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1.
F. Bella R. Bella P. F. Biagi M. Caputo G. Della Monica A. Ermini E. Pettinelli V. Sgrigna 《Pure and Applied Geophysics》1993,141(1):125-137
Prototype instrumentation, able to automatically measure groundwater radon content variations, is presented. The equipment is made of stainless steel and has spherical valves with automatic and pneumatic control. The deemanation of the gases from the water is obtained by evacuating a suitable expansion chamber. The instrumentation can make discrete sampling ranging from 1 per hour to 1 per 99 hours. The equipment was tested in the laboratory: the efficiency was measured by means of a266Ra solution. A mean value of (0.65±0.07) count/s/Bq was obtained. A calibration test was carried out by comparing countings from the automatic equipment with those obtained by the standard laboratory cell. Results of an operational check over a period of approximately one year indicate that variations in radon at the calibration site are attributable more to meteorological than to tectonic causes. 相似文献
2.
F. Bella P. F. Biagi M. Caputo G. Della Monica A. Ermini P. V. Manjgaladze V. Sgrigna D. O. Zilpimiani 《Pure and Applied Geophysics》1995,144(2):277-300
Daily averaged tilt component data from two sites of the Central Apennines (Italy) and of the Southern Caucasus (Georgia), respectively, revealed intermediate-term tilts as possible precursors to earthquakes (M=3.0÷4.7) which occurred in the above-mentioned seismic areas within a distance of 50 km from the sites. A good temporal correlation as well as a fair spatial correspondence between these residual tilts (with amplitude and duration of some microradians and months, respectively) and main shocks were pointed out, by removing both secular trends and seasonal thermoelastic effects from the raw tilts. An attempt was made to justify the above-mentioned results, based on the assumption that the observed intermediate-term preseismic tilts are the manifestation of aseismic creep episodes of comparable duration in the fault materials of thrust faults close to the tilt sites. The mechanism refers to a strain field slowly propagating from the preparation focal area to the tilt site, through crustal blocks separated by weak transition zones. This propagation is thought to be the cause of the local aseismic fault slip recorded by the tiltmeters. Previously, both discrete structures and strain propagation effects were revealed in the Central Apennines and are thought also to exist in the Southern Caucasus. As in the past, the rheological properties of fault materials are revealed as viscoelastic ones. In fact, creep equations obtained by applying several viscoelastic models on our data, proved to fit quite well some of the observed tilt precursors, producing viscosity and rigidity values very similar to those reported in literature.Professor Petr Viktorovich Manjgaladze died during the writing of this paper 相似文献
3.
A consensual set of definitions regarding bioinvasions is essential in order to facilitate discourse among the science, policy and management communities dealing with the issue. Considering both the mode of entry and the extent of the impact of an alien species into a new environment, a set of key terms is proposed as an operative tool for marine scientists. 相似文献
4.
T Njanko C Njiki Chatué M Kwékam B E Bella Nké A F Yakeu Sandjo E M Fozing 《Journal of Earth System Science》2017,126(2):23
The Numba ductile deformation zone (NDDZ) is characterised by folds recorded during the three deformation phases that affected the banded amphibole gneiss. Fold-shape analyses using the program Fold Profiler with the aim to show the importance of folding events in the structural analysis of the NDDZ and its contribution to the Pan-African orogeny in central Africa have been made. Classical field method, conic sections method and Ramsay’s fold classification method were applied to (i) have the general orientation of folds, (ii) analyze the fold shapes and (iii) classify the geometry of the folded bands. Fold axes in banded amphibole gneiss plunge moderately (\(<\)15\(^{\circ }\)) towards the NNE or SSW. The morphology of F\(_{1}\), F\(_{2}\) and F\(_{3}\) folds in the study area clearly points to (i) Z-shape folds with SE vergence and (ii) a dextral sense of shear motion. Conic section method reveals two dominant families: F\(_{1}\) and F\(_{3}\) folds belong to parabolic shape folds, while F\(_{2}\) folds belong to parabolic shape and hyperbolic shape folds. Ramsay’s scheme emphasizes class 1C (for F\(_{1}\), F\(_{2}\) and F\(_{3}\) folds) and class 3 (for F\(_{2}\) folds) as main fold classes. The co-existence of the various fold shapes can be explained by (i) the structuration of the banded gneiss, (ii) the folding mechanisms that associate shear with a non-least compressive or flattening component in a ductile shear zone and (iii) the change in rheological properties of the band during the period of fold formation. These data allow us to conclude that the Numba region underwent ductile dextral shear and can be integrated (i) in a correlation model with the Central Cameroon Shear Zone (CCSZ) and associated syn-kinematic intrusions and (ii) into the tectonic model of Pan-African belt of central Africa in Cameroon. 相似文献
5.
