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131.
Stefano Tinti Francesco Latino Chiocci Filippo Zaniboni Gianluca Pagnoni Giovanni de Alteriis 《Marine Geophysical Researches》2011,32(1-2):287-297
The island of Ischia, Gulf of Naples, Italy, like many other volcanic islands is affected by mass failures, that are mainly related to secondary volcanic processes such as slope steepening and seismic shaking. The block resurgence of its main relief, Mount Epomeo, has been recognised to contribute cyclically to mass instability and cause landslides, that occasionally may reach the sea and start tsunamis. In this work we explore the consequences of the Ischia Debris Avalanche (IDA), a flank collapse that occurred in historical times, and involved the whole Mount Epomeo edifice including its submarine portion, and that may have caused gigantic sea waves affecting all the coasts of Ischia and of the Gulf of Naples. The IDA and the generated tsunami have been taken as the worst-case scenario for the occurrence of a new tsunami in the area. They have been simulated through numerical codes developed and maintained by the University of Bologna. The simulation shows that the IDA-induced tsunami attacks severely all the coasts of the Gulf of Naples with the highest waves obtained for the island of Ischia, the island of Capri and the peninsula of Sorrento. The propagation pattern of the IDA tsunami can be used to get hints on the impact that such an event may have had on early populations habiting Gulf of Naples, but also to get clues on the area that could be most severely hit by a tsunami generated by a smaller-scale landslide that may occur in the same source zone. 相似文献
132.
Paolo D’Adda Andrea Zanchi Maria Bergomi Fabrizio Berra Marco G. Malusà Annalisa Tunesi Stefano Zanchetta 《International Journal of Earth Sciences》2011,100(5):1095-1113
The Triassic succession of the central Southern Alps (Italy) is stacked into several units bounded by south-verging low-angle
thrust faults, which are related to two successive steps of crustal shortening. The thrust surfaces are cut by high-angle
extensional and strike-slip faults, which controlled the emplacement of hypabissal magmatic intrusions that post-date thrusts
motions. Intrusion ages based on SHRIMP U–Pb zircon dating span between 42 ± 1 and 39 ± 1 Ma, suggesting close time relationships
with the earliest Adamello intrusion stages and, more in general, with the widespread calc-alkaline magmatism described in
the Southern Alps. Fission-track ages of magmatic apatites are indistinguishable from U–Pb crystallization ages of zircons,
suggesting that the intrusion occurred in country rocks already exhumed above the partial annealing zone of apatite (depth < 2–4 km).
These data indicate that the central Southern Alps were already structured and largely exhumed in the Middle Eocene. Although
we describe minor faults affecting magmatic bodies and local reactivations of older structures, no major internal deformations
have occurred in the area after the Bartonian. Neogene deformations were instead concentrated farther south, along the frontal
part of the belt. 相似文献
133.
Jian-Yang Li Lucille Le Corre Stefan E. Schröder Vishnu Reddy Brett W. Denevi Bonnie J. Buratti Stefano Mottola Martin Hoffmann Pablo Gutierrez-Marques Andreas Nathues Christopher T. Russell Carol A. Raymond 《Icarus》2013
Dawn spacecraft orbited Vesta for more than one year and collected a huge volume of multispectral, high-resolution data in the visible wavelengths with the Framing Camera. We present a detailed disk-integrated and disk-resolved photometric analysis using the Framing Camera images with the Minnaert model and the Hapke model, and report our results about the global photometric properties of Vesta. The photometric properties of Vesta show weak or no dependence on wavelengths, except for the albedo. At 554 nm, the global average geometric albedo of Vesta is 0.38 ± 0.04, and the Bond albedo range is 0.20 ± 0.02. The bolometric Bond albedo is 0.18 ± 0.01. The phase function of Vesta is similar to those of S-type asteroids. Vesta’s surface shows a single-peaked albedo distribution with a full-width-half-max ∼17% relative to the global average. This width is much smaller than the full range of albedos (from ∼0.55× to >2× global average) in localized bright and dark areas of a few tens of km in sizes, and is probably a consequence of significant regolith mixing on the global scale. Rheasilvia basin is ∼10% brighter than the global average. The phase reddening of Vesta measured from Dawn Framing Camera images is comparable or slightly stronger than that of Eros as measured by the Near Earth Asteroid Rendezvous mission, but weaker than previous measurements based on ground-based observations of Vesta and laboratory measurements of HED meteorites. The photometric behaviors of Vesta are best described by the Hapke model and the Akimov disk-function, when compared with the Minnaert model, Lommel–Seeliger model, and Lommel–Seeliger–Lambertian model. The traditional approach for photometric correction is validated for Vesta for >99% of its surface where reflectance is within ±30% of global average. 相似文献
134.
