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41.
Scaling of peak ground motions from digital recordings of small earthquakes at Campi Flegrei,southern Italy 总被引:2,自引:0,他引:2
The dependence of peak ground acceleration and velocity on seismic moment is studied for a set of small earthquakes (0.7<M
L<3.2) recorded digitally at distances of a few km in the Campi Flegrei volcanic area near Naples, Italy, during the ground uplift episode of 1982–1984. Numerical simulations, using the -square spectral model with constant stress drop and ane
–kf high frequency decay, fit well both the velocity and acceleration data for an averagek=0.015. The observed ground motions in the 1–24 Hz frequency band appear to consist of radiation from simple sources modified only slightly by attenuation effects. Moreover, the scaling of peak values agrees closely with those determined in nonvolcanic areas, once the difference in stress drop is taken into account. 相似文献
42.
Aldo Del Moro Antonio Paglionico Giuseppe Piccarreta Alessandro Rottura 《Tectonophysics》1986,124(3-4)
Conflicting opinions exist concerning the structure and the post-Hercynian evolution of the Serre. The present paper deals with these topics on the basis of new geological, petrological and radiometric evidence. The composition of the so-called Stilo and Polia-Copanello units has been redefined. The above domains—former sections of upper and lower Palaeozoic continental crust respectively—came into contact, due to transcurrent movements 130–140 Ma ago. A significant vertical component during the transcurrent movements, probably, exhumed the former section of lower crust. The above domains, juxtaposed, were successively involved as a single kinematic body in the Alpine orogenesis. The results enable us to make inferences for the Calabrian Arc evolution and call attention to similarities between an Austro-Alpine element (Stilo + Polia-Copanello) of the Calabrian chain and a South-Alpine sector of the Alps (Ivrea + Ceneri zones). 相似文献
43.
Giulio Bigazzi Aldo Del Moro Patrizia Macera 《Contributions to Mineralogy and Petrology》1986,94(1):46-53
A development of De Paolo's mathematical procedure (1981) for magmatic AFC (Assimilation-Fractional Crystallization) processes is discussed with respect to both trace element and Sr isotopic ratio behaviours during the genesis and evolution of Adamello batholith (northern Italy). Resolution of a two equation-system (one relative to 87Sr/86Sr ratio variation in a magma generated by an AFC process, the other to its trace element content variations) gives the F (mass of magma at time t/mass of initial magma) and D (bulk partition coefficient) values, by which one can deduce the r (rate of assimilation/rate of crystallization) value during each step of magmatic evolution. This quantitative approach suggests that: 1) there was a common precursor magma for all the Adamello granitoids, with a Mg-rich tholeiitic composition; 2) each intrusive unit appears to have been generated by different extents of AFC; 3) the trace element distribution in the magma seems essentially influenced by mineral fractionation, rather than by the composition of the assimilated crustal material. 相似文献
44.
A procedure for landslide susceptibility zonation by the conditional analysis method 总被引:7,自引:0,他引:7
Numerous methods have been proposed for landslide probability zonation of the landscape by means of a Geographic Information System (GIS). Among the multivariate methods, i.e. those methods which simultaneously take into account all the factors contributing to instability, the Conditional Analysis method applied to a subdivision of the territory into Unique Condition Units is particularly straightforward from a conceptual point of view and particularly suited to the use of a GIS. In fact, working on the principle that future landslides are more likely to occur under those conditions which led to past instability, landslide susceptibility is defined by computing the landslide density in correspondence with different combinations of instability factors. The conceptual simplicity of this method, however, does not necessarily imply that it is simple to implement, especially as it requires rather complex operations and a high number of GIS commands. Moreover, there is the possibility that, in order to achieve satisfactory results, the procedure has to be repeated a few times changing the factors or modifying the class subdivision. To solve this problem, we created a shell program which, by combining the shell commands, the GIS Geographical Research Analysis Support System (GRASS) commands and the gawk language commands, carries out the whole procedure automatically. This makes the construction of a Landslide Susceptibility Map easy and fast for large areas too, and even when a high spatial resolution is adopted, as shown by application of the procedure to the Parma River basin, in the Italian Northern Apennines. 相似文献
45.