Raffaele Azzaro Domenico Bella Luca Ferreli Alessandro Maria Michetti Federica Santagati Leonello Serva Eutizio Vittori 《Journal of Geodynamics》2000,29(3-5)
Paleoseismology, the study of past earthquakes based on their geological record in the stratigraphy and landscape, is a successful newly developing field of research. The application of fault trench studies in volcanic environments is one of the youngest branches of paleoseismology. In this paper, we present the results of the first exploratory trenches excavated at Mt. Etna in Sicily, the largest European volcano. Modern surface faulting at Etna is a very well known feature, which poses significant hazard to the local community, both in terms of ground displacement of essential lifelines and ground shacking from frequent damaging earthquakes. However, while the geomorphology and the seismicity of the active fault in the Etna region consistently show very high rates of tectonic activity, the Holocene cumulative throw and slip-rates, along with the nature (coseismic vs. creeping fault slip), dimension and timing of the displacement events, are still poorly constrained. For this purpose, we selected as a sample area the Moscarello fault, one of the most outstanding segment of the Timpe system of active normal faults in the volcano’s lower eastern flank. Displaced landforms and volcanic units at the Fondo Macchia basin, in the central sector of this fault, indicate some hundreds of meters of vertical offset in the last ca. 80 kyr, with a long-term slip-rate substantially higher than 1.5–2.0 mm/yr. According to the historical sources and instrumental observations, the Moscarello fault ruptured four times in the last 150 years during shallow (H < 5 km) and moderate magnitude (M < 4.8) earthquakes. These events were associated with severe damage in a narrow epicentral area (macroseismic intensities up to the IX–X grade of the MSK scale) and extensive surface faulting (end-to-end rupture length up to 6 km, vertical offsets up to 90 cm). This clearly indicates very high modern rates of deformation along this fault. We conducted trench investigations at the Fondo Macchia site, in a point where eyewitnesses observed ca. 20 cm of coseismic vertical displacement after the April 21, 1971, Ms=3.7, earthquake. The excavated sections provided direct stratigraphic evidence for a vertical slip-rate of 1.4–2.7 mm/yr in the last ca. 6 kyr. This should be regarded as a minimum slip-rate for the central section of the fault. We explored a single scarp at a single site, while we know from recent historical observations that several parallel scarps may rupture coseismically at Fondo Macchia. Thus, the relevant deformation rate documented for the modern period might be likely extended back in the past to a time-span of some thousands of years at least. As expected, for such a volcanic environment, the activity rates of the Moscarello fault are also significantly higher than for the Apennines normal faults, typically showing slip-rates lower than 1 mm/yr. The agriculturally reworked trench hangingwall stratigraphy did not allow to recognize individual displacement events. Nevertheless, the sedimentary structures observed in the trench footwall strongly suggest that, as for the last 150–200 years of detailed historical record, fault behavior at Fondo Macchia is governed by coseismic surface displacement rather than fault creep. This research confirms that paleoseismology techniques can be effectively applied also in active volcanic environments, typically characterized by rheology and, consequently, seismicity and fault dynamics very different from those of other tectonic environments in which paleoseismology has been firstly developed and is today extensively applied. 相似文献
6.
Long-lasting floods buffer the thermal regime of the Pampas 总被引：1，自引：0，他引：1
Javier?HouspanossianEmail author Sylvain?Kuppel Marcelo?Nosetto Carlos?Di Bella Patricio?Oricchio Mariana?Barrucand Matilde?Rusticucci Esteban?Jobbágy 《Theoretical and Applied Climatology》2018,131(1-2):111-120
The presence of large water masses influences the thermal regime of nearby land shaping the local climate of coastal areas by the ocean or large continental lakes. Large surface water bodies have an ephemeral nature in the vast sedimentary plains of the Pampas (Argentina) where non-flooded periods alternate with flooding cycles covering up to one third of the landscape for several months. Based on temperature records from 17 sites located 1 to 700 km away from the Atlantic coast and MODIS land surface temperature data, we explore the effects of floods on diurnal and seasonal thermal ranges as well as temperature extremes. In non-flooded periods, there is a linear increase of mean diurnal thermal range (DTR) from the coast towards the interior of the region (DTR increasing from 10 to 16 K, 0.79 K/100 km, r 2 = 0.81). This relationship weakens during flood episodes when the DTR of flood-prone inland locations shows a decline of 2 to 4 K, depending on surface water coverage in the surrounding area. DTR even approaches typical coastal values 500 km away from the ocean in the most flooded location that we studied during the three flooding cycles recorded in the study period. Frosts-free periods, a key driver of the phenology of both natural and cultivated ecosystems, are extended by up to 55 days during floods, most likely as a result of enhanced ground heat storage across the landscape (~2.7 fold change in day-night heat transfer) combined with other effects on the surface energy balance such as greater night evaporation rates. The reduced thermal range and longer frost-free periods affect plant growth development and may offer an opportunity for longer crop growing periods, which may not only contribute to partially compensating for regional production losses caused by floods, but also open avenues for flood mitigation through higher plant evapotranspirative water losses. 相似文献
7.
