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91.
Twenty years of paleoseismology in Italy 总被引:1,自引:0,他引:1
Italy has one of the most complete and historically extensive seismic catalogues in the World due to a unique and uninterrupted flow of written sources that have narrated its seismic history since about the end of the Iron Age. Seismic hazard studies have therefore always been mainly based upon this huge mass of data. Nevertheless, the Italian catalogue probably “lacks” many M ≥ 6.5 events, the seismogenetic structures responsible for which are characterized by recurrence times that are longer than the time span covered by our historical sources. For these reasons, and as in other countries, earthquake data that in Italy have been derived from paleoseismological studies should finally become a necessary ingredient in seismic risk assessment. Indeed, over the past 20 years, some hundred trenches have been excavated, supplying reliable and conclusive data on the recent activities of many faults. Through to many robust datings of surface fault events, these studies have provided the ages of several unknown or poorly known M ≥ 6.5 earthquakes. Here, we summarize the state of the art of paleoseismology in Italy, and present a first catalogue of 56 paleoearthquakes (PCI) that occurred mainly in the past 6 kyr. The PCI integrates the historical/instrumental seismic catalogue, and extends it beyond the recurrence time of the seismogenetic faults (2000 ± 1000 yr). We feel confident that the use of the PCI will enhance future probabilistic seismic hazard assessment, and thus contribute to more reliable seismic risk mitigation programs. 相似文献
92.
93.
Distribution and population structure of deep‐dwelling red coral in the Northwest Mediterranean
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Michela Angiolillo Andrea Gori Simonepietro Canese Marzia Bo Cristina Priori Giorgio Bavestrello Eva Salvati Fabrizio Erra Michael Greenacre Giovanni Santangelo 《Marine Ecology》2016,37(2):294-310
Commercially harvested since ancient times, the highly valuable red coral Corallium rubrum (Linnaeus, 1758) is an octocoral endemic to the Mediterranean Sea and adjacent Eastern Atlantic Ocean, where it occurs on rocky bottoms over a wide bathymetric range. Current knowledge is restricted to its shallow populations (15–50 m depth), with comparably little attention given to the deeper populations (50–200 m) that are nowadays the main target of exploitation. In this study, red coral distribution and population structure were assessed in three historically exploited areas (Amalfi, Ischia Island and Elba Island) in the Tyrrhenian Sea (Western Mediterranean Sea) between 50 and 130 m depth by means of ROV during a cruise carried out in the summer of 2010. Red coral populations showed a maximum patch frequency of 0.20 ± 0.04 SD patches·m?1 and a density ranging between 28 and 204 colonies·m?2, with a fairly continuous bathymetric distribution. The highest red coral densities in the investigated areas were found on cliffs and boulders mainly exposed to the east, at the greatest depth, and characterized by medium percentage sediment cover. The study populations contained a high percentage (46% on average) of harvestable colonies (>7 mm basal diameter). Moreover, some colonies with fifth‐order branches were also observed, highlighting the probable older age of some components of these populations. The Ischia population showed the highest colony occupancy, density and size, suggesting a better conservation status than the populations at the other study locations. These results indicate that deep dwelling red coral populations in non‐stressed or less‐harvested areas may diverge from the inverse size‐density relationship previously observed in red coral populations with increasing depth. 相似文献
94.
95.
Evaluation of the influence of experimental conditions on H/V results from ambient noise recordings 总被引:5,自引:2,他引:3
Jean-Luc Chatelain Bertrand Guillier Fabrizio Cara Anne-Marie Duval Kuvvet Atakan Pierre-Yves Bard 《Bulletin of Earthquake Engineering》2008,6(1):33-74
The H/V-noise technique is now widely used to estimate site effect parameters (fundamental frequency and sometimes the associated soil amplification), and many surveys using this technique have provided convincing results. However, a general agreement on a methodology for data acquisition, data processing and result interpretation has yet to be found. H/V measurements from ambient noise recordings imply both reliability of the results and rapidity of data collection. It is therefore important to understand which experimental conditions (1) influence data quality and reliability, and (2) can help speeding up the recording process. Within the framework of the SESAME European project, a specific task was defined to investigate the reliability of the H/V spectral ratio technique in assessing the site effects. The aim of WP02, one specific Work Package of the SESAME project, is to study the effects of experimental conditions on both stability and reproducibility of H/V results. This study has been conducted in a purely experimental way, by testing the possible influence of various experimental conditions on H/V results both on the frequency peak value and on its amplitude. WP02 results help setting up the experimental conditions under which ambient noise recordings have to be performed in order to provide reproducible, reliable and meaningful H/V results. In this paper we present the results of the WP02 SESAME project concerning the evaluation of the influence of experimental conditions of ambient noise recording on H/V results. 相似文献
96.