Axelle Bouiges Amir Yassin Maya Ikogou Clément Lelarge Axelle-Rolande Sikoa Stefano Mona Michel Veuille 《Comptes Rendus Geoscience》2013,345(7-8):297-305
Previous genetic studies showing evidence of past demographic changes in African drosophilids suggested that these populations had strongly responded to Quaternary climate changes. We surveyed nine species of Zaprionus, a drosophilid genus mostly present in Africa, in forests located between southern Senegal and Gabon. The mitochondrial COI gene showed contrasted levels of sequence variation across species. Populations of the only cosmopolitan species of the genus, Z. indianus, and of its closely related sibling species, Z. africanus, are highly polymorphic and appear to have undergone a continuous population expansion beginning about 130,000 years ago. Five less variable species probably underwent a population expansion beginning only about 20,000–30,000 years ago. One of them, Z. taronus, was significantly structured between forest blocks. The last two species were nearly monomorphic, probably due to infection by Wolbachia. These results are similar to those obtained in three species from the melanogaster subgroup, and may be typical of the responses of African drosophilid populations to glacial cycles. 相似文献
135.
A DNA tracer used in column tests for hydrogeology applications 总被引:1,自引:1,他引:0
Lucia Aquilanti Francesca Clementi Sara Landolfo Torquato Nanni Stefano Palpacelli Alberto Tazioli 《Environmental Earth Sciences》2013,70(7):3143-3154
Tracing techniques are commonly used to investigate groundwater quality and dynamics, as well as to measure the hydrogeological parameters of aquifers. The last decade has seen a growing interest in environmentally friendly tracers, including single-stranded DNA molecules. In this study, an electrolytic tracer and a synthetic DNA tracer are comparatively evaluated in laboratory scale tests to assess their potential application in field studies aimed at investigating groundwater environments. A real-time quantitative Polymerase Chain Reaction assay was developed and optimized to detect and quantify the DNA tracer, while tracer column tests were performed to investigate the DNA tracer behavior and to compare it to the electrolytic tracer. The results show that the DNA tracer has an almost pure convective flow, while the KCl tracer experiences dispersive behavior. The tracing method proposed can be applied in hydrogeological field studies involving calcareous fractured rock systems, with the DNA tracer particularly suitable in tracing karst systems, which are often characterized by several conduits of flow. To test the DNA tracer in operation, a preliminary test was conducted in the field. 相似文献
136.
A review of research on seismic behaviour of irregular building structures since 2002 总被引:1,自引:1,他引:0
The paper presents an overview of the progress in research regarding seismic response of plan and vertically irregular building
structures. Three areas of research are surveyed. The first is the study of the effects of plan-irregularity by means of single-storey
and multi-storey building models. The second area encompasses passive control as a strategy to mitigate torsional effects,
by means of base isolation and other types of devices. Lastly, the third area concerns vertically irregular structures and
setback buildings. Although fewer papers have been published in this last area with respect to the former ones, this state-of-the-art
reports extensively on research efforts and progress into the seismic behaviour of irregular buildings in elevation to show
the growing interest among specialists in the field. 相似文献
137.
