Improvement and development of the tiltmetric monitoring networks of Neapolitan volcanoes

Ciro Ricco,Ida Aquino,Giovanni Scarpato,Carlo Del Gaudio,Vincenzo Augusti,Luca D'Auria

doi:10.4401/ag-7496

Abstract

The goal of this work is to illustrate the technological development of the tiltmetric monitoring network of Osservatorio Vesuviano, since 1986, retracing the technical steps that led to the current network configuration. This network is devoted to the monitoring of the three Neapolitan volcanoes: Vesuvius, Phlegrean Fields and Ischia Island, which are widely recognized among the volcanic areas with the highest risk worldwide. Ground tilt monitoring had to face numerous technical obstacles, mainly due to background noise characterizing densely urbanized areas like the Neapolitan volcanoes. The network started with the first installations of horizontal optical pendulums that recorded analog signals. In the following years, the network was equipped with electronic sensors more handy and easy to install. A technological leap forward occurred when the first digital sensors were installed in deep boreholes, allowing them to record tilt signals not affected by thermal disturbances. These data are digitally acquired and managed by a datalogger for the data storage and exchange. Currently the network consists of 10 sensors in Phlegrean Fields, 8 in Vesuvius and 3 in Ischia Island, making it one of the densest tiltmetric volcano monitoring network worldwide. This network can boast a database containing thirty years of data acquired by both analog and digital stations. Data consists of both ground tilt and meteorological signals, such as temperature and atmospheric pressure. In these areas they allow a continuous monitoring of the temporal variations of the ground tilt with important implications in understanding the dynamics of these active volcanoes.

Highlights

Ground tilt monitoring is the continuously measurement of changes in the slope of the ground surface
It is able to detect slight tilt variations, in both direction and amplitude, of the volcano edifice caused by the volcano dynamics
With other geodetic methods, the study of the angular component of strain allows scientists to better understand the nature of geophysical phenomenon going on in a certain volcanic area [Ricco et al 2003]

Summary

Introduction

Ground tilt monitoring is the continuously measurement of changes in the slope of the ground surface. The flanks of volcanoes deform reaching variations of inclination of the order of about ten microradians [Dzurusin 2006]. With other geodetic methods, the study of the angular component of strain allows scientists to better understand the nature of geophysical phenomenon going on in a certain volcanic area [Ricco et al 2003]. Together with tensor strainmeters are used to measure the non-diagonal components (i≠j) of the deformation tensor (pure tilt in a solid halfspace), while the diagonal components (i=j) of it are filled using data recorded by volumetric strainmeters or dilatometers [Zadro and Braitenberg 1999]. In practice it provides a parameter used to immediately integrate the displacements observed (i.e. by optical levelling, GPS or SAR) on a restless volcanic area [Ricco et al 2007]

Objectives

Conclusion