The Huelva (Spain) Tsunami-Ready Station and Its Interaction with Storm Emma (March 2018)     

Jue Lin-Ye  Begoña Pérez-Gómez  Enrique Álvarez-Fanjul  Javier García-Valdecasas 《Marine Geodesy》2020,43(5):509-539

Abstract

The sea level station operating since 1996 at Mazagón (Huelva, Spain) has been progressively upgraded to fit tsunami warning requirements, due to its location in one of the main regions at risk. Its radar water level sensor was complemented in 2017, with the addition of a pressure sensor. The performance of both sea level sensors and their response to sea level oscillations, at different frequencies, is assessed. Particular emphasis is put on the effect of extreme events, such as Storm Emma, when alternative methods to obtain 1-min data are tested, in contrast to the one based on arithmetic means. The overall differences are small, for the whole period of study (centered-root-mean-square-error below 1?cm, for 5-min, and hourly data; similar tidal parameters and sea level oscillations with periods between 30?s and 5?min). However, during Storm Emma, the pressure sensor presents sensibly lower readings than the radar, with the centered-root-mean-square-error rising to 80?mm on the March 2^nd 2018. A new method to compute 1-min data, based on medians, reduced this value to 10?mm for the same day.  相似文献   

Otolith shape as a stock discrimination tool for ling (Genypterus blacodes) in the fjords of Chilean Patagonia     

Rodrigo Wiff  Andrés Flores  Angel M. Segura  Mauricio A. Barrientos  Vilma Ojeda 《新西兰海洋与淡水研究杂志》2020,54(2):218-232

ABSTRACT

Genypterus blacodes, in terms of its fishing history and local economic importance, is an emblematic species harvested in Chilean Patagonia (41°00’–57°00’S). Most of the current fisheries and biological knowledge of this species come from the open ocean, whereas information about the species in fjords and inner channels is fragmentary. In 2018, two research surveys targeting G. blacodes were conducted in the fjords and inner channels of Chilean Patagonia. A total of 253 pairs of sagittal otoliths were sampled at three different localities, and their contours were modelled using wavelet analysis as a tool for stock discrimination. Contours were compared using canonical analysis, and classification was performed using linear discriminant and Random Forest analyses. The results indicated that the wavelet method is efficient in modelling otolith contours, and the discriminant analyses showed differences among fishing grounds across the latitudinal gradient, thus confirming the hypothesis that G. blacodes conform to at least two separate stock units in Chilean Patagonia. Fishing grounds that were closer in space showed higher levels of misclassification. The discussion focuses on how environmental variables and the geography of fjords shape stock differences and how this information can be used for the sustainable management of G. blacodes.  相似文献   

Preliminary attempt to characterize the rotation of seafloor in the Pito Deep area of the Easter Microplate using a submersible magnetometer     

R.N. Hey  F. Martinez  S. Diniega  D.F. Naar  J. Francheteau  R. Armijo  M. Constantin  J.P. Cogné  J. Girardeau  R. Hekinian  R. Searle 《Marine Geophysical Researches》2002,23(1):1-12

Several mechanisms have been proposed to account for the rotation of the nearly north-south abyssal hill fabric formed on the East Pacific Rise north of the Easter Microplate to the nearly east-west trends in the northern microplate interior. Proposed mechanisms include rigid microplate rotation, transform fault – parallel shear, and bookshelf faulting during the transfer of lithosphere from the Nazca Plate to the microplate. We used a submersible magnetometer on a NAUTILE dive program to measure the magnetic vector rotation of a pillow basalt and dike spur near Pito Deep, the present location of the tip of the propagating rift system that created the microplate. Our results, although too limited to draw strong conclusions from, suggest clockwise rotations of the seafloor magnetic vectors inconsistent with the transform-parallel shear model, and larger than can be explained solely by rigid microplate rotation.  相似文献   

The Equatorial Atlantic Mid-Ocean Channel: An Ultra High-Resolution Image of Its Burial History Based on TOPAS Profiles     

Baraza  J.  Ercilla  G.  Farrán  M.  Casamor  J. L.  Sorribas  J.  Flores  J. A.  Sierro  F.  Wersteeg  W. 《Marine Geophysical Researches》1997,19(2):115-135

