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Durán R., Guillén J. (2018)
Submarine Geomorphology. Ed. A. Micallef, S. Krastel, A. Savini. Springer. 185-206. DOI: 10.1007/978-3-319-57852-1_11. ISBN. 978-3-319-57851-4. (BibTeX: duran.guillen.2018a)
Abstract: See
Continental shelves comprise the zone adjacent to the continents, extending from the infralittoral to a marked change in slope known as the shelf break. The shelf break is located at a variable depth from 20 to 550 m, with a global average depth of 140 m. They develop in passive and active margins and can be dominated by different processes, which include tides, waves and currents. The present day geomorphology of the continental shelf comprises a wide variety of modern and relict features as a result of different controlling factors—geological structure, sea-level change, and sediment delivery and dispersal systems—acting at varying time scales. This chapter illustrates the most common landforms observed in siliciclastic continental shelves, with special attention to the processes that generate them. Landforms include consolidated bottoms, erosive morphologies, prograding landforms, bedforms, gas-related morphologies and anthropogenic features.
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Demestre M., Muntadas A., Duran R., García-de-Vinuesa A., Sánchez P., Mas J., Franco I., Muñoz A., Guillén J. (2017)
Atlas of Bedforms in the Western Mediterranean. Ed. J. Guillén, J. Acosta, F.L. Chiocci, A. Palanques. Springer. Chap. 32. 207-214. DOI: 10.1007/978-3-319-33940-5_32. ISBN. 978-3-319-33938-2. (BibTeX: demestre.etal.2017a)
Abstract: See
Multibeam swath bathymetry, sediment and benthos samples (including both epifauna and infauna) and submarine images were explored to characterize benthic communities in a subaqueous dune field on the Mar Menor middle shelf (western Mediterranean). The dunes are 2–5 m high and spaced 400–1100 m apart, with a predominant NE-SW orientation oblique to the shoreline. The benthic communities show high spatial variability in diversity. Three types of habitat showing a different species composition are distinguished in the subaqueous dune field.
Keywords: Benthic communities, Bedforms, Epifauna, Infauna, Middle shelf, Mediterranean
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Demestre M., Muntadas A., Sanchez P., Garcia-de-Vinuesa A., Mas J., Franco I., Duran R., Guillén J. (2017)
Atlas of Bedforms in the Western Mediterranean. Ed. J. Guillén, J. Acosta, F.L. Chiocci, A. Palanques. Springer. Chap. 33. 215-219. DOI: 10.1007/978-3-319-33940-5. ISBN. 978-3-319-33938-2. (BibTeX: demestre.etal.2017c)
Abstract: See
Maërl habitats are of great biological value due to their high