New insights on the relative sea level change during Holocene along the coasts of Tunisia and western Libya from archaeological and geomorphological markers

New data of sea level changes for the Mediterranean region along the coasts of northern Africa are presented. Data are inferred from archaeological sites of Punic-Roman age located along the coast of Tunisia, between Tunis and Jerba island and along the western coast of Libya, between Sabratha and Leptis Magna. Data are based on precise measures of presently submerged archaeological markers that are good indicators of past sea-level elevation. Nineteen selected archaeological sites were studied in Tunisia and four in Libya, all aged between w2.0 and w1.5 ka BP. The functional elevations of significant archaeological markers were measured with respect to the sea level at the time of measurements, applying corrections for tide and atmospheric pressure values. The functional elevations of specific architectural parts of the sites were interpreted, related to sea level at the time of their construction providing data on the relative changes between land and sea. Observations were compared against sea level change predictions derived from the glacio-hydro-isostatic model associated with the Last Glacial cycle. The results indicate that local relative sea level change along the coast of Tunisia and Libya, has increased 0.2 O 0.5 m since the last w2 ka. Besides minor vertical tectonic movements of the land, the observed changes are produced by eustatic and glacio-hydro-isostatic variations acting in the Mediterranean basin since the end of the last glacial maximum

Modeling ground deformations of Panarea volcano hydrothermal/geothermal system (Aeolian Islands, Italy) from GPS data.

Panarea volcano (Aeolian Islands, Italy) was considered extinct until November 3, 2002 when a submarine gas eruption began in the area of the islets of Lisca Bianca, Bottaro, Lisca Nera, Dattilo and Panarelli, about 2.5 km east of Panarea Island. The gas eruption decreased to a state of low degassing by July 2003. Before 2002 the activity of Panarea volcano was characterized by mild degassing of hydrothermal fluid. The compositions of the 2002 gases and their isotopic signatures suggested that the emissions originated from a hydrothermal/geothermal reservoir fed by magmatic fluids. We investigate crustal deformation of Panarea volcano using the GPS velocity field obtained by the combination of continuous and episodic site observations of the Panarea GPS network in the time span 1995-2007. We present a combined model of Okada sources which explains the GPS results acquired in the area after December 2002. The kinematics of Panarea volcano show two distinct active crustal domains characterized by different styles of horizontal deformation, supported also by volcanological and structural evidences. A subsidence in the order of several mm/yr is affecting the entire Panarea volcano and a shortening of 10-6 yr-1 has been estimated in the Islets area. Our model reveals that the degassing intensity and distribution are strongly influenced by geophysical-geochemical changes within the hydrothermal/geothermal system. These variations may be triggered by changes in the regional stress field as suggested by the geophysical and volcanological events that occurred on 2002 in the Southern Tyrrhenian area

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

Relationship between white matter hyperintensities volume and the circle of Willis configurations in patients with carotid artery pathology

Purpose We aimed to assess if there is a difference of distribution and volume of white matter hyperintensities (WMH) in the brain according to the Circle of Willis (CoW) configuration in patients with carotid artery pathology. Material and methods One-hundred consecutive patients (79 males, 21 females; mean age 70 years; age range 46–84 years) that underwent brain MRI before carotid endarterectomy (CEA) were included. FLAIR-WMH lesion volume was performed using a semi-automated segmentation technique and the status of the circle of Willis was assessed by two neuroradiologists in consensus. Results We found a prevalence of 55% of variants in the CoW configuration; 22 cases had one variants (40%); 25 cases had two variants (45.45%) and 8 cases showed 3 variants (14.55%). The configuration that was associated with the biggest WMH volume and number of lesions was the A1 + PcoA + PcoA. The PcoA variants were the most prevalent and there was no statistically significant difference in number of lesions and WMH for each vascular territory assessed and the same results were found for AcoA and A1 variants. Conclusion Results of our study suggest that the more common CoW variants are not associated with the presence of an increased WMH or number of lesions whereas uncommon configurations, in particular when 2 or more segment are missing increase the WMH volume and number of lesions. The WHM volume of the MCA territory seems to be more affected by the CoW configuration

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

Semiautomated and automated algorithms for analysis of the carotid artery wall on computed tomography and sonography: a correlation study.

Objectives—The purpose of this study was to compare automated and semiautomated algorithms for analysis of carotid artery wall thickness and intima-media thickness on multidetector row computed tomographic (CT) angiography and sonography, respectively, and to study the correlation between them. Methods—Twenty consecutive patients underwent multidetector row CT angiographic and sonographic analysis of carotid arteries (mean age, 66 years; age range, 59–79 years). The intima-media thickness of the 40 carotid arteries was measured with novel and dedicated automated software analysis and by 4 observers who manually calculated the intima-media thickness. The carotid artery wall thickness was automatically estimated by using a specific algorithm and was also semiautomatically quantified. The correlation between groups was calculated by using the Pearson ρ statistic, and scatterplots were calculated. We evaluated intermethod agreement using Bland-Altman analysis. Results—By comparing automated carotid artery wall thickness, automated intima-media thickness, semiautomated carotid artery wall thickness, and semiautomated intima-media thickness analyses, a statistically significant association was found, with the highest values obtained for the association between semiautomated and thickness analyses(Pearson ρ = 0.9; 95% confidence interval, 0.82–0.95; P = 0.0001). The lowest values were obtained for the association between semiautomated intima-media thickness and automated carotid artery wall thickness analyses (Pearson ρ = 0.44; 95% confidence interval, 0.15–0.66; P = 0.0047). In the Bland-Altman analysis, the better results were obtained by comparing the semiautomated and automated algorithms for the study of intima-media thickness, with an interval of –16.1% to +43.6%. Conclusions—The results of this preliminary study showed that carotid artery wall thickness and intima-media thickness can be studied with automated software, although the CT analysis needs to be further improved

The interseismic velocity field of the Central Apennine from a dense GPS network

Since 1999 we have repeatedly surveyed the Central Apennines by means of a dense survey style geodetic network (CAGeoNet) consisting in 123 benchmarks distributed in an area of ~180 x 130 km extended from the Tyrrhenian Sea to the Adriatic Sea with an average inter-site distance of 3-5 km. The network is located across the main seismogenic structures of the region, able to generate destructive earthquakes. Here we show the horizontal GPS velocity field of the CaGeoNet and the available continuous GPS (CGPS) stations in this region, that are estimated from their position time series in the time span 1999-2007. Data have been analyzed using Bernese and Gamit software and the two solutions have been rigorously combined to minimize software-dependent systematic errors. We analyze the strain rate field, which shows a region characterized by extension located along the axis of the Apennines chain, with values ranging from 2 to 66 10-9 yr-1 and a relative minimum of 20 10-9 yr-1 located in the L’Aquila basin area. Our velocity field represents an improved estimation of the ongoing elastic inter-seismic deformation of central Apennines in particular of the L’Aquila earthquake of April 6th, 2009 area

Reply to comment by C. Morhange, C. Flaux, P.A. Pirazzoli, M.B. Carre on \u201cHolocene Sea level Change in Malta\u201d

The pits of Birzebbugia are located near the present-day mean sea level, and some are partially submerged. They were dated using pottery discovered in an archaeological site close to the coast, dated to the Bronze Age (Zammit, 1928; Abela, 1999). As they have been interpreted as sites for the retting of flax, during their utilization they should have remained dry and the sea could not submerge them. This is the reason why these structures are not directly related to the sea level, as suggested by Biolchi et al. (2011), so they represent an upper limit.peer-reviewe

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