46.
José Guerreiro Aldo Chircop Catarina Grilo Ana Viras Raquel Ribeiro Rudy van der Elst 《Marine Policy》2010
International conservation efforts and cooperation are increasingly necessary, particularly at an ecoregion level, for the achievement of international targets for protecting biodiversity and degradation of ecosystems. Whereas more than 11 percent of land is protected, less than 1 percent of marine space is similarly protected. Transboundary networks of marine protected areas and transboundary marine protected areas (TBMPAs) are an essential form of cooperation for meeting these international targets. This paper explores the diplomatic and political options for regional and sub-regional cooperation between Tanzania, Mozambique, and South Africa, for the establishment of transboundary conservation mechanisms in the Eastern African Marine Ecoregion (EAME). Five options for the establishment and management of these mechanisms are presented, together with actions to be taken to facilitate cooperation. The paper deal with a proposed strategy for the implementation of transboundary conservation mechanisms, focusing on TBMPAs, between the three countries at a biogeographical/sub-regional level, supported by lessons learnt in other transboundary marine conservation experiences. The paper concludes that although political will may exist among States sharing borders to establish TBMPAs, the complexity of dealing with sub-regional realities is a difficult obstacle to overcome in a single step. The situation at each border must be taken into account in order that different multi-scale and multivariate solutions, supported by a common baseline will ultimately converge in a common trilateral framework. Finally, a two-step approach seems to be in course with the declaration (October 2009) of a TBMPA linking Ponta do Ouro in Mozambique to iSimangaliso Wetland Park in South Africa, following one of the options formerly presented. 相似文献
47.
H. Evangelista J. Maldonado R. H. M. Godoi E. B. Pereira D. Koch K. Tanizaki-Fonseca R. Van Grieken M. Sampaio A. Setzer A. Alencar S. C. Gonçalves 《Journal of Atmospheric Chemistry》2007,56(3):225-238
The total extent of the atmospheric impacts associated to the aerosol black carbon (BC) emissions from South America is not
completed described. This work presents results of BC monitored during three scientific expeditions (2002, 2003 and 2004)
on board of a Brazilian oceanographic vessel Ary Rongel that covered the South–West Atlantic coast between 22–62°S. This latitudinal
band encloses major urban regions of South America and the outflow region of the SACZ (South Atlantic Convergent Zone), which
is an important mechanism of advective transport of heat, moisture, minor gases and aerosols from the South America continental
land to the Southern Atlantic Ocean. Our results showed that aerosol BC enhanced concentrations from urban/industrial origin
can be transported to the South–West Atlantic Ocean due to the migration of sub-polar fronts that frequently reach tropical/subtropical
regions. Despite the decrease of aerosol BC concentrations southwards (from ∼1,200 ng m−3 at latitude 22°S to ∼10 ng m−3 at latitude 62°S), several observed peak events were attributed to regional urban activities. Most of such events could be
explained by the use of air mass back trajectories analysis. In addition, a global model simulation is presented (Goddard
Institute for Space Studies – GISS GCM BC simulation) to explore the origins of aerosol BC in the South–West Atlantic. The
model allowed isolating the biomass emissions from South America and Africa and industrial (non-biomass) pollution from other
regions of the globe. This model suggests that the apportionment of about half of the aerosol BC at the South–West Atlantic
may derive from South American biomass burning. 相似文献
48.
