An archaeo-seismological study of the Nîmes Roman aqueduct,France: indirect evidence for an <Emphasis Type="Italic">M</Emphasis> > 6 seismic event?     

Philippe Volant  Agnès Levret  David Carbon  Oona Scotti  Didier Combescure  Thierry Verdel  Anne Piant  Philippe Laurent 《Natural Hazards》2009,49(1):53-77

This paper presents a synthesis of a multidisciplinary study carried out along the Nîmes Roman aqueduct, located in the southeast part of France. The study was motivated by archaeologists attempting to explain the partial destructions of only one aerial bridge of the aqueduct (Pont de la Lône). Given its close proximity to the Nîmes seismically active fault, a possible seismic origin for the destructions was invoked. Seismologists and structural engineers thus carried out a variety of field and numerical investigations to test the seismic hypothesis. Supporting field evidence was found first along the aerial bridge section of the aqueduct: broken stalactites, arch warping, cracks and destruction of the bridge just above a breast wall shortly after its construction. Secondly, the underground part of the canal was analysed: irregularity in the thickness of calcite deposits of the canal walls, presence of numerous cracks, horizontal shift of the otherwise linear structure of the canal and presence of calcite twins in the deposits, found only where the canal crosses the Nîmes fault system. Numerical modelling and experimental results show that (1) only the Pont de la Lône would have suffered serious damage under seismic solicitation (assuming an M6 earthquake at 10 km distance). The second aerial bridge, the three levels arches Pont du Gard, an historical monument still standing today, would have suffered less damage, due to its very different fundamental frequency of around 0.4 Hz, far from the amplified seismic near-field spectrum; (2) the numerical models also show that a fall of the canal wall would require a higher magnitude event (M > 6); (3) the presence of calcite twinning requires a differential static stress of 4 MPa or greater, which can only be achieved very close to the fault rupture of a M > 6 earthquake; (4) finally, local surface rupturing of such a fault would also corroborate the hypothesis that the observed offset of the canal may be partly seismically induced. Although other possible origins for each individual evidence may not be excluded, the observed spatiotemporal concentration of architectural/geological anomalies together with the numerical results allow us to support a possible co-seismic origin for these disorders, indirectly attesting to the potential seismic activity (M > 6) of the nearby Nîmes fault. Furthermore, following the conclusions of archaeological studies, the disorders occurred between 250 and 350 year AD, thus providing timing for this possible seismic event, an essential parameter in seismic hazard analysis. These results validate the archaeo-seismological approach as a tool that may help improve the knowledge of major infrequent earthquakes in areas of moderate seismic activity.  相似文献   

The structure of coronal magnetic loops     

Claudio Chiuderi  Riccardo Giachetti  Gerard Van Hoven 《Solar physics》1977,54(1):107-122

We present here a model, based on observations, for the magnetic-field equilibrium of a cool coronal loop. The pressure structure, taken from the Harvard/Skylab EUV data, is used to modify the usual force-free-field form in quasi-cylindrical symmetry. The resulting field, which has the same direction but different strength, is calculated and its variation displayed. Finally, localized interchange stability is evaluated and discussed, as the first step in a subsequent complete magnetohydrodynamic-stability analysis.  相似文献   

Dissolution of nanocrystalline fluorite powders: An investigation by XRD and solution chemistry     

Giovanni De Giudici  Riccardo Biddau  Matteo Leoni 《Geochimica et cosmochimica acta》2005,69(16):4073-4083

The effect of lattice disorder and mineral surface area on the reactivity of finely ground fluorite was studied on ball-milled powders. Structural information was provided by X-ray whole powder pattern modeling (WPPM). The mean size of coherent scattering domains decreases with milling time from 70 nm to ∼20 nm, whereas the density of lattice defects increases with both time and intensity of milling treatment, from 4 × 10¹⁵ m^-2 to 24 × 10¹⁵ m^-2. High resolution transmission electron microscopy (HRTEM) of ground fluorite grains shows several line defects and a general tendency of nanometric crystalline domains to agglomerate in larger grains.Solution chemistry was investigated using batch reactors with free drift of solution saturation state with respect to fluorite. Total surface area was measured by the Brunaver, Emmet and Teller (BET) method, and dissolution rates were measured at pH = 2 (HCl) and T = 295 K. In far from equilibrium conditions, dissolution rates normalized by BET area do not increase with the dislocation density. In near-equilibrium condition, however, measured stationary ionic product clearly increases with both time and intensity of milling treatment. Thermodynamic predictions of the solubility constant indicate negligible or little effect of total surface area. Consequently, the observed increase in the stationary ionic product can be related to the increasing lattice defect content. This confirms the significant role of dislocation outcrops on mineral dissolution in close to equilibrium conditions.  相似文献   

