Horizontal and vertical crustal movements from three-dimensional very long baseline interferometry kinematic reference frame: Implication for the reversal timescale revision

Three-dimensional kinematic reference frame of geodetic very long baseline interferometry (VLBI) stations, tied to a geologic plate motion model, was established using the GLB907 solution by first selecting globally distributed stable plate interior stations and then applying a small translation and a rotation for the entire network in a three-dimensional space so that the differences in the ''horizontal'' velocities between the VLBI observations and the model predictions are minimized. Since the VLBI network is global, we only assume that the horizontal movements of tectonically stable stations obey a plate motion model; we need not introduce any unwarranted constraints to the vertical velocities of specific stations to realize the frame. A suggestive correlation was found between the estimated vertical velocities of North American stations and those predicted by a postglacial rebound model. The revision of the magnetic polarity timescale (MPTS) causes a uniform increase or decrease of the predicted velocities, which could be detected as the small difference between tile measured and the predicted relative plate velocities. Direct estimation of the correction suggests that the VLBI data fit best to the model when the NUVEL1 model is corrected by +3.4% (+/- 1.2%), which differs significantly from the -4.5% deduced from the astronomical MPTS calibration. This was further confirmed by estimating the rotation rates for individual plate pairs.