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851.
Hervé Nouzé Isabelle Contrucci Jean-Paul Foucher Bruno Marsset Yannick Thomas Estelle Thereau Alain Normand Éliane Le Drezen Stéphane Didailler Jean-Pierre Regnault Sandie Le Conte Stéphanie Guidart Wim Lekens Simon Dean Alexandre Throo 《Comptes Rendus Geoscience》2004,336(13):1181-1189
The Storegga slides, off Norway, are among the largest submarine slides ever known on a continental slope. The HYDRATECH cruise on N/O Le Suroît aimed at a high-resolution survey of an area at the northern boundary of the slides. This survey images in great detail the bottom simulating reflector (BSR) extent and properties, the various fluid escape structures and the sediment deformations. The combination and the quality of the data help to understand the still poorly constrained relationships between fluid escapes, gas hydrates and slope stability in the survey area. To cite this article: H. Nouzé et al., C. R. Geoscience 336 (2004). 相似文献
852.
Marie Abboud-Abi Saab Jean-Claude Romano Nathaniel Bensoussan Milad Fakhri 《Comptes Rendus Geoscience》2004,336(15):1379-1390
Vertical temperature profiles were recorded from June 1999 to October 2002 (at least once a month) at two Mediterranean sites, in the eastern basin (Batroun, Lebanon; 0–100 m) and in the northwestern basin (Marseilles, France; 0–55 m). At the two sites, the thermal seasonal evolution and the thermocline time dynamics are quite identical. But in the Lebanese waters, at comparable water depths, temperatures are currently 4 to 5?°C higher than in the French waters, the thermocline is longer (more than 6 months), permanent and deeper (40–50 m) than in Marseilles (20–30 m). The latter frequently disappears in summer due to northwest winds inducing cold waters. This is principally due to differences in prevailing wind regimes at each site. Such evaluation, coupled with long-term observations of temporal evolution of coastal water at the regional level of the Mediterranean basins, will shed light on temperature regime fluctuations and their consequences in the context of global warming of the Mediterranean. To cite this article: M. Abboud-Abi Saab et al., C. R. Geoscience 336 (2004). 相似文献
853.
A spatial and temporal analysis, at a city wide scale, is given of the main type of informal housing (favelas) in Rio de Janeiro.
Rapid change in the number and distribution of favelas and their inhabitants (favelados) over time is seen as the outcome
of two opposing sets of factors. Demand-led housing factors, including population growth and variations in levels of poverty
in the city, have constantly outstripped the supply side of the housing equation where inadequate housing policies and investment,
together with restricted building land have been characteristic. Added to these factors are a set of more specific developments
which shape the favela geography, including the timing and location of urban redevelopment, favela eradication and recognition,
transport development and access by the favelados to employment sources. Evidence shows that the contemporary distribution
of favelas in the city does not conform to spatial models of this urban form, and that any interpretation of the Rio favelas,
including their growth, development and diversity, needs to be space and time specific.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
854.
Servando De la Cruz-Reyna Gerardo Carrasco-Núez 《Journal of Volcanology and Geothermal Research》2002,113(1-2)
Citlaltépetl or Pico de Orizaba is the highest active volcano in the North American continent. Although Citlaltépetl is at present in repose, its eruptive history reveals repetitive explosive eruptions in the past. Its relatively low eruption rate has favored significant population growth in areas that may be affected by a potential eruptive activity. The need of some criteria for hazards assessment and land-use planning has motivated the use of statistical methods to estimate the time and space distribution of volcanic hazards around this volcano. The analysis of past activity, from late Pleistocene to historic times, and the extent of some well-identified deposits are used to calculate the recurrence probabilities of eruptions of various size during time periods useful for land-use planning. 相似文献
855.
A spectral approach to simulating intrinsic random fields with power and spline generalized covariances 总被引:4,自引:0,他引:4
This article presents a variant of the spectral turning bands method that allows fast and accurate simulation of intrinsic
random fields with power, spline, or logarithmic generalized covariances. The method is applicable in any workspace dimension
and is not restricted in the number and configuration of the locations where the random field is simulated; in particular,
it does not require these locations to be regularly spaced. On the basis of the central limit and Berry–Esséen theorems, an
upper bound is derived for the Kolmogorov distance between the distributions of generalized increments of the simulated random
fields and the normal distribution. 相似文献
856.
Analysis, in a free surface steady flow, of the interstitial velocity field inside a sedimentary bed
The objective of our study is to exploit ultrasonic Doppler velocimetry (UDV) to analyze the velocity field within a steady flow on a porous sedimentary bottom. Velocities are measured for several sedimentary beds, as well within the fluid vein as within the sediment. Our results highlight an exponential distribution of the velocities inside the sediment and a discontinuity of the velocity at the interface water–sediment, between the velocity in the free flow and the velocity within the sediment. These results highlight the need to base the analysis of sedimentary transport on the reality of the physical processes at the interface water–sediment. 相似文献
857.
