Ionospheric total electron content and critical frequencies over Europe at solar minimum     

Ljiljana R. Cander  Luigi Ciraolo 《Acta Geophysica》2010,58(3):468-490

The paper presents results obtained by analyzing high-resolution ionospheric vertical total electron content (vTEC) data set evaluated from a chain of European ground-based Global Positioning System (GPS) stations and its equivalent slab thickness, as well as the F2-layer critical frequency foF2 and propagation factor M(3000)F2 from nearby ionosonde stations over the period 2006–2007. The study covers data within an area between 36°N and 68°N geographic latitude, and 7°W and 21°E geographic longitude during these last two years of minimum solar activity in the 23rd solar cycle. It reveals 15 extraordinary events, all of which exhibited some form of large short-lived vTEC and foF2 enhancements of the duration of small-magnitude solar-terrestrial events. The results clearly show a well-defined vTEC and foF2 storm-like disturbance patterns developed under these conditions. They prove that there are still some open questions related to the large electron density variations during weak disturbances that require additional study for both their relevance to different Global Navigation Satellite Systems (GNSS) applications and their role in the formation and evolution of the daytime ionosphere at middle latitudes.  相似文献   

Soil–pile–structure interaction: experimental outcomes from shaking table tests          下载免费PDF全文

Maria Giovanna Durante  Luigi Di Sarno  George Mylonakis  Colin A. Taylor  Armando Lucio Simonelli 《地震工程与结构动力学》2016,45(7):1041-1061

An effective way to study the complex seismic soil‐structure interaction phenomena is to investigate the response of physical scaled models in 1‐g or n‐g laboratory devices. The outcomes of an extensive experimental campaign carried out on scaled models by means of the shaking table of the Bristol Laboratory for Advanced Dynamics Engineering, University of Bristol, UK, are discussed in the present paper. The experimental model comprises an oscillator connected to a single or a group of piles embedded in a bi‐layer deposit. Different pile head conditions, that is free head and fixed head, several dynamic properties of the structure, including different masses at the top of the single degree of freedom system, excited by various input motions, e.g. white noise, sinedwells and natural earthquake strong motions recorded in Italy, have been tested. In the present work, the modal dynamic response of the soil–pile–structure system is assessed in terms of period elongation and system damping ratio. Furthermore, the effects of oscillator mass and pile head conditions on soil–pile response have been highlighted, when the harmonic input motions are considered. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Amplifying (or Reversing) the Territorial Disparities in Land Vulnerability to Soil Degradation: The Case of Italy     

Luca Salvati  Sofia Bajocco  Tomaso Ceccarelli  Luigi Perini 《The Professional geographer》2013,65(4):647-663

This article analyzes the territorial disparities in the level of land vulnerability (TDLV) to soil degradation caused by five processes (soil erosion, salinization, sealing, contamination, and compaction) as well as by climate variations in Italy in 1990 and 2000. The analysis reveals, for each soil degradation process, a typical spatial distribution across Italy. Three processes (soil salinization, compaction, and sealing) contribute significantly to the increase in land vulnerability, which is mainly concentrated in risky areas. The observed disparities highlight a growing environmental divide between northern Italy (an economically developed region, not at risk of desertification) and southern Italy and the two main islands (dry, disadvantaged regions at risk of desertification). The knowledge of such a territorial divide and of the underlying soil degradation processes is regarded as important for environmental policies at the country and regional scales aimed at sustaining the economic and socioenvironmental cohesion between areas that are either vulnerable or nonvulnerable to soil degradation. The proposed approach should be seen as part of a decision-making tool informing policies and supporting the design of management solutions, hopefully reversing disparities in land vulnerability to soil degradation.  相似文献   

The predictability of meteo-oceanographic events   总被引：1，自引：1，他引：0  

Luciana Bertotti  Luigi Cavaleri 《Ocean Dynamics》2011,61(9):1391-1402

We have explored the predictability of storms in a small enclosed basin with a complicated surrounding orography. We have considered two exceptional storms in the far past and three mild events happened in recent years. A posteriori forecasts have been done up to 6 days before the events. The results have been compared versus measured data and the related analysis. Good predictability (10–15% error in surface wind speed and wave height) have been found up to day 4, mildly larger (<30%) up to day 6 before the event. In no case was a storm missed. This suggests that the effective predictability in more open basins may extend to even larger ranges.  相似文献   

