Procedura automatica per lo studio dei segnali registrati da una stazione tiltmetrica

La Tiltmetria costituisce un metodo di misura in continuo della deformazione del suolo attraverso il monitoraggio delle variazioni di inclinazione nel tempo sia in ampiezza che in direzione ed è particolarmente utilizzata nelle aree vulcaniche e sismogenetiche attive [Wyatt et al., 1988; Ricco et al., 1991; Ricco et al., 2000; Ricco et al., 2003; Ricco et al., 2007]. La rete tiltmetrica gestita dalla Sezione Osservatorio Vesuviano dell’ INGV è composta da 7 stazioni in registrazione continua ai Campi Flegrei, 5 delle quali (DMA, DMB, DMC, BAI ed OLB) sono equipaggiate con sensori di superficie e 2 (OLB e TOI) anche con sensori borehole; al Vesuvio invece esistono 2 stazioni con sensori di superficie (OVO e CMD) (fig. 1) [Aquino et al., 2006]

Ground tilt monitoring at Phlegraean Fields (Italy): a methodological approach

Among geodetic methods used for monitoring ground deformation in volcanic areas, tiltmetry represents the most rapid technique and therefore it is used by almost all the volcanological observatories in the world. The deformation of volcanic building is not only the result of endogenous causes (i.e. dykes injection or magma rising), but also non-tectonic environmental factors. Such troubles cannot be removed completely but they can be reduce. This article outlines the main source of errors affecting the signals recorded by Phlegraean tilt, network, such as the dependence of the tilt response on temperature and to the thermoelastic effect on ground deformation. The analytical procedure used to evaluate about such errors and their reduction is explained. An application to data acquired from the tilt network during two distinct phases of ground uplift and subsidence of the Phlegraean Fields is reported

Monitoraggio geodetico dell’area vulcanica napoletana: risultati della livellazione geometrica di precisione eseguita ai Campi Flegrei a settembre 2008

Lo studio ed ilmonitoraggio deimovimenti verticali del suolo ai Campi Flegrei (Italy) sono effettuati con continuità da oltre 30 anni, operando su linee di livellazioni preesistenti istituite e/o ampliate da vari Enti a partire dal 1905 (IGM, Genio Civile e lo stesso INGV- NA Oss. Vesuviano). Attraverso i dati rilevati dal 1970 ad oggi sono state acquisite molte informazioni sulla deformazione del suolo durante le varie fasi di bradisismo discendente e ascendente ed attualmente si dispone di un importante data-base che può essere integrato con i risultati ottenuti dalle altre metodologie geodetiche. In questa nota presentiamo i risultati della campagna di livellazione geometrica di precisione eseguita su alcuni tratti della rete altimetrica dei Campi Flegrei nel Settembre 2008. Dopo la fase di lento sollevamento, iniziata nel 2004 e culminata alla fine del 2006 con un valore massimo di 55 mm rilevato a Pozzuoli (Lungomare Pertini) al caposaldo n. 23, nell’area flegrea è ripresa una fase di lenta subsidenza caratterizzata da una evidente decelerazione durante il 2008 rispetto all’anno precedente. Per delineare meglio e dettagliare l’attuale fase del bradisismo flegreo, si è ritenuto utile effettuare il confronto tra i dati altimetrici acquisiti nelle ultime 3 campagne (2006, 2007 e 2008) da cui è emersa una evidente disomogeneità del campo di spostamento verticale osservato

A study of tilt change recorded from July to October 2006 at the Phlegraean Fields (Naples, Italy)

The tiltmetric dataset of Phlegraean Fields area showed a discrete correlation with the volcanic dynamics, suggesting that tiltmetric monitoring is important for the surveillance of active volcanic areas. Tilt data recorded in 2006 at 2 stations belonging to the monitoring network of the Osservatorio Vesuviano (INGV, National Institute for Geophysics and Volcanology, Italy) in the Phlegraean Fields are discussed in this paper. The acquired signals have shown a strong tiltmetric inversion that took place from the end of July 2006. After correcting tilt variations to eliminate the influence of temperature (influencing 90% of the signal at OLB station, hereafter OLB) a significant value of the tilt still remains. This change is related to a local inflation episode lasting 3 months, during an unrest phase that started 2 years before. It is interesting to note that tilt amplitude is much greater at OLB than the slope of the displacement field predicted by the theoretical inflation models, but data show that this field is not homogeneous and in some areas very tilted. Moreover, in the last days before the end of tilt inversion, a low energy seismic swarm happened at about 1 km of distance from the tiltmetric station by hundreds of VT (Volcano-Tectonics) and LP (Long-Period) events

INTEGRATED ANALYSIS OF GROUND DISPLACEMENT DATA, SEISMIC ACTIVITY AND MORPHOMETRIC DATA OF THE CAMPI FLEGREI (CAMPANIA, SOUTHERN ITALY) 2000-2006 RECENT BRADYSEISMIC CRISES, IN GIS ENVIRONMENT.