Magnitude versus faults'' surface parameters: quantitative relationships from the Aegean Region     

Spyros Pavlides  Riccardo Caputo   《Tectonophysics》2004,380(3-4):159-188

Historical and seismotectonic data from the broader Aegean Region have been collected and all possible information relative to ground deformation associated to earthquakes that hit the area have been re-evaluated. All events associated to co-seismic surface faulting have been selected and further investigated, while geomorphologic and geological criteria have been used to recognise and characterise the seismogenic faults associated to these ‘morphogenic earthquakes’ (sensu [Bull. INQUA 16 (1993) 24]). In particular, in order to perform seismic hazard analyses, we compiled a list of all earthquakes where the surface rupture length (SRL), the maximum vertical displacement (MVD) or the average displacement (AD) is available. We thus obtained reliable values of these source parameters for 36 earthquakes, of which 26 occurred during the 20th century, 6 in the 19th century and the 3 remaining earlier. Magnitude versus SRL and MVD has been compiled for estimating empirical relationships. The calculated regression equations are: Ms=0.90·log(SRL)+5.48 and Ms=0.5·9log(MVD)+6.75, showing good correlation coefficients equal to 0.84 and 0.82, respectively. Co-seismic fault rupture lengths and especially maximum displacements in the Aegean Region have systematically lower values than the same parameters worldwide, but are similar to those of the Eastern Mediterranean–Middle East region. The envelopes of our diagrams are also calculated and discussed for estimating the worst-case scenario. Furthermore, for all investigated seismogenic structures, based on several geological criteria, we measured the ‘geological’ fault length (GFL), which is the total length of the neotectonic faults showing cumulative recent activity. We then compared SRL with GFL and their ratio shows a clear bimodal distribution with a major peak at 0.8–1.0, indicating that about 50% of the investigated earthquakes ruptured almost the entire fault length, while a second peak around the value of 0.5 is clearly related to a segmentation process of longer neotectonic structures. Further implications of this distribution are also discussed. Eventually, from the distribution of GFL versus magnitude we also infer an important geological threshold for the occurrence of ‘morphogenic earthquakes’ at about 5.5 degrees.  相似文献   

Archaeo- and palaeoseismological investigations in Northern Thessaly (Greece): Insights for the seismic potential of the region     

Riccardo Caputo  Bruno Helly  Spyros Pavlides  Gerassimos Papadopoulos 《Natural Hazards》2006,39(2):195-212

Northern Thessaly may represent an important seismic gap within the broader Aegean Region, with major faults bordering the ESE–WNW trending Late Pleistocene–Holocene Tyrnavos Basin. In order to obtain information about the characteristics of past earthquakes and improve our knowledge on the seismic potential of the investigated area, historical and archaeological observations are analysed and compared with the results of palaeoseismological trenches excavated across one of the major bordering structures, the Tyrnavos Fault. The former data clearly document (i) a strong seismic activity affecting the area during the last 2–3 ka and (ii) the occurrence of recent earthquakes not included in the seismic catalogues. Also, the sedimentological, structural and chronological data (TL, OSL and AMS) obtained from the palaeoseismological trenches indicate Late Pleistocene to Holocene morphogenic activity of the Tyrnavos Fault, characterised by vertical co-seismic displacements of 20–40 cm and possible return periods of a few thousands of years. Advantages and limitations in using historical and archaeoseismological data are discussed, as well as the problems arising from analysing low slip-rate faults.  相似文献   

From Middle Jurassic heating to Neogene cooling: The thermochronological evolution of the southern Alps     

