In recent years, observational and theoretical descriptions of spatio-temporal patterns of seismicity have focused on two fundamental (and controversial) observations: static stress (Coulomb) interactions between earthquakes and accelerating seismic moment release before large earthquakes. While there have been several documented examples of static stress changes influencing the space-time pattern of seismicity following great earthquakes (main shocks and aftershocks), there have been few attempts to link this method to the evolution of seismicity before great earthquakes (precursory seismicity and foreshocks). In this paper, we describe a simple physical model that links static stress modeling to accelerating moment release before a large event. For practical reasons, it is not straightforward to apply this technique as a method of forecasting future large earthquakes. However, after the large event has occurred, the region of stress accumulation can be calculated with precision based on the known source parameters of the earthquake. This region can then be examined for seismic moment rate changes prior to the event. As examples, we have examined all M greater than or equal to 6.5 earthquakes in California since 1950 in regions defined by their pre-event stress fields, and find a period of accelerating moment release before all of these events. While we illustrate the model using seismicity in California, the technique is general and can be applied to any tectonically active region. Where sufficient knowledge of the regional tectonics exists, this method can be used to augment current techniques for seismic hazard estimation. (C) 2001 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.
The Messinian deposits from Salemi area display carbonate masses of several metres or tens of metres in size, which are regarded as microbial mud-mounds. The framework is mainly composed of dominantly clotted fabrics. Various encrusting organisms are associated to the microbial micritic framework. Depositional features and associated fauna reflect an open shallower marine environment. The occurrence of microbial mud-mounds during Messinian times in such an environment reassesses the question of disappearance of mud-mounds in the Cainozoic and subsequently that of their perennity until the Present. (C) 2001 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.
Remains of dinosaurian embryos, hatchlings and early juveniles are currently the subject of increasing interest, as new discoveries and techniques now allow to analyse palaeobiological subjects such as growth and life history strategies of dinosaurs. So far, available 'embryonic' material mainly involved Ornithopods and some Theropods of Upper Cretaceous age. We describe here the histology of several bones (vertebrae, limb bones) from the tiny but exceptionally well preserved in ovo remains of Upper Jurassic Theropod dinosaurs from the Paimogo locality near Lourinha (Portugal). This Jurassic material allows to extend in time and to considerably supplement in great details our knowledge of early phases of growth in diameter and in length of endoskeletal bones of various shape, as well as shape modelling among carnivorous dinosaurs. Endochondral ossification in both short and long bones involves extensive pads of calcified cartilages permeated by marrow buds. We discuss the likely occurrence of genuine cartilage canals in dinosaurs and of an avian-like 'medullary cartilaginous cone' in Theropods, :Patterns of periosteal ossification suggest high initial growth rates (20 mum . day(-1) or more), at once modulated by precise and locally specific changes in rates of new bone deposition. The resulting very precise shape modelling appears to start early and to involve at once some biomechanical components. (C) 2001 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.
The present study characterizes the effluents of the ‘Maroc Phosphore’ factories III and IV (of Jorf Lasfar coastal zone). The results show that the effluent (Cs/l) is very acid, very phosphate-rich, high in suspended matter and calcium-rich. Hydrological parameters indicate an important content of phosphates, especially in the stations located in the South of Cs/l. Tissues of mussel Mytilus galloprovincialis from the Jorf Lasfar zone present high concentrations of Cd and Cu.
Hercynian metamorphism in the axial zone of the Pyrenees is mainly represented by a low-pressure (LP) episode with andalousite-sillimanite, but a later kyanite-bearing medium-pressure (NIP) event has been described in the most oriental part of the chain. This article shows that, in the Canigou region, the main episode was preceded by a MP event characterised by a kyanite-staurolite assemblage, which is in agreement with Early Hercynian tangential tectonics. It appears that the low-pressure event has been framed by two medium pressure episodes during the Hercynian evolution. (C) 2001 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.
The Tithonian–Berriasian series of the western Basse Provence carbonate platform (southeast France) is made of the stacking of very high frequency elementary depositional sequences, of metric scale, generally shallowing upward and frequently with emergent caps. The study of this series brings a better understanding of the controlling factors of these sequences. Fischer plots built from the sequence thicknesses and analogous diagrams built from the palaeodepths data suggest that the variations of positive accommodation do not exclusively control the development of these sequences. Variations of neritic carbonate production and/or accumulation have a considerable importance as far as they directly modify the ratio positive accommodation/sedimentary supplies.
Using backscattered image analysis, the area-perimeter technique (AP) allows quantifying the pore wall surface roughness by estimation of its fractal dimension (D-c). The results show that D-c decreases from core fresh basalt to the outer weathered rinds and is well correlated with porosity process and mineralogical weathering transformations. (C) 2001 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.
