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排序方式: 共有96条查询结果,搜索用时 15 毫秒
11.
Using earthquakes relocated in north‐east Taiwan, we estimated b‐value distribution along a cross‐section located near the Ryukyu slab edge, and four b‐value anomalous areas are evidenced: (1) a high b‐value body lying on top of a low Vp, low Vs and high Vp/Vs sausage‐like body was considered as a region of enhanced partial melt or water supply above which seismicity occurs; (2) beneath the Ilan Plain, an anomalous area characterized by b‐values slightly higher than 1.1 might give evidence to the magma conduits to the Kueishantao Island; (3) above the Ryukyu Wadati‐Benioff zone, at depths ranging from 90 to 110 km, a high b‐value anomaly might correspond to the depth where dehydration occurs in the subducting oceanic plate; and (4) a low b‐value area located within the Ryukyu slab, at depths ranging from 70 to 90 km, might be linked to the compressive mechanisms shown by focal mechanisms and the bending of the subducting plate. 相似文献
12.
Abundances of the fireworm Hermodice carunculata were counted through a monitoring assessment study of fish cages in Barranco Hondo(NE Tenerife). Seven campaigns were conducted from November 2007 to June 2010 and temporal variations were found, as well as differences among sampling stations. The polychaete H. carunculata obtained its highest abundance in sediments beneath fish cages throughout the study period. Thus, the assemblages of this omnivorous species were favoured by the presence of fish cages. 相似文献
13.
Erzinger Jörg Hinz Karl Sibuet Jean-Claude Talwani Manik 《Marine Geophysical Researches》1998,20(4):251-252
Marine Geophysical Research - 相似文献
14.
As hypoxic conditions spread in our oceans, indices that quickly and efficiently assess oxygen content in sediment pore water, and habitat quality are increasingly becoming desirable. Depth to the appa... 相似文献
15.
Nabil Sultan Antonio Cattaneo Jean-Claude Sibuet Jean-Luc Schneider the Sumatra Aftershocks team 《International Journal of Earth Sciences》2009,98(4):823-837
The swath bathymetric data acquired during the “Sumatra Aftershocks” cruise from the Sunda trench in the Indian Ocean to the
north of the Sumatra Island imaged several scars and deposits. In situ pore pressure measurements using the Ifremer piezometer
and coring demonstrate that high excess pore pressure and sediment deformation was generated by a recent event in the scar
of the slope failure zone identified by J.T. Henstock and co-authors. This excess pore pressure is localized in the upper
sedimentary layers and is not related to an interplate subduction process. Numerical simulations of the hydrological system
that take into account the hydro-mechanical properties of the upper sediment layer show that the excess pore pressure and
sediment deformations could be generated at the time of the December 26, 2004 Great Sumatra Earthquake.
The Sumatra Aftershocks team: J.-C. Sibuet, S. Singh, R. Apprioual, N.C. Aryanto, J. Begot, A. Cattaneo, A.P.S. Chauchan,
R. Creach, J. Crozon, A. Domzig, N. Falleau, D. Graindorge, F. Harmegnies, Y. Haryadi, F. Klingelhoffer, S.K. Kolluru, J.-Y.
Landuré, C. Le Lann, J. Malod, A. Normand, G. Oggian, C. Rangin, D. Restunin Galih, J.-L. Schneider, N. Sultan, M. Taufik,
M. Umber and H. Yamaguchi. 相似文献
16.
