Altres

Els filtres actuals son: Any inici = 2012, Any final = 2017
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Durán R., Alonso B., Ercilla G., Estrada F., Casas D., Muñoz A. (2017)
Atlas of Bedforms in the Western Mediterranean. Ed. J. Guillén, J. Acosta, F.L. Chiocci, A. Palanques. Springer. 135-141. DOI: 10.1007/978-3-319-33940-5_22. ISBN. 978-3-319-33938-2. (BibTeX: duran.etal.2017a)
Resum: Veure
The dynamics of sorted bedforms on the inner shelf off El Masnou coast (NW Mediterranean) was investigated based on time-series of swath bathymetry and backscatter and grain-size analysis of grab samples spanning 4 years (2006–2009). The sorted bedforms are superimposed on the edge of a shallow infralittoral wedge with an orientation nearly perpendicular to the slope and oblique to the shoreline. They commonly display lateral asymmetry in backscatter, with the high backscatter domain on the depression and on the eastern side of the bedforms. The short-term evolution of these bedforms evidenced changes in the location of the bedform boundaries, widening and narrowing, predominant migration towards the southwest in the direction of the net alongshore sediment transport, and formation of new sorted bedforms. The analysis of repeated bathymetries also revealed the impact of dredging activities on the sorted bedforms, resulting in the destruction of part of the bedform pattern, which started to recover over the subsequent months. This behaviour suggests that the sorted bedforms off El Masnou are persistent and dynamic over a 4 year time span
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Gutt J., Cummings V., Dayton P., Isla E., Jentsch A., Schiaparelli S. (2016)
Marine Animal Forests : The Ecology of Benthic Biodiversity Hotspots. Ed. S. Rossi, L. Bramanti, A. Gori, C. Orejas Saco del Valle. Springer. 1-30. DOI: 10.1007/978-3-319-17001-5_8-1. ISBN. 978-3-319-17001-5. (BibTeX: gutt.etal.2016a)
Resum: Veure
Both Southern Ocean and terrestrial systems contain three-dimensional biotic components that are key in shaping and defining their respective ecosystems and communities. Antarctic suspension-feeding communities, which inhabit the shelf of the Southern Ocean, resemble “Terrestrial Vegetation Forests” (TVF) or shrublands and support the concept of “Antarctic Marine Animal Forests” (AMAF). They comprise mostly sessile animals, provide microniches for an associated mobile fauna, and are fragmented and regionally mixed with other communities. On land, only high mountains and very dry regions are unsuitable for TVF, analogous to the virtual absence of AMAF from the deep sea (>1000 m). Besides fundamental differences between these systems in energy flow and other ecological drivers such as light requirements and dispersal opportunities, both “forests” experience similar disturbances, which impact ecosystem dynamics and diversity in similar ways. While land use affects and reduces terrestrial forests, climate change and fishing impacts are the most serious threats to the Southern Ocean ecosystem. Research priorities for a better understanding of “Antarctic Marine Animal Forests” demand (1) mapping biotic communities and their structural and functional diversity, especially in terms of hot and cold spots; (2) understanding ecological function, including ecosystem productivity and dynamics; (3) cross-system comparison to identify generality or uniqueness in ecosystem structure and dynamics; and (4) implication of existing and new research approaches and conservation strategies.
Paraules clau: Limiting factors, ecological drivers, areal coverage, three-dimensional structure, interactions, energy, flow, disturbance, climate change, conservation
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Isla E. (2016)
Source-to-Sink Fluxes in Undisturbed Cold Environments. Ed. A.A. Beylich, J.C. Dixon, Z. Zwoliński. Cambridge University Press. Chap. 16. 199-212. ISBN. 9781107068223. (BibTeX: isla.2016c)
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Durán R., Guillén J., Simarro G., Ribó M., Puig P., Muñoz A., Palanques A. (2015)
The Proceedings of the Coastal Sediments 2015. Ed. P. Wang, J.D. Rosati, J. Cheng. World Scientific Publishing. DOI: 10.1142/9789814689977_0111. ISBN. 978-981-4689-98-4. (BibTeX: duran.etal.2015a)
Resum: Veure
An extensive dataset of vibrocores and high-resolution seismic data allowed characterizing a sand ridge field in the Valencia mid-outer shelf. Sediment coring revealed a layer of coarse sand to gravel with pebbles corresponding with the basal reflector which is identified in the seismic profile and interpreted as the Holocene ravinement surface. Internally, the sand ridges displays medium to high-angle dipping reflectors indicating long-term migration towards the southeast, in the direction of present-day sediment transport. In addition, the occurrence of interbedded mud layers within the ridge sand unit, together with the dipping internal reflectors suggests episodic ridge migration and reactivation. The internal structure of small sand ridges also provides additional information about the mechanisms of ridge degradation. Regarding to the use of the Valencia sand ridges as potential borrow area, it was identified a sand deposit of 22·million m of relatively well-sorted medium and coarse sand with a limited mud content, that must be preserved as strategic sand reservoir.
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Palomino D., Alonso B., Lo Iacono C., Casas D., d\'Acremont E., Ercilla G., Gorini C., Vázquez J.-T. (2015)
Atlas of the Mediterranean Seamounts and Seamount-like Structures. Ed. M. Würtz, M. Rovere. IUCN. Chap. 1. 19-55. ISBN. 978-2-8317-1750-0. (BibTeX: palomino.etal.2015a)
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Alonso B., Ercilla G., Garcia M., Vázquez J.T., Juan C., Casas D., Estrada F., D´Acremont E., Gorini Ch., El Moumni B., Farran M. (2014)
Submarine Mass Movements and Their Consequences. In: Advances in Natural and Technological Hazards Research 37. Ed. S. Krastel et al. Springer. Chap. 50. 561-570. DOI: 10.1007/978-3-319-00972-8_50. ISBN. 978-3-319-00972-8. (BibTeX: alonso.etal.2014b)
Resum: Veure
The Quaternary stratigraphic architecture of seamounts and surrounding deposits in the eastern Alboran Sea reveals at least 53 stacked MTDs in the Pollux Bank, Sabinar Bank (Sabinar Platform and Western Sabinar), Maimonides Ridge, and Adra Ridge. These MTDs are grouped into two types based on their size: smallscale MTDs (length <5 km and thickness <18 ms) and large-scale MTDs (length >5 km and thickness >18 ms). The study of these deposits has allowed us to define a close relationship between size (thickness-length) and source area gradients. The frequency of MTD events has varied between 40 and 373 kyr throughout the Quaternary (1.8 Ma to present). Correlation between individual MTDs is difficult but could be done for at least one local MTD event between Sabinar Platform and Western Sabinar (Sabinar Bank); in addition, one regional MTD event has been recognized around all of the studied seamounts. These failure events could have been triggered by tectonically controlled seismicity at both regional and local scale.
