Reappraisal of great historical earthquakes in the northern Chile and southern Peru seismic gaps   总被引：2，自引：0，他引：2  

Diana Comte  Mario Pardo 《Natural Hazards》1991,4(1):23-44

A critical reappraisal of great historical interplate earthquakes in the occidental margin of South America, including southern Peru and northern Chile, is carried out.A spacetime distribution of the earthquakes associated to the seismotectonics regions defined by the rupture zones of the greatest events (1868, Mw = 8.8 and 1877, Mw = 8.8) is obtained. Both regions are seismic gaps that are in the maturity state of their respective earthquake cycles. The region associated to the 1868 earthquake presents a notable seismic quiescence in the present century.  相似文献   

Magnetic Characteristics of Different Soil Types from Bulgaria   总被引：3，自引：0，他引：3  

Jordanova  Diana  Jordanova  Neli 《Studia Geophysica et Geodaetica》1999,43(3):303-318

Magnetic studies of different soil types can provide valuable information about palaeoenvironmental conditions at the time they were formed. Results of investigations of rock-magnetism of genetically different soil types, which developed over varying time intervals (Meadow Chernozem - formed during the last 6000 years BP; Leached Cinnamonic soil - formed since the 3rd-2nd century BC and Pellic Vertisoil - the oldest, formed since the Late Pliocene) are presented. The soil profiles of the Leached Cinnamonic and Pellic Vertisoil are characterized by lower values of magnetic susceptibility, as compared to that of the parent materials. It is shown that using percentage frequency-dependent susceptibility (Xfd%) and viscous remanent magnetization (VRM), pedogenic alteration could be detected even in such circumstances. The variations of the parameters measured along the depth of the studied Meadow Chernozem soil profile are characterized by gradual smooth magnetic enhancement, pointing to the absence of secondary redistribution of pedogenic magnetites. In contrast to this case, the two other profiles (Leached Cinnamonic and Pellic Vertisoil) show magnetically enhanced lower (illuvial) horizons due to processes of acid destruction and re-precipitation of the original pedogenic ferromagnetic minerals down the profiles. These specific magnetic properties are of particular importance in using susceptibility variations as a palaeoclimatic proxy record.  相似文献   

The Aeroelastic Study of the Messina Straits Bridge     

Diana  G.  Falco  M.  Cheli  F.  Cigada  A. 《Natural Hazards》2003,30(1):79-106

The Tacoma Bridge disaster, in the 40s, has opened a new interesting chapter in the study of suspension bridges. This is still open today, as the need of making connections easier leads to bridge spans which are longer and longer. Table I gives a list of the suspension bridges with the longest main span, while Figure 1 shows the trend in the main span length for different kind of bridges: a sharp growth is clear in the last years. The complex development of the Messina Strait Bridge project is part of this scenario, in which longer and longer bridges are being built. The project has been brought to an end by 1992 (Ponte sullo Stretto di Messina, 1992): it is a road and railway crossing, with a main span of 3300 m. This paper resumes the huge research carried out about the wind actions on the bridge, which is for sure one among the most critical aspects of the project. Into details, the main purpose has been a careful design and improvement in the shape of both the deck and the towers. An outline of the research carried out on this topic is going to be presented, together with the main results (see also Diana et al., 1999b;Diana et al., 1998;Cigada, 1994;Brancaleoni, 1993;Simiu and Scanlan, 1986).  相似文献   

Anisotropy of magnetic susceptibility of heated rocks     

Bernard Henry  Diana Jordanova  Neli Jordanova  Christine Souque  Philippe Robion 《Tectonophysics》2003,366(3-4):241-258

Heating produces changes, which does not always correspond to simple enhancement of the magnetic fabric. Two methods are proposed to determine the anisotropy of magnetic susceptibility of the ferrimagnetic minerals formed or that have disappeared by chemical change during successive heating. The first diagonalizes the tensor from the difference between each tensor term before and after heating. The second employs linear regression for each tensor term made with the values obtained throughout a thermal treatment. When the same magnetic fabric is obtained from several thermal steps, it cannot be related to randomly oriented ferrimagnetic minerals. Instead, the newly formed fabric must be related to characteristics of the pre-existing rock. By comparing this ferrimagnetic minerals fabric with the initial whole rock fabric, we can distinguish cases where heating simply enhances pre-existing fabric from those where thermal treatment induces a different fabric. Relative to the pre-heating fabric, this different fabric may simply be an inverse fabric or one whose principal susceptibility axes are oriented in a different direction, related to petrostructural elements other than those defining the initial fabric.  相似文献   

Temporary exposures of the Eocene London Clay Formation at Highgate, north London: rediscovery of a fossiliferous horizon ‘lost’ since the nineteenth century     

Steve TraceyStephen K. Donovan  Diana ClementsJohn Cooper  Phil RyeCaroline Hensley 《Proceedings of the Geologists' Association. Geologists' Association》2002,113(4):319-331

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The UK Climate Change Programme and communication with local authorities     