David Drolet Michael R. S. Coffin Myriam A. Barbeau Diana J. Hamilton 《Estuaries and Coasts》2013,36(5):940-950
Movement of animals on intertidal mudflats can have profound consequences for population and community dynamics. Such movement is often influenced by biotic interactions, but the abiotic environment can also be important, affecting the strength of species’ interactions and even changing their outcome. Here, we focused on two biotic interactions and examined their effect on movement of the burrow-dwelling amphipod Corophium volutator: intraspecific interactions (specifically, the effect of conspecific density) and interspecific interactions with a competitor–predator, the mud snail Ilyanassa obsoleta (=Nassarius obsoletus). We assessed the magnitude of the temporal variation and examined the influence of pertinent abiotic variables (lunar cycle, presence of tide pools). Despite substantial temporal variation in movement levels, density of conspecifics did not influence emigration or immigration rates of C. volutator. Mud snails negatively affected immigration of C. volutator, and this was consistent across all lunar phases. However, mud snails influenced mortality and emigration of C. volutator in a contrasting way relative to lunar phases; sometimes amphipods evaded snails and survived, but at other times did not emigrate and were killed. The presence of tide pools did not change the nature or strength of the snail–amphipod interaction. Our results further clarify the complex interactions between C. volutator and I. obsoleta and suggest that resources on the mudflat are sufficient to sustain high densities of amphipods in a density-independent manner. Further, they highlight the importance of considering multiple environmental variables when examining interspecific interactions. 相似文献
17.
Olivier J. Hardy Céline Born Katarina Budde Kasso Daïnou Gilles Dauby Jérôme Duminil Eben-Ezer B.K. Ewédjé Céline Gomez Myriam Heuertz Guillaume K. Koffi Andrew J. Lowe Claire Micheneau Dyana Ndiade-Bourobou Rosalía Piñeiro Valérie Poncet 《Comptes Rendus Geoscience》2013,345(7-8):284-296
The biogeographic history of the African rain forests has been contentious. Phylogeography, the study of the geographic distribution of genetic lineages within species, can highlight the signatures of historical events affecting the demography and distribution of species (i.e. population fragmentation or size changes, range expansion/contraction) and, thereby, the ecosystems they belong to. The accumulation of recent data for African rain forests now enables a first biogeographic synthesis for the region. In this review, we explain which phylogeographic patterns are expected under different scenarios of past demographic change, and we give an overview of the patterns detected in African rain forest trees to discuss whether they support alternative hypotheses regarding the history of the African rain forest cover. The major genetic discontinuities in the region support the role of refugia during climatic oscillations, though not necessarily following the classically proposed scenarios. We identify in particular a genetic split between the North and the South of the Lower Guinean region. Finally we provide some perspectives for future study. 相似文献
18.
Wafa Abouchami Stephen J. G. Galer Tristan J. Horner Mark Rehkämper Frank Wombacher Zichen Xue Myriam Lambelet Melanie Gault‐Ringold Claudine H. Stirling Maria Schönbächler Alyssa E. Shiel Dominique Weis Philip F. Holdship 《Geostandards and Geoanalytical Research》2013,37(1):5-17
Research into natural mass‐dependent stable isotope fractionation of cadmium has rapidly expanded in the past few years. Methodologies are diverse with MC‐ICP‐MS favoured by all but one laboratory, which uses thermal ionisation mass spectrometry (TIMS). To quantify the isotope fractionation and correct for instrumental mass bias, double‐spike techniques, sample‐calibrator bracketing or element doping has been used. However, easy comparison between data sets has been hampered by the multitude of in‐house Cd solutions used as zero‐delta reference in different laboratories. The lack of a suitable isotopic reference material for Cd is detrimental for progress in the long term. We have conducted a comprehensive round‐robin assay of NIST SRM 3108 and the Cd isotope offsets to commonly used in‐house reference materials. Here, we advocate NIST SRM 3108 both as an isotope standard and the isotopic reference point for Cd and encourage its use as ‘zero‐delta’ in future studies. The purity of NIST SRM 3108 was evaluated regarding isobaric and polyatomic molecular interferences, and the levels of Zn, Pd and Sn found were not significant. The isotope ratio 114Cd/110Cd for NIST SRM 3108 lies within ~ 10 ppm Da?1 of best estimates for the Bulk Silicate Earth and is validated for all measurement technologies currently in use. 相似文献
19.