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Bartolomé R., Córdoba D., Nuñez F., Dañobeitia J.J., L. Alonso J., L. Cameselle A., Castellón Arturo, Estrada F., Farran M., Perea H., Prada M., Working Group TSUJAL (2014)
Una aproximación multidisciplinar al estudio de las fallas activas, los terremotos y el riesgo sísmico. In: Segunda reunión ibérica sobre fallas activas y paleosismología, Lorca, (Murcia, España). Ed. J.A. Álvarez-Gomez, F. Martín González. Instituto Geológico y Minero de España. 117-120. ISBN. 978-84-617-2049-1. (BibTeX: bartolome.etal.2014c)
Resum: Veure
During the spring of 2014, scientists onboard the RSS James Cook explored the western margin of Mexico through a dense geophysical sampling of the plates. Data obtained during the oceanographic survey images the crustal transition from an active margin where the Rivera Plate subducts beneath the North American plate, a process that has been taking place since Middle Miocene (10 Ma), to the rifting zone in the Gulf of California. The tectonic processes occur in a geological setting of high seismicity, where earthquakes M= 8.2 have taken place and where a high probability of tsunami generation exists. From a tectonic point of view, this is a complex region where several plates interact with accretionary processes in the East Pacific Rise, subduction processes occurs in the Middle American Trench and an important segmentation of extensional faults exists in the mouth of the Gulf of California. The new TSUJAL seismic images and models recently obtained unravel the geometry and morphology of faults and mass wasting, possible sources of seismic and tsunami events, as well as the crustal structure in the different domains of the Mexican margin. Proyecto y campaña marina TSUJAL: caracterización del peligro sísmico y tsunamigénico asociado a la estructura cortical del contacto Placa de Rivera-Bloque de Jalisco.
Paraules clau: Multichannel seismic, wide angle seismics, west margin of Mexico, seismic hazard asessment
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Cameselle A.L., Ranero C.R., Franke D., Barckhausen U. (2014)
EGU General Assembly 2014. In: Geophysical Research Abstracts. ol. 16, 14917. (BibTeX: cameselle.etal.2014e)
Resum: Veure
The continent to ocean transition (COT) architecture of rifted margins represents a key aspect in the study of the variability of different rifting systems and thus, to understand lithospheric extension and final break-up processes. We used 2250 km of reprocessed multichannel seismic data along 4 regional lines and magnetic data acquired across the NW South China continental margin to investigate a previously poorly defined COT. The along-strike structure of the NW subbasin of the South China Sea presents different amounts of extension allowing the study of conjugate pairs of continental margins and their COT in a relative small region. The time-migrated seismic sections allow us to interpreted clear continental and oceanic domains from differences in internal reflectivity, faulting style, fault-block geometry, the seismic character of the top of the basement, the geometry of sediment deposits, and Moho reflections. The continental domain is characterized by arrays of normal faults and associated tilted blocks overlaid by syn-rift sedimentary units. The Moho is imaged as sub-horizontal reflections that define a fairly continuous boundary typically at 8-10 s TWT. Estimation of the thickness of the continental crust using 6 km/s average velocity indicates a ∼22 km-thick continental crust under the uppermost slope thinning abruptly to ∼9-6 km under the lower slope. The oceanic crust has a comparatively highly reflective top of basement, little-faulting, not discernible syn-tectonic strata, and fairly constant thickness (4-8 km) over tens of km distance defined by usually clear Moho reflections. The COT can be very well defined based on MSC images and occurs across a ∼5-10 km narrow zone. Rifting in the NW subbasin resulted in asymmetric conjugate margins. Arrays of tilted fault blocks covered by abundant syn-rift sediment are displayed across the northwestern South China continental margin, whereas the conjugate Macclesfield Bank margin shows abrupt thinning and little faulting. Seismic profiles also show a clear change in the tectonic structure of the margin from NE to SW. On the two NE-most lines, the abrupt crustal thinning occurs over a 20-40 km wide area resulting in final breakup. To the SW, the area of stretched continental crust extends over a comparatively broader ∼100-110 km segment of tilted fault-blocks. We interpret that the 3D structural variability and the narrow COT is related to the lateral NE to SW propagation of a spreading center. The early spreading center propagation in the NE suddenly stopped continental stretching during ongoing rifting, causing an abrupt break-up and a narrow COT. Later arrival of spreading center to the SW resulted in a comparatively broader segment of highly stretched continental crust. We suggest that the final structure of the northwest South China continental margin have been governed by the 3D interaction between rifting and oceanic spreading center propagation to a degree larger than by the local lithospheric structure during rifting.
, Bartolome R., Perea H., Moreno X., Gómez de la Peña L., Ranero C.R., Lo Iacono C., Martínez-Loriente S., , Masana E., Dañobeitia J. (2014)
Una aproximación multidisciplinar al estudio de las fallas activas, los terremotos y el riesgo sísmico. In: Segunda reunión ibérica sobre fallas activas y paleosismología, Lorca, (Murcia, España). Ed. J.A. Álvarez Gómez, F. Martín González. Instituto Geológico y Minero de España. 101-104. ISBN. 978-84-617-2049-1. (BibTeX: .etal.2014f)
Resum: Veure
During the last ten years we have carried out successive marine geological and geophysical cruises in the Alboran Sea, where present-day crustal deformation is driven mainly by the NW-SE convergence (4.5-5.6 mm/yr) between the African and Eurasian plates. We present an overview of selected active faults recently characterized in the Alboran Sea. The dataset, from very high-resolution to deep penetration, has been acquired in the frame of national (IMPULS, EVENT and SHAKE) and European projects (WESTMED and TOPOMED-GASSIS). We will mainly focus in a) the southern marine termination of the Eastern Betic Shear Zone, the left-lateral Carboneras Fault; b) the extensional features in the Adra region and southern continuation to the Al-Idrissi fault; and c) the largest structure, the dextral Yusuf fault, lithospheric boundary between crustal domains. Our main goal is to characterize the shallow and crustal structure of these active faults in order to evaluate their seismic potential, which may represent a significant earthquake and potential tsunami hazard for the coasts of Western Europe and North Africa. Potencial sísmico de fallas activas del Mar de Alboran en base a investigaciones de paleosismología marina
Paraules clau: Active faulting, acoustic and seismic imaging, fault seismic parameters, earthquake and tsunami hazard assessment.
Estrada F., Vázquez J.T., Ercilla G., Alonso B., d’Acremont E., Gorini C., Gómez M., Fernández-Puga M.C., Ammar A., El Moumni B. (2014)
Una aproximación multidisciplinar al estudio de las fallas activas, los terremotos y el riesgo sísmico. In: Segunda reunión ibérica sobre fallas activas y paleosismología, Lorca, (Murcia, España). Ed. J.A. Álvarez Gómez, F. Martín González. Instituto Geológico y Minero de España. 93-96. ISBN. 978-84-617-2049-1. (BibTeX: estrada.etal.2014e)
Resum: Veure
La zona central de la Cuenca de Alborán se caracteriza por presentar los elementos fisiográficos más importantes de Alborán, como son las dorsales de Alborán y Adra que limitan la depresión del Canal de Alborán. Estos elementos morfoestructurales son el resultado de la convergencia de las placas Africana y Euroasiática. El análisis de datos batimétricos y de perfiles de sísmica con diferentes grados de resolución, ha permitido establecer dos fases de deformación recientes: una de carácter transcurrente de salto normal y otra posterior compresiva que produce una inversión tectónica. Esta última fase sería el resultado de la colisión del Bloque tectónico de la Dorsal de Alborán con el de Adra al consumirse el espacio del curso medio del Canal de Alborán. Recent tectonic inversion of the Central Alboran Zone. The central zone of the Alboran Basin is characterized by presenting the major physiographic elements, the Alboran and Adra Ridges and the Alboran Channel. These morphostructural elements result from the convergence of the african and eurasian plates. Two recent phases of deformation have been differentiated, one predominantly transcurrent with normal component and a subsequent compression that produced a tectonic inversion. The later phase results from the collision of the Alboran Ridge block against the Adra’s one.
