Prediction of ground displacements and velocities from groundwater level changes at the Vallcebre landslide (Eastern Pyrenees, Spain)   总被引：2，自引：5，他引：2  

Jordi Corominas  José Moya  Alberto Ledesma  Antonio Lloret  Josep A. Gili 《Landslides》2005,2(2):83-96

In active landslides, the prediction of acceleration of movement is a crucial issue for the design and performance of warning systems. The landslide of Vallcebre in the Eastern Pyreenes, Spain, has been monitored since 1996 and data on rainfall, groundwater levels and ground displacements are measured on a regular basis. Displacements observed in borehole wire extensometers have shown an immediate response of the landslide to rainfall episodes. This rapid response is likely due to the presence of preferential drainage ways. The occurrence of nearly constant rates of displacement in coincidence with steady groundwater levels suggests the presence of viscous forces developed during the movement. An attempt to predict both landslide displacements and velocities was performed at Vallcebre by solving the momentum equation in which a viscous term (Bingham and power law) was added. Results show that, using similar rheological parameters for the entire landslide, computed displacements reproduce quite accurately the displacements observed at three selected wire extensometers. These results indicate that prediction of displacements from groundwater level changes is feasible.  相似文献   

Les laves du mont Bangou : une première manifestation volcanique éocène, à affinité transitionnelle,de la Ligne du Cameroun     

Jacob Fosso  Jean-Jacques Ménard  Jacques-Marie Bardintzeff  Pierre Wandji  Félix M. Tchoua  Hervé Bellon 《Comptes Rendus Geoscience》2005,337(3):315-325

Mount Bangou, an Eocene volcano (⁴⁰K–⁴⁰Ar ages between 44.7 and 43.1 ± 1 Ma) is the oldest dated volcano of the Cameroon Line. In this region, two magmatic series, evolving by fractional crystallization, show transitional affinities that are exceptionally known in this sector. Mineral compositions of basaltic rocks (scarce modal olivine and occurrence of normative hypersthene) as well as geochemical characteristics (low Ba, La, Ta contents and high Y/Nb ratios) are in agreement with this trend. The succession of magmas evolving in time from transitional to more typical alkaline compositions is evidenced in a continental setting. To cite this article: J. Fosso et al., C. R. Geoscience 337 (2005).  相似文献   

Applications géodésiques du système DORIS à l'Institut géographique national     

Pascal Willis  Claude Boucher  Hervé Fagard  Zuheir Altamimi 《Comptes Rendus Geoscience》2005,337(7):653-662

IGN is in charge of the installation and maintenance of the DORIS orbit determination network. More recently, in collaboration with JPL, precise geodetic computations were performed. The goal of this paper is to recall the various historic contributions of IGN to the DORIS system in their international context and then to describe a new estimation technique developed for a multi-satellite mode, making full profit of a better modeling for satellites and ground clocks as well as tropospheric correction parameters. Derived geodetic results demonstrate a precision in the order of 1 cm for station positions. To cite this article: P. Willis et al., C. R. Geoscience 337 (2005).  相似文献   

Preliminary data on chemical changes in the Aral Sea during low-level periods from the last 9000 years     

Laurence Le Callonnec  Alain Person  Maurice Renard  René Létolle  Nathalie Nebout  Leila Ben Khelifa  Ivan Rubanov 《Comptes Rendus Geoscience》2005,337(12):1035-1044

The withdrawal of the Aral Sea tributaries (Amu and Syr Daria) for cultures has led to significant falls of its level and an important increase in its salinity. During the Holocene, a succession of low and high water inputs occurred. Silty deposits correspond to the high levels and carbonates to the low levels. This study makes a distinction between the Syr Daria and the Amu Daria water inputs during low-level periods by using mineralogical and chemical compositions of the carbonates deposits. Waters from the Syr Daria are more sulphatic and have a low iron content in comparison with that of the Amu Daria. The Syr Daria was the major tributary around 7500, 4956 and 970 yr?BP, whereas around 6200 and 3610 yr?BP, inflow also from the Amu Daria is observed. To cite this article: L. Le Callonnec et al., C. R. Geoscience 337 (2005).  相似文献   

