Combining inland and offshore paleotsunamis evidence: the Augusta Bay (eastern Sicily, Italy) case study

Offshore and inland geological evidence for multiple tsunami inundations was found in the Augusta Bay area: (1) the main local historical tsunamis (1908, 1693, 1169), (2) two far-generated tsunamis (i.e. Crete 365AD and Santorini, 3600 BP), and (3) seven unknown tsunamis). Average tsunami recurrence intervals from inland and offshore investigations of about 550 and 320 yr, respectively were obtained for the past 4 ka. The history of paleotsunamis from the marine record appears to be as complete as the historical one for the past millennium, yielding an average tsunami recurrence interval of 250 yr for the Augusta Bay. Geological data allow also estimating a minimum tsunami inundation distance of 530m and a minimum run-up of 5 m. The marine record contains evidence for more paleotsunamis with respect to the inland one because of continuous sedimentation and better preservation of stratigraphy in the offshore with respect to coastal areas, which are commonly affected by intermittent-erosion and sedimentation and anthropic activities. This work shows that the integration of geological and historical data can provide critical information regarding the extent and age of tsunamis of the past (e.g. inundation distance, age, and frequency), which is of immediate relevance for tsunami hazard assessment

Geological Evidence of Paleotsunamis at Torre degli Inglesi (northeast Sicily)

Two layers of fine sand of marine origin occur in a sequence of organic rich colluvia in an archaeological excavation at Torre degli Inglesi, on Capo Peloro, northeast Sicily. Stratigraphic and micropaleontologic analyses support the hypothesis that these layers are related to deposition due to paleotsunami waves. Their ages are constrained both with radiocarbon and archaeological datings. The age of the oldest layer is coincident with the 17 A.D. earthquake that hit Reggio Calabria but for which no tsunami was previously reported. The age of the youngest layer can be only constrained in the range 3rd– 19th century and is tentatively associated to the 6 Feb. 1783 event

Effect of time-dependence on probabilistic seismic hazard maps and deaggregation for the central apennines, Italy

We produce probabilistic seismic hazard assessments for the Central Apennines, Italy, using time-dependent models that are characterized using a Brownian Passage Time (BPT) recurrence model. Using aperiodicity parameters,  of 0.3, 0.5, and 0.7, we examine the sensitivity of the probabilistic ground motion and its deaggregation to these parameters. For the seismic source model we incorporate both smoothed historical seismicity over the area and geological information on faults. We use the maximum magnitude model for the fault sources together with a uniform probability of rupture along the fault (floating fault model) to model fictitious faults to account for earthquakes that cannot be correlated with known geologic structural segmentation. We show maps for peak ground acceleration (PGA) and 1.0-Hz spectral acceleration (SA1) on rock having 10% probability of exceedence (PE) in 50 years. We produce maps to compare the separate contributions of smoothed seismicity and fault components. In addition we construct maps that show sensitivity of the hazard for different  parameters and the Poisson model. For the Poisson model, the addition of fault sources to the smoothed seismicity raises the hazard by 50 % at locations where the smoothed seismicity contributes the highest hazard, and up to 100 % at locations where the hazard from smoothed seismicity is low. For the strongest aperiodicity parameter (smallest ), the hazard may further increase 60-80 % or more or may decrease by as much as 20 %, depending on the recency of the last event on the fault that dominates the hazard at a given site. In order to present the most likely earthquake magnitude and/or the most likely source-site distance for scenario studies, we deaggregate the seismic hazard for SA1 and PGA for two important cities (Roma and l’Aquila) . For PGA, both locations show the predominance of local sources, having magnitudes of about 5.3 and 6.5 respectively. For SA1 at a site in Rome, there is significant contribution from local smoothed seismicity, and an additional contribution from the more distant Apennine faults having magnitude around 6.8. For l’Aquila, the predominant sources remain local. In order to show the variety of impact of different  values we also obtained deaggregations for another three sites. In general, as  decreases (periodicity increases), the deaggregation indicates that the hazard is highest near faults with the highest earthquakes rates. This effect is strongest for the long-period (1 s) ground motions

Short-term vertical velocity field in the Appennines (Italy) revealed by geodetic levelling data

We estimate current vertical movements along the Apennines (Italy) through repeatedly measured high precision levelling routes. In order to highlight regional crustal deformation the analysis of a geodetic database, with a minimum benchmark density of 0.7 bm/km (1943–2003 time period), is carried out. We evaluate systematic and random error and their propagation along the levelling routes. Tests on original raw height data have been carried out to define error propagation. The computed relative vertical rates stand significantly above error propagation. A series of traverses along and across the Apennines and a map of relative vertical velocities reveal a geodetic signal characterised by values up to 2.5–3.0 mm/a and by wavelengths up to 100 km. © 2006 Elsevier B.V. All rights reserved

Identification of tsunami deposits and liquefaction features in the Gargano area (Italy): paleoseismological implication

The Gargano region (Southeastern Italy) was hit by a M = 6.8 earthquake and inundated by a subsequent tsunami in 1627. To better define the hazard in the region, we searched for evidence of this and prior earthquakes in the geologic record. We identified potential earthquake-related liquefaction features and tsunami deposits in the stratigraphic sequences of the marsh areas both north and south of the Gargano promontory. We recognized clear liquefaction features and possible tsunamigenic sands that can be related to the 1627 seismic event in irrigation ditch exposures and gouge cores along the Northern Gargano coast. In total, six potential tsunami sand deposits have been recognized in two areas located close to the northern and southern coasts of the Gargano promontory. However, ambiguous evidence comes from the paleontological analysis of these sands. Although fragments of marine shells have been found in the coarser portion of the sand samples, foraminifera and ostracods assemblages are typical of brackish water condition. Radiocarbon dating of three of these deposits from the Northern Gargano coast, near the town of Lesina, suggests an average recurrence interval of 1700 years for tsunami events in this area. Assuming that all the paleotsunamis are related to the same seismogenic source responsible for the 1627 earthquake, this average recurrence interval may be typical for that source. Radiocarbon dating of three sand layers observed on the southern coast, close to the city of Manfredonia, suggests that the average recurrence time for violent sea inundation there is about 1200 years

