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91.
F. Bozzano L. Lenti Salvatore Martino A. Paciello G. Scarascia Mugnozza 《International Journal of Earth Sciences》2011,100(4):861-879
The basin-like setting of stiff bedrock combined with pre-existing landslide masses can contribute to seismic amplifications
in a wide frequency range (0–10 Hz) and induce a self-excitation process responsible for earthquake-triggered landsliding.
Here, the self-excitation process is proposed to justify the far-field seismic trigger of the Cerda landslide (Sicily, Italy)
which was reactivated by the 6th September 2002 Palermo earthquake (M
s = 5.4), about 50 km far from the epicentre. The landslide caused damage to farm houses, roads and aqueducts, close to the
village of Cerda, and involved about 40 × 106 m3 of clay shales; the first ground cracks due to the landslide movement formed about 30 min after the main shock. A stress–strain
dynamic numerical modelling, performed by FDM code FLAC 5.0, supports the notion that the combination of local geological
setting and earthquake frequency content played a fundamental role in the landslide reactivation. Since accelerometric records
of the triggering event are not available, dynamic equivalent inputs have been used for the numerical modelling. These inputs
can be regarded as representative for the local ground shaking, having a PGA value up to 0.2 m/s2, which is the maximum expected in 475 years, according to the Italian seismic hazard maps. A 2D numerical modelling of the
seismic wave propagation in the Cerda landslide area was also performed; it pointed out amplification effects due to both
the structural setting of the stiff bedrock (at about 1 Hz) and the pre-existing landslide mass (in the range 3–6 Hz). The
frequency peaks of the resulting amplification functions (A(f)) fit well the H/V spectral ratios from ambient noise and the H/H spectral ratios to a reference station from earthquake records, obtained by in situ velocimetric measurements. Moreover,
the Fourier spectra of earthquake accelerometric records, whose source and magnitude are consistent with the triggering event,
show a main peak at about 1 Hz. This frequency value well fits the one amplified by the geological setting of the bedrock
in correspondence with the landslide area, which is constituted of marly limestones and characterised by a basin-like geometry. 相似文献
92.
93.
Restoration of the eutrophic Orbetello lagoon (Tyrrhenian Sea, Italy): water quality management 总被引:2,自引:0,他引:2
The Orbetello lagoon (Tyrrhenian coast, Italy) receives treated urban and land based fishfarms wastewater. The development of severe eutrophication imposed the three main activity adoption focuses on (1) macroalgae harvesting; (2) pumping of water from the sea; (3) confining wastewater to phytotreatment ponds. The responses to these interventions were rapid and macroalgal reduction growth and seagrass return were recorded. Since 1999, a new macroalgal development was recorded. The aim of this research was to discover whether the recent macroalgal growth can be attributed to the continuing wastewater influx from the remaining persistent anthropic sources (PAS) or from the sediment nutrient release. A monitoring programme was carried out between August 1999 and July 2000 in order to measure dissolved inorganic nitrogen and phosphorus in the wastewaters entering into the lagoon and in central lagoon areas, seaweed and seagrass distribution and lagoon N, P annual budgets. The results showed higher N and P values close to PAS. The distribution of the macroalgal species confirms that the available P comes almost entirely from these remaining PAS. In conclusion, the environmental measures adopted produced a significant reduction in algal biomass development in the lagoon; the macroalgal harvesting activities produced a sediment disturbance with following oxidize conditions, which make P unavailable in the lagoon water, excepting close the PAS. 相似文献
94.