Massimiliano Zattin  Andrea Cuman  Roberto Fantoni  Silvana Martin  Paolo Scotti  Cristina Stefani 《Tectonophysics》2006,414(1-4):191

The Dolomite region is located in the Southern Alps, which were affected by Mesozoic extensional tectonics and by consequent thermal perturbations. In this work, vitrinite reflectance and apatite fission-track analysis are used to estimate the thermal evolution. These methodologies have been applied to the Permo-Mesozoic succession, which crops out along the TRANSALP seismic profile. The regional distribution of the organic matter maturity seems to be mainly controlled by different burials reached during the Norian-Liassic extensional phase, in connection with high heat flow values. The best solutions obtained from thermal modelling of both vitrinite and fission-track data suggest that peak of high heat flow occurred during Bajocian–Bathonian ages, when western Tethys was characterized by intrusions of gabbros and plagiogranites and extrusion of tholeiite basalts. This time coincides with the onset of the drifting phase and related thermal subsidence. The following thermal relaxation occurred during continuous sedimentation and the maximum burial does not coincide with peak temperatures. Cooling history has been carefully analysed through apatite fission-track data on samples collected close to the Valsugana overthrust, which document an important exhumation event at about 10 Ma. The related erosion has been analysed through the combined use of arenite petrography and fission-track analysis on detrital samples of the Veneto foredeep succession, which represents the storage of detritus during Tertiary. These data confirm that after Serravalian the Southalpine domain and related covers were affected by subaerial erosion.  相似文献   

Transport of trace elements under different seasonal conditions: Effects on the quality of river water in a Mediterranean area   总被引：1，自引：0，他引：1  

Rosa Cidu  Riccardo Biddau 《Applied Geochemistry》2007,22(12):2777

Concentrations of total and dissolved elements were determined in 35 water samples collected from rivers in Sardinia, a Mediterranean island in Italy. The overall composition did not change for waters sampled in both winter and summer (i.e., January at high-flow condition and June at low-flow condition), but the salinity and concentrations of the major ions increased in summer. Concentrations of elements such as Li, B, Mn, Rb, Sr, Mo, Ba and U were higher in summer with only small differences between total and dissolved (i.e., in the fraction <0.4 μm) concentrations. The fact that these elements are mostly dissolved during low flow periods appears to be related to the intensity of water–rock interaction processes that are enhanced when the contribution of rainwater to the rivers is low, that is during low-flow conditions. In contrast, the concentrations of Al and Fe were higher in winter during high flow with total concentrations significantly higher than dissolved concentrations, indicating that the total amount depends on the amount of suspended matter. In waters filtered through 0.015 μm pore-size filters, the concentrations of Al and Fe were much lower than in waters filtered through 0.4 μm pore-size filters, indicating that the dissolved fraction comprises very fine particles or colloids. Also, Co, Ni, Cu, Zn, Cd and Pb were generally higher in waters collected during the high-flow condition, with much lower concentrations in 0.015 μm pore-size filtered waters; this suggests aqueous transport via adsorption onto very fine particles. The rare earth elements (REE) and Th dissolved in the river waters display a wide range in concentrations (∑REE: 0.1–23 μg/L; Th: <0.005–0.58 μg/L). Higher REE and Th concentrations occurred at high flow. The positive correlation between ∑REE and Fe suggests that the REE are associated with very fine particles (>0.015 and <0.4 μm); the abundance of these particles in the river controls the partitioning of REE between solution and solid phases.Twenty percent of the water samples had dissolved Pb and total Hg concentrations that exceeded the Italian guidelines for drinking water (>10 μg/L Pb and >1 μg/L Hg). The highest concentrations of these heavy metals were observed at high-flow conditions and they were likely due to the weathering of mine wastes and to uncontrolled urban wastes discharged into the rivers.  相似文献   

Hydrogeological and multi-isotopic approach to define nitrate pollution and denitrification processes in a coastal aquifer (Sardinia,Italy)     

Daniele Pittalis  Raul Carrey  Stefania Da Pelo  Alberto Carletti  Riccardo Biddau  Rosa Cidu  Fulvio Celico  Albert Soler  Giorgio Ghiglieri 《Hydrogeology Journal》2018,26(6):2021-2040

