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991.
992.
Matt A. King Zuheir Altamimi Johannes Boehm Machiel Bos Rolf Dach Pedro Elosegui François Fund Manuel Hernández-Pajares David Lavallee Paulo Jorge Mendes Cerveira Nigel Penna Riccardo E. M. Riva Peter Steigenberger Tonie van Dam Luca Vittuari Simon Williams Pascal Willis 《Surveys in Geophysics》2010,31(5):465-507
The provision of accurate models of Glacial Isostatic Adjustment (GIA) is presently a priority need in climate studies, largely due to the potential of the Gravity Recovery and Climate Experiment (GRACE) data to be used to determine accurate and continent-wide assessments of ice mass change and hydrology. However, modelled GIA is uncertain due to insufficient constraints on our knowledge of past glacial changes and to large simplifications in the underlying Earth models. Consequently, we show differences between models that exceed several mm/year in terms of surface displacement for the two major ice sheets: Greenland and Antarctica. Geodetic measurements of surface displacement offer the potential for new constraints to be made on GIA models, especially when they are used to improve structural features of the Earth’s interior as to allow for a more realistic reconstruction of the glaciation history. We present the distribution of presently available campaign and continuous geodetic measurements in Greenland and Antarctica and summarise surface velocities published to date, showing substantial disagreement between techniques and GIA models alike. We review the current state-of-the-art in ground-based geodesy (GPS, VLBI, DORIS, SLR) in determining accurate and precise surface velocities. In particular, we focus on known areas of need in GPS observation level models and the terrestrial reference frame in order to advance geodetic observation precision/accuracy toward 0.1 mm/year and therefore further constrain models of GIA and subsequent present-day ice mass change estimates. 相似文献
993.
François Ayoub Sébastien Leprince Jean-Philippe Avouac 《ISPRS Journal of Photogrammetry and Remote Sensing》2009,64(6):551-560
We describe and test a procedure to accurately co-register and correlate multi-temporal aerial images. We show that this procedure can be used to measure surface deformation, and explore the performance and limitations of the technique. The algorithms were implemented in a software package, COSI-Corr (available from the Caltech Tectonics Observatory website). The technique is validated on several case examples of co-seismic deformation. First, we measure co-seismic ground deformation due to the 1992, Mw 7.3, Landers, California, earthquake from 1 m resolution aerial photography of the National Aerial Photography Program (United States Geological Survey). The fault ruptures are clearly detected, including small kilometric segments with fault slip as small as a few tens of centimeters. We also obtained similar performance from images of the fault ruptures produced by the 1999 Mw 7.1 Hector Mine, California, earthquake. The measurements are shown to be biased due to the inaccuracy of the Digital Elevation Model, film distortions, scanning artifacts, and ignorance of ground displacements at the location of the tie points used to co-register the multi-temporal images. We show that some of these artifacts can be identified and corrected. 相似文献
994.
Isabel Caçador Miguel Caetano Bernardo Duarte Carlos Vale 《Marine environmental research》2009,67(2):75-82
Pools of Zn, Cu, Cd and Co in the leaf, stem and root tissues of Sarcocornia fruticosa, Sarcocornia perennis, Halimione portulacoides and Spartina maritima were analysed for a Tagus estuary (Portugal) salt marsh. Pools of Cu and Cd in the salt marsh were higher in spring/summer, indicating a net uptake of these metals during the growing season. Standing stocks of Zn, Cu, Cd and Co in the leaf and stem biomass of S. fruticosa, S. perennis and H. portulacoides showed a strong seasonal variation, with higher values recorded in autumn. The metal-containing leaves and stems that shed in the autumn become metal-containing detritus. The amount of this material washed out from the total marsh area (200 ha) was estimated as 68 kg of Zn, 8.2 kg of Cu, 13 kg of Co and 0.35 kg of Cd. The high tidal amplitude, a branched system of channels and semi-diurnal tidal cycle greatly favour the export of the organic detritus to adjoining marsh areas. 相似文献
995.
