Experimentation of two coupled gravity meters in continuous recording with a high sampling rate at Etna volcano

Abstract

During the summer of 2005, we performed a 2-month lasting experiment (29 July - 29 September), using two spring gravimeters installed side-by-side at Mt. Etna. Two LaCoste & Romberg gravimeters were utilized (G594 and G1190), each equipped with an Aliod 100 electronic feedback system. Data were acquired at a sampling rate (2 Hz) higher than that normally used for gravimetric recordings. Apparent fluctuations (i.e. instrumental, not due to actual changes of the gravity field) dominated by a component with period of about 20 seconds appear over the gravity recordings when both high-frequency (local earthquakes) and low-frequency (teleseisms) components dominate the ensuing seismic wavefield. Though it has only an instrumental character, the outcome of this study represent an important further step towards the development of any a-priori or a-posteriori system aimed at reduce the effect of seismic shocks on the signal from continuously recording gravimeters.