Temporal gravity and height changes of the Yellowstone caldera, 1977 - 1994

Abstract

This paper describes the longest record of gravity measurements in the area of the Yellowstone caldera, Wyoming. The temporal gravity changes, at the ±12 μGal (10-8 ms-2) precision level, are compared with changes in heights from leveling and GPS. The gravity field decreased across the caldera from 1977 to 1983 during the uplift and attained a maximum decrease of up to -60 ± 12 μGal along the Caldera axis. The gravity field then reversed polarity to increasing values, of up to 60 ± 12 μGal between 1986 and 1993. The ratio between height and gravity changes varied during the entire time, but converged over the latter period following the free-air gravity gradient. General ground deformation deduced from leveling showed caldera-wide uplift of ∼15 mm/a during the period of gravity decrease, then from leveling and GPS, subsidence of ∼ 25 mm/a during the gravity increase. Copyright 1997 by the American Geophysical Union.