Paraules clau: Inversión tectónica, Cuenca de Alborán, Plio-Cuaternario, Tectonic inversion, Alboran Basin, Plio-Quaternary
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Ferrater M., Ortuño M., Masana E., Perea H., Baize S., Martínez-Díaz J.J., Pallàs R., García-Meléndez E., Echeverría A., Corominas O., Rockwell T. (2014)
Una aproximación multidisciplinar al estudio de las fallas activas, los terremotos y el riesgo sísmico. In: Segunda reunión ibérica sobre fallas activas y paleosismología, Lorca, (Murcia, España). Ed. J.A. Álvarez Gómez, F. Martín González. Instituto Geológico y Minero de España. 19-22. ISBN. 978-84-617-2049-1. (BibTeX: ferrater.etal.2014b)
Resum: Veure
La Falla de Alhama de Murcia (FAM, SE Península Ibérica) es una falla de salto en dirección izquierda con componente vertical. Estudios paleosísmicos previos caracterizaron la falla como sismogénica pero no consiguieron acotar de forma precisa su velocidad lateral, lo que limita el conocimiento real de su peligrosidad. Se presenta un estudio de trincheras 3D en el paraje de El Saltador (entre Lorca y Totana) con el objetivo de estimar la velocidad de deslizamiento lateral de la FAM. Se han identificado dos paleocanales de una edad calibrada máxima de 23,883-23,279 aC. dislocados lateralmente entre 20.2 y 7.6 m. Con estos valores, la velocidad mínima de deslizamiento lateral de la FAM es mayor a la considerada hasta el momento: 0.29-0.80 mm/año. Estos trabajos siguen en curso y se prevé mejorar la acotación temporal de esta dislocación. Preliminary lateral slip-rate based on 3D trenches and 3D software at the Alhama de Murcia fault (Murcia, Spain). The Alhama de Murcia fault is a left-lateral strike-slip fault with a reverse component. Previous paleoseismic studies demonstrated its seismogenic nature but they did not obtained well constrained slip rate values, a good indicator of the seis mic potential of a fault. In this paper we present new results from 3D trenching at the El Saltador site (between Lorca and Totana) with the aim to estimate the first tentative lateral slip rate for the AMF. We excavated nine new trenches and identified several channels that can be correlated on both sides of the fault. These channels indicate offsets that range between 20.2 and 7.6 m and are less than 23,883-23,279 B.C. calibrated age. The derived left-lateral slip-rate ranges between 0.29 and 0.80 mm/yr, a larger rate than considered in prior studies for the AMF.Work is still in progress to better constrain the ages of the offset channels.
Paraules clau: Falla de salto en dirección, velocidad deslizamiento, trincheras 3D, software 3D, left-lateral strike-slip fault, lateral slip-rate, 3D trenches
Harders R., Ranero C.R., Weinrebe W. (2014)
Submarine Mass Movements and Their Consequences. 6th International Symposium. In: Advances in Natural and Technological Hazards Research. Ed. S. Krastel, J.-H. Behrmann, D. Völker, M. Stipp, C. Berndt, R. Urgeles, J. Chaytor, K. Huhn, M. Strasser, C.B. Harbitz. Springer. ol. 37, 381-390. DOI: 10.1007/978-3-319-00972-8_34. ISBN. 978-3-319-00971-1. (BibTeX: harders.etal.2014c)
Resum: Veure
Offshore Costa Rica large seamounts under-thrust the continental convergent margin causing slides of complex morphology. The large dimension of the structures has attracted previous investigations and their basic characteristics are known. However, no detailed mapping of their complex morphology has been reported. Here we present a detailed mapping of the failure-related structures and deposits. We use deep-towed sidescan sonar data, aided by multibeam bathymetry to analyze their geometry, geomorphologic character, backscatter intensity, and spatial distribution. Those observations are used to analyze the relationship between landslide characteristics and abundance, to the changes in the style of deformation caused by the subduction of seamounts to progressively greater depth under the margin.
Lo Iacono C., Urgeles R., Polizzi S., Grinyó J., Gili J.M., Acosta J. (2014)
Submarine Mass Movements and Their Consequences. 6th International Symposium. In: Advances in Natural and Technological Hazards Research. Ed. S. Krastel, J.-H. Behrmann, D. Völker, M. Stipp, C. Berndt, R. Urgeles, J. Chaytor, K. Huhn, M. Strasser, C.B. Harbitz. Springer. ol. 37, Chap. 29. 329-338. DOI: 10.1007/978-3-319-00972-8_29. ISBN. 978-3-319-00971-1. (BibTeX: loiacono.etal.2014c)
Resum: Veure
Sediment starved passive margins, particularly those of insular slopes, display significant mass transport activity despite the absence of environmental stresses from high sedimentation rates. The “Menorca Channel” represents the up to 120 m deep shelf sector connecting the Menorca and Mallorca Islands (Balearic Islands – Western Mediterranean). South of the Menorca Channel submarine gravitational processes have been mapped and interpreted from swath-bathymetry, TOPAS parametric echosounder and deep-towed videos. The shelf-break is located at an average depth of 140 m, and sediment instability is a widespread phenomenon. The slope region south the Menorca Channel shows a number of submarine canyons disrupting the outer shelf. The north-easternmost canyon is the more active feature, with an incised axis and scars shaping the flanks up to their edges. Headwall scarps, between 140 and 700 m depth, are up to 20 m high. The shallower scarps producing slab-type failures have carved the outer edges of planar sedimentary bodies interpreted as formed in shallow environments during previous glacial stages. Results show that a variety of sediment instability processes extensively shape the southern upper slope of the Menorca Channel. Submarine canyons develop on the Emile Bodout Escarpment (EBE), a passive tectonic feature which bounds the slope region of the study area. A number of knickpoints within the canyons suggest backward erosion control on mass wasting and, at the same time, that slope failure is one of the main drivers for canyon upslope migration. Steep gradients of the upper slope, the presence of weak layers and the action of major storms during lowstand stages are additional factors likely to influence the distribution and frequency of mass wasting processes in this area.