Early Bartonian orthophragminids (Foraminiferida) from Reineche Limestone,north African platform,Tunisia: taxonomy and paleobiogeographic implications     

Kmar Ben İsmail-Lattrache  Kamel Boukhalfa  Pratul Kumar Saraswati  Mohamed Soussi  Luigi Jovane 《Geodinamica Acta》2013,26(1-2):94-121

The orthophragminids in lower Bartonian Reineche Limestone member, a fossiliferous shallow-marine unit exposed in Cap Bon peninsula in Tunisia, are represented by 17 species assigned to Discocyclinidae Galloway 1928 and Orbitoclypeidae Brönnimann 1946. These taxa, associated with nummulitids and alveolinids, belong to the lineages of Discocyclina Gümbel 1870, Nemkovella, 1987, Orbitoclypeus Silvestri 1907, and Asterocyclina Gümbel 1870, described for the first time from north Africa lying at the southern margin of Tethyan ocean during Paleogene. We identified Nemkovella evae, previously not recorded in upper Lutetian/lower Bartonian and younger Eocene deposits of northern Tethyan platforms, and erected a new subspecies, N. evae reinechensis n. ssp. A comparison of Reineche orthophraminids, assigned to orthophragmines zone (OZ) 12 and shallow benthic zone (SBZ 17), to the well-described coeval assemblages at northern Tethyan platforms in Italy, Hungary, Turkey, and to those in Kutch Basin in the Indian subcontinent suggests that some species are confined to certain paleogeographic domains. Orbitoclypeus haynesi, the only orbitoclypeid and the most abundant orthophragminid in lower Bartonian deposits in Kutch, appears to be the most common orbitoclypeid in Reineche Limestone. In Europe, this species is not known and is replaced by Orbitoclypeus varians, the most common orbitoclypeid in middle Eocene of central Europe. Both species occur in varying proportions in marine successions in Turkey. Asterocyclina sireli, identified so far only in Turkey, occurs in Reineche Limestone and in lower Bartonian deposits in Kutch. This species is recorded for the first time in the Indian subcontinent. Relying on present study, as well as our recent studies in Kutch Basin, we conclude that the generic and specific diversity of orthophragminids decreases eastward from the peri-Mediterranean region to Indian subcontinent and to the western Pacific.  相似文献   

Discriminating the long distance dispersal of fine ash from sustained columns or near ground ash clouds: The example of the Pomici di Avellino eruption (Somma-Vesuvius,Italy)     

Roberto Sulpizio  Rosanna Bonasia  Pierfrancesco Dellino  Mauro A. Di Vito  Luigi La Volpe  Daniela Mele  Giovanni Zanchetta  Laura Sadori 《Journal of Volcanology and Geothermal Research》2008

Ash samples from tephra layers correlated with the Pomici di Avellino (Avellino Pumice) eruption of Somma-Vesuvius were collected in distal archives and their composition and particle morphology investigated in order to infer their behaviour of transportation and deposition. Differences in composition and particle morphologies were recognised for ash particles belonging to the magmatic Plinian and final phreatomagmatic phases of the eruption. The ash particles were dispersed in opposite directions during the two different phases of the eruption, and these directions are also different from that of coarse-grained fallout deposits. In particular, ash generated during magmatic phase and injected in the atmosphere to form a sustained column shows a prevailing SE dispersion, while ash particles generated during the final phreatomagmatic phase and carried by pyroclastic density currents show a general NW dispersion. These opposite dispersions indicate an ash dispersal influenced by both high and low atmosphere dynamics. In particular, the magmatic ash dispersal was first driven by stratospheric wind towards NE and then the falling particles encountered a variable wind field during their settling, which produced the observed preferential SE dispersal. The wind field encountered by the rising ash clouds that accompanied the pyroclastic density currents of the final phreatomagmatic phase was different with respect to that encountered by the magmatic ash, and produced a NW dispersal. These data demonstrate how ash transportation and deposition are greatly influenced by both high and low atmosphere dynamics. In particular, fine-grained particles transported in ash clouds of small-scale pyroclastic density currents may be dispersed over distances and cover areas comparable with those injected into the stratosphere by Plinian, sustained columns. This is a point not completely addressed by present day mitigation plans in case of renewal of activity at Somma-Vesuvius, and can yield important information also for other volcanoes potentially characterised by explosive activity.  相似文献   