Historical, archeological and geological records of strong earthquakes at Capo Peloro (southern Italy)

During the 4th century AD southern Calabria and eastern Sicily were hit by an earthquake documented by archaeoseismic analyses, which was interpreted by Guidoboni et al. (2000) as the predecessor of the well-know 1908 earthquake, located in Messina Strait, whereas Galli and Bosi (2002) interpreted this event as the precedessor of the 1783 earthquake. The purpose of this paper is to find further evidence of these earthquakes in Messina area by a multidisciplinary study aimed to recognize and date historical and paleo-earthquakes. For this goal we have analyzed historical, archaeological and geological information of excavations performed at Capo Peloro near the Torre del Faro village (Fig. 1) in the Torre degli Inglesi (English Tower), built on an abandoned Roman tower

A unique 4000 year long geological record of multiple tsunami inundations in the Augusta Bay (eastern Sicily, Italy)

We present the geological evidence for a 4000 year long record of multiple tsunami inundations along the coast of the Augusta Bay (eastern Sicily)and discuss its implications. The research was carried out through a multi-theme approach which benefited from an extraordinarily long historical record that we used to guide detailed geomorphologic and geologic surveys, coring campaigns and laboratory analyses. Two sites, named the Augusta Hospital and Priolo Reserve, were selected and investigated in detail along the 25 km-long coastline of Augusta Bay. We found evidence for six (possibly seven) tsunami deposits; three of them may be tentatively associated with the 1693 and 365 AD Ionian Sea historical tsunamis and the ~3600 BP Santorini event. The other three (possibly four) deposits are evidence for unknown paleo-inundations dated at about 650–770 AD, 600–400 BC and 975–800 BC (at Augusta Hospital site), and 800–600 BC (at Priolo Reserve site). We use these ages to extend further back the historical record of tsunamis available for this coastal area. The exceptional number of tsunami deposits found with this study allowed us to derive an average geologic tsunami recurrence interval in the Augusta Bay of about 600 years for the past 4 ka. Conversely, the historical tsunami data for the past millennium suggest an average tsunami recurrence interval of about 250 years. This difference in the average recurrence intervals suggests that only the strongest inundations may leave recognizable geological signatures at the investigated sites (i.e. the evidence for the 1908 and 1169 tsunamis is missing) but also that the geomorphological setting of the site and its erosional/depositional history are critical aspects for the data recording. Thus, an average recurrence interval derived from the geological record should be considered as a minimum figure. The identification and age estimation of tsunami deposits represent a new and independent contribution to tsunami scenarios and modeling for coastal hazard assessment in Civil Protection applications. Furthermore, our study cases provide new elements on tsunami deposit recognition related to exceptionally large events that occurred in the Aegean Sea

Geological evidence for paleotsunamis along eastern Sicily (Italy): an overview

Abstract. We present geological evidence for paleotsunamis along the ~230 km-long coast of eastern Sicily (Italy); combining this information with historical data, we reconstruct a unique history of tsunami inundations. We integrate data on 38 paleotsunami deposits (from fine sand layers to boulders) collected at 11 sites (one offshore). The geological data record traces of large tsunamis which have occurred during the past 4 millennia. Chronological constrains include 14C, 210Pb and 137Cs, OSL and tephrochronology. When compatible, the age of the paleotsunami deposits is associated to historical events, but it is also used to highlight unknown tsunamis. Average tsunami recurrence interval (between 320 and 840 yr) and minimum inland tsunami ingressions (often greater than the historical ones) were estimated at several sites. On the basis of this work, the tsunami catalogue is implemented by two unknown tsunamis which occurred during the first millennium BC and by one unknown regional tsunami, which occurred in 650–770 AD. By including this latter event in the eastern Sicily catalogue, we estimate an average recurrence interval for strong tsunamis of ca. 385 yr. Comparison and merging of historical and geological data can definitely contribute to a better understanding of regional and local tsunami potential and provides robust parameters to be used in tsunami hazard estimates

No evidence of colonization with community-acquired methicillin-resistant Staphylococcus aureus in HIV-1-infected men who have sex with men.

SUMMARYTo assess the prevalence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) colonization in HIV-1-infected men who have sex with men (MSM), a cross-sectional study was conducted on 104 persons attending a large STI/HIV unit in Rome, Italy in the period June 2007–June 2008. Swabs obtained from both anterior nares and S. aureus isolates were characterized by phenotypic and genotypic methods. A total of 24 individuals (23·1%) were colonized with S. aureus but none carried MRSA. No statistically significant association between colonization with S. aureus and behavioural, clinical, virological or immunological characteristics was identified. This study indicates a lack of circulation of CA-MRSA in HIV-1-infected MSM in Italy and underscores large epidemiological differences between the USA and a European country, so that only locally conducted epidemiological studies can provide insight into the local circulation of CA-MRSA in general and selected populations

Il nuovo portale web dell'Istituto Nazionale di Geofisica e Vulcanologia

The web portal of Istituto Nazionale di Geofisica e Vulcanologia represents a point of access to studies and data which are available on line and, among others, contribute to the seismicity of the territory. Main features of the portal are presented