Stefano Lanzoni 《Acta Geophysica》2008,56(3):734-752
The paper describes the derivation of a depth-averaged, two-dimensional form of the sediment balance equation, suitable to study the morphodynamics of movable sediment beds even when the flow depth attains values comparable to bed irregularities. This equation is derived by double-averaging in time and in space the instantaneous three-dimensional sediment balance equation. For this, a proper phase function is introduced, which depends on the statistics of bed topography. The structure of the macroscopic volumetric sediment discharge vector resulting from the averaging procedure is discussed for the case of dominant bedload transport. The theoretical framework developed within the paper sets the stage for a proper parametrization of the physical processes acting at spatial scales smaller than those usually resolved by depthaveraged numerical models. 相似文献
138.
Alberto?RenzulliEmail author Stefano?Del?Moro Michele?Menna Patrizia?Landi Marco?Piermattei 《Bulletin of Volcanology》2009,71(7):795-813
We describe the mineralogy, geochemistry, and mesomicrostructure of fresh subvolcanic blocks erupted during the 5 April 2003
paroxysm of Stromboli (Aeolian Islands, Italy). These blocks represent ∼50 vol.% of the total erupted ejecta and consist of
fine- to medium-grained basaltic lithotypes ranging from relatively homogeneous dolerites to strongly or poorly welded magmatic
breccias. The breccia components are represented by angular fragments of dolerites entrapped in a matrix of vesiculated (lava-like
to scoriae) crystal-rich (CR) basalt. All of the studied blocks are cognates with the CR basalt of the normal Strombolian
activity or lavas and they are often coated by a few-centimeter thick layer of crystal-poor (CP) basaltic pumice erupted during
the paroxysm. We suggest that they result from the rapid increase of pressure and related subvolcanic rock failure that occurred
shortly before the 5 April 2003 explosion, when the uppermost portion of the edifice inflated and suffered brecciation as
the result of the sudden rise of the gas-rich CP basalt that triggered the eruption. Dolerites and magmatic matrix of the
breccias show major and trace element compositions that match those of the CR basalts erupted during normal Strombolian activity
and effusive events at Stromboli volcano. Dolerites consist of (a) phenocrysts normally found in the CR basalts and (b) late-stage
magmatic minerals such as sanidine, An60-28 plagioclase, Fe–Mn-rich olivines (Fo68-48), phlogopite, apatite, and opaque mineral pairs (magnetite and ilmenite), most of which are never found both in lava flows
and scoriae erupted during the persistent explosive activity that characterizes typical Strombolian behavior. Subvolcanic
crystallization of the Stromboli CR magma, leading to slowly cooled equivalents of basalts, could result from transient drainage
of the magma from the summit craters to lower levels. Fingering and engulfing of the material that collapsed from the summit
crater floor into the shallow basaltic system during the late evening of 28 December 2002 coupled with the short break in
the summit persistent explosions between December 2002 and March 2003 permitted the CR magma pockets to solidify as dolerites,
which were confined to the uppermost portion of the system and thus not involved in the ongoing flank effusive activity. Crystal
size distribution of the basaltic blocks and crystallization of the finer-grained (<0.1 mm) mafic minerals of the dolerites
over a time interval of ∼100 days closely agrees with the above interpretation. Vesicle filling (miarolitic cavities) locally
found in some dolerites, with minerals deposited as vapor-phase crystallization is a result of continuous gas percolation
through the rocks of the uppermost portion of the volcanic system. Poorly welded magmatic breccias formed during syn-eruptive processes of 5 April 2003, when the paroxysm strongly shattered the shallow subvolcanic system and many dolerite
fragments were entrapped in the CR magma. In contrast, the high degree of welding between the dolerite clasts and the CR basaltic
matrix in the strongly welded magmatic breccias provides a snapshot of subvolcanic intrusions of the CR basalt into the dolerite
when, after a 2-month break in activity, CR magmas started to rise again to the summit craters. Blocks similar to these subvolcanic
ejecta of 5 April 2003 were also erupted during previous paroxysms (e.g., 1930) suggesting that changes in the usual Strombolian
activity (e.g., short breaks in the persistent mild explosions and/or flank effusive activity) lead to transient crystallization
of dolerites in the shallow plumbing system. 相似文献
139.