Diagenetic paths in the margin of a Triassic Basin: NW zone of the Iberian Chain, Spain     

Maria Ochoa  José Arribas 《International Journal of Earth Sciences》2005,94(2):256-266

Buntsandstein deposits generated in a slowly subsiding basin on the western margin of the Iberian Chain are represented by a stratigraphic succession of fluvial deposits less than 100 m thick (conglomerates, sandstones, and shales). Diagenetic processes in sandstones can be grouped as eodiagenetic, mesodiagenetic, and telodiagenetic. Eodiagenesis can be associated with Muschelkalk, Keuper, and probably early Jurassic times. Mesodiagenesis is probably related to Jurassic times. Diagenetic chemical reactions suggest a maximum burial less than 1.5 km and low temperatures (<120°C). Patterns of porosity reduction by compaction and cementation suggest four diagenetic stages: (1) Loss of primary porosity by early mechanical compaction; (2) early cementation (K-feldspar and dolomite); (3) dissolution of cements; and (4) framework collapse by re-compaction. These stages are manifested by the presence of two types of sandstone. Type I sandstones present high intergranular volume (mean, 30%). Type II sandstones are characterized by high compactional porosity loss and exhibit low values of intergranular volume (mean, 16.9%). Type II sandstones are associated with the dissolution of cement and later re-compaction of type I sandstones. An intermediate telodiagenetic phase is deduced and related to the sharp unconformity between Lower Cretaceous sediments and the underlying sediments. This suggests that a mechanically unstable framework collapsed during the Cretaceous, generating type II sandstones. The analyzed diagenetic paths have a wide applicability on similar marginal areas of rift basins.  相似文献   

Geochronology of granulites from the south Itabuna-Salvador-Curaçá Block,São Francisco Craton (Brazil): Nd isotopes and U–Pb zircon ages     

Jean-Jacques Peucat  Johildo Salomão Figueiredo Barbosa  Ivana Conceição de Araújo Pinho  Jean-Louis Paquette  Hervé Martin  C. Mark Fanning  Angela Beatriz de Menezes Leal  Simone Cruz 《Journal of South American Earth Sciences》2011,31(4):397-413

This work provides five new U–Pb zircon dating and the corresponding Nd isotope data for felsic granulites from the south Itabuna-Salvador-Curaçá Block (ISCB), in the São Francisco Craton, Brazil. Three major sets of felsic granulites can be recognised. The oldest set is tonalitic in composition and of TTG affinity. It is Archaean in age with magmatic zircon cores dated at 2675 ± 11 Ma by LA-ICPMS and up to ca 2.7–2.9 Ga by SHRIMP on an other sample. It exhibits epsilon Nd values between ?8 and ?11 at 2.1 Ga. This Nd signature is similar to that of granulites found in the western Archaean Jequié Block. Cartographically, this set of Archaean terrains represents at least 50% of the granulites in the studied area. The second set corresponds to a Palaeoproterozoic calc-alkaline tonalitic suite with zircon ages from 2019 ± 19 Ma to 2191 ± 10 Ma and epsilon Nd values between ?3 and ?4 at 2.1 Ga, corresponding partially to a newly formed crust. The third set of granulites is also Palaeoproterozoic. It is shoshonitic to monzonitic in composition and synchronous with the high grade metamorphism dated by metamorphic zircons at 2086 ± 7 Ma (average of five samples). The Nd isotope signature for this alkaline set is similar to that of the Palaeoproterozoic calc-alkaline one. Nd isotopes appear to be a very efficient tool to distinguish Archaean from Palaeoproterozoic felsic protoliths in granulitic suites of the Itabuna-Salvador-Curaçá Block (ISCB). Finally, the southern part of the ISCB is composed of a mixture of Archaean and Palaeoproterozoic protoliths, in similar amounts, suggesting that it was probably an active margin between 2.1 and 2.2 Ga located on the eastern border of the Archaean Jequié Block. A major crustal thickening process occurred at ca 2.09 Ga in the ISCB and seems significantly younger towards the west, in the Jequié granulites, where an average of 2056 ± 9 Ma is determined for the high grade event.  相似文献   