Salvatore Alparone Graziella Barberi Alessandro Bonforte Vincenza Maiolino Andrea Ursino 《Bulletin of Volcanology》2011,73(7):869-885
We carried out a study of the seismicity and ground deformation occurring on Mt. Etna volcano after the end of the 2002–2003
eruption and before the onset of the 2004–2005 eruption. Data were recorded by the permanent local seismic network run by
Istituto Nazionale di Geofisica e Vulcanologia – Sezione di Catania and by geodetic surveys carried out in July 2003 and July 2004 on the GPS network. Most earthquakes were grouped in two main
clusters located in the northeastern and southeastern sectors of the volcano. The areal distribution of seismic energy associated
with the recorded earthquakes allowed us to highlight the main seismogenic areas of Mt. Etna. In order to better understand
the kinematic processes of the volcano, 3D seismic locations were used to compute fault plane solutions, and a selected dataset
was inverted to determine stress and strain tensors. The focal mechanisms in the northeastern sector show clear left-lateral
kinematics along an E-W fault plane, consistent with events occurring along the Pernicana Fault system. The fault plane solutions
in the southeastern sector show mainly right-lateral kinematics along a NNE and ENE fault plane and left lateral-kinematics
along NW fault planes that together suggest roughly E-W oriented compression. Surface ground deformation affecting Mt. Etna
measured by GPS surveys highlighted a marked inflation during the same period and exceptionally strong seawards motion of
its eastern flank. The 2D geodetic strain tensor distribution was calculated and the results show mainly ENE-WSW extension
coupled with WNW-ESE contraction, indicating right-lateral shear along a NW-SE oriented fault plane. The different deformation
of the eastern sector of the volcano, as measured by seismicity and ground deformation, must be interpreted by considering
the different depths of the two signals. Seismic activity in the southeastern sector of volcano is located between 3 and 8 km b.s.l.
and can be associated with a very strong additional E-W compression induced by a pressurizing source just westwards and at
the same depth, located by inverting GPS data. Ground deformation, in contrast, is mainly affected by the shallower dynamics
of the fast moving eastern flank which produces a shallower opposing E-W extension. The entire dataset shows that two different
processes affect the eastern flank at the same time but at different depths; the boundary is clearly located at a depth of
3 km b.s.l. and could represent the décollement surface for the mobile flank. 相似文献
95.
Louise Crochemore Charles Perrin Vazken Andréassian Uwe Ehret Simon P. Seibert Salvatore Grimaldi 《水文科学杂志》2013,58(3):402-423
AbstractThis paper investigates the relationship between expert judgement and numerical criteria when evaluating hydrological model performance by comparing simulated and observed hydrographs. Using a web-based survey, we collected the visual evaluations of 150 experts on a set of high- and low-flow hydrographs. We then compared these answers with results from 60 numerical criteria. Agreement between experts was found to be more frequent in absolute terms (when rating models) than in relative terms (when comparing models), and better for high flows than for low flows. When comparing the set of 150 expert judgements with numerical criteria, we found that most expert judgements were loosely correlated with a numerical criterion, and that the criterion that best reflects expert judgement varies from expert to expert. Overall, we identified two groups of 10 criteria yielding an equivalent match with the expertise of the 150 participants in low and high flows, respectively. A single criterion common to both groups (the Hydrograph Matching Algorithm with mean absolute error) may represent a good indicator for the overall evaluation of models based on hydrographs. We conclude that none of the numerical criteria examined here can fully replace expert judgement when rating hydrographs, and that both relative and absolute evaluations should be based on the judgement of multiple experts.
Editor D. Koutsoyiannis 相似文献
96.
97.
Andrea Cannata Iole Serena Diliberto Salvatore Alparone Salvatore Gambino Stefano Gresta Marcello Liotta Paolo Madonia Vincenzo Milluzzo Marco Aliotta Placido Montalto 《Pure and Applied Geophysics》2012,169(1-2):167-182
Seismic activity, ground deformation, and soil and fumarole temperatures acquired during 2004–2007 at Vulcano (Aeolian Islands) are analysed and the time relations among the different time series are discussed. Changes in temperature of fumarolic gases took place during four “anomalous” periods (November 2004–March 2005; October 2005–February 2006; August–October 2006; July–December 2007) at the same time as an increasing number of volcano-seismic events. In particular, the temperatures at high temperature vents and at steam heated soil ranged in time from 180 to 440°C and from 20 to 90°C, respectively. The maximum daily number of volcano-seismic events was 57, reached during the second anomalous period. This seismicity, characterised by focal depth generally lower than 1?km below sea level (b.s.l.) and composed of different kinds of events associated to both resonance and shear failure processes, is related to the shallow dynamics of the hydrothermal system. During the analysed period, very few volcano-tectonic earthquakes took place and tilt recordings showed no sharp or important changes. In light of such observations, the increases in both temperature and volcano-seismic events number were associated to increases in the release of gas from a deep and stable magma body, without magma intrusions within the shallow hydrothermal system. Indeed, a greater release of gas from depth leads to increased fluid circulation, that can promote increases in volcano-seismic events number by both fracturing processes and resonance and vibration in cracks and conduits. The different trends observed in the measured geochemical and geophysical series during the anomalous periods can be due to either time changes in the medium permeability or a changing speed of gas release from a deep magma body. Finally, all the observed variations, together with the changing temporal distribution of the different seismic event kinds, suggest that the hydrothermal system at Vulcano can be considered unsteady and dynamic. 相似文献
98.