Krastel S., Behrmann J.-H., Völker D., Stipp M., Berndt C., Urgeles R., Chaytor J., Huhn K., Strasser M., Harbitz C.B. (2014)
6th International Symposium. In: Advances in Natural and Technological Hazards Research. Ed. S. Krastel, J.-H. Behrmann, D. Völker, M. Stipp, C. Berndt, R. Urgeles, J. Chaytor, K. Huhn, M. Strasser, C.B. Harbitz. Springer. ol. 37, DOI: 10.1007/978-3-319-00972-8. ISBN. 978-3-319-00971-1. (BibTeX: krastel.etal.2014a)
Krastel S., Behrmann J.-H., Völker D., Stipp M., Berndt C., Urgeles R., Chaytor J., Huhn K., Strasser M., Harbitz C.B. (2014)
Submarine Mass Movements and Their Consequences. 6th International Symposium. In: Advances in Natural and Technological Hazards Research. Ed. S. Krastel, J.-H. Behrmann, D. Völker, M. Stipp, C. Berndt, R. Urgeles, J. Chaytor, K. Huhn, M. Strasser, C.B. Harbitz. Springer. ol. 37, V-VII. ISBN. 978-3-319-00971-1. (BibTeX: krastel.etal.2014b)
Llopart J., Urgeles R., Camerlenghi A., G. Lucchi R., De Mol B., Rebesco M., T. Pedrosa M. (2014)
Submarine Mass Movements and Their Consequences. 6th International Symposium. In: Advances in Natural and Technological Hazards Research. Ed. S. Krastel, J.-H. Behrmann, D. Völker, M. Stipp, C. Berndt, R. Urgeles, J. Chaytor, K. Huhn, M. Strasser, C.B. Harbitz. Springer. ol. 37, Chap. 9. 95-104. DOI: 10.1007/978-3-319-00972-8_9. ISBN. 978-3-319-00971-1. (BibTeX: llopart.etal.2014)
Resum: Veure
Climate variations control sediment supply to the continental slope as well as glacial advances and retreats, which (a) cause significant stress changes in the sedimentary column and redistribution of interstitial fluids, (b) induce a particular margin stratigraphic pattern and permeability architecture and (c) are at the origin of isostatic adjustments that may reactivate faults. We test this hypothesis using a combination of geophysical and geotechnical data from the Storfjorden Trough Mouth Fan, off southern Svalbard. The results of compressibility and permeability testing are used together with margin stratigraphic models obtained from seismic reflection data, as input for numerical finite elements models to understand focusing of interstitial fluids in glaciated continental margins and influence on timing and location of submarine slope failure. Available results indicate values of overpressure of 0.23–0.5 (slope-shelf) that persist to present-day. This overpressure started to develop in response to onset of Pleistocene glaciations and reduced by half the factor of safety of the continental slope.
Paraules clau: Storfjorden, overpressure, hydrogeology, hydrogeologic model, Barents Sea, factor of safety
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Lobo F.J., Ercilla G., Fernández-Salas L.M., Gámez D. (2014)
Continental Shelves of the World: Their Evolution During the Last Glacio-Eustatic Cycle. In: Geological Society, London, Memoirs. Ed. F.L. Chiocci, R. Chivas. The Geological Society of London. ol. 41, Chap. 11. 147-170. DOI: 10.1144/M41.11. ISBN. 978-1-86239-686-9. (BibTeX: lobo.etal.2014a)
Resum: Veure
The Iberian Mediterranean shelves are divided into three different geographical segments (the Northeastern Shelf, the South-eastern Shelf and the Northern Alboran Sea Shelf ), the understanding of which has evolved over the years. The best known sector is the Northeastern Shelf, comprising the narrow, abrupt and prograding Catalonia Shelf and the wider, prograding Ebro Shelf – Gulf of Valencia, where pioneering Spanish marine geology studies have been conducted since the 1970s. The knowledge of the Quaternary stratigraphic architecture of the Northeastern Shelf is very detailed, and provides an outstanding example of regressive – transgressive cycles leading to shelf build-up with various margin configurations. The Southeastern Shelf exhibits a change of margin configuration from intermediate to abrupt in response to declining fluvial influence. The knowledge of this shelf is limited in comparison with the rest of the Iberian Mediterranean shelves. Abundant studies have also been performed on the Northern Alboran Sea Shelf, which, in contrast to the Northeastern Shelf, does not have a major fluvial source but numerous short, mountain rivers draining from the Betic Cordillera. For this shelf, a high-resolution sequence stratigraphy model has been proposed for the most recent Late Quaternary depositional sequence.
Løvholt F., Harbitz C.B., Vanneste M., De Blasio F.V., Urgeles R., Iglesias O., Canals M., Lastras G., Pedersen G., Glimsdal S. (2014)
Submarine Mass Movements and Their Consequences. 6th International Symposium. In: Advances in Natural and Technological Hazards Research. Ed. S. Krastel, J.-H. Behrmann, D. Völker, M. Stipp, C. Berndt, R. Urgeles, J. Chaytor, K. Huhn, M. Strasser, C.B. Harbitz. Springer. ol. 37, Chap. 45. 507-515. DOI: 10.1007/978-3-319-00972-8_45. ISBN. 978-3-319-00971-1. (BibTeX: lovholt.etal.2014a)
Resum: Veure
The BIG’95 landslide was emplaced 11,500 years ago and is one of the largest known submarine landslides in the Mediterranean Sea. The simulated landslide dynamics matches the observed run-out and deposited thickness. Water elevation simulated by using a dispersive tsunami model exceed 10 m close to the landslide area and at the nearest shorelines. Modeling further indicates that the tsunami probably had widespread consequences in the Mediterranean. Compared to previous studies, this new simulation provides larger waves. There is, however, still a need to better constrain the landslide dynamics in order to illuminate the uncertainties related to the tsunamigenic power of this, and other, submarine landslides.
Martínez-Loriente S., Gràcia E., Bartolome R., Sallarès V., Perea H. (2014)
Una aproximación multidisciplinar al estudio de las fallas activas, los terremotos y el riesgo sísmico. In: Segunda reunión ibérica sobre fallas activas y paleosismología, Lorca, (Murcia, España). Ed. J.A. Álvarez Gómez, F. Martín González. Instituto Geológico y Minero de España. 81-84. ISBN. 978-84-617-2049-1. (BibTeX: martinezloriente.etal.2014a)
Resum: Veure
Newly acquired high-resolution multichannel seismic profiles together with bathymetric and subbottom profiler data from the external part of the Gulf of Cadiz (Iberia-Africa plate boundary) reveal active deformation involving old (Mesozoic) oceanic lithosphere. This area is located 180 km offshore the SW Iberian Margin and embraces the prominent NE-SW trending Coral Patch Ridge, and part of the surrounding deep Horseshoe and Seine abyssal plains. E-W trending dextral strike-slip faults showing surface deformation of flower-like structures predominate in the Horseshoe Abyssal Plain, whereas NE-SW trending compressive structures prevail in the Coral Patch Ridge and Seine Hills. Although the Coral Patch Ridge region is characterized by subdued seismic activity, the area is not free from seismic hazard. Most of the newly mapped faults correspond to active blind thrusts and strike-slip faults that are able to generate large magnitude earthquakes (Mw 7.2–8.4). This may represent a significant earthquake and tsunami hazard that has been overlooked so far. Fallas activas en la litosfera oceánica mesozoica offshore del Margen SO Ibérico. Significado para el riesgo de terremotos y tsunamis
Paraules clau: Multichannel seismics; blind thrusts; strike-slip faults; Iberia-Africa boundary
Masana E., Ortuño M., Ferrater M., Perea H., Baize S., Echeverria A., Pallàs R., García Meléndez E., Martínez-Díaz J.J., Rockwell T. (2014)
Una aproximación multidisciplinar al estudio de las fallas activas, los terremotos y el riesgo sísmico. In: Segunda reunión ibérica sobre fallas activas y paleosismología, Lorca, (Murcia, España). Ed. J.A. Álvarez Gómez, F. Martín González. Instituto Geológico y Minero de España. 23-26. ISBN. 978-84-617-2049-1. (BibTeX: masana.etal.2014a)
Resum: Veure
The AMF has been identified as seismogenic but its seismic characterization requires a better establishment of the seismic sequence. To this aim, we studied three trenches at El Saltador where we observed interstratified, fine-grained units with no internal structure that show maximum thickness next to the fault scarp and lack lithological analogues in the source area. Given that massive rock falls produced a large amount of dust after Lorca 2011 earthquake, we suggest these units may be the product of erosion of the dust during past earthquakes, its transport by mudflow, and its accumulation against uphill-facing fault scarp. According to this, the trench exposures provide evidence for up to eight paleoearthquakes, which would constitute the longest seismic sequence established on this fault segment to date. Depósitos de granulometría fina como evidencia de paleoterremotos en el registro geológico de la falla de Alhama de Murcia. La FAM ha sido ya catalogada como sismogénica. Para mejorar su caracterización sísmica es necesario establecer detalladamente su secuencia de paleoterremotos. Se presentan aquí tres trincheras excavadas en El Saltador donde se han identificado interestratificadas en la secuencia aluvial varias unidades de sedimentos finos sin clasificación interna, con espesores máximos en la zona de falla y sin sedimentos análogos en el área fuente. Dado que durante el terremoto de Lorca de 2011 se describieron gran cantidad de caídas de bloques y nubes de polvo asociadas, sugerimos que estas unidades son el producto de la concentración de dicho polvo durante terremotos pasados en canales. Su transporte habría sido en forma de mudflows y el depósito se habría bloqueado contra el escarpe de falla a contrapendiente. Teniendo en cuenta esta interpretación las trincheras muestran evidencias de hasta ocho paleoterremotos que constituyen la secuencia sísmica más larga descrita en este segmento de la falla.
