Investigation of active faults in Morocco using morphometric methods and drainage pattern analysis     

Dr. Beonoit Deffontaines  Dr. Pierre Chotin  Dr. Lahsen Aït Brahim  Dr. Michel Rozanov 《International Journal of Earth Sciences》1992,81(1):199-210

A survey has been done of recently active faults in Morocco. In addition to field observations, morphometric methods were applied and an analysis was made of the drainage pattern. In the morphometric analysis, a map of vertical deformation was established from the elevations of summit level surfaces. This enables the recognition of neotectonic discontinuities and lithological contrasts; the actual discrimination of different rock-types can only be achieved by comparison with field observations. The analysis of drainage patterns — including their perturbations and anomalies — can also reveal the presence of features due to neotectonics, structural control or lithological variation. Certain faults can be detected which correspond to structures known from field geology or remote sensing (NE-SW and NW-SE oriented sets). Some new faults are observed which belong to these sets, as well as others which define a new N-S trending set. The present analysis leads to a distinction between ancient faults and currently active faults. The results of this study are shown on a map of recently active faults where the respective vertical displacements are also indicated.

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Zusammenfassung Bei einer Untersuchung der heute aktiven Störungen in Marokko wurden zusätzlich zu Feldbeobachtungen morphometrische Untersuchungen sowie eine Analyse des Entwässerungsnetzes durchgeführt. Bei der morphometrischen Analyse wurde eine Karte der vertikalen Deformationen von Aufragungen aus den Gipfelfluren abgeleitet. Dadurch können neotektonische Diskontinuitäten sowie lithologische Kontraste erkannt werden; die wirkliche Unterscheidung verschiedener Gesteinstypen kann aber nur im Vergleich mit Feldbeobachtungen erreicht werden. Die Analyse des Gewässernetzes — auch seiner Komplikationen und Anomalien — kann gleichfalls Elemente aufdecken, welche neotektonischen Ursprungs bzw. strukturell bedingt oder aber auf lithologische Unterschiede zurückzuführen sind. Bestimmte Störungen korrespondieren mit Strukturen, die aus der Feldgeologie oder der Fernerkundung bekannt sind (NE/ SW- und NW/SE-gerichtete Scharen). Einige neu entdeckte Störungen gehören zu diesen Scharen, während andere ein neues, N/S-streichendes System deutlich machen. Die vorgelegte Analyse erlaubt, zwischen älteren und noch heute aktiven Störungen zu unterscheiden. Unsere Ergebnisse sind in einer Karte der aktiven Störungen zusammengefaßt, in die die vertikalen Versätze gleichfalls eingetragen wurden.

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Résumé Un recensement des failles à jeu récent (néotectonique) a été fait sur l'ensemble du Maroc. Outre les observations de terrain, les méthodes de la morphométrie et celles de l'analyse du réseau hydrographique sont appliquées. En morphométrie, l'établissement d'une carte de la déformation verticale d'après la situation altimétrique de la surface sommitale permet la reconnaisance de structures (discontinuités) néotectoniques et d'alternances lithologiques (la discrimination ne peut être faite que sur le terrain). De même l'analyse du réseau hydrographique, de ses perturbations et de ses anomalies (cf. infra) met en évidence des discontinuités dues à la néotectonique, à la structure des terrains et à la lithologie. Les ensembles morphostructuraux marocains (Meseta, Rif, Atlas), ressortent nettement de la carte de synthèse. On y retrouve les failles connues par la géologie de terrain et par l'analyse des images satellitaires (ensembles de direction NE-SW et NW-SE), de nouvelles failles appartenant à ces deux familles, ainsi qu'un nouvel ensemble de failles de direction N-S. Cette analyse permet de distinguer failles actives et failles anciennes. Les résultats sont portés sur la carte des principales failles à jeu récent avec leurs rejets verticaux respectifs.