Multibeam bathymetric and ultra high-resolution seismic data reveal that the distal course of the Equatorial Atlantic Mid-Ocean Channel (EAMOC) extends further east and south than was previously known, and is controlled by the presence of morphologic highs related to the Fernando de Noronha Fracture Zone. Distal course of the EAMOC is buried by sediments, and does not have bathymetric expression on the seafloor. The channel fill consists of three seismic sequences, suggesting that the recent geological evolution of the channel is composed of successive phases of decreasing sedimentary activity that finally resulted in its complete burial. Tectonic and volcanic activity related to the Fernando de Noronha Fracture Zone and Ridge, together with the effect of strong pulses of the Antarctic bottom water current during the upper Pliocene are suggested to have contributed to the progressive burial and the final abandonment of the EAMOC.  相似文献   

Active spreading and hydrothermalism in North Fiji Basin (SW Pacific). Results of Japanese French Cruise Kaiyo 87     

Jean-Marie Auzende  Eiichi Honza  Xavier Boespflug  Satendra Deo  Jean-Philippe Eissen  Jun Hashimoto  Philippe Huchon  Junichiro Ishibashi  Yo Iwabuchi  Philip Jarvis  Masato Joshima  Kiyoyuki Kisimoto  Yasuto Kuwahara  Yves Lafoy  Tsuyoshi Matsumoto  Jean-Pierre Maze  Kiyohiko Mitsuzawa  Hiroyasu Monma  Takeshi Naganuma  Yukihiro Nojiri  Suguru Ohta  Kiyoshi Otsuka  Yoshihisa Okuda  Hélène Ondreas  Akira Otsuki  Etienne Ruellan  Myriam Sibuet  Manabu Tanahashi  Takeo Tanaka  Tetsuro Urabe 《Marine Geophysical Researches》1990,12(4):269-283

The aim of the Japanese-French Kaiyo 87 cruise was the study of the spreading axis in the North Fiji Basin (SW Pacific). A Seabeam and geophysical survey allowed us to define the detailed structure of the active NS spreading axis between 16° and 22° S and its relationships with the left lateral motion of the North Fiji Fracture Zone. Between 21° S and 18°10′ S, the spreading axis trends NS. From 18°10 S to 16°40 S the orientation of the spreading axis changes from NS to 015°. North of 16°40′ S the spreading axis trends 160°. These two 015° and 160° branches converge with the left lateral North Fiji fracture zone around 16°40′ S to define an RRFZ triple junction. Water sampling, dredging and photo TV deep towing give new information concerning the hydrothermal activity along the spreading axis. The discovery of hydrothermal deposits associated with living communities confirms this activity.  相似文献   

Sediment transport pattern at the Barra Nova inlet, south Portugal: a conceptual model     

Yann Balouin  Hélène Howa 《Geo-Marine Letters》2002,21(4):226-235

The Barra Nova inlet, in south Portugal, is known to migrate progressively southeastwards under wave action. The morphodynamics of this system during a representative year suggests that this long-term evolution is dependent on a seasonal behavior of the tidal inlet which can be described through a three-stage model of post-storm, transition and extended fair-weather conditions. Processes involved in this evolution indicate that the historical migration of the Barra Nova is not dependent on the longshore drift forcing constricting the channel on the updrift coast, but rather on the adjustment of the system to a major erosion of the downdrift coast during short storm events.  相似文献   

Diet of Phycis blennoides (Gadidae) in Relation to Fish Size and Season in the Western Mediterranean (Spain)     

Maria Salomé Morte  Manuel J. Redón  & Antonio Sanz-Brau 《Marine Ecology》2002,23(2):141-155

Abstract. Despite its commercial value, little is known about the feeding ecology of the greater forkbeard, Phycis blennoides (Brünnich 1768). The stomach contents of 2631 greater forkbeard were taken at monthly intervals off the coast of the Gulf of Valencia (western Mediterranean). They were examined in order to assess the diet and to determine the fish size- and season-related dietary variation of the species. Prey items were identified to the lowest taxonomic level possible. The basic food consisted of epibenthic species, mostly Decapoda, Mysidacea and Teleostei. A change in food composition based on fish size was observed and seasonal variation in diet was also recorded. The food overlap analysis indicated a high convergence in diet among similar size groups.  相似文献   

