[J05-4] Crustal dynamics: Multidisciplinary approach to seismogenesis IV

[J05-4-02] Taiwan vertical velocity field from precise leveling observations, 2000-2015

^○Kwo-Hwa Chen¹, Kuo-En Ching² (1.National Taipei University, New Taipei City, Taiwan, 2.National Cheng Kung University, Tainan, Taiwan)

The active Taiwan mountain belt is located at the plate convergence boundary between the Eurasian plate and the Philippine Sea plate. Therefore, a high accuracy vertical velocity field is very important to understand the on-going mountain building mechanism and the earthquake potential of reverse faults. The precise leveling is always the best way to obtain the high accuracy vertical velocity field until now even though it has the limitation of high field surveying cost. In this study, five precise leveling measurements during 2000-2015 from a whole-island leveling network including 2137 benchmarks were used to infer a high accuracy vertical velocity field in Taiwan. First, the systematic errors of the leveling observations listed in the specification of first-order leveling were corrected. Second, the leveling network adjustment of which was minimum constrained to the orthometric height of K999 benchmark was estimated to obtain the orthometric height of the benchmarks distributed in the main roads of Taiwan. The slope-dependent errors of the leveling observations were also analyzed in this study. By means of the coordinate time series analyses and the accommodations of the effects of coseismic displacements, the vertical velocity of each benchmark was estimated by Least-squares Estimation (LSE), respectively. Finally, a GNSS-derived surface vertical velocity field in Taiwan, 2000-2015, was used for the comparisons to examine the performance of the leveling-derived one in this study.