The chemical composition of water samples was studied from different caves in Slovakia. The water samples were collected from caves of two karst regions: (1) the Demänovský Cave System (DCS), situated in the Low Tatra Mountains (Northern Slovakia), which is mainly formed of limestone and dolomites; and (2) the Slovakian Karst to the Southeast is formed of limestone. A considerable difference between water from the two regions was shown. The waters from the DCS, that were controlled by vadose water percolating through different types of host rocks, contained more Mg ions than those from the Slovakian Karst caves whereas, the concentration of SO4 was controlled by the dissolution of displacive gypsum and/or oxidation of pyrite. The distribution of NO3 in the studied samples was random, hence nitrates probably derived from few pollution sources. The total mineralization of the water was covariant with calcite and aragonite saturation indices. In general, both parameters are higher in the Slovakian Karst caves than in the DCS. It is controlled probably by differences in climatic conditions, soil and plant covers between these two regions. The main goal of this article is to characterize the major-ion water chemistry within the studied caves as well as some microelements. The results have confirmed the dominant role of the bedrock petrography in forming the general chemistry of cave waters. 相似文献
8.
Sebastiano Imposa Francesco Barone Domenico Bella Massimo Cristaldi Stefano Gresta 《Environmental Earth Sciences》2011,64(7):1777-1786
A “standard procedure” to characterize the seismic hazard of a given area was proposed. It is based on a multidisciplinary
approach implying: (1) the knowledge of the seismic history of the area; (2) detailed geological surveys; (3)seismic noise
measurements; (4) simulations of earthquake scenarios. The downtown of Acireale, a typical baroque town located on Eastern
Sicily, was chosen as the “test area”. A catalog of the local seismogenic faults (able to generate earthquakes in historical
times) has been compiled, as well as a seismic catalog for the effects of both local and regional earthquakes. The analysis
of both catalogs allowed us to make the following conclusions: (1) the most important seismogenic faults affecting the Acireale
municipality do not affect the downtown, while the related local earthquakes attenuate their energy (and intensity) in short
(few km) distances; (2) the highest seismic intensity (degree X) experienced in Acireale downtown was caused by the 1693 regional earthquake; (3) over the last 140 years, the downtown has
experienced the highest intensity value of VII only once, while six times the intensity was VI. On the whole, this implies
a moderate seismic hazard. The estimation of the seismic hazard has been also approached by the experimental method of recording
seismic noise. Measurements have been performed at seven different sites, where drills gave detailed information on the shallow
subsurface geology to obtain HV (horizontal/vertical) spectral ratios. On the whole, the highest site amplification factor
was moderate (about 7). A further investigation based on synthetic seismograms (and spectra) produced by simulating two given
earthquake scenarios was also performed. The two scenarios are, respectively, representative of the largest expected earthquake
in the area (the 1693 shock) and of a moderate (magnitude ca. 5.5) local earthquake (as the 1818 one). Moderate to strong
locally expected accelerations were evidenced. 相似文献
9.
It is found that perturbations presumedly associated with swarms, the B patterns and the BG pattern precursors of strong earthquakes in New Zealand, California and Apennines, propagate in the crust of the Earth with a velocity of the order of cm1 . The hypothesis that a single travelling elastic perturbation causes a set of precursors of the same strong earthquake is discussed and it is concluded that each precursor is associated with a different perturbation. 相似文献
10.
When using least squares to fit the linear model of coregionalization to multivariate geostatistical data, the sill matrices
for the different regions must be estimated, subject to the constraint that they be non-negative definite. In 1992, Goulard
and Voltz proposed and empirically examined an iterative algorithm for doing this. Although no proof was given for its convergence
or for the uniqueness of the solution to the problem, the algorithm has subsequently been extensively and successfully used.
In this paper, we prove that the minimization problem, in fact, has a unique solution and that the algorithm is guaranteed
to converge to it from any starting point. We also discuss the effect of the starting point on the speed of convergence. 相似文献