datum.