Paraules clau: Alhama de Murcia fault, Paleoearthquake evidence, seismic dust record, Falla de Alhama de Murcia, caracterización de paleoterremotos, registro de nubes de polvo sísmicas
Gómez de la Peña L., Ranero C.R., Gràcia E., Bartolome R., cruise party TopoMed (2014)
Una aproximación multidisciplinar al estudio de las fallas activas, los terremotos y el riesgo sísmico. In: Segunda reunión ibérica sobre fallas activas y paleosismología, Lorca, (Murcia, España). Ed. J.A. Álvarez-Gomez, F. Martín González. 229-232. ISBN. 978-84-617-2049-1. (BibTeX: gomezdelapena.etal.2014c)
Resum: Veure
Along the Alboran Basin (Western Mediterranean) is located the diffuse plate boundary between Iberia and Africa. This wide deformation zone is controlled by the NW-SE convergence of these two plates. Deformation is accommodated by a large number of faults, where are placed offshore and onshore. The Alboran basin has a complex evolution, and the processes which led to the basin formation in the early Miocene are still under discussion. It is an active zone, so it involves a seismic and tsunamigenic hazard for the region. With the objective of improve the knowledge of this area, the TOPOMED-GASSIS cruise took place in October 2011. During this cruise, a deep penetration dataset was acquired using new instruments that allow the imaging of the basin at a crustal scale. The result is a series of multichannel seismic profiles with unprecedented quality in the region, which permit to use state of the art processing and imaging techniques to obtain the deep tectonic structure of the plate boundary and also a good resolution in the sedimentary infill of the basin. Moreover, we carried out Pre-Stack Depth Migration algorithms to selected profiles, in order to show the real geometry of the structures in depth and also to obtain the fault parameters. Técnicas avanzadas de procesado de datos de sísmica de reflexión multicanal aplicadas a mejorar la visualización de fallas activas del mar de Alborán. En la cuenca de Alborán (Mediterráneo Occidental) se sitúa el límite entre las placas Iberia y África, un límite difuso donde la convergencia NO-SE se acomoda en una ancha zona de deformación a lo largo de numerosas fallas. La evolución de la cuenca es compleja, y los procesos de formación siguen siendo objeto de debate. Sísmicamente es una zona activa, suponiendo un riesgo para la región. Para ampliar el conocimiento de esta zona, se realizó la campaña TOPOMED-GASSIS (Octubre 2011), en la que el uso de nuevos instrumentos de adquisición permitió obtener datos de sísmica de reflexión multicanal profunda con una calidad sin precedentes en la zona. Utilizando técnicas de procesado punteras, se ha conseguido una imagen a escala cortical de la cuenca. Además, se ha realizado la migración en profundidad de ciertos perfiles, para obtener la geometría real de las estructuras y los parámetros de falla.
Paraules clau: Alboran Basin, multichannel seismic reflection, advanced processing techniques, seismic hazards, cuenca de Alborán, sísmica de reflexión multicanal
Perea H., Gràcia E., Martínez-Loriente S., Bartolomé R. (2014)
Una aproximación multidisciplinar al estudio de las fallas activas, los terremotos y el riesgo sísmico. In: Segunda reunión ibérica sobre fallas activas y paleosismología, Lorca, (Murcia, España). Ed. J.A. Álvarez Gómez, F. Martín González. Instituto Geológico y Minero de España. 121-124. ISBN. 978-84-617-2049-1. (BibTeX: perea.etal.2014b)
Resum: Veure
The Bajo Segura basin is located at the northern termination of the East Betic Shear Zone. The geological evolution of this basin is controlled by a number of active faults and folds that accommodates part of the deformation driven by the convergence between the Nubian and Eurasian plates. The Santa Pola fault is one of the active structures located on the offshore of the Bajo Segura basin. In a high resolution sparker single channel seismic profile we have performed a submarine direct on-fault paleoseismic analysis resulting in the identification of 5 to 10 post-seismic growth sequences. These sequences may be related to 6 to 10 paleoearthquakes occurred between 140 ka and 444 ka, accounting for a recurrence interval ranging from 30 ka to 50 ka. It has also been possible to obtain a long term vertical slip rate, the vertical slip per event and the maximum magnitude of each one. Paleosismología submarina en la falla de Santa Pola (Cuenca del Bajo Segura, Mediterraneo Occidental): Obteniendo el registro de paleoterremotos directamente de una falla. La cuenca del Bajo Segura está localizada en la terminación norte de la Zona de Cizalla de las Béticas Orientales. La evolución geológica de esta cuenca está controlada por varias estructuras activas que acomodan parte de la deformación derivada de la convergencia entre Nubia y Eurasia. La falla de Santa Pola es una de las estructuras activas localizadas en la zona marina de la cuenca. En un perfil de alta resolución hemos realizado un análisis de paleosismología submarina que ha dado como resultado la identificación de entre 6 y 10 paleoterremotos ocurridos entre 140 ka y 444 ka, resultando en un intervalo de recurrencia que varía entre 30 ka y 50 ka. También ha sido posible obtener una tasa de deslizamiento vertical, el salto vertical por evento y la magnitud máxima para cada uno de ellos.
