Data analysis of Permanent GPS networks in Italy and surrounding region: application of a distributed processing approach

We describe the procedures used to combine into a uniform velocity solution the observations of more than 80 continuous GPS stations operating in the central Mediterranean in the 1998-2004 time interval. We used a distributed processing approach, which makes efficient use of computer resources, while producing velocity estimates for all stations in one common reference frame, allowing for an effective merging of all the observations into a self-consistent network solution. We describe the CGPS data archiving and processing procedures, and provide main results in terms of position time-series and velocities for all stations that observed more than three years. We computed horizontal and vertical velocities accounting for the seasonal (annual and semi-annual) signals, and considering the off-sets in the coordinate time-series caused by station equipment changes. Weighted post-fit RMS of the north, east and vertical velocity components are in the range of 1.57-2.08 mm, 1.31-3.28 mm, and 3.60-7.24 mm, respectively, which are reduced by solving for seasonal signals in the velocity estimates. The annual and semi-annual signals in the height components, with amplitudes up to 4.8 mm, are much stronger than those in the horizontal components. The mean amplitudes of annual and semi-annual signals are within 0.18-0.47 mm, 0.23-0.52 mm and 0.55-1.92 mm in the north, east and vertical components, respectively

Geodetic deformation Across the Central Apennines from GPS Data in the time span 1999-2003

Abstract During the time span 1999-2003 was set up and repeatedly surveyed a not permanent GPS network located across one of the highest seismic areas of the central Apennines (Italy). The Central Apennine Geodetic Network (CA-GeoNet), extends across Umbria, Abruzzo, Marche and Lazio regions, in an area of ∼180x130 km, from Tyrrhenian to the Adriatic sea. It consists in 125 GPS stations distributed at 3-5 km average grid and includes 7 permanent GPS stations operated by the Italian Space Agency (ASI) and the Istituto Nazionale di Geofisica and Vulcanologia (INGV). With the aim to estimate the active strain rate across this part of the chain, the GPS sites have been located on the main geological units of the area and across the typical basin and range structures, related with the main seismogenic faults. In this paper we show the network and the first results obtained for a subset of 23 stations that have been occupied at least during three repeated campaigns, in the time span 1999-2003. Data analysis, performed by Bernese 4.2 software, shows an extensional rate normal to the chain, in agreement with geological and seismic data. The strain rates in the inner chain are ranging from 12x10-9±11yr-1 to 16x10-9±11yr-1 and from -14x10-9±11yr-1 to -3x10-9±11yr-1. This result provides an improved estimation of the ongoing deformation of this area with respect to previous studies and is in agreement with the style of deformation inferred from seismicity and with the features of the main seismogenic sources from recent geological and seismological investigations

Evidence of relative sea level change and vertical motion of the land along the coast of Calabria inferred from maritime archaeological indicators

Calabria is one of the most complex regions of the Mediterranean basin, which experienced large earthquakes and uplift and is still undergoing to active tectonics. Along its coasts, are located several archaeological sites of roman and pre-roman age, that can be used as powerful indicators of the relative vertical movements between land and sea since their construction. In this paper we show and discuss data on the relative sea-level change as estimated from maritime archaeological indicators of the last ~2.3 ka BP existing along the Tyrrhenian and Ionian coasts of Calabria

Active strain-rate Across the Messina Straits and Kinematics of Sicily and Calabria From GPS Data