Differential response at the seafloor during Palaeocene and Eocene ocean warming events at Walvis Ridge,Atlantic Ocean (ODP Site 1262)          下载免费PDF全文

Arne Deprez  Sofie Jehle  André Bornemann  Robert P. Speijer 《地学学报》2017,29(1):71-76

The Latest Danian Event (LDE, c. 62.1 Ma) is an early Palaeogene hyperthermal or transient (<200 ka) ocean warming event. We present the first deep‐sea benthic foraminiferal faunal record to study deep‐sea biotic changes together with new benthic (Nuttallides truempyi) stable isotope data from Walvis Ridge Site 1262 (Atlantic Ocean) to evaluate whether the LDE was controlled by similar processes as the minor early Eocene hyperthermals. The spacing of the double negative δ¹³C and δ¹⁸O excursion and the slope of the δ¹⁸O–δ¹³C regression are comparable, strongly suggesting a similar orbital control and pacing of eccentricity maxima as well as a rather homogeneous carbon pool. However, in contrast to early Eocene hyperthermals, the LDE exhibits a remarkable stability of the benthic foraminiferal fauna. This lack of benthic response could be related to the absence of threshold‐related circulation changes or better pre‐adaptation to elevated deep‐sea temperatures, as the LDE was superimposed on a cooling trend, in contrast to early Eocene warming.  相似文献   

Plio-Pleistocene mammals from Mille-Logya,Ethiopia, and the post-Hadar faunal change     

Denis Geraads  Denne Reed  W. Andrew Barr  René Bobe  Peter Stamos  Zeresenay Alemseged 《第四纪科学杂志》2021,36(6):1073-1089

We describe the non-primate mammalian fauna from the late Pliocene to earliest Pleistocene deposits of Mille-Logya in the Lower Awash Valley, Ethiopia, dated to c. 2.9–2.4 Ma, and divided into three successive units: Gafura, Seraitu, and Uraitele. We identify 41 mammalian taxa (including rodents), the most diverse group being the Bovidae, with 17 taxa. While the Gafura assemblage still resembles those from the earlier Hadar Formation, the younger Seraitu assemblage documents a major turnover. While there is little change in the species present across this interval, the relative abundances of various taxa change dramatically, with suids being largely replaced by open-country bovids (Alcelaphini and Antilopini). We interpret this faunal change as reflective of an environmental shift, contemporaneous with the replacement of Australopithecus afarensis by Homo in the area.  相似文献   

Regional map of earthquake-induced liquefaction hazard using the lateral spreading displacement index D LL     

Miguel A. Jaimes  Mauro Niño  Eduardo Reinoso 《Natural Hazards》2015,77(3):1595-1618

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Generalized plasticity state parameter‐based model for saturated and unsaturated soils. Part 1: Saturated state     

Diego Manzanal  José Antonio Fernández Merodo  Manuel Pastor 《国际地质力学数值与分析法杂志》2011,35(12):1347-1362

The behavior of granular materials is known to depend on its loose or dense nature, which in turns depends both on density and confining pressure. Many models developed in the past require the use of different sets of constitutive parameters for the same material under different confining pressures. The purpose of this paper is to extend a basic generalized plasticity model for sands proposed by Pastor, Zienkiewicz and Chan by modifying the main ingredients of the model flow—rule, loading–unloading discriminating direction and plastic modulus—to include a dependency on the state parameter. The proposed model is tested against the available experimental data on three different sands, using for each of them a single set of material parameters, finding a reasonably good agreement between experiments and predictions. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献