The identification of seismogenic faults in regions with low level seismicity is a major problem in earth sciences. Recent developments of tectonic studies in earthquake-prone areas point out critical questions such as (1) what is the probability of occurrence of a large earthquake (M > 6.5) in intraplate Europe? and (2) how much the morphology may record and preserve successive coseismic movements in regions with fault slip rates lower than 1 mm(.)yr(-1)? In palaeoseismology, the identification of coseismic movements and related active fault parameters results from integrated field investigations that include geomorphic analysis of fault scarps, geophysical prospecting and trench investigations. Methodologies developed in regions with high seismic strain rates (fault slip rates higher than 1 mm(.)yr(-1), interplate regions) are of primary importance for the fault identification in regions with low level of seismicity (intraplate domains). Examples of active faults illustrate their physical properties and contribute to a better understanding of the faulting behaviour and related seismic hazard. (C) 2001 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.
Here are presented the renewable energies composed of all energy sources deriving directly or indirectly from the sun, including solar, wind and hydraulic energies as well as the energies available from bioconversion. These energies are characterised by the fact that they are inexhaustible but available only in limited quantities at a given place and time. They have only a very slight impact on the environment. The development of renewable energy sources in Europe will receive a strong stimulus in the coming decade by the adoption of a European directive on electricity from renewable sources, designed to foster compliance with the European commitments made in Kyoto. In France, the goal is to increase the portion of electrical energy from renewable sources from 15 to 21% by 2010.
The world demand for primary energy keeps increasing and has little chance to decrease over the next decades, when considering the desirable and necessary development of the less wealthy countries. The two weightiest questions are to provide electricity to megalopolis, and fuels for transportation. In the present situation, fossil fuels (crude oil, natural gas and coal) provide 90 % of primary energy. Furthermore, hydrocarbons (crude oil and gas) are considered as closing energies to balance the level of demand. However, the link between fossil fuel consumption for one and a half century and climate chancre is now considered as highly probable. Crude oil and natural gas reserves are substantial, but limited. One half of the proven reserves of crude oil, and one third of gas reserves will be already used in year 2020. Gas reserves will be sufficient to reach 2050, but proven reserves of crude oil will not last until that year. Coal only, which is the largest source Of CO2 and pollutants, provides enough reserves for several centuries. A considerable effort of scientific and technological research is the only way to reach the end of the century using oil and gas, plus a drastic effort for saving energy. This effort in research is discussed in the paper, but it does not provide until now an answer to the climate problem. (C) 2001 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.
The Rheouis and Boudinar Eocene outcrops located along the Tunisian 'north-south axis' show continental deposits similar to those already described in the west-central and meridional Atlas in the Jebel Chaambi and Chebket Bouloufa. The field investigations of these levels conduct to the discovery of Bulimes' terrestrial Gastropods known in the Mediterranean domain. The presence of palygorskite in the clay minerals confirms the emerged tendency of these deposits. The continental palaeogeography might have been induced by the Triassic halokinetic movements along the Atlasic anticlines. (C) 2001 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.
Microdioritic intrusives crosscut the Hercynian structures of the Jbilet massif in the western Morocco. Their mineralogical, petrological and geochemical compositions display the main characteristics of calc-alkaline magmas and any of the alkaline ones. This magmatic event occurred at ca 255 Ma, as indicated by the 40K–40Ar age of fresh kaersutite crystals, but seven ages for whole-rock samples, scattered between 231 and 180 Ma, reflect the general rejuvenation of the ages linked to a latter penetrative alteration event of their feldspars and groundmass.
The determination of the origin of the salinity in the superficial aquifer of Djebeniana (South-East of Tunisia), and the understanding of its hydrogeological and geochemical behaviours related to severe natural and anthropic constraints, were approached by the combined survey of some dissolved ions (especially the conservative elements: Br- and Cl-), and by oxygen-18, one of the stable isotopes of water molecules. These 'tracers' indicate that: (1) the present recharge during rainwater infiltration brings downward a high content of nitrates and other dissolved salts; (2) two other sources of dissolved salts in groundwater exist, favoured by the intensive exploitation of the phreatic aquifer. The first one is due to mineralised water uprising from a deep and confined aquifer. The sea intrusion is the second source of salinity. (C) 2001 Academic des sciences / Editions scientifiques et medicales Elsevier SAS.
The Mw7.1, Hector Mine, California earthquake of October 16, 1999 produced a 50 km-long surface rupture, similar to 20 km east of the surface rupture of the 1992 Landers earthquake. ERS2 radar data acquired before and after the event provide geodetic measurements of two components of the co-seismic surface displacement field. (1) Interferometric processing of the data provides the range (radar line of sight) component of the displacement field with a precision of a few millimeters. (2) The sub-pixel correlation of the before and after amplitude images provides a second component of the surface displacement field, parallel to the satellite track, with a precision of similar to 20 cm. The azimuth offset map reveals a similar to 50 km long, NNW surface rupture formed of three sections: a N40 degreesW southern section following the Bullion fault, a N10 degreesW central section cutting through the Bullion Mountains, and a northern N40 degreesW section extending up to the Lavic Lake. A north-south-trending, localized gradient in the azimuth offset field suggests that the central section of the fault extends to the north at depth over a distance of similar to 10 km. The slip distribution curve constructed using the azimuth offsets has a bell shape, with a maximum of 6.5 m at the north end of the central fault section. The fault slip model derived from the inversion of the azimuth and from range displacement data indicates that 3-5.8 m of right-lateral slip occurred between the depths of 0 and 8 km along the northern and the central sections of the fault. The solution bears a down-dip component of slip of similar to2 m, west side down, along the southern part of the northern fault section. The down-dip component of slip is consistent with compression on a northeast dipping fault. (C) 2001 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.
