Radiocarbon Data on Lateglacial and Holocene Landslides in the Northern Apennines     

Giovanni Bertolini  Nicola Casagli  Leonardo Ermini  Claudio Malaguti 《Natural Hazards》2004,31(3):645-662

The Emilia Romagna slope of the Northern Apennines is strewnwith over 32,000 landslides, 5,000 of which are larger than 1 million cubic metres. They representthe remains of geomorphic agents that shaped the Apennines during the Holocene. Dating themby means of radiocarbon methods adds a contribution to the knowledge about the last periodof the geological geomorphological history of the Apennines. They can also be used to examinethe influence of Quaternary climatic changes on the instability of slopes and, for practicalor planning functions, to assess the periodicity of activity phases of the landslides. Thedating has been carried out on wood remnants buried under the landslide bodies. In some cases theentire tree trunk was found.In this paper we present radiocarbon dating of 20 casestudies in the Northern Apennines. Results range approximately from 13790–13670 cal y BP to950–790 cal`y BP. The oldest case is that of the Morsiano earth-flow, while the younger datedevent is represented by the Marano case that represents an example of how radiometric analysescan further enhance the available historical data. In the Cavola case, wood remnants of different ageswere found at different depths (from 9 to 45 m), allowing the dating of the first and followingperiods of activity of the landslide. The results are discussed and some considerations on the correlationbetween landslide occurrence and Holocene climate changes are proposed.  相似文献   

SiGOG: simulated GPS observation generator   总被引：3，自引：0，他引：3  

Elsa Mohino  Mauricio Gende  Claudio Brunini  Miguel Heraiz 《GPS Solutions》2005,9(3):250-254

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Shaking table tests on reinforced concrete frames without and with passive control systems     

Mauro Dolce  Donatello Cardone  Felice C. Ponzo  Claudio Valente 《地震工程与结构动力学》2005,34(14):1687-1717

An extensive experimental program of shaking table tests on reduced‐scale structural models was carried out within the activities of the MANSIDE project, for the development of new seismic isolation and energy dissipation devices based on shape memory alloys (SMAs). The aim of the experimental program was to compare the behaviour of structures endowed with innovative SMA‐based devices to the behaviour of conventional structures and of structures endowed with currently used passive control systems. This paper presents a comprehensive overview of the main results of the shaking table tests carried out on the models with and without special braces. Two different types of energy dissipating and re‐centring braces have been considered to enhance the seismic performances of the tested model. They are based on the hysteretic properties of steel elements and on the superelastic properties of SMAs, respectively. The addition of passive control braces in the reinforced concrete frame resulted in significant benefits on the overall seismic behaviour. The seismic intensity producing structural collapse was considerably raised, interstorey drifts and shear forces in columns were drastically reduced. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Seismic preprocessing and amplitude cross-calibration for a time-lapse amplitude study on seismic data from the Oseberg reservoir     

E. Stucchi  A. Mazzotti †  S. Ciuffi ‡ 《Geophysical Prospecting》2005,53(2):265-282

The cross‐calibration of different vintage data is an important prerequisite in attempting to determine the time‐lapse seismic effects induced by hydrocarbon production in a reservoir. This paper reports the preprocessing and cross‐calibration procedures adopted to modify the data of four seismic vintages (1982, 1989, 1992 and 1999) from the Oseberg field in the North Sea, for optimal conditions for a time‐lapse seismic amplitude analysis. The final results, in terms of time‐lapse variations, of acoustic impedance and of amplitude‐versus‐offset, are illustrated for selected data sets. The application of preprocessing to each individual vintage data set reduces the effects of the different acquisition and noise conditions, and leads to consistency in the amplitude response of the four vintages. This consistency facilitates the final amplitude cross‐calibration that is carried out using, as reference, the Cretaceous horizon reflections above the Brent reservoir. Such cross‐calibration can be considered as vintage‐consistent residual amplitude correction. Acoustic impedance sections, intercept and gradient amplitude‐versus‐offset attributes and coherent amplitude‐versus‐offset estimates are computed on the final cross‐calibrated data. The results, shown for three spatially coincident 2D lines selected from the 1982, 1989 and 1999 data sets, clearly indicate gas‐cap expansion resulting from oil production. Such expansion is manifested as a decrease in acoustic impedance and a modification of the amplitude‐versus‐offset trends in the apical part of the reservoir.  相似文献   

Nd isotopic composition of Paleoproterozoic volcanic and granitoid rocks of Vila Riozinho: implications for the crustal evolution of the Tapajós gold province, Amazon craton     

Claudio Nery Lamaro  Roberto Dall'Agnol  Marcio Martins Pimentel 《Journal of South American Earth Sciences》2005,18(3-4):277-292

Nd data from the Paleoproterozoic magmatic rocks of Vila Riozinho and Jamanxim (Tapajós gold province) indicate that original magmas were not produced exclusively by the remelting of Archean sialic crust and point to dominant Paleoproterozoic sources. ε_Nd(T) values preclude derivation from mantle sources for the ca. 2.0 Ga Vila Riozinho volcanics and older São Jorge granite. They may represent a subduction-related magmatic arc with magmas modified by interaction with crust or a post- to late-orogenic remelting of an older Paleoproterozoic juvenile arc with minimal contribution from the Archean crust. The origin of the 1.88 Ga Parauari, Maloquinha, Iriri, and Moraes Almeida igneous associations and the Jamanxim rhyolites has been attributed to large-scale taphrogenesis that marked the breakup of a large Paleoproterozoic continent. Derivation of the original magmas from the remelting of crustal sources older than ca. 1.9 Ga is consistent with geochemical and Nd isotopic data. Archean remnants probably occur between the Paleoproterozoic terrains of the Ventuari-Tapajós province. Archean terrains of the Amazon craton extend from the Xingu to the Itaituba region but have not been identified in the southern Guyana shield. Thus, data reveal that the boundaries between the central Amazon and Ventuari-Tapajós provinces need better definition and more detailed field and geochronological work.  相似文献   