David Demeritt  Diana Langdon 《Global Environmental Change》2004,14(4):271

Drawing on results of a 2003 survey of environmental officers in every Local Authority (LA) in England and Wales, this paper assesses the reception and response of local government to the information being provided through the UK Climate Change Programme. Over three quarters of respondents (n=184) felt they did not have access to the best information about the impacts of climate change on their areas. Although up-to-date information is freely available from a number of official Government sources, those official sources are not consulted as consistently as the media or as intensively as the internet, despite being consistently regarded as much more accurate, credible, and appropriate to LA needs. We interpret this apparent contradiction between LA officer confidence in official sources and their relatively infrequent use as a consequence, first, of technical–cognitive and practical–temporal difficulties accessing and understanding official sources of climate change information and, second, of concerns about the practical relevance of that information for the administrative functions of local government and thus for any meaningful response by LAs to climate change. Our survey recorded considerable levels of stress, cynicism, and futility among LA officials that not only complicate communication efforts but also call into question the central assumption of the UK Climate Change Programme that simply making more locally specific information about climate change impacts available will motivate appropriate action.  相似文献   

Indigenous knowledge and the desertification debate: problematising expert knowledge in North Africa     

Diana K. Davis 《Geoforum》2005,36(4):509-524

In Morocco the crisis narrative of desertification has been invoked for decades to facilitate and justify policy and legal changes that have systematically disadvantaged pastoralists and damaged the environment. The existing data from southern Morocco, however, do not support the claims of widespread desertification due to overgrazing or other pastoral activities. Furthermore, many anti-desertification and range improvement projects in southern Morocco have not succeeded. In an effort to rethink desertification and range ecology in Morocco, this paper presents an overview of the indigenous knowledge of range ecology among the Aarib, a group of camel pastoralists in southern Morocco, and compares it to the “expert” knowledge of Moroccan range managers. It suggests that this expert knowledge is based on questionable evidence and that it has been privileged over local knowledge primarily for political, economic and administrative reasons. The discrepancies between expert and indigenous knowledges of range ecology presented here underscore the need to reconsider range ecology in Morocco, taking indigenous ecological knowledge into account. Doing so may point the way to more successful development and conservation projects which are more environmentally appropriate and socially just. Not doing so will likely exacerbate environmental degradation in the region.  相似文献   

Radium isotopes in river sediments of Czech Republic     

Eduard Hanslík  Eva Kalinov  Martina Brtvov  Diana Ivanovov  Barbora Sedl&#x;ov  Jitka Svobodov  Vra Jedinkov-K&#x;íov  Mark Rieder  Ji&#x;í Medek  Karel Forejt  Ladislav Vondrk  Karel Jahn  Ji&#x;í Jusko 《Limnologica》2005,35(3):177-184

In the Czech Republic, river bottom sediments have been systematically monitored since 1999. In the paper, their radioactive contamination due to uranium mining and milling is assessed. The sediments samples were analyzed by gamma spectrometry. Especially the radium-226 and radium-228 activities were further evaluated.The highest values of the radium-226 activities were found at river profiles where the uranium industry impact was obvious. It turned out that the radium-226 and radium-228 activities ratio is more convenient to assess the level of radium-226 contamination than only the radium-226 activity itself. Based on this hypothesis, the sediment classification scheme for uranium industry contamination was suggested. The natural background activities of radium-226 and radium-228 in the Czech Republic were also evaluated. The case of radium-226 contamination due to the uranium industry was studied in details at the Ploučnice River.  相似文献   

Rock magnetic properties of recent soils from northeastern Bulgaria   总被引：1，自引：0，他引：1  

Diana Jordanova  Eduard Petrovsky  Neli Jordanova  Jordan Evlogiev  Vesselina Butchvarova 《Geophysical Journal International》1997,128(2):474-488

In this paper, basic rock magnetic studies of Holocene loess-soil samples from northeastern Bulgaria are reported. The sites are related to the Danube river and located at different distances southwards, thus representing various pedogenic conditions. The study is primarily aimed at determining the main magnetic carrier(s) and their physical characteristics (grain-size distribution, magnetic enhancement, etc.). Oxyhydroxides, maghemite and titanomagnetites of various oxidation degrees are assumed to be the main ferromagnetic minerals present. Our results suggest that the uppermost part of recent soil profiles is rich in stable, near-single-domain (SD) particles, while the illuvial horizons are characterized by a gradual decrease in grain sizes, from highly viscous to a true superparamagnetic (SP) domain state. The properties of samples from carbonate-rich horizons of recent soils are basically controlled by detrital minerals, while those from sites with more intensive pedogenesis and especially grey forest soils are influenced by strongly magnetic minerals formed ' in situ '.  相似文献   

In situ experimental study of the evolution and recolonization of polluted sediments     

A. Arnoux  G. Stora  C. Diana 《Marine pollution bulletin》1985,16(8):313-318

When perturbing conditions influencing a benthic ecosystem improve, an extremely polluted sediment may very rapidly be colonized by a structured assemblage. This study was made after the implantation of modules containing chemically very contaminated sediment from a polluted biotope, in a lesser contaminated site. The colonization and dynamic processes of the studied mollusc populations do not depend on the concentrations of the solid phase pollutants but are related to the release of these pollutants in the interstitial water of sediments, which in turn is induced by ambiant condition variations and particularly by salinity.  相似文献