The Messina Straits is the locus of one of the strongest seismic event that ever hit Italy during historical times, the 1908 Mw 7.1 earthquake, and the same region also suffered major damage from other strong earthquakes in the last few centuries. However, despite the large amount of data and studies carried out, our knowledge of the present-day deformation of this area is still debated. While a general consensus has been reached about the kinematics of the 1908 causative fault, less is known about the rate and shape of interseismic loading across the Straits, and debate continues also about the general kinematics and geodynamic framework of this region which are strongly influenced by subduction and retreat of Ionian lithosphere. Thanks to the increasing number of GPS Networks in the study region it is now possible to study both the regional kinematics and strain loading across active faults. In this work we analyze all the observations collected over the Messina non-permanent GPS Network for the 1994-2008 time span, and data from about 600 CGPS stations in the Euro-Mediterranean region, using the GAMIT software. The output of our analysis is a new and denser velocity field, which is used to study the plate kinematics and the rate of interseismic strain building across the Straits. GPS velocities show a sudden change in their orientation across the Straits moving to NNW-ward, in Estern Sicily, to NNE-ward in Western Calabria, depicting this area as a primary boundary between two different tectonic domains. The maximum strain-rates observed across the Straits are about 120 nanostrain/yr, with extension oriented about normal to the coasts of Sicily according to the presence of a normal fault. The measured velocity gradient can be used to model the creeping dislocation at depth, however, over the Messina Straits the interseismic elastic strains accumulating across other nearby active faults can significantly affect the observed velocity gradient.For this reason we investigate, using a regional elastic block-modeling approach, these effects. We use the block model to test for different microplates configurations and to account for nearby active faults while inverting for optimal fault geometry and intersismic slip-rates across the Straits

Kinematics of the Central Mediterranean Plate Boundary, Internal Deformation of Sicily and Interseismic Strain Accumulation Across the Messina Straits

In this work we present a new velocity field, obtained by analyzing continuous GPS (CGPS) stations operating in the Mediterranean area (updated to September 2007)and epoch GPS (EGPS) stations in the 1991-2006 time span, particularly denser in the Iblean plateau and across the Messina Straits

Applicazione di metodi di potenziale in aree attive: uno studio sistematico e multiparametrico dell’Arcipelago di Panarea (Isole Eolie)

La caratteristica generale dei metodi gravimetrici, magnetici ed elettromagnetici, è quella di aver il pregio di integrare gli effetti di un fenomeno su un grande volume; anche in assenza di manifestazioni locali, come un terremoto o l’apertura di una frattura, le modificazioni del campo di stress o dello stato termodinamico, ad esempio all’interno di un edificio vulcanico, possono indurre variazioni della densità, della magnetizzazione e della resistività elettrica delle rocce. In questa ottica nel maggio 2005 è stata condotta una campagna nell’Arcipelago di Panarea, area di attuale interesse per fenomeni di attività esalativa (S.G.A.,1993; Italiano e Nuccio, 1991) attraverso uno studio microgravimetrico, magnetico e prelievo di campioni per analisi di suscettività magnetica e di densità. Lo scopo è quello di acquisire un gran numero di informazioni geofisiche differenti da affiancare alle attuali misurazioni geodetiche e di batimetria condotte dal gruppo INGV-CNT (Anzidei, 2000; Anzidei et al., 2003a) per produrre modelli dell’area sempre più vincolati e nello stesso tempo attraverso una ripetizione delle campagne nel tempo ottenere una visione 4D dei fenomeni finalizzati al monitoraggio dell’assetto dinamico dell’apparato di Panarea. Nel presente lavoro vengono presentati i risultati preliminari ottenuti dalla prima campagna di misure in cui sono state acquisite 53 stazioni microgravimetriche e magnetiche totali (di cui 6 sugli isolotti di Bottaro e Lisca Bianca) distribuite nel modo più omogeneo possibile compatibilmente con la logistica del territorio. Sono stati inoltre prelevati 14 campioni di rocce nelle principali litologie dell’isola su cui sono state eseguite misure di suscettività magnetica in laboratorio. Per le misure di gravità sono stati utilizzati Microgravimetri L&R modello Alliod 100x (di proprietà ENI) mentre per le misure di campo magnetico, un magnetometro portatile a protoni Scintrex. I risultati delle prime elaborazioni (fig.1) mostrano un’andamento qualitativo dei principali trends di anomalie in generale accordo tra loro. Nella carta residuata di anomalia di Bouguer, preliminarmente corretta per un valore di densità standard di 2.67 g/cm3 (in attesa di poter effettuare sui campioni delle misure di densità) ed ottenuta mediante sottrazione dall’anomalia in aria libera del contributo relativo alla topografia dell’isola mediante un Digital elevation terrain model, si nota una anomalia negativa localizzata nel fianco occidentale dell’isola (zona con quote più elevate) che sembra svilupparsi lungo gli affioramenti della formazione Punta Cardosi (PC2 e PC2a) costituita da colate di lava omogenee andesitiche e duomi di lava dacitici (Calanchi et al., 1999) di età più recente. La stessa formazione presenta i valori di suscettività più elevati misurati sull’isola, tra 3 e 4x10-2 SI (insieme alla formazione della fossa affiorante nella parte centro-orientale dell’isola tra il paese di San Pietro e Drauto) che si riflettono anche nella mappa di anomalia magnetica di campo totale, con un trend di anomalie con valori elevati in direzione circa Sud-Ovest. La fascia di anomalie distribuite lungo la costa risentono di un effetto spurio di bordo (limite del campionamento) e quindi per poterne meglio descriverne la forma sarebbe necessario poter condurre un rilievo marino circostante l’isola utile anche per collegare le misure acquisite sugli isolotti