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Long-Term Validation of Wave Height Measurements from Altimeters   总被引：1，自引：0，他引：1  

Pierre Queffeulou 《Marine Geodesy》2004,27(3):495-510

Since July 1991, six altimeter missions have been launched successfully, and they have provided almost continuous wave height measurements for more than 12 years. Long-term series of wave height measurements are of major interest for climatology and oceanic wave modeling. Before using such data, the measurements have to be validated, and the homogeneity of the data from various satellites has to be checked. Significant wave height measurements from ERS, TOPEX/Poseidon, GEOSAT Follow-on, Jason-1 and ENVISAT altimeters are validated using cross-altimeter and buoy comparisons. Emphasis is put on the two recent missions Jason-1 and ENVISAT. Corrections for biases and trends are proposed for the six altimeters, allowing the generation of consistent and homogeneous data. Tests of these corrections are performed over global ocean simple statistics.  相似文献   

Hawaii Cyclonic Eddies and Blue Marlin Catches: The Case Study of the 1995 Hawaiian International Billfish Tournament   总被引：6，自引：0，他引：6  

Michael P. Seki  Rick Lumpkin  Pierre Flament 《Journal of Oceanography》2002,58(5):739-745

The combination of prevailing northeasterly tradewinds and island topography results in the formation of vigorous, westward propagating cyclonic eddies in the lee of the Hawaiian Islands on time scales of 50–70 days. These mesoscale (∼10² km) features are nowhere more conspicuous or spin up more frequently than in the Alenuihaha Channel between the Island of Maui and the Big Island of Hawaii. Cyclonic eddies in subtropical waters such as those around Hawaii vertically displace the underlying nutricline into the overlying, nutrient-depleted euphotic zone creating localized biologically enhanced patches. Insight into how these eddies may directly influence pelagic fish distribution is provided by examination of recreational fish catch data coinciding with the presence of eddies on the fishing grounds. We highlight the 1995 Hawaii International Billfish Tournament in which a cyclonic eddy dominated the ocean conditions during the weeklong event and the fish catch distribution differed significantly from the average historical tournament catch patterns. On the tournament fishing grounds, well-mixed surface layers and strong current flows induced by the eddy's presence characterized the inshore waters where the highest catches of the prized Pacific blue marlin (Makaira mazara) occurred, suggesting possible direct (e.g., physiological limitations) or indirect (e.g., prey availability) biological responses of blue marlin to the prevailing environment. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Characterization of multiple functional groups on kaolinite     

James R. Kramer  Pamela Collins  Pierre Brassard 《Marine Chemistry》1991,36(1-4)

Multiple proton functional group conditional binding constants (K′_i) and their concentrations (C_i) are determined from detailed acid/base titration data. The C-K′ information is obtained for kaolinite by assuming that the distribution can be approximated by cumulative independent mono protic groups. Linear programming optimization techniques are used to Fit the data. In addition, the electrode calibration is optimized in the data fit. This adjustment is important for high and low pHs. Discrete concentration dependent pXs of about 3.4, 4.5, 6.7 and 9.8 are determined for a reference kaolinite. These correspond reasonably well to designations made by Wehrli et al. (1990, Aquatic Sciences, Vol. 52, pp. 1–31 ) to A10H2 and AlOH proton reactions at edge and surface sites and to silanol exchange. There is an ionic strength effect for one site. Long and short reaction times and reversibility affect the results.  相似文献   

Analysis of vessel influence on spatial behaviour of fish schools using a multi-beam sonar and consequences for biomass estimates by echo-sounder     

Soria  Marc; Freon  Pierre; Gerlotto  Francois 《ICES Journal of Marine Science》1996,53(2):453-458

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Indices for capturing spatial patterns and their evolution in time, with application to European hake (Merluccius merluccius) in the Bay of Biscay     

Woillez  Mathieu; Poulard  Jean-Charles; Rivoirard  Jacques; Petitgas  Pierre; Bez  Nicolas 《ICES Journal of Marine Science》2007,64(3):537-550

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New data on the distribution of the 'deep-sea' sponges Asbestopluma hypogea and Oopsacas minuta in the Mediterranean Sea     

Tatjana Bakran-Petricioli  Jean Vacelet  Helmut Zibrowius  Donat Petricioli  Pierre Chevaldonné  & Ton&#;i Ra&#;a 《Marine Ecology》2007,28(S1):10-23

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Dosage de l'ammonium dans l'eau de mer: comparaison entre deux methodes d'analyse automatique     

Le Corre  Pierre; Treguer  Paul 《ICES Journal of Marine Science》1978,38(2):147-153

