Absolute Gravity Changes In Alaska

Visco-elastic deformation models such as that of Soldati et al. [1999] predict time varying gravity signals associated with post-seismic deformation following the 1964 Prince William Sound earthquake (Mw=9.2). The rates of change are a function of the upper mantle viscosity. Aseismic creep is also a candidate mechanism for the deformation. The models differ in the spatial distribution of gravity changes; visco-elastic signals span a much larger region. Previous absolute gravity measurements have been made in Fairbanks, Alaska and Palmer, Alaska, during 1990-1991. Estimated uncertainties are in the 3-5 uGal range Visco-elastic gravity changes for Palmer are predicted to range from zero to tens of uGal, depending on the model viscosity and thickness parameters. New absolute gravity measurements at these sites are scheduled for September 2001, with 2 uGal estimated uncertainty. We hope to present initial results of the new measurements, with discussion of their implications for model testing. Different time series and instruments will be merged, and necessary corrections will be discussed