HORIZONTAL AND VERTICAL CRUSTAL MOVEMENTS FROM 3-DIMENSIONAL VERY LONG-BASE-LINE INTERFEROMETRY KINEMATIC REFERENCE FRAME - IMPLICATION FORTHE REVERSAL TIMESCALE REVISION

Three-dimensional kinematic reference frame of geodetic very long base line interferometry (VLBI) stations, tied to a geologic plate motion m odel, was established using the GLB907 solution by first selecting glo bally distributed stable plate interior stations and then applying a s mall translation and a rotation for the entire network in a three-dime nsional 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 velo cities of specific stations to realize the frame. A suggestive correla tion was found between the estimated vertical velocities of North Amer ican stations and those predicted by a postglacial rebound model. The revision of the magnetic polarity timescale (MPTS) causes a uniform in crease or decrease of the predicted velocities, which could be detecte d as the small difference between tile measured and the predicted rela tive plate velocities. Direct estimation of the correction suggests th at the VLBI data fit best to the model when the NUVEL1 model is correc ted by +3.4% (+/- 1.2%), which differs significantly from the -4.5% de duced from the astronomical MPTS calibration. This was further confirm ed by estimating the rotation rates for individual plate pairs.