Stefano Catalano Giorgio De Guidi Gianni Lanzafame Carmelo Monaco Luigi Tortorici 《Journal of Geodynamics》2009,48(2):75-82
Structural observations carried out on the volcanic Island of Pantelleria show that the tectonic setting is dominated by NNE trending normal faults and by NW-striking right-lateral strike-slip faults with normal component of motion controlled by a ≈N 100°E oriented extension. This mode of deformation also controls the development of the eruptive fissures, dykes and eruptive centres along NNE–SSW belts that may thus represent the surface response to crustal cracking with associated magma intrusions. Magmatic intrusions are also responsible for the impressive vertical deformations that affect during the Late Quaternary the south-eastern segment of the island and producing a large dome within the Pantelleria caldera complex. The results of the structural analysis carried out on the Island of Pantelleria also improves the general knowledge on the Late Quaternary tectonics of the entire Sicily Channel. ESE–WNW directed extension, responsible for both the tectonic and volcano-tectonic features of the Pantelleria Island, also characterizes, at a greater scale, the entire channel as shown by available geodetic and seismological data. This mode of extension reactivates the older NW–SE trending fault segments bounding the tectonic troughs of the Channel as right-lateral strike-slip faults and produces new NNE trending pure extensional features (normal faulting and cracking) that preferentially develop at the tip of the major strike-slip fault zones. We thus relate the Late Quaternary volcanism of the Pelagian Block magmatism to dilatational strain on the NNE-striking extensional features that develop on the pre-existing stretched area and propagate throughout the entire continental crust linking the already up-welled mantle with the surface. 相似文献
140.
Exploring the impact of diagenesis on (isotope) geochemical and microstructural alteration features in biogenic aragonite 下载免费PDF全文
Ann‐Christine Ritter Vasileios Mavromatis Martin Dietzel Ola Kwiecien Felix Wiethoff Erika Griesshaber Laura A. Casella Wolfgang W. Schmahl Jennifer Koelen Rolf D. Neuser Albrecht Leis Dieter Buhl Andrea Niedermayr Sebastian F. M. Breitenbach Stefano M. Bernasconi Adrian Immenhauser 《Sedimentology》2017,64(5):1354-1380
For the Quaternary and Neogene, aragonitic biogenic and abiogenic carbonates are frequently exploited as archives of their environment. Conversely, pre‐Neogene aragonite is often diagenetically altered and calcite archives are studied instead. Nevertheless, the exact sequence of diagenetic processes and products is difficult to disclose from naturally altered material. Here, experiments were performed to understand biogenic aragonite alteration processes and products. Shell subsamples of the bivalve Arctica islandica were exposed to hydrothermal alteration. Thermal boundary conditions were set at 100°C, 175°C and 200°C. These comparably high temperatures were chosen to shorten experimental durations. Subsamples were exposed to different 18O‐depleted fluids for durations between two and twenty weeks. Alteration was documented using X‐ray diffraction, cathodoluminescence, fluorescence and scanning electron microscopy, as well as conventional and clumped isotope analyses. Experiments performed at 100°C show redistribution and darkening of organic matter, but lack evidence for diagenetic alteration, except in Δ47 which show the effects of annealing processes. At 175°C, valves undergo significant aragonite to calcite transformation and neomorphism. The δ18O signature supports transformation via dissolution and reprecipitation, but isotopic exchange is limited by fluid migration through the subsamples. Individual growth increments in these subsamples exhibit bright orange luminescence. At 200°C, valves are fully transformed to calcite and exhibit purple‐blue luminescence with orange bands. The δ18O and Δ47 signatures reveal exchange with the aqueous fluid, whereas δ13C remains unaltered in all experiments, indicating a carbonate‐buffered system. Clumped isotope temperatures in high‐temperature experiments show compositions in broad agreement with the measured temperature. Experimentally induced alteration patterns are comparable with individual features present in Pleistocene shells. This study represents a significant step towards sequential analysis of diagenetic features in biogenic aragonites and sheds light on reaction times and threshold limits. The limitations of a study restricted to a single test organism are acknowledged and call for refined follow‐up experiments. 相似文献