The contribution of nano- and micro-planktonic assemblages in the surface layer (0-30 m) under different hydrographic conditions in the upwelling area off Concepción, central Chile     

V. Anabalón  R. Escribano  M. Angélica Varas 《Progress in Oceanography》2007,75(3):396-414

In the highly productive region off central Chile, the structure and temporal and spatial variability of planktonic assemblages, and the factors that determine changes in this structure are poorly understood. In the region, wind-driven upwelling, heating by solar radiation and freshwater inputs are highly seasonal processes, which, together with higher frequency events, can promote changes in the planktonic communities, especially in the upper layer. This study focuses on the structure of nano- through to micro-planktonic assemblages (2-200 μm) of unicellular organisms (protists) in surface waters (0-30 m) during different hydrographic conditions. Samples were taken from a fixed shelf station off Concepción (COPAS time series Station 18) on eight occasions between September 2003 and August 2004. The nano-plankton flagellate-dominated fraction was numerically important during the whole period. Maxima in flagellate abundance and biomass occurred during the upwelling period (November-April samplings) but these maxima appear to be unrelated to the degree of water column stratification. The micro-plankton diatom-dominated fraction was usually the largest component in terms of biomass during the study period and the diatoms made important numerical contributions during the upwelling period, with maxima in abundance and biomass when water column stability was lowest. The dominant genera and morphotypes in each functional group were found throughout the study period, with maxima in abundance and biomass co-occurring under similar environmental upwelling conditions. The mean macro-nutrient concentrations (nitrate and silicate) were relatively high in the top 30 m during both upwelling and non-upwelling periods, and did not explain the maxima in plankton or functional group replacements. The persistence of the dominant taxa in the planktonic assemblages suggests a high degree of flexibility, though probably not at the specific level, to withstand the highly variable environmental conditions in this upwelling area.  相似文献   

Evidence for sinistral strike-slip deformation in The Solomon Island arc     

J. -M. Auzende  L. Géli  H. Ondréas  J. -Y. Collot  Y. Lafoy  J. -P. Eissen  E. Gracia  M. B. Larue  C. Olisukulu  D. Tolia  N. Biliki 《Geo-Marine Letters》1994,14(4):232-237

During the SOPACMAPS 2 crusie carried out by IFREMER (Institut Français de Recherche pour l'Exploitation de la Mer) and ORSTOM (Institut Français de Recherche Scientifique pour le dévelopement en Coopération) on theR/V L'Atalante, in the Central Solomon Arc area, multibeam bathymetric and imagery data and single-channel seismic reflection profiles were collected from an area of about 3500 km², to evaluate regional tectonics. Structural data geophysical profiles interpretation provide evidence for left-lateral transtensional tectonics on the southern edge of the Central Solomon Trough. This transtensional deformation is represented by faulting, block tilting, and rhombohedral deformation. The regional geology and the analysis of the sedimentary cover allow us to demonstrate that this tectonic occurred in two different phases during Oligocene to Miocene and Pliocene to Pleistocene times.  相似文献   

Geodynamic Evolution of the Eastern Segment of the Azores-Gibraltar Zone: The Gorringe Bank and the Gulf of Cadiz Region     

Tortella  D.  Torne  M.  Pérez-Estáun  A. 《Marine Geophysical Researches》1997,19(3):211-230

Detailed structural interpretation of the recently acquired deep seismic multichannel profiles along the Iberian Atlantic Margins (IAM Project) provides new results on the geodynamic evolution of the eastern part of the Azores-Gibraltar plate boundary. Thrusting and folding of the oceanic basement and of Mesozoic and Cenozoic sedimentary cover of the Gorringe Bank region are consistent with the N–S convergence of Iberia and Africa. Compressive structures in the Gorringe Bank region are spread over a wide area. Deformation under compression took place mainly in Tertiary times, as is evidenced by a basal unconformity and several discontinuities in Tertiary sediments, although some deformation has also been recorded in Quaternary sediments. The compressive structures in the Gulf of Cadiz are E–W oriented thrusts, folds and related diapiric structures. N–S oriented transpressive deformation is likely to occur in the western Portuguese platform. There is no continuity of structures from the oceanic to the continental domain, suggesting that deformation transfers from one side to the other through a transcurrent fault zone. The fault contact between the two domains is located in the ocean-continent transition zone.  相似文献