Paraules clau: Submarine paleoseismology, Active faults, High resolution seismics, Bajo Segura Basin, Paleosismología submarina, Fallas activas, Sísmica de alta resolución, Cuenca del Bajo Segura
Perea H., Gràcia E., Bartolomé R., Gómez de la Peña L., Martínez-Loriente S., Moreno X., De Mol B., Tello O., Ballesteros M., cruise party EVENT-DEEP (2014)
Una aproximación multidisciplinar al estudio de las fallas activas, los terremotos y el riesgo sísmico. In: Segunda reunión ibérica sobre fallas activas y paleosismología, Lorca, (Murcia, España). Ed. J.A. Álvarez Gómez, F. Martín González. Instituto Geológico y Minero de España. 97-100. ISBN. 978-84-617-2049-1. (BibTeX: perea.etal.2014d)
Resum: Veure
A small amount of the total strain produced by the convergence between the Nubian and Eurasian plates is accommodated in the Alboran Sea basin by different fault systems. High resolution bathymetric maps show several NE-SW lineaments across the Djibouti High, among them the Djibouti fault, that have lengths up to 30 km and are apparently offsetting the Adra Ridge in a right-lateral movement. High-resolution multichannel seismic profiles acquired in the area show that these lineaments correspond to faults that are displacing the reflectors corresponding to the Plio-Quaternary units and some of the faults affect the seafloor. Therefore, these lineaments are associated to Quaternary active faults and their location and characterization improves our knowledge about earthquake and tsunami hazard around the Alboran Sea. Evidencias de fallas activas cuaternarias a través del Alto de Djibouti y de la Cresta de Adra (Mar de Alboran). Una fracción de la deformación producida por la convergencia entre las placas de Nubia y Eurasia es acomodada en la cuenca del Mar de Alborán por diferentes sistemas de fallas. En los mapas batimétricos de alta resolución hemos identificado varios lineamientos con dirección NE-SW a través del Alto de Djibouti. Estos lineamientos, destacando entre ellos el correspondiente a la falla de Djibouti, tienen longitudes de hasta 30 km y aparentemente desplazan la Cresta de Adra en sentido lateral derecho. Los perfiles de sísmica multicanal de alta resolución adquiridos en la zona muestran que estos lineamientos corresponden a fallas que están rompiendo los reflectores correspondientes a las unidades Plio-Cuaternarias y en algunos casos incluso la superficie del fondo marino. Por lo tanto, estos lineamientos estás asociados a fallas activas Cuaternarias y su localización y caracterización ayuda a mejorar nuestro conocimiento sobre la peligrosidad sísmica y de tsunamis alrededor del Mar de Alborán.
Paraules clau: Active faults, Strike-slip faults, Alboran Sea, Geophysical methods, Fallas activas; Fallas direccionales, Mar de Alborán, Métodos geofísicos
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Jimenez Tejero C.E., Dagnino D., Sallarés V., Ranero C. (2014)
76 EAGE Conference & Exhibition 2014, Amsterdam RAI, The Netherlands, 16-19 June 2014. (BibTeX: jimeneztejero.etal.2014b)
Resum: Veure
The FWI method is a powerful tool that allows one to obtain high-resolution information from the subsurface. However, the method is highly non-linear as in the convergence to the solution it might get trapped in local-minima. Among other techniques, it becomes crucial a suitable choice of the objective function. We have selected five objective functions to perform a comparative study under a common 2D-acoustic FWI scheme: the L2-nom, cross-correlation travel time (CCTT), non-integration-method (NIM), envelope and phase objective functions. We test with a 2D-canonical model the susceptibility of the functions to the initial model perturbations. To complete de study with a more realistic synthetic example we test the functions with the Marmousi model. The L2-norm and phase objective functions give the highest resolution images and the CCTT, NIM and envelope objective functions lead to smooth models. However in realistic initial conditions, L2 and phase misfits fail in recovering the velocity model in contrast to the CCTT, NIM and envelope functions that maintain a more consistent behavior.
Vázquez J.T., Estrada F., Vegas R., Ercilla G., d’Acremont E., Fernández-Salas L.M., Alonso B., Fernández-Puga M.C., Gómez-Ballesteros M., Gorini Ch., Bárcenas P., Palomino D. (2014)
Una aproximación multidisciplinar al estudio de las fallas activas, los terremotos y el riesgo sísmico. In: Segunda reunión ibérica sobre fallas activas y paleosismología, Lorca, (Murcia, España). Ed. J.A. Álvarez Gómez, F. Martín González. Instituto Geológico y Minero de España. 89-92. ISBN. 978-84-617-2049-1. (BibTeX: vazquez.etal.2014a)
Resum: Veure
The analysis of multibeam bathymetric data and high resolution seismic profiles has allowed us to define the tectonic geomorphology of the Adra margin, northern Alboran Sea. Four geomorphic tectonic-related structures have been analyzed: (i) Longitudinal ridges (N50-70); (ii) Linear scarps (N30, N55, N130, N165, N-S); (iii) Tectonic depressions (N130, N165, N-S), and (iv) Lines of changes in the slope gradient (N130). In the northwestern sector morphostructure is related to a blind thrust (NE-SW), which folds Quaternary units, and in the eastern sector is linked to the NE-SW sinistral strike slip fault of La Serrata (NE-SW). Between these two structures, a NW-SE dextral strike-slip fault system, including the Adra Fault, and a NNE-SSW highly deformed corridor constituted by secondary NNW-SSE faults have been developed. Minor high angle N-S reverse faults can be related to secondary deformation features, due mainly to the interference of Chella Bank and the regional main fault systems. Influencia de la tectónica cuaternaria sobre la morfología del talud continental de la región de Adra (Mar de Alborán septentrional). El análisis de un mosaico batimétrico y de perfiles sísmicos de alta resolución ha permitido definir la geomorfología tectónica del Margen de Adra, sector norte del Mar de Alborán. Se han identificado cuatro tipos morfológicos relacionados con estructuras tectónicas: (i) Crestas longitudinales (N50-70); (ii) Escarpes lineales (N30, N55, N130, N165, N-S); (iii) Depresiones tectónicas (N130, N165, N-S), y (iv) Líneas de cambio de la pendiente (N130). Este esquema morfoestructural se relaciona con un cabalgamiento ciego (NO-SE) en el sector NO, y en el oriental con la falla de desgarre siniestra de La Serrata (NE-SO). Entre estas dos estructuras se ha desarrollado un sistema de fallas de desgarre diestras (NO-SE) que incluye a la Falla de Adra, y un corredor NNE-SSO constituido por fallas secundarias NNO-SSE. Además se han observado fallas inversas menores N-S que pueden ser consecuencia de la interferencia de los principales sistemas de fallas de la región con el Banco de Chella.