Françoise Bourrouilh 《Marine Geology》1974,16(4):213-235
A geomorphological study of the east coast of Andros (Fresh Creek area) shows the existence of a paleotopography represented by low-altitude hills (few metres). This paleotopography is protected by the presence of a calcitic Quaternary crust which covers Pleistocene calcarenite.In the western part of the area, there are long woody axes, oriented NE-SW, parallel to the channels of the creek. They end at two kilometres from the coast, along which is a second kind of lower hills, orthogonal to the first.The first axes can be interpreted as megaripples as seen at the present time on modern deposits (on the Great Bahama Bank) and fossilized by the upper crust. The second direction is made by accretion ripples along the coast.The surface of the Bahamian calcarenite has been studied. The Bahamian karst presents two topographical forms: “blue holes” like those outside the island, which are 60–80 m in diameter and both sparse and deep; and “washtub” dolines; these are numerous and shallow, and, from low altitude, exhibit a honeycombed aspect on the surface. This karstic topography with dolines and blue holes is also seen through the water of the Creek the hard bottom of which is covered only here and there with a few centimetres of sediments. Hence, there is a submerged karstic topography, made of the same elements as the aerial karst, but submerged by the Holocene transgression. The present karstic relief, in relation with the different eustatic levels of the Quaternary, has begun 120,000 years ago, according to the isotopic ages, and might be composed by different steps, difficult to show now, in the topography.The blue holes in the interior of the island of young and little evolved karst, were formed more by solution than by collapse of the karstic caves, because of the absence of a real river to drain the Andros shelf at the time of low sea levels. Blue holes of the inside of the island, as they are called, with submarine openings, have the same salinity as the water of the creek (17.5 g/l). The dolines with very low salinity (0.7 g/l to 3.8 g/l) are filled with stromatolites and charophytes, slowly forming sediments made up essentially of high-magnesian calcite.It seems that the Andros Island karst can be compared with that of the Yucatan, where there are round and deep open pits, called cenote, of which the Bahamian equivalent would be the blue holes which were drowned by the Holocene transgression. 相似文献
996.
This study reported the mass mortality events (MMEs) of Pinna nobilis based on diving surveys in Turkey. Data were collected across 12 sites in the Aegean Sea, and one site in the Sea of Marmara, within the period of June-September 2019. The results showed that a low mortality rate of 10% was found in the Sea of Marmara, and a MME was not detected for this area. In contrast, 97% mortality was recorded for the P. nobilis population distributed in the Turkish Aegean Sea. This discrepancy might be related to the seawater temperature and salinity values of these two seas. The waters of the Sea of Marmara were colder and less salty than the Aegean Sea. The findings highlighted the importance of protecting the healthy population of critically endangered fan mussels in the Sea of Marmara. It was recommended that sound management plans comprising of monitoring, enforcement and public awareness activities could be implemented in order to achieve this. 相似文献
997.
C. Kurtuluş B. Doğan F. Sertçelik M. Canbay H. M. Küçük 《Marine Geophysical Researches》2009,30(2):121-134
The Edremit Gulf, which developed during the Neogene-Quaternary, is a seismically active graben in NW Anatolia (Turkey) surrounded
by the Sakarya continent. The sedimentary deposits in the gulf overlie the bedrock unconformably and can be separated into
two parts as upper and lower deposits based on similarity of their seismic characteristics, and because the contact between
them is clear. The lower deposits are characterized in the seismic profiles by the absence of well defined, continuous reflectors
and are strongly disturbed by faults. A tectonic map and structural model of the Edremit Gulf was derived from interpreting
21 deep seismic profiles trending NE–SW and NW–SE within the gulf. Two fault systems were distinguished on the basis of this
compilation. The NNW–SSE trending parallel faults are low-angle normal faults formed after compression. They controlled and
deformed the lower basin deposits. A syncline and anticline with a broad fold-curvature length resulted in folds that developed
parallel to basin boundaries in the lower basin deposits. The ENE–WSW trending high-angle faults have controlled and deformed
the northern basin of the Edremit Gulf. The folds developed within the northern lower deposits originated from the listric
geometry of the faults. These faults are normal faults associated with regional N–S extension in western Anatolia. The Edremit
Gulf began to open under the control of low-angle NNW–SSE trending faults that developed after the compression of western
Anatolia in an E–W direction in the early Neogene. Subsequently, regional N–S extensional stress and high-angle normal faults
cut the previous structures, opened the northern basin, and controlled and deformed the lower basin deposits in the gulf.
As a result, the Edremit Gulf has not been controlled by any strike-slip faults or the Northern Anatolian Fault. The basin
developed in the two different tectonic regimes of western Anatolia as an Aegean type cross-graben from the Neogene to Holocene. 相似文献
998.
Jean-François Balmat Frédéric Lafont Robert Maifret Nathalie Pessel 《Ocean Engineering》2009,36(15-16):1278-1286
This paper presents a fuzzy approach for the MAritime RISk Assessment (MARISA) applied to safety at sea. The aim of this work is to define automatically an individual ship risk factor which could be used in a decision making system. To achieve this purpose, a modular and hierarchical structure using fuzzy logic has been developed. It allows us to obtain a fuzzy risk factor (FRF) composed of a static risk factor (SRF) and a dynamic risk factor (DRF). The static risk factor assessment takes into account several static data relative to the ship (age, flag, gross tonnage, number of companies, duration of detention and type). The dynamic risk factor is evaluated by considering the meteorological conditions (sea state, wind speed and visibility) and the moment of the day. Moreover, the MARISA graphic interface developed with the Labview software is presented. This interface allows several simulations to be carried out to validate the fuzzy method proposed. Simulation results are presented. 相似文献
999.
