Sea level rise in the Mediterranean Sea: High resolution constraints from vermetid reefs

The Mediterranean Sea (MS), is extremely sensitive to rising sea-levels (SL) as attested by drowned archeological remains from the Roman Period. Due to theabsence of coral reefs, evidence for recent and Holocene SL change has so far mainly been restricted to coastal cores archeological remains and submerged speleothem deposits. Vermetid reefs are an extremely sensitive high resolution carbonate archive and they are mainly formed in the lower intertidal zone by gregarious and sessile gastropods belonging to the genus Dendropoma (family Vermetidae). Since their interval of growth is restricted to the tidal zone, they can be used as precise SL proxies (about ±0.1 m in lowrange tidal areas). Here, we report new SL data covering two time-windows: between 2,380 and 1,520 years cal BP and during the last 300 yrs. These data have been obtained from two quasi-stable areas of the Western MS: S. Vito Lo Capo (N Sicily, Italy)and Cabo de Gata(SE Spain), opening new perspectives to understand the response of the global changes on this semienclosed basin

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

Static stress drop as determined from geodetic strain rates and statistical seismicity

Two critical items in the energetic budget of a seismic province are the strain rate, which is measured geodetically on the Earth’s surface, and the yearly number of earthquakes exceeding a given magnitude. Our study is based on one of the most complete and recent seismic catalogs of Italian earthquakes and on the strain rate map implied by a multi-year velocity solution for permanent GPS stations. For 36 homogeneous seismic zones, we used the appropriate Gutenberg Richter relation based on the seismicity catalog to estimate a seismic strain rate, which is the strain rate associated with the mechanical work due to a co-seismic displacement. The volume storing most of the elastic energy is associated with the long-term deformation of each seismic zone, and therefore, the seismic strain rate is inversely proportional to the static stress drop. The GPS-derived strain rate for each seismic zone limits the corresponding seismic strain rate, and an upper bound for the average stress drop is estimated. These results demonstrated that the implied regional static stress drop ranged from 0.1 to 5.7 MPa for catalog earthquakes in the moment magnitude range [4.5–7.3]. These results for stress drop are independent of the “a” and “b” regional parameters and heat flow but are very sensitive to the assumed maximum magnitude of a seismic province. The data do not rule out the hypothesis that the stress drop positively correlates with the time elapsed after the largest earthquake recorded in each seismic zone

The brittle-ductile transition as the switch of earthquakes: applications for seismic prediction

The brittle-ductile transition (BDT) separates the lower crust where deformation occurs in steady-state regime, from the upper crust where it is rather dominated by stick-slip. The fault hangingwall above BDT accumulates elastic energy during the interseismic period, without significant evidence of surface strain rate Faults activate in areas of high strain rate gradients along the segments with lower strain rates Fluid discharge varies as a function of the tectonic setting The phenomenology gives insights for the parameters to be monitored in earthquake forecastin

Geodetic model of the 2016 Central Italy earthquake sequence inferred from InSAR and GPS data

We investigate a large geodetic data set of interferometric synthetic aperture radar (InSAR)and GPS measurements to determine the source parameters for the three main shocks of the 2016Central Italy earthquake sequence on 24 August and 26 and 30 October (Mw6.1, 5.9, and 6.5,respectively). Our preferred model is consistent with the activation of four main coseismic asperitiesbelonging to the SW dipping normal fault system associated with the Mount Gorzano-Mount Vettore-Mount Bove alignment. Additional slip, equivalent to aMw~ 6.1–6.2 earthquake, on a secondary (1) NEdipping antithetic fault and/or (2) on a WNW dipping low-angle fault in the hanging wall of the mainsystem is required to better reproduce the complex deformation pattern associated with the greatestseismic event (theMw6.5 earthquake). The recognition of ancillary faults involved in the sequencesuggests a complex interaction in the activated crustal volume between the main normal faults and thesecondary structures and a partitioning of strain releas

Interseismic ground velocities in Central Apennines from GPS and InSAR measurements: new contributions for seismic hazard models by preliminary results of ESA CHARMING project