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Microzooplankton Grazing in the Southern Ocean: Implications for the Carbon Cycle     

Pierre  Froneman Renzo  Perissinotto 《Marine Ecology》1996,17(1-3):99-115

Abstract. Microzooplankton grazing and protozooplankton community structure was investigated in austral summer (Jan./Feb.) and winter (June/July) 1993 in the Atlantic sector of the Southern Ocean during the SAAMES (South African Antarctic Marine Ecosystem Study) Il and III cruises. Grazing was estimated at 22 stations in summer and at 15 stations in winter by employing the sequential dilution technique. Nano-heterotrophic flagellates (< 20 μm) and ciliates (aloricate ciliates and tintinnids) dominated the protozooplankton assemblages along both transects. Densities in winter were, however, nearly an order of magnitude lower than in summer. Microzooplankton grazing removed between 0 and 28% (mean = 13.2%) of the initial phytoplankton stock in summer and, between 24 and 51 % of the initial stock (mean = 37.6%) in winter. The potential primary production removed during summer ranged between 0 and 46% (mean = 22.0%) compared with the winter range of 56–83% (mean = 67.2%). Size selectivity grazing experiments conducted during both studies suggest that microzooplankton preferentially graze on the nano- (20–2.0μm) and picophytoplankton (2.0–0.2μm) size fractions. These results have important implications for the efficiency of the carbon pump in the Southern Ocean. During summer when the larger cells dominate phytoplankton biomass, the bulk of the photosynthetically fixed carbon appears to be channelled to the meso- and macrozooplankton fractions. This results in a rapid transfer of organic carbon out of the zone of regeneration to the deep ocean via vertical migration and large faecal pellet production. During winter, however, an increase in the contribution of the smaller size fractions to total phytoplankton biomass results in a greater proportion of the photosynthetically fixed carbon being channelled to the microzooplankton fraction. The efficiency of the carbon pump is, therefore, reduced in that the transfer of carbon below the zone of regeneration is reduced as carbon is recycled mostly within the microbial loop in the upper mixed layer.  相似文献   

Direction de croissance des eperons sur le front d''un recif barriere — L''exemple du Grand Recif de Tulear (Madagascar)     

Pierre Weydert 《Marine Geology》1979,30(3-4):M9-M19

A study has been made of the orientation of the spurs of the outer front of a barrier coral-reef tract in the Bay of Tuléar on the southwest coast of Madagascar. All types of coral reef tracts are present: outer or barrier reefs, lagoon reefs and coral banks. The orientation of the spurs was studied as a function of the direction of the swell crests which are either parallel or oblique to the alignment of the reef front of the “Grand Récif” which extends over 18 km. When the swell is oblique, the spurs are not, as is generally held, perpendicular to the crests of the swell. The orientation of the spurs is a resultant direction between the direction of the swell orthogonals and the direction of the slope of the outer reef flat. From aerial photographs one can determine the directions of the spurs and of the slope of the outer reef flat. It is easy to obtain the direction of the crests of the swell and then to construct the wave diagram. The morphological aspects and the distribution of the deposits on the inner flat of the coral reef tract depend on the orientation of the swell.

Résumé

L'étude de l'orientation des éperons d'un front récifal externe a été réalisée dans la baie de Tuléar sur la côte sud-ouest de Madagascar. Dans ce secteur, tous les types d'édifices récifaux sont présents: récifs barrières externes, récifs de lagon et bancs coralliens. Nous avons étudié l'orientation des éperons en fonction de la direction de la houle qui est soit parallèle, soit oblique par rapport au front récifal du Grand Récif qui s'étend sur 18 km. Quand la houle est oblique, les éperons ne sont pas — comme on le dit généralement — perpendiculaires à la houle, mais leur orientation est une direction résultante entre la direction de propagation de la houle et celle de la pente du platier récifal au point considéré. Sur les photographies aériennes, on détermine la direction des éperons et celle de la pente. Une construction simple permet d'obtenir la direction de la crête des vagues et de construire le plan de vagues. Toute la morphologie et la répartition des dépôts du platier d'un édifice récifal sont sous la dépendance de l'orientation de la houle.  相似文献