Jaime Urrutia-Fucugauchi Jose Maria Chavez-Aguirre Ligia Prez-Cruz Jose Luis De la Rosa 《Comptes Rendus Geoscience》2008,340(12):801-810
The Chicxulub 200 km diameter crater located in the Yucatan platform of the Gulf of Mexico formed 65 Myr ago and has since been covered by Tertiary post-impact carbonates. The sediment cover and absence of significant volcanic and tectonic activity in the carbonate platform have protected the crater from erosion and deformation, making Chicxulub the only large multi-ring crater in which ejecta is well preserved. Ejecta deposits have been studied by drilling/coring in the southern crater sector and at outcrops in Belize, Quintana Roo and Campeche; little information is available from other sectors. Here, we report on the drilling/coring of a section of der="0">34 m of carbonate breccias at 250 m depth in the Valladolid area (120 km away from crater center), which are interpreted as Chicxulub proximal ejecta deposits. The Valladolid breccias correlate with the carbonate breccias cored in the Peto and Tekax boreholes to the south and at similar radial distance. This constitutes the first report of breccias in the eastern sector close to the crater rim. Thickness of the Valladolid breccias is less than that at the other sites, which may indicate erosion of the ejecta deposits before reestablishment of carbonate deposition. The region east of the crater rim appears different from regions to the south and west, characterized by high density and scattered distribution of sinkholes. 相似文献
858.
Adam Ahmed Ali Paul Roiron Lucie Chabal Paul Ambert Jean Gasco Joël Andr Jean-Frdric Terral 《Comptes Rendus Geoscience》2008,340(6):356-366
A geobotanical study of the travertine system of Saint-Guilhem-le-Désert (southern France) was carried out in order to reconstruct the local Holocene environment in a region where the postglacial vegetation history is poorly documented. The travertinisation process has started at ca. 8500 cal. BP, in a landscape dominated by Pinus sylvestris type (probably Pinus nigra sub sp. salzmannii). Around 7000 cal. BP, the travertine system recorded torrential events not evidenced at the regional scale, showing the particularity of the Verdus hydrological regime. More recently, ca. 5100 cal. BP, a lake or a marsh was filled within the Verdus plain, as attested to by sand and silt particles accumulated in the sequence. The present-day vegetation dominated by Quercus ilex, on south facing slopes, was most likely established between the Bronze Age and the Gallo-Roman period correlatively to the decline of Pinus nigra and deciduous Quercus, most probably under human influence. 相似文献
859.
Changyi Shi Tiexin Gu Wei Bu Weidong Yan Mei Liu Mingcai Yan 《Geostandards and Geoanalytical Research》2008,32(3):337-345
The Institute of Geophysical and Geochemical Exploration in China recently prepared ten biogeochemical certified reference samples GSB1‐10 (CRMs). The samples are primary agricultural products such as rice, wheat, corn, soybean, cabbage, spinach, tea, powder, chicken and apple. Lyophilisation technology and a high‐alumina ball mill were used to process the samples. Fourteen laboratories and hundreds analysts in China participated in the certification analysis. Over ten reliable analytical methods, predominately ICP‐MS, ICP‐AES and INAA, were used for analysing the samples for fifty‐nine elements. A total of 22477 determinations led to 5136 average data sets. Certified values of fifty‐four elements were assigned. 相似文献
860.
《Geofísica Internacional》2014,53(4):411-423
An investigation of the effect of some human activities on the magnetic susceptibility and frequency dependent susceptibility was conducted on top soil samples from, a commercial area, a motor park and a school environment in Jalingo, Taraba State, N-E Nigeria. The purpose was to assess the variation of magnetic susceptibility with different land use, detect pollution hotspots using magnetic proxy parameters and evaluate the contribution of superparamagnetic (SP) grain size contribution to the magnetic susceptibility from calculation of the frequency dependence of magnetic susceptibility (MS). The results of the mass specific low frequency magnetic susceptibility measurements showed significant enhancement with values ranging from 67.8 − 495.3 × 10−8 m3kg−1 with a mean value of 191.61 × 10−8 × m3kg−1 for the Jalingo College of Education (JCOE) data; 520.1 − 1612.8 × 10−8 m3kg−1 with a mean value of 901.34 × 10−8 m3kg−1 for the Jalingo main Market (JMM) and 188.5 − 1203.6 × 10−8m3kg−1 with an average value of 574 92 × 10−6 m3kg−1 for the Jalingo Motor Park (JMP). The significant magnetic enhancement indicates high concentration of ferrimagnetic minerals in the soil and hence increased pollution. The magnetic susceptibility of the different land use studied decreased in the order commercial area (market) > motor park > school premises. The results of the percentage frequency dependence susceptibility showed that most of the samples had a mixture of SP and coarse multi domain grains or SP grains < 0.05 µm. The value of χfd% range from 2.68 to 13.80% with an average value of 8.67% in the JCOE samples, 0.49 to 10.04% with an a-verage of 5.05% in the JMM samples and 0.56 to 13.04% with an average value of 5.86% in the JMP samples. 相似文献