The contribution of space geodetic techniques to interseismic velocity estimation, and thus seismic hazard modelling, has been recognized since two decades and made possible in more recent years by the increased availability and accuracy of geodetic measurements. We present the preliminary results of a feasibility study performed within the CHARMING project (Constraining Seismic Hazard Models with InSAR and GPS), funded by the European Space Agency (ESA). For a 200 km x 200 km study area, covering the Abruzzi region (central Italy) we measure the mean surface deformation rates from Synthetic Aperture Radar and GPS, finding several local to regional deformation gradients consistent with the tectonic context. We then use a kinematic finite element model to derive the long-term strain rates, as well as earthquake recurrence relations. In turn these are input to state-of-the-art probabilistic seismic hazard models, the output of which is validated statistically using data from the Italian national accelerometric and macroseismic intensity databases.Published373-3773T. Pericolosità sismica e contributo alla definizione del rischioN/A or not JCRope

Mid-term review results of the ESA STSE Pathfinder CHARMING project (Constraining Seismic Hazard Models with InSAR and GPS)

We probe the feasibility of integrating GPS and Synthetic Aperture Radar deformation rates within the seismic hazard models of the central Apennines (Italy), exploiting data from over 100 GPS stations and the ~20- year long ERS and ENVISAT SAR image archive. We then use a kinematic finite element model to derive the long-term strain rates, as well as earthquake recurrence relations. In turn these are input to state-of-the-art probabilistic seismic hazard models, the output of which is validated statistically using data from the Italian national accelerometric and macroseismic intensity databases.Published23-273T. Pericolosità sismica e contributo alla definizione del rischioN/A or not JCRrestricte

Has VZV epidemiology changed in Italy? Results of a seroprevalence study

The aim of the study was to evaluate if and how varicella prevalence has changed in Italy. In particular a seroprevalence study was performed, comparing it to similar surveys conducted in pre-immunization era. During 2013–2014, sera obtained from blood samples taken for diagnostic purposes or routine investigations were collected in collaboration with at least one laboratory/center for each region, following the approval of the Ethics Committee. Data were stratified by sex and age. All samples were processed in a national reference laboratory by an immunoassay with high sensitivity and specificity. Statutory notifications, national hospital discharge database and mortality data related to VZV infection were analyzed as well. A total of 3707 sera were collected and tested. In the studied period both incidence and hospitalization rates decreased and about 5 deaths per year have been registered. The seroprevalence decreased in the first year of life in subjects passively protected by their mother, followed by an increase in the following age classes. The overall antibody prevalence was 84%. The comparison with surveys conducted with the same methodology in 1996–1997 and 2003–2004 showed significant differences in age groups 1–19 y. The study confirms that in Italy VZV infection typically occurs in children. The impact of varicella on Italian population is changing. The comparison between studies performed in different periods shows a significant increase of seropositivity in age class 1–4 years, expression of vaccine interventions already adopted in some regions

Assessing vermetid reefs as indicators of past sea levels in the Mediterranean

The endemic Mediterranean reef building vermetid gastropods Dendropoma petraeum complex (Dendropoma spp) and Vermetus triquetrus develop bio-constructions (rims) on rocky shorelines at about Mean Sea Level (MSL) and are therefore commonly used as relative sea-level (RSL) markers. In this study, we use elevations and age data of vermetid reefs to (1) re-assess the vertical uncertainties of these biological RSL indicators, and (2) evaluate the vertical growth rates along a Mediterranean east-west transect, in attempt to explain the differences found in both growth rates and uncertainties. In Israel, Differential Global Positioning System (DGPS) and laser measurements relative to the local datum show that the reef surfaces mainly occupy the upper intertidal zone with variations in elevation from +0.51 ± 0.07 m to +0.13 ± 0.05 m along the coast. However, in specific sites the vertical uncertainty exceeds the tidal range. In some places the local vermetid species D. anguliferum and V. triquetrus appear to alternate along the vertical rim profiles. This study documents a spatial variability of vertical growth rates, ranging from ~1 mm yr−1 in Israel and Crete, to ~0.1–0.2 mm yr−1 in NW Sicily and Spain. The order of magnitude of the difference in growth rates correlates with the east-west spatial thermal gradient of Sea-Surface Temperature (SST). Preferential skeleton deposition of D. petraeum and V. triquetrus measured by growth axis δ18O analysis shows that most calcification occurs at SST above the mean annual value. These findings indicate that vermetid reefs are a site-specific RSL indicator, displaying various vertical uncertainties and inner-structure complexities. Local data on the indicative range of vermetids are required when reconstructing relative sea-level changes using fossil vermetids