Miriam Colombi Barbara Borzi Helen Crowley Mauro Onida Fabrizio Meroni Rui Pinho 《Bulletin of Earthquake Engineering》2008,6(3):485-504
The concerted effort to collect earthquake damage data in Italy over the past 30 years has led to the development of an extensive
database from which vulnerability predictions for the Italian building stock can be derived. A methodology to derive empirical
vulnerability curves with the aforementioned data is presented herein and the resulting curves have been directly compared
with mechanics-based vulnerability curves. However, it has been found that a valid comparison between the empirical and analytical
vulnerability curves is not possible mainly due to a number of shortcomings in the database of surveyed buildings. A detailed
discussion of the difficulties in deriving vulnerability curves from the current observed damage database is thus also presented. 相似文献
97.
98.
Matteo Lelli Sergio Grassi Michele Amadori Fabrizio Franceschini 《Environmental Earth Sciences》2014,71(9):3907-3919
A detailed hydrogeochemical study of groundwater in the Cecina coastal plain (Livorno province, Italy) and its inner sectors was undertaken in 2008, as chemical analyses carried out on groundwater since 2006 have revealed Cr(VI) concentrations of up to 49 μg/L (well above the permissible limit of 5 μg/L). Ophiolite outcrops are present throughout the study area, and their fragments likely represent a significant portion of the existing multilayered aquifer skeleton. Waters delivered by the serpentinite outcrops have a typically Mg–HCO3 composition, whereas those of the coastal plain are prevailingly of the Ca/Mg–HCO3 type with significant Mg contents. Significant NO3 contamination characterises the studied coastal plain, and an interesting negative correlation exists between Cr(VI) and both NO3 and SO4 deriving from the widespread use of (NH4)2SO4 as a farm fertilizer. Chromium speciation calculations carried out using the EQ3NR code reveal that the prevailing Cr(VI) species in solution is CrO4 2?; however, CaCrO4° and MgCrO4° neutral complexes represent significant percentages (up to 42 %). These findings suggest that the mobility and consequently the bioavailability of Cr(VI) can be significantly enhanced by these neutral complexes, which are not considered to be affected by adsorption/desorption processes. The Cr(VI) source, investigated by means of the Mg/SiO2 molar ratio, seems to be represented mainly by Mg-bearing minerals of the chlorite group. Petrographic observations confirm the occurrence of this mineral group. The interaction between rainwater and the local serpentinite rock was simulated at different $P_{{{\text{CO}}_{ 2} }}$ and $P_{{{\text{O}}_{ 2} }}$ conditions by reaction path modelling using the EQ3/6 software package. $P_{{{\text{O}}_{ 2} }}$ was varied in accordance with the assumption that redox conditions are determined in part by NO3. Results are in good agreement with experimental data on spring waters and subordinately with data on some coastal plain groundwater, which plot in a rather wide $P_{{{\text{CO}}_{ 2} }}$ and $P_{{{\text{O}}_{ 2} }}$ field. Although the dissolved Cr content is mostly of natural origin, fertilization may affect its fate. 相似文献
99.
Antigorite equation of state and anomalous softening at 6 GPa: an in situ single-crystal X-ray diffraction study 总被引:1,自引:0,他引:1
Fabrizio Nestola Ross J. Angel Jing Zhao Carlos J. Garrido Vicente López Sánchez-Vizcaíno Giancarlo Capitani Marcello Mellini 《Contributions to Mineralogy and Petrology》2010,160(1):33-43
The compressibility of antigorite has been determined up to 8.826(8) GPa, for the first time by single crystal X-ray diffraction in a diamond anvil cell, on a specimen from Cerro del Almirez. Fifteen pressure–volume data, up to 5.910(6) GPa, have been fit by a third-order Birch–Murnaghan equation of state, yielding V 0 = 2,914.07(23) Å3, K T0 = 62.9(4) GPa, with K′ = 6.1(2). The compression of antigorite is very anisotropic with axial compressibilities in the ratio 1.11:1.00:3.22 along a, b and c, respectively. The new equation of state leads to an estimation of the upper stability limit of antigorite that is intermediate with respect to existing values, and in better agreement with experiments. At pressures in excess of 6 GPa antigorite displays a significant volume softening that may be relevant for very cold subducting slabs. 相似文献
100.
Massimo Cerdonio Fabrizio De Marchi Roberto De Pietri Philippe Jetzer Francesco Marzari Giulio Mazzolo Antonello Ortolan Mauro Sereno 《Celestial Mechanics and Dynamical Astronomy》2010,107(1-2):255-264
The analysis of non-radiative sources of static or time-dependent gravitational fields in the Solar System is crucial to accurately estimate the free-fall orbits of the LISA space mission. In particular, we take into account the gravitational effects of Interplanetary Dust (ID) on the spacecraft trajectories. The perturbing gravitational field has been calculated for some ID density distributions that fit the observed zodiacal light. Then we integrated the Gauss planetary equations to get the deviations from the LISA Keplerian orbits around the Sun. This analysis can be eventually extended to Local Dark Matter (LDM), as gravitational fields are expected to be similar for ID and LDM distributions. Under some strong assumptions on the displacement noise at very low frequency, the Doppler data collected during the whole LISA mission could provide upper limits on ID and LDM densities. 相似文献