Simulations of the 2004 lava flow at Etna volcano using the magflow cellular automata model     

Ciro Del Negro  Luigi Fortuna  Alexis Herault  Annamaria Vicari 《Bulletin of Volcanology》2008,70(7):805-812

Since the mechanical properties of lava change over time, lava flows represent a challenge for physically based modeling. This change is ruled by a temperature field which needs to be modeled. MAGFLOW Cellular Automata (CA) model was developed for physically based simulations of lava flows in near real-time. We introduced an algorithm based on the Monte Carlo approach to solve the anisotropic problem. As transition rule of CA, a steady-state solution of Navier-Stokes equations was adopted in the case of isothermal laminar pressure-driven Bingham fluid. For the cooling mechanism, we consider only the radiative heat loss from the surface of the flow and the change of the temperature due to mixture of lavas between cells with different temperatures. The model was applied to reproduce a real lava flow that occurred during the 2004–2005 Etna eruption. The simulations were computed using three different empirical relationships between viscosity and temperature.  相似文献   

Late Quaternary deformation on the island on Pantelleria: New constraints for the recent tectonic evolution of the Sicily Channel Rift (southern Italy)     

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   

Latest Miocene to Quaternary horizontal and vertical displacement rates during simultaneous contraction and extension in the Southern Apennines orogen, Italy     

Luigi Ferranti  John S. Oldow 《地学学报》2005,17(3):209-214

Foreland contraction and hinterland extension in the Southern Apennines orogen of Italy produced a complex spatial and temporal pattern of vertical and horizontal displacement. Remarkably, Late Miocene to mid-Pleistocene foreland migration of the contractional front at ∼16 mm yr⁻¹ was not accompanied by uplift and the frontal thrust belt remained at or below sea level. Only following a mid-Pleistocene reduction in horizontal displacement did the frontal thrust belt and foreland begin uplift at ∼0.5 mm yr⁻¹, a rate that increased to ∼1 mm yr⁻¹ after 125 ka. Although the extensional hinterland experienced net subsidence during formation of the Tyrrhenian basin, an extensional transition zone adjacent to the frontal thrust belt records sustained uplift at ∼0.3 mm yr⁻¹. The interaction of preexisting crustal structure and deep tectonic processes resulted in time-integrated displacement rates suggesting steady-state deformation for periods of 10⁶ years. Displacement rate changes were abrupt and occurred over intervals of 10⁵ years or less.  相似文献   

Active thrust tectonics in western Sicily (southern Italy): the 1968 Belice earthquake sequence     

Carmelo Monaco  Stefano Mazzoli  Luigi Tortorici 《地学学报》1996,8(4):372-381

The 1968 Belice earthquake sequence, characterized by six main shocks with 5 < M < 5.4, represents the strongest seismic event recorded in western Sicily in historical times. The epicentral area is located in the Belice Valley, a region lacking any topographic lineament likely to result from a fault with significant offsets of any kind. Instrumental data show that hypocentres of the major shocks are distributed along a roughly N-dipping plane extending from about 36 km to 1 km depth. Fault plane solutions show pure thrusting mechanisms on N-dipping, ENE-trending planes, or oblique slip with a right-lateral component of motion along steep WSW-dipping planes, both as a result of approximate N-S shortening. The observed destruction indicates that isoseismal areas are elongated in an ENE direction. Similarly, the epiccntral distribution of events with M ≥ 4 outlines a roughly elliptical ENE-elongated area located 20 km NW of the Sciacca-Rocca Ficuzza thrust front. This ENE-striking structure, representing the regional morphotectonic feature closest to the epicentral area, consists of two main imbricate fan systems. In the southernmost system, Quaternary deposits (tentatively dated as 1.0–0.7 Myr old) are involved in a large ramp anticline uplifting them to a maximum altitude of 346 m. The occurrence of Holocene lacustrine piggy-back basins on the rear of this structure also indicates late Quaternary activity of the underlying thrust. Seismological, structural and morphotectonic observations suggest that multiple ruptures might have occurred during the 1968 sequence on a blind crustal thrust ramp located beneath the epicentral area. Slip propagated southwards along the shallow ramp-flat system characterizing the thin-skinned foreland fold and thrust belt of southwestern Sicily, being dispersed in flexural folding processes and diffuse strain along this path.  相似文献