REMARKABLE CYCLIC GROUND DEFORMATION MONITORED IN REAL-TIME ON MONTSERRAT, AND ITS USE IN ERUPTION FORECASTING

Telemetered high-resolution tiltmeters were installed in Montserrat in summer of 1995, in December 1996, and in May 1997. The 1995 installat ions, several km from the Soufriere Hills vent, were too distant to yi eld useful data. However, the 1996 and 1997 installations on the crate r rim revealed 6-14 h inflation cycles caused by magma pressurization at shallow depths (< 0.6 km below the base of dome). The tilt data cor related with seismicity, explosions, and pyroclastic flow activity, an d were used to forecast times of increased volcanic hazard to protect scientific field workers and the general public.