Agricultural coastal areas are frequently affected by the superimposition of various processes, with a combination of anthropogenic and natural sources, which degrade groundwater quality. In the coastal multi-aquifer system of Arborea (Italy)—a reclaimed morass area identified as a nitrate vulnerable zone, according to Nitrate Directive 91/676/EEC—intensive agricultural and livestock activities contribute to substantial nitrate contamination. For this reason, the area can be considered a bench test for tuning an appropriate methodology aiming to trace the nitrate contamination in different conditions. An approach combining environmental isotopes, water quality and hydrogeological indicators was therefore used to understand the origins and attenuation mechanisms of nitrate pollution and to define the relationship between contaminant and groundwater flow dynamics through the multi-aquifer characterized by sandy (SHU), alluvial (AHU), and volcanic hydrogeological (VHU) units. Various groundwater chemical pathways were consistent with both different nitrogen sources and groundwater dynamics. Isotope composition suggests a mixed source for nitrate (organic and synthetic fertilizer), especially for the AHU and SHU groundwater. Moreover, marked heterotrophic denitrification and sulfate reduction processes were detected; although, for the contamination related to synthetic fertilizer, the attenuation was inefficient at removing NO₃^? to less than the human consumption threshold of 50 mg/L. Various factors contributed to control the distribution of the redox processes, such as the availability of carbon sources (organic fertilizer and the presence of lagoon-deposited aquitards), well depth, and groundwater flow paths. The characterization of these processes supports water-resource management plans, future actions, and regulations, particularly in nitrate vulnerable zones.  相似文献   

Integration of rainfall thresholds and susceptibility maps in the Emilia Romagna (Italy) regional-scale landslide warning system   总被引：2，自引：2，他引：0  

Samuele Segoni  Daniela Lagomarsino  Riccardo Fanti  Sandro Moretti  Nicola Casagli 《Landslides》2015,12(4):773-785

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Exploring controls of the early and stepped deglaciation on the western margin of the British Irish Ice Sheet     

Sara Benetti  Richard C. Chiverrell  Colm Ó Cofaigh  Matt Burke  Alicia Medialdea  David Small  Colin Ballantyne  Mark D. Bateman  S. Louise Callard  Peter Wilson  Derek Fabel  Chris D. Clark  Riccardo Arosio  Sarah Bradley  Paul Dunlop  Jeremy C. Ely  Jenny Gales  Stephen J. Livingstone  Steven G. Moreton  Catriona Purcell  Margot Saher  Kevin Schiele  Katrien Van Landeghem  Kasper Weilbach 《第四纪科学杂志》2021,36(5):833-870

New optically stimulated luminescence dating and Bayesian models integrating all legacy and BRITICE-CHRONO geochronology facilitated exploration of the controls on the deglaciation of two former sectors of the British–Irish Ice Sheet, the Donegal Bay (DBIS) and Malin Sea ice-streams (MSIS). Shelf-edge glaciation occurred ~27 ka, before the global Last Glacial Maximum, and shelf-wide retreat began 26–26.5 ka at a rate of ~18.7–20.7 m a^–1. MSIS grounding zone wedges and DBIS recessional moraines show episodic retreat punctuated by prolonged still-stands. By ~23–22 ka the outer shelf (~25 000 km²) was free of grounded ice. After this time, MSIS retreat was faster (~20 m a^–1 vs. ~2–6 m a^–1 of DBIS). Separation of Irish and Scottish ice sources occurred ~20–19.5 ka, leaving an autonomous Donegal ice dome. Inner Malin shelf deglaciation followed the submarine troughs reaching the Hebridean coast ~19 ka. DBIS retreat formed the extensive complex of moraines in outer Donegal Bay at 20.5–19 ka. DBIS retreated on land by ~17–16 ka. Isolated ice caps in Scotland and Ireland persisted until ~14.5 ka. Early retreat of this marine-terminating margin is best explained by local ice loading increasing water depths and promoting calving ice losses rather than by changes in global temperatures. Topographical controls governed the differences between the ice-stream retreat from mid-shelf to the coast.  相似文献