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|Authors: ||Berrino, G.*|
|Title: ||On the capability of recording gravity stations to detect signals coming from volcanic activity: the case of Vesuvius.|
|Title of journal: ||Journal of Volcanology and Geothermal Research|
|Series/Report no.: ||/150 (2006)|
|Issue Date: ||2006|
|Abstract: ||The goal of this paper is to describe how continuous gravity measurements can improve the geophysical monitoring of a
volcano. Here the experience of 15 yr in continuous gravity on Vesuvius is presented.
A wide set of dynamic phenomena (i.e. geodynamics, seismicity, volcanic activity) can produce temporal gravity changes,
with a spectrum varying from short (1–10 s) to longer (more than 1 yr) periods. An impending eruption, for instance, is
generally associated with the ascent of magma producing changes in the density distribution at depth, and leading to ground
deformation and gravity changes observed at surface. The amplitude of such gravity variations is often quite small, on the order
of 10 9–10 8 g (10–102 nm/s2; 1–10 AGal), where g is the mean value of normal gravity (9.806 199 203 m/s2), so their
detection requires instruments with high sensitivity and stability, providing high quality data. Natural, man-made and
instrumental sources are present on the gravity records affecting the Signal to Noise Ratio. Such effects may hide the subtle
volcanic signals. The main natural noise is due to ocean–atmosphere dynamics and seismic activity.
New approaches to model the instrumental response of mechanical gravity sensors (based on the inter-comparison among
superconducting, mechanical and absolute gravimeters) and to investigate the temporal trends of the instrumental sensitivity are
proposed. In fact, variations of the calibration factors can be considered the main cause preventing the repeatability of highprecision
gravity measurements and inducing phase and amplitude perturbations in recorded gravity signals. A modelling of the
background gravity noise level was performed at the Vesuvius station.
Moreover, the bfar fieldQ effects produced by large earthquakes on the gravity station have been also investigated.
Finally, the time dependent behaviour of the tidal gravimetric factors, the non-stationary components of the gravity field
detected at Vesuvius and the results of absolute and relative gravity measurements are interpreted in the framework of its
present-day dynamics, mainly characterized by the low level of seismicity, small ground deformation, gravity changes and
moderate gas emission.|
|Appears in Collections:||04.03.05. Gravity variations|
Papers Published / Papers in press
04.08.06. Volcano monitoring
04.03.06. Measurements and monitoring
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