Paraules clau: Geomorphology, Faults, Tectonics, Quaternary, Alboran Sea, Geomorfología, Fallas, Tectónica, Cuaternario, Mar de Alborán
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Buffett G.G., Hobbs R.W., Vsemirnova E.A., Klaeschen D., Hurich C.A., Ranero C., Sallarès V. (2013)
ol. 19, Chap. 1. 005013. DOI: 10.1121/1.4799057. (BibTeX: buffett.etal.2013b)
Resum: Veure
Processed multi-channel seismic (MCS) data acquired in the Tyrrhenian Sea in April-May 2010 provide images of oceanic thermohaline staircases. Using Stochastic Heterogeneity Mapping we characterize spatial reflector variations. This method is based on the band-limited von Kármán function. For scale sizes smaller than the correlation length, the von Kármán model describes a power law (fractal) process. We are most interested in the extraction of the exponent in the power law (The Hurst exponent) because it allows us to characterize the richness of scales present in the data set. Lower Hurst exponents represent a richer range of wavenumbers and therefore correspond to a broader range of heterogeneity in the observed seismic reflection events. The Hurst exponent is related to the fractal dimension and to the slope in the Garrett-Munk wavenumber spectrum. We interpret a richer range of heterogeneity as indicative of a greater degree of turbulent mixing. Data are presented alongside benchmark calibrations of synthetic seismic data generated from random fractal surfaces. We observe an oscillation in the Hurst exponent spectra as a function of frequency that is interpreted to represent a preferential coupling of energy across different spatial scales
Cameselle A.L., Ranero C.R., Franke D., Barckhausen U. (2013)
American Geophysical Union (AGU) Fall Meeting. (BibTeX: cameselle.etal.2013c)
Resum: Veure
Rifted continental margins form by lithospheric extension and break-up. The continent to ocean transition (COT) architecture depends on the interplay between tectonic and magmatic processes, and thus, to study the COT variability of different systems is key to understand rifting. We use MCS data and magnetic lineations across the Pearl River margin (PRM) of South China Sea to investigate a previously poorly defined COT. The structure of the PRM presents different amounts of extension allowing the study of conjugate pairs of continental margins and their COT in a relative small region. We reprocessed about 2250 km of MCS data along 4 regional, crustal-scale lines and found that 3 of them possibly display the COT. The time-migrated seismic sections show differences in internal reflectivity, faulting style, fault-block geometry, the seismic character of the top of the basement, in the geometry of sediment deposits, and Moho reflections, that we interpret to represent clear continental and oceanic domains. The continental domain is characterized by arrays of normal faults and associated tilted blocks overlaid by syn-rift sedimentary units. The Moho is imaged as sub-horizontal reflections that define a fairly continuous boundary typically at 8-10 s TWT. Estimation of the thickness of the continental crust using 6 km/s average velocity indicates a ~22 km-thick continental crust under the uppermost slope passing abruptly to ~9-6 km under the lower slope. Comparatively the oceanic crust has a highly reflective top of basement, little-faulting, not discernible syn-tectonic strata, and fairly constant thickness (4-8 km) defined by usually clear Moho reflections. The COT occurs across a ~5-10 km narrow zone. Rifting resulted in asymmetric conjugate margins. The PRM shows arrays of tilted fault blocks covered by abundant syn-rift sediment, whereas the conjugate Macclesfield Bank margin displays abrupt thinning and little faulting. Seismic profiles also show a change in the tectonic structure from NE to SW. On the two NE-most lines, crustal thinning and break-up occur over 20-40 km wide segments. To the SW, continental extension occurred over a comparatively broader ~100-110 km segment of tilted fault-block structure. We interpret, that this 3D structural variability and the narrow COT was caused by the lateral NE to the SW propagation of a spreading center. In the NE, early spreading center propagation during ongoing rifting stopped continental stretching, causing an abrupt break-up and a narrow COT to seafloor spreading. Later arrival of spreading center propagated to the SW, resulted in a comparatively broader segment with fault-block structures of extended continental crust. However, the COT to clear oceanic crust is narrow. Spreading center propagation in the basin is however not a simple phenomena and ridge jumps and abrupt cessation of spreading contributed to form narrow COT that laterally change to highly thinned continental crust segments. We suggest that the tectonic architecture of continental extension and the abrupt COT along the PRM have been controlled by 3D oceanic spreading center propagation to a degree larger than by the local lithospheric structure during rifting
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Emelianov M., Font J., Puig P., Martín J., García Ladona E., Salat J., Ostrovskii A., Zatsepin A., Kremenetskiy V., Soloviev V., Tsibulskiy A., Shvoev D. (2013)
Rapports et Proces-verbaux des Réunions. Com. Int. Explor. Sci. Mer Mediterranée, CIESM.. ol. 40, (BibTeX: emelianov.etal.2013a)
Resum: Veure
A pilot experiment aiming at investigating the small scale dynamics and variability of the seawater fine thermohaline structure, the processes of vertical exchange of momentum and mass, and mechanisms of the nepheloid layer formation in the Besòs submarine canyon, situated in the continental slope close to Barcelona, was carried out by using the prototype moored profiler “Aqualog”.
Paraules clau: Instruments and techniques, North-Western Mediterranean
Meléndez A., Korenaga J., Sallarès V., Ranero C.R. (2013)
75th EAGE Conference & Exhibition incorporating SPE EUROPEC 2013. DOI: 10.3997/2214-4609.20130372. (BibTeX: melendez.etal.2013c)
Resum: Veure
TOMO3D is a code for three-dimensional refraction and reflection travel-time tomography of wide-angle seismic data that inverts for the velocity field and the geometry of a reflector. Ray tracing is performed by a hybrid method combining the graph and bending methods, and the inversion is iteratively solved using an LSQR algorithm. We present a series of benchmark tests with synthetic data for the forward and inverse problems, as well as other more complex tests comparing inversions with refraction travel times only (i.e. first arrivals) to others with refraction and reflection travel times. The combination of refraction and reflection data increases ray coverage and thus velocity resolution, while allowing the determination of major geological interfaces, and reducing the velocity-depth trade-off.
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Ramírez-Pérez M., Torrecilla E., Guillén J., Piera J. (2013)
Instrumentation Viewpoint. ol. 15, 14. (BibTeX: ramirezperez.etal.2013b)
Resum: Veure
A method is described for discriminating the size of inorganic suspended particles based on hyperspectral attenuation spectra. In this study, the beam attenuation spectra of different samples with different suspended sediment sizes (i.e., from mud, <5 μm, to fine sand, 125-250 μm), were measured in the laboratory using a hyperspectral attenuation meter (VIPER instrument with a 5 cm path length and 1.7 nm spectral resolution). In order to classify the measured spectra according to their relative similarity, a hierarchical cluster analysis has been applied and the results have been represented in a Multi-dimensional scaling graphic. Our results show that the changes in the attenuation spectral signature are according to the particle size. The applied methodology clearly allows discriminating samples with different particle size ranges. The hyperspectral attenuation meter can therefore be considered a powerful instrument for these purposes, because of the high spectral resolution and relative lower cost compared to other commercial instruments. Furthermore, it is possible to design hyperspectral attenuation meters with smaller size and relatively low-consumption that could be incorporated into different observing autonomous platforms, such as gliders, profilers and autonomous underwater vehicles.
Paraules clau: hyperspectral attenuation spectra, particle size distribution, hierarchical cluster analysis, multidimensional scaling
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Company J.B., Ramirez-Llodra E., Sardà F., Aguzzi J., Puig P., Canals M., Calafat A., Palanques A., Solé M., Sanchez-Vidal A., Martín J., Lastras G., Tecchio S., Koenig S., Fernandez-Arcaya U., Mechó A., Fernández P. (2012)
Mediterranean Submarine Canyons: Ecology and Governance. Ed. Würtz M. (Ed.). IUCN. Chap. 3.8. 133-144. ISBN. 978-2-8317-1469-1. (BibTeX: company.etal.2012b)
Resum: Veure
IUCN, Centre for Mediterranean Cooperation; UNEP, Mediterranean Action Plan for the Barcelona Convention (MAP); Regional Activity Center for Specially Protected Areas (RAC/SPA); IUCN, Global Marine Programme; France, Ministère de l\'Ecologie, de l\'Energie, du Développement Durable, des Transports et du Logement; France, Ministère des Affaires Etrangères et Européennes; France, Agence des aires marines protégées; Fondation MAVA pour la nature; Total Foundation; Musée océanographique de Monaco, MC; Musée océanographique; Institut océanographique, Fondation Albert 1er, Prince de Monaco, MC Although there is a common agreement on the importance of conservation of Mediterranean submarine canyons amongst international organizations, their governance is complex: the canyons\' extension covers waters and seabeds under various types of jurisdictions (territorial waters, Fisheries Protection Zone, Ecological Protection Zone, including delimitation issues). Conservation of deep-sea features, such as canyons, requires improving our understanding of the biological and ecological role of these ecosystems, threats and conservation issues, limits and chances of national and international jurisdictions. This report has been written with the intention of meeting this need by reviewing interdisciplinary contributions of experts from various Mediterranean countries.