Cold-seep assemblages on a giant pockmark off West Africa: spatial patterns and environmental control 总被引:1,自引:0,他引:1
K. Olu-Le Roy J.-C. Caprais A. Fifis M.-C. Fabri J. Galéron H. Budzinsky K. Le Ménach A. Khripounoff H. Ondréas & M. Sibuet 《Marine Ecology》2007,28(1):115-130
A giant pockmark colonised by dense cold‐seep assemblages near 3160 m depth along the Congo‐Angola margin has been surveyed by the ROV Victor 6000. The quantitative distribution of chemosynthetic communities was mapped along the dive tracks from a video study using GIS and image mosaicking. Several types of faunal assemblages, either dominated by bivalves of the families Mytilidae (Bathymodiolus sp.) or Vesicomyidae (Calyptogena sp., ‘Vesicomya’ aff. chuni), or by Siboglinidae polychaetes (Escarpia southwardae) were mapped over the 800‐m diameter pockmark area and sampled for fauna, water and sediment. The isotopic analyses (δ13C) of tissues from symbiont‐bearing species were within the range typical of nutrition via symbiosis using methane for mussels and sulphide for vesicomyids and siboglinids. The living chemosynthetic communities were distributed on a SW‐NE axis, corresponding to the expression at the sediment surface of a main buried channel providing fluids to the pockmark. The site was characterised by a more active central part in a depression with abundant carbonate concretions where high‐density clusters of siboglinids and mytilids dominate. Large fields of dead and live vesicomyids with a lower mean density were observed in the external areas. The mean coverage of each of the three symbiotic taxa in these two contrasted areas was estimated from mosaic analysis and was up to 30% in the central area dominated by E. southwardae bushes (23%). Symbiont‐bearing species distribution was consistent with methane concentrations in seawater that were generally higher in mytilid beds than in the vicinity of siboglinids and vesicomyids. A Principal Component Analysis performed on environmental factors at the ten sampling sites revealed that 37% of the observed variance in the distribution of symbiont‐bearing species may be explained by variation in both methane and oxygen concentrations, while a Canonical Redundancy Analysis selected methane concentration as the only variable which explains symbiont‐bearing species densities. This spatial distribution of chemosynthetic species at the pockmark scale may reflect temporal patterns of succession of both substrate and fauna, and may be related to different individual pockmarks visible on the microbathymetry mapped using ROV data. 相似文献
20.
Nouzé Hervé Sibuet Jean-Claude Savoye Bruno Marsset Bruno Thomas Yannick 《Marine Geophysical Researches》1997,19(5):379-395
The Pasisar seismic acquisition system combines a source at the sea surface and a deep-towed single channel streamer. This unconventional device geometry reduces the width of the first Fresnel zone which increases the lateral resolution. However, the device acquisition geometry generates artifacts on seismic profiles and induces large incidence angles of the seismic signal. A specific processing sequence must be applied to the data to obtain a readable seismic section. Penetration of the seismic signal depends on the energy of the signal reaching the seafloor and on its incidence angle. Because of smaller source energy, 800 Joules Sparker data cannot be acquired in water depth larger than 1500 m for example, whereas there is no depth limit for the use of this system with air gun sources. Differential acoustic absorption of seismic frequencies (below 1000 Hz) in the water column is negligible when compared with wave fronts expansion. Thus, the horizontal resolution of any seismic system strongly depends on the frequency spectrum of the seismic source and on the travel distances. Pasisar and conventional seismic profiles being usually simultaneously recorded, we illustrate the interest of using a hybrid seismic device by comparing horizontal resolutions as well as signal-to-noise ratio obtained with both the Pasisar and conventional systems. In addition, by carefully picking time arrivals of a reflection on simultaneously recorded surface and deep-towed seismic records, it is possible to estimate the average interval seismic velocity. We present the simplified example of a horizontal reflector. 相似文献