Sea level changes and vertical land movements in the Mediterranean from historical and geophysical data and modelling

The Mediterranean basin is a natural laboratory for the reconstruction of the sea level variations since paleo-historical times. During the Holocene, sea level variations in this region have been mainly determined by the response of the geoid and of the solid Earth to the melting of remote ice aggregates, which has produced spatially variable signals mostly governed by the effect of ocean loading. An analysis of past and recent sea level variations is possible from various indicators, which provide data on relative sea level and crustal vertical movements on different time scales.PublishedBurlington house, London3.3. Geodinamica e struttura dell'interno della Terraope

Studio multiparametrico dell’arcipelago di Panarea (Isole Eolie): primi risultati dei rilievi geodetici, geofisici e geologici

La recente crisi esalativa di Panarea ha indotto ad effettuare uno studio sistematico dell’area con tecniche GPS, batimetrie ad alta risoluzione, rilievi gravimetrici e di suscettività magnetica, rilievi geologici sottomarini e terrestri. I rilievi batimetrici hanno permesso di individuare la posizione e la estensione dei centri esalativi principali e il campo di fratturazione; quelli gravimetrici e di suscettività magnetica mostrano anomalie nel fianco occidentale di Panarea (formazione Punta Cardosi). I dati GPS, acquisiti sia sulla rete locale che nelle stazioni continue di Lisca Bianca e Panarea, mostrano una deformazione dell’area che è in accordo con il trend del campo di fratturazione attivo stimato dai rilievi geologici sottomarini e terrestri

Looking inside the Panarea Island (Aeolian Archipelago, Italy) by gravity and magnetic data

In this paper we show and discuss the results of gravity and magnetic surveys of Panarea Island and its archipelago. The most recent volcanic manifestation occurred in November 2002 with a shallow submarine gas eruption between the islets of Dattilo, Panarelli, Lisca Bianca, Bottaro and Lisca Nera. Currently, the activity of Panarea is monitored through a multidisciplinary study under the umbrella of the Italian Department of Civil Protection with the goal of defining the hazard of this area. With this aim, in May 2006 the first gravity and magnetic surveys of Panarea Island and its archipelago were performed. The offshore magnetic data were obtained using a marine magnetometer, a Geometrics G880, from the Istituto Idrografico dell Marina (IIM). Onshore and offshore magnetic data were integrated into an unique dataset for complete magnetic coverage of the study area. By using two micro-gravimeters (LaCoste & Romberg), gravity data were collected along tracks every 250 meters. The gravity dataset was processed using the standard method. A Bouguer reduction was applied to the free-air gravity dataset using a detailed digital elevation model of the island and the neighbouring sea after evaluation of the optimal Bouguer density to reduce the topographic effect. The result is a Bouguer anomaly map that shows lateral variations in density distribution and the relationships between the shallow volcanic/crustal features and tectonic lineaments. This evidence is also highlighted by the magnetic pattern, which suggests the importance of the youngest volcanic deposits with respect to the magnetic features of the island

Implicazioni geodinamiche delle recenti misure geodetiche nello Stretto di Messina

Il 28 dicembre 1908 lo Stretto di Messina veniva colpito da un disastroso evento sismico di ms=7.5. L'evento è il più forte tra i terremoti italiani degli utimi 100 anni.Published3-143.3. Geodinamica e struttura dell'interno della TerraN/A or not JCRrestricte