Seasonal variability of living benthic foraminifera from the outer continental shelf of the Bay of Biscay 总被引:1,自引:0,他引:1
Grald Duchemin Frans J. Jorissen Franois Le Loc'h Franoise Andrieux-Loyer Christian Hily Grard Thouzeau 《Journal of Sea Research》2008,59(4):297-319
Living benthic foraminiferal faunas of six stations from the continental shelf of the Bay of Biscay have been investigated during three successive seasons (spring, summer and autumn 2002). For the three investigated stations, bottom water oxygen concentration, oxygen penetration into the sediment and sediment organic carbon contents are all relatively similar. Therefore, we think that the density and the composition of the foraminiferal faunas is mainly controlled by the quantity and quality of organic input resulting from a succession of phytoplankton bloom events, occurring from late February to early September. The earliest blooms are positioned at the shelf break, late spring and early summer blooms occur off Brittany, whereas in late summer and early autumn, only coastal blooms appear, often in the vicinity of river outlets. In spring, the benthic foraminiferal faunas of central (B, C and D) and outer (E) continental shelf stations are characterised by strong dominance in the first area and strong presence in the second area of Nonionella iridea. In fact, station E does not serve as a major depocenter for the remains of phytoplankton blooms. If station E is not considered, the densities of this taxon show a clear gradient from the shelf-break, where the species dominates the assemblages, to the coast, where it attains very low densities. We explain this gradient as a response to the presence, in early spring, of an important phytoplankton bloom, mainly composed of coccolithophorids, over the shelf break. This observation is supported by the maximum particles flux values at stations close to the shelf break (18.5 g m− 2 h− 1) and lower values in a station closer to the coast (6.8 g m− 2 h− 1). In summer, the faunal density is maximum at station A, relatively close to more varied phytoplancton blooms that occur off Brittany until early June. We suggest that the dominant species, Nonion fabum, Cassidulina carinata and Bolivina ex. gr. dilatata respond to phytodetritus input from these blooms. In autumn, the rich faunas of inner shelf station G are dominated by N. fabum, B. ex. gr. dilatata, Hyalinea balthica and Nonionella turgida. These taxa seem to be correlated with the presence of coastal blooms phenomena, in front of river outlets. They may be favoured by an organic input with a significant contribution of terrestrial, rather low quality organic matter. 相似文献
1000.
Yavuz Özdemir Jon Blundy Nilgün Güleç 《Contributions to Mineralogy and Petrology》2011,162(3):573-597
Süphan is a 4,050 m high Pleistocene-age stratovolcano in eastern Anatolia, Turkey, with eruptive products consisting of transitional
calc-alkaline to mildly alkaline basalts through trachyandesites and trachytes to rhyolites. We investigate the relative contributions
of fractional crystallization and magma mixing to compositional diversity at Süphan using a combination of petrology, geothermometry,
and melt inclusion analysis. Although major element chemistry shows near-continuous variation from basalt to rhyolite, mineral
chemistry and textures indicate that magma mixing played an important role. Intermediate magmas show a wide range of pyroxene,
olivine, and plagioclase compositions that are intermediate between those of basalts and rhyolites. Mineral thermometry of
the same rocks yields a range of temperatures bracketed by rhyolite (~750°C) and basalt (~1,100°C). The linear chemical trends
shown for most major and trace elements are attributed to mixing processes, rather than to liquid lines of descent from a
basaltic parent. In contrast, glassy melt inclusions, hosted by a wide range of phenocryst types, display curved trends for
most major elements, suggestive of fractional crystallization. Comparison of these trends to experimental data from basalts
and trachyandesites of similar composition to those at Süphan indicates that melt inclusions approximate true liquid lines
of descent from a common hydrous parent at pressures of ~500 MPa. Thus, the erupted magmas are cogenetic, but were generated
at depths below the shallow, pre-eruptive magma storage region. We infer that chemical differentiation of a mantle-derived
basalt occurred in the mid- to lower crust beneath Süphan. A variety of more and less evolved melts with ≥55 wt% SiO2 then ascended to shallow level where they interacted. The presence of glomerocrysts in many lavas suggests that cogenetic
plutonic rocks were implicated in the interaction process. Blending of diverse, but cogenetic, minerals, and melts served
to obscure the true liquid lines of descent in bulk rocks. The fact that chemical variation in melt inclusions preserves deep-seated
chemical differentiation indicates that inclusions were trapped in phenocrysts prior to shallow-level blending. Groundmass
glasses evolved after mixing and display trends that are distinct from those of melt inclusions. 相似文献