Leonardo Sagnotti Aldo Winkler Laura Alfonsi Fabio Florindo Fabrizio Marra 《Earth and Planetary Science Letters》2000,180(3-4):243-257
We report on new paleomagnetic results obtained from 27 sites sampled in the Plio–Pleistocene sequences at the external front of the central–northern Apennines. Previous analyses of Miocene (Messinian) sediments indicated that the present shape of the northern Apenninic arc is due to the oroclinal bending of an originally straight belt oriented around N320° and that vertical axis rotations accompanied the migration of the thrust fronts toward the Adriatic foreland [F. Speranza et al., J. Geophys. Res. 102 (1997) 3153–3166]. We tried to provide new paleomagnetic constraints for the timing and rates of the oroclinal bending process during the Pliocene and the Pleistocene. The results suggest that CCW rotations observed in the northern part of the studied area are possibly younger than 3 Ma. No regional rotation is recorded in the Pliocene and Pleistocene sediments from the southern part of the study area, analogously to the Messinian sediments of the ‘Acquasanta’ domain of Speranza et al. [F. Speranza et al., J. Geophys. Res. 102 (1997) 3153–3166]. A local significant CCW rotation (23°±10°) is identified in the Early Pleistocene sediments that crop out along the Adriatic coast between Ascoli and Pescara, indicating differential motion of the thrust sheets. This rotation must be younger than 1.43 Ma. 相似文献
49.
Salvatore Inguaggiato Fabio Vita Dmitri Rouwet Nicole Bobrowski Sabina Morici Aldo Sollami 《Bulletin of Volcanology》2011,73(4):443-456
On 27 February 2007, a new eruption occurred on Stromboli which lasted until 2 April. It was characterized by effusive activity
on the Sciara del Fuoco and by a paroxysmal event (15 March). This crisis represented an opportunity for us to refine the
model that had been developed previously (2002–2003 eruption) and to improve our understanding of the relationship between
the magmatic dynamics of the volcano and the geochemical variations in the fluids. In particular, the evaluation of the dynamic
equilibrium between the volatiles (CO2 and SO2) released from the magma and the corresponding fluids discharged from the summit area allowed us to evaluate the level of
criticality of the volcanic activity. One of the major accomplishments of this study is a 4-year database of summit soil CO2 flux on the basis of which we define the thresholds (low–medium–high) for this parameter that are empirically based on the
natural volcanological evolution of Stromboli. The SO2 fluxes of the degassing plume and the CO2 fluxes emitted from the soil at Pizzo Sopra la Fossa are also presented. It is noteworthy that geochemical signals of volcanic
unrest have been clearly identified before, during and after the effusive activity. These signals were found almost simultaneously
in the degassing plume (SO2 flux) and in soil degassing (CO2 flux) at the summit, although the two degassing processes are shown to be clearly different. The interpretation of the results
will be useful for future volcanic surveillance at Stromboli. 相似文献
50.
Bernhard Chapligin Melanie J. Leng Anne Alexandre Akira Ijiri Aldo Shemesh Ulrike Herzschuh Hanno Meyer Yusuke Okazaki Zachary D. Sharp Corinne Sonzogni Florence Sylvestre Ruth Yam 《Geochimica et cosmochimica acta》2011,75(22):7242-7256
Several techniques have been introduced in the last decades for the dehydration and release of O2 from biogenic silica (opal-A) for oxygen-isotope analysis. However, only one silica standard is universally available: a quartz standard (NBS28) distributed by the IAEA, Vienna. Hence, there is a need for biogenic silica working standards. This paper compares the existing methods of oxygen-isotope analyses of opal-A and aims to characterize additional possible working standards to calibrate the δ18O values of biogenic silica. For this purpose, an inter-laboratory comparison was organized. Six potential working standard materials were analysed repeatedly against NBS28 by eight participating laboratories using their specific analytical methods. The materials cover a wide range of δ18O values (+23 to +43‰) and include diatoms (marine, lacustrine), phytoliths and synthetically-produced hydrous silica. To characterize the proposed standards, chemical analyses and imaging by scanning electron microscopy (SEM) were also performed. Despite procedural differences at each laboratory, all methods are in reasonable agreement with a standard deviation (SD) for δ18O values between 0.3‰ and 0.9‰ (1σ). Based on the results, we propose four additional biogenic silica working standards (PS1772-8: 42.8‰; BFC: 29.0‰; MSG60: 37.0‰; G95-25-CL leaves: 36.6‰) for δ18O analyses, available on request through the relevant laboratories. 相似文献