Hominid fossils have been recovered from four localities within the Late Miocene Lukeino Formation, Tugen Hills, Kenya. The sediments from which the fossils came consist of fluvial and shallow lacustrine deposits. Some of the specimens are coated in a thin layer of carbonate of organic origin, suggesting deposition and preservation in slightly alkaline water, while others are riddled with superficial cracks indicating exposure at the surface prior to burial, Radioisotopic age determinations from lavas underlying and overlying: the Lukeino Formation, and from crystals from the sediments themselves, indicate an age of ca 6 Ma for these hominids. (C) 2001 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.
The observation with the scanning electron microscope of polished, etched sections of Palaeozoic limestones enables the discovery of calcareous micro- and nannofossils, which can be attributed to the Incertae Sedis family Ovummuridae Munnecke, Servais and Vachard, 2000. These microfossils are only preserved in Konservat-Lagerstutten without late diagenetic overprint. New findings are made in sections of the Upper Silurian of the Barrandian area, Czech Republic, the Upper Carboniferous of the Donetz basin, Ukraine, the Lower Permian of the Ural mountains, Russia, and the Upper Permian of the Hindu Kush, Afghanistan. The Ovummuridae, which were totally unknown up to now, were possibly very abundant in carbonate platforms of all Palaeozoic periods. at least from the Silurian onward. (C) 2001 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.
The Saint-Lawrence Lowlands correspond to the Cambrian-Early Ordovician passive margin of the Iapetus Ocean, overlain by Ordovician deposits of the Appalachian foreland. A structural and palaeostress study of this platform near Quebec City allowed reconstructing its tectonic evolution since the Palaeozoic. The collapse of the Iapetus margin (NW-SE extension) has induced N040 normal faults. Appalachian compressions (WNW and north-south) have reactivated these border faults, and induced strike-slip faults trending N090 and N140. During the Mesozoic, NNE to NNW extensions have reactivated N090 and N040 faults. The following NE-SW compression has been active until today. (C) 2001 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.
Some anomalous transient electric signals in the ULF band, the so-called SES, are claimed to be earthquake precursors. However, their origin remains widely unknown. Anomalous signals having the same characteristics as the SES have been observed at the 'Centre de recherche geophysique' (CRG), Garchy (France) and their origin has now been clearly identified with the leak-age of electric and phone networks of the CRG. They can be generated by two electrochemical mechanisms of the metallic electrode polarization: the galvanic cell and the AC electrolytic cell. These two mechanisms were controlled by field experiments, and their existence can be generalized and extrapolated to different scales. Any lack of insulation of grounded metallic bodies (underground electric and phone networks, pipelines, gas and water metallic conduits, railways, grounded towers of high power electric lines etc.) could lead to the generation of DC signals looking like the so-called SES. The greatest care must then be taken when claiming the existence of electric precursors of seismic or volcanic significance. (C) 2001 Academie des sciences Editions scientifiques et medicales Elsevier SAS.
Interpenetrating network polymers (IPN) have broad development prospects because of achieving the expected performance characteristics via the selection of functional groups and the ratio of components. In this work, the as-prepared waterborne fluorinated polyacrylate (F-PA) complex latex particles using emulsion polymerization were introduced into waterborne epoxy resin (EP) coatings for improving its hydrophobicity, toughness and compactness. The structure and physicochemical properties of prepared samples were characterized by TEM, SEM, XPS, FTIR and DMA techniques. The results indicate that EP/F-PA with a dense IPN structure successfully solves poor compatibility between F-PA and EP, which leads to excellent mechanical and damping properties. Both increased by 33.2% and 26.8% respectively. The friction test shown that the negative volume was reduced by 50.6%, the composite coating displayed excellent wear resistance. In addition, the fluorinated components and IPN structure increase the diffusion path of the corrosive medium, which has been demonstrated by molecular dynamics simulations, providing outstanding corrosion resistance for coatings. The |Z|0.01 Hz of composite coating had increased by 3.4 times. Novel composite coating with an IPN structure can offer a feasible strategy for the development and real-world application of multifunctional coatings.
Hydrogeomorphological, archaeological and geohistorical integrated studies of the very urbanised Nimes area attest of piedmont slopes and torrential alluvial fan existence from the beginning of digging of the Vistre valley since the end of the ancient Pleistocene. The urbanisation is situated on top of a major superior Pleistocene-Holocene alluvial fan. This fan existed during the old Antiquity, and has been widely truncated by the anthropisation during the High Empire. This fan is connected to other little ones, and becomes a colluvial-alluvial fan landform connected to the present flood plain of the Vistre River. It is still functioning now, as during the recent flash flood disaster of 3 October 1988. (C) 2001 Acaddmie des sciences / Editions scientifiques et medicales Elsevier SAS.