A cosmological hydrodynamic code based on the piecewise parabolic method     

Claudio Gheller  Ornella Pantano  & Lauro Moscardini 《Monthly notices of the Royal Astronomical Society》1998,295(3):519-533

We present a hydrodynamical code for cosmological simulations which uses the piecewise parabolic method (PPM) to follow the dynamics of the gas component and an N -body particle–mesh algorithm for the evolution of the collisionless component. The gravitational interaction between the two components is regulated by the Poisson equation which is solved by a standard fast Fourier transform (FFT) procedure. In order to simulate cosmological flows we have introduced several modifications to the original PPM scheme which we describe in detail. Various tests of the code are presented including adiabatic expansion, single and multiple pancake formation and three-dimensional cosmological simulations with initial conditions based on the cold dark matter scenario.  相似文献   

Geochemistry of granitic rocks from the Hercynian Sardinia-Corsica batholith: Implication for magma genesis   总被引：5，自引：0，他引：5  

Giampiero Poli  Claudio Ghezzo  Sandro Conticelli 《Lithos》1989,23(4):247-266

The Sardinia-Corsica batholith was structured in the late stage of the Hercynian orogenesis. The granitoids intrude mainly metamorphic complexes grading from zeolite up to amphibolite facies. The batholith is heterogeneous consisting of complexes with different affinity, chemical composition, age and degree of deformation. The present paper reports major-and trace-element data for selected samples coming only from Sardinian outcrops.

The rocks range from gabbro-diorite to tonalite, monzogranite and leucogranite. The two latter lithologies are the most abundant, gabbrodiorites and tonalites occurring in minor amounts and mainly in northern-central Sardinia. Over 75% of the granitoids contain microgranular enclaves of magmatic origin. The age of the rocks falls in the interval between 307 and 281 Ma. Sr isotope initial ratios are high, ranging between 0.7083 and 0.7107.

REE, Rb, Sr, Ba, Zr, Th, Ta, Hf, Co and Sc abundances were determined on selected samples. All elements follow three types of trends vs. CaO, which is used as differentiation index. Two trends show positive and negative correlations while the third one shows a bell-shaped pattern. LREE have different degrees of enrichment (La = 20−120× ch) and HREE show variable fractionation with prevailing (Tb/Yb)_n<1. The two peraluminous samples have very different geochemical characteristics.

From the geochemical point of view all the rocks coming from the Sardinian segment of the batholith display a typical calc-alkaline chemical character showing the imprint of both “normal and mature” continental arc geodynamic environments.

Geochemical trends suggest some petrogenetic constraints. The complete sequence of differentiation can be neither the product of crystal/liquid fractionation processes starting from a single basic parent magma nor the product of an AFC process. On the contrary, a two-stage model can be proposed. In the first stage a mafic melt of subcrustal origin interacted with monzogranitic magmas derived from 25–35% degree of melting of a crustal biotite amphibolitic source. Such a mixing process acted together with a crystal/liquid fractionation process to give tonalites and granodiorites. In the second stage lesser degrees of melting of the same crustal source could give the late-stage leucogranitic masses.

A possible scenario, able to take into account field and geochemical data, can be suggested for the genesis of this suite and we propose it as a working model for future investigations.  相似文献   

The Buffon's needle problem and the design of a geophysical survey     

Luigi Sambuelli  Claudio Strobbia 《Geophysical Prospecting》2002,50(4):403-409

A logical procedure for designing a geophysical survey when sampling an area with a regular grid can be summarized as follows: model the expected anomaly, estimate the expected noise level, estimate the area of the anomaly above the noise level, choose the spacing, in both the x - and y -directions, of the measurement grid. This last step can be approached according to two main strategies: either when applying the sampling theorem to the shortest dimension of the anomaly or when using a coarser grid, leaving a more complete definition of the anomaly to a later fitting. When following this second option, it can be constructive to estimate the probability of intercepting a given anomaly with a specific segment of profile and a given profile spacing. This latter procedure is analysed by considering a rectangle approximating the plane projection of the anomaly shape and taking into account various ratios between the grid spacing and the rectangle sides. The formulae for estimating the probability of intersecting a given anomaly with a given segment of a given profile spacing are calculated. To demonstrate the accuracy of the results, a Monte-Carlo simulation on a synthetic magnetic map was performed, obtaining, for different ratios between the sides, segment length and profile interval, an agreement better than 0.1% with the analytical formulae.  相似文献   

A procedure for landslide susceptibility zonation by the conditional analysis method   总被引：7，自引：0，他引：7  

Aldo Clerici  Susanna Perego  Claudio Tellini  Paolo Vescovi 《Geomorphology》2002,48(4):274

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   

Influence of strain history on the mechanical and micro-fabric evolution of calcite rocks: insights from torsion experiments     

Claudio Delle Piane  Luigi Burlini 《Swiss Journal of Geoscience》2008,101(2):361-375

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