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Goldfinger C., Hans Nelson C., Morey A.E., Johnson J.E., Patton J.R., Karabanov E., Gutiérrez-Pastor J., Eriksson A.T., Gràcia E., Dunhill G., Enkin R.J., Dallimore A., Vallier T. (2012)
In: Earthquake hazards of the Pacific Northwest coastal and marine regions.; Professional paper (Geological Survey (U.S.)), no. 1661-F. U.S. Geological Survey. 170. (BibTeX: goldfinger.etal.2012a)
Resum: Veure
Turbidite systems along the continental margin of Cascadia Basin from Vancouver Island, Canada, to Cape Mendocino, California, United States, have been investigated with swath bathymetry; newly collected and archive piston, gravity, kasten, and box cores; and accelerator mass spectrometry radiocarbon dates. The purpose of this study is to test the applicability of the Holocene turbidite record as a paleoseismic record for the Cascadia subduction zone. The Cascadia Basin is an ideal place to develop a turbidite paleoseismologic method and to record paleoearthquakes because (1) a single subduction-zone fault underlies the Cascadia submarine-canyon systems; (2) multiple tributary canyons and a variety of turbidite systems and sedimentary sources exist to use in tests of synchronous turbidite triggering; (3) the Cascadia trench is completely sediment filled, allowing channel systems to trend seaward across the abyssal plain, rather than merging in the trench; (4) the continental shelf is wide, favoring disconnection of Holocene river systems from their largely Pleistocene canyons; and (5) excellent stratigraphic datums, including the Mazama ash and distinguishable sedimentological and faunal changes near the Pleistocene-Holocene boundary, are present for correlating events and anchoring the temporal framework. Multiple tributaries to Cascadia Channel with 50- to 150-km spacing, and a wide variety of other turbidite systems with different sedimentary sources contain 13 post-Mazama-ash and 19 Holocene turbidites. Likely correlative sequences are found in Cascadia Channel, Juan de Fuca Channel off Washington, and Hydrate Ridge slope basin and Astoria Fan off northern and central Oregon. A probable correlative sequence of turbidites is also found in cores on Rogue Apron off southern Oregon. The Hydrate Ridge and Rogue Apron cores also include 12–22 interspersed thinner turbidite beds respectively. We use 14C dates, relative-dating tests at channel confluences, and stratigraphic correlation of turbidites to determine whether turbidites deposited in separate channel systems are correlative—triggered by a common event. In most cases, these tests can separate earthquake-triggered turbidity currents from other possible sources. The 10,000-year turbidite record along the Cascadia margin passes several tests for synchronous triggering and correlates well with the shorter onshore paleoseismic record. The synchroneity of a 10,000-year turbidite-event record for 500 km along the northern half of the Cascadia subduction zone is best explained by paleoseismic triggering by great earthquakes. Similarly, we find a likely synchronous record in southern Cascadia, including correlated additional events along the southern margin. We examine the applicability of other regional triggers, such as storm waves, storm surges, hyperpycnal flows, and teletsunami, specifically for the Cascadia margin. The average age of the oldest turbidite emplacement event in the 10–0-ka series is 9,800±~210 cal yr B.P. and the youngest is 270±~120 cal yr B.P., indistinguishable from the A.D. 1700 (250 cal yr B.P.) Cascadia earthquake. The northern events define a great earthquake recurrence of ~500–530 years. The recurrence times and averages are supported by the thickness of hemipelagic sediment deposited between turbidite beds. The southern Oregon and northern California margins represent at least three segments that include all of the northern ruptures, as well as ~22 thinner turbidites of restricted latitude range that are correlated between multiple sites. At least two northern California sites, Trinidad and Eel Canyon/pools, record additional turbidites, which may be a mix of earthquake and sedimentologically or storm-triggered events, particularly during the early Holocene when a close connection existed between these canyons and associated river systems. The combined stratigraphic correlations, hemipelagic analysis, and 14C framework suggest that the Cascadia margin has three rupture modes: (1) 19–20 full-length or nearly full length ruptures; (2) three or four ruptures comprising the southern 50–70 percent of the margin; and (3) 18–20 smaller southern-margin ruptures during the past 10 k.y., with the possibility of additional southern-margin events that are presently uncorrelated. The shorter rupture extents and thinner turbidites of the southern margin correspond well with spatial extents interpreted from the limited onshore paleoseismic record, supporting margin segmentation of southern Cascadia. The sequence of 41 events defines an average recurrence period for the southern Cascadia margin of ~240 years during the past 10 k.y. Time-independent probabilities for segmented ruptures range from 7–12 percent in 50 years for full or nearly full margin ruptures to ~21 percent in 50 years for a southern-margin rupture. Time-dependent probabilities are similar for northern margin events at ~7–12 percent and 37–42 percent in 50 years for the southern margin. Failure analysis suggests that by the year 2060, Cascadia will have exceeded ~27 percent of Holocene recurrence intervals for the northern margin and 85 percent of recurrence intervals for the southern margin. The long earthquake record established in Cascadia allows tests of recurrence models rarely possible elsewhere. Turbidite mass per event along the Cascadia margin reveals a consistent record for many of the Cascadia turbidites. We infer that larger turbidites likely represent larger earthquakes. Mass per event and magnitude estimates also correlate modestly with following time intervals for each event, suggesting that Cascadia full or nearly full margin ruptures weakly support a time-predictable model of recurrence. The long paleoseismic record also suggests a pattern of clustered earthquakes that includes four or five cycles of two to five earthquakes during the past 10 k.y., separated by unusually long intervals. We suggest that the pattern of long time intervals and longer ruptures for the northern and central margins may be a function of high sediment supply on the incoming plate, smoothing asperities, and potential barriers. The smaller southern Cascadia segments correspond to thinner incoming sediment sections and potentially greater interaction between lower-plate and upper-plate heterogeneities. The Cascadia Basin turbidite record establishes new paleoseismic techniques utilizing marine turbidite-event stratigraphy during sea-level highstands. These techniques can be applied in other specific settings worldwide, where an extensive fault traverses a continental margin that has several active turbidite systems.
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Urgeles R., Cattaneo A., Puig P., Liquete C., De Mol B., Sultan N., Trincardi F. (2012)
Submarine Mass Movements and Their Consequences. In: Advances in Natural and Technological Hazards Research 31. Ed. Yamada, Y., Kawamura, K., Ikehara, K., Ogawa, Y., Urgeles, R., Mosher, D., Chaytor, J., Strasseret, M. (Eds.). Springer. Chap. 21. 233-244. DOI: 10.1007/978-94-007-2162-3_21. ISBN. 978-94-007-2162-3. (BibTeX: urgeles.etal.2012b)
Resum: Veure
Most Mediterranean prodeltas show undulated sediments on the foresets of their Holocene wedges. These features have been described all along the Mediterranean and interpreted as either soft sediment deformation or, more recently, as sediment bedforms. We present a detailed analysis of these features using ultrahighresolution seismic and bathymetric data, as well as geotechnical information and hydrodynamic time series and hydrographic transects. We show that the characteristics of the sediment undulations (morphology and configuration of the reflectionsdown section and between adjacent undulations) are incompatible with a genesis by sediment deformation.
Paraules clau: Undulated sediments. Prodeltas. Slope failure. Sediment bedforms