The baseline length changes of circumpacific VLBI networks and their bearing on global tectonics

A baseline length changing rates predicted by plate motion models and those observed in global very-long-baseline interferometry (VBLI) are compared. A widely distributed 1979-1986 baseline length data set shows the rates to be in good agreement with the predictions. The deviations from the predicted rates, however, are found to have a negative correlation (significant at ⩾99.99% by t-test) with the baseline lengths, as if the whole region were secularly contracting. The authors´ analyses for 15 circumpacific and transpacific baselines in joint-US VLBI experiments since 1984 reproduce a similar apparent uniform contraction