Luigia Di Nicola Stefan Strasky Maria Cristina Salvatore Peter W. Kubik Haino Uwe Kasper Carlo Baroni 《Quaternary Research》2009,71(1):83-149
Geomorphological and glacial geological surveys and multiple cosmogenic nuclide analyses (10Be, 26Al, and 21Ne) allowed us to reconstruct the chronology of variations prior to the last glacial maximum of the East Antarctic Ice Sheet (EAIS) and valley glaciers in the Terra Nova Bay region. Glacially scoured coastal piedmonts with round-topped mountains occur below the highest local erosional trimline. They represent relict landscape features eroded by extensive ice overriding the whole coastal area before at least 6 Ma (pre-dating the build-up of the Mt. Melbourne volcanic field). Since then, summit surfaces were continuously exposed and well preserved under polar condition with negligible erosion rates on the order of 17 cm/Ma. Complex older drifts rest on deglaciated areas above the younger late-Pleistocene glacial drift and below the previously overridden summits. The combination of stable and radionuclide isotopes documents complex exposure histories with substantial periods of burial combined with minimal erosion. The areas below rounded summits were repeatedly exposed and buried by ice from local and outlet glaciers. The exposure ages of the older drift(s) indicate multiple Pleistocene glacial cycles, which did not significantly modify the pre-existing landscape. 相似文献
99.
Herbert W. Schnopper Eric Silver Stephen Murray Suzanne Romaine Simon Bandler Christine Jones William Forman Norman Madden Jeffery Beeman Eugene Haller Finn Christensen Niels Westergaard Juan Fabregat Victor Reglero Alvaro Gimenez Noah Brosch Elia Liebowitz Hagai Netzer Marco Barbera Alfonso Collura Salvatore Sciortino 《Astrophysics and Space Science》2001,276(1):49-65
The X-Ray Spectroscopic Explorer (XRASE) has a unique combination of features that will make it possible to address many of NASA's scientific goals. These include how galaxy clusters form, the physics and chemistry of the ISM, the heating of stellar coronae, the amount and content of intergalactic baryonic matter, the mass of black holes and the formation of disks and jets in AGN and galactic binaries. XRASE has a thin foil, multilayered telescope with a large collecting area up to 10 keV, especially in the Fe K region (1100 cm2). Its microcalorimeter array combines high energy resolution (7 eV at 6 keV) and efficiency with a field-of-view of 26 arcmin2 . A deep orbit allows for long, continuous observations. Monitoring instruments in the optical (WOM-X), UV (TAUVEX) and hard X-RAY (GRAM) bands will offer exceptional opportunities to make simultaneous multi-wavelength observations. 相似文献
100.
Plutonic and gneissic rocks of the Sila Massif in the uppermost portion of the Neto drainage basin (Calabria, Southern Italy) weather and erode under a humid Mediterranean climate. During the development of weathering profiles, a combination of chemical weathering and granular disintegration processes occurred. Chemical weathering involves a loss of both plagioclase (mainly during grus generation) and K-feldspar (mainly during soil formation). This loss is attributed to transformation of plagioclase to clay minerals and to leaching and dissolution of K-feldspar. Sand composition is quartzofeldspathic and nearly homogeneous along the main channel of the Neto River, even where the river cuts across a blanket of sedimentary cover. Thus, fluvial transport does not alter sand composition within the Neto drainage basin. Petrographic indices are effective in (1) discriminating between contributions from similar (granite and gneiss) source rocks (Qm/F); (2) relating the provenance of plutoniclastic and gneissiclastic sand found in the headwaters to grus horizons (Qm/F; Q/Rg); and (3) distinguishing between upstream first-cycle and downstream multicycle sand (Q/Rg). This last distinction is further emphasized by considering both aphanitic and phaneritic varieties of rock fragments (RgRmRs diagram). Chemical weathering is the main sand producer within the regolithic environment in northern Calabria. In addition, rapid erosion resulting from steep slopes removes weathered products, and rapid and short transport leads to minimal sediment maturation. In general, the F/Q index is climate and relief dependent; thus, it should be used in conjunction with palaeoclimatic and palaeophysiographic evidence for provenance interpretations of ancient quartzofeldspathic sandstones. 相似文献