In this paper the results of an integrated analysis of ground displacement data, local seismic activity and DEM image analysis, in GIS environment, which has been performed for the Campi Flegrei volcanic area, are presented and discussed. The study has been carried out for the recent bradyseismic crises of 2000-2006, with the aim of working out a preliminary interpretation of the recent dynamics of the area

Water sorption and diffusion in cellulose acetate: The effect of plasticisers

The conservation of cellulose acetate plastics in museum collections presents a significant challenge, due to the material's instability. Several studies have led to an understanding of the role of relative humidity (RH) and temperature in the decay process. It is well established that the first decay mechanism in cellulose acetate museum objects is the loss of plasticiser, and that the main decay mechanism of the polymer chain involves hydrolysis reactions. This leads to the loss of sidechain groups and the breakdown of the main polymer backbone. However, interactions between these decay mechanisms, specifically the way in which the loss of plasticiser can modify the interaction between cellulose acetate and water, has not yet been investigated. This research addresses the role of RH, studying the sorption and diffusion of water in cellulose acetate and how this interaction can be affected by plasticiser concentration using Dynamic Vapour Sorption (DVS)

Unveiling the importance of diffusion on the deterioration of cellulose acetate artefacts: The profile of plasticiser loss as assessed by infrared microscopy

Cellulose acetate (CA) artefacts are one of the most valued plastic items in museum collections and are known to present stability issues, with the loss of plasticiser being among the main degradation processes. This study investigates the concentration distribution of diethyl phthalate (DEP) plasticiser throughout the dimensions of CA using infrared microscopy for the first time. Artificial ageing experiments using reference and historic CA plasticised with DEP were performed to assess the change in the concentration profiles as a function of ageing time. Our analysis indicates that the plasticiser loss from CA artefacts is likely controlled by its diffusion, resulting in a concentration gradient in which lower plasticiser contents are observed at the external layers of the material

Characterising plasticised cellulose acetate-based historic artefacts by NMR spectroscopy: a new approach for quantifying the degree of substitution and diethyl phthalate contents

As one of the first semi-synthetic plastics produced industrially, cellulose acetate (CA)-based artefacts represent valued items in museum collections and archives which, however, present stability issues. High temperature and relative humidity conditions have long been known to promote changes in CA properties, for instance, due to the deacetylation of CA polymer chains and the loss of plasticiser from the polymer matrix. However, there is a need for improved methods for the quantification of plasticiser loss and CA deacetylation. In this context, this contribution presents a new approach for enabling the investigation of plasticiser loss and deacetylation degradation processes in historic plasticised CA-based artefacts which is based on high-resolution proton nuclear magnetic resonance spectroscopy (1H NMR). The proposed methods allow for simple and fast quantification of diethyl phthalate contents and average degree of substitution (DS), while requiring no need for extractive separation between the plasticiser and the CA polymer matrix prior to analysis. Both methods are demonstrated by their application towards a series of reference samples, historic artefacts and artificially aged plasticised CA materials. Our analysis indicates that plasticiser content and DS can be accurately quantified by using high-resolution 1H NMR and both methods have been compared to analyses performed using infrared spectroscopy

A study of tilt change recorded from July to October 2006 at the Phlegraean Fields (Naples, Italy)

The tiltmetric dataset of Phlegraean Fields area showed a discrete correlation with the volcanic dynamics, suggesting that tiltmetric monitoring is important for the surveillance of active volcanic areas. Tilt data recorded in 2006 at 2 stations belonging to the monitoring network of the Osservatorio Vesuviano (INGV, National Institute for Geophysics and Volcanology, Italy) in the Phlegraean Fields are discussed in this paper. The acquired signals have shown a strong tiltmetric inversion that took place from the end of July 2006. After correcting tilt variations to eliminate the influence of temperature (influencing 90% of the signal at OLB station, hereafter OLB) a significant value of the tilt still remains. This change is related to a local inflation episode lasting 3 months, during an unrest phase that started 2 years before. It is interesting to note that tilt amplitude is much greater at OLB than the slope of the displacement field predicted by the theoretical inflation models, but data show that this field is not homogeneous and in some areas very tilted. Moreover, in the last days before the end of tilt inversion, a low energy seismic swarm happened at about 1 km of distance from the tiltmetric station by hundreds of VT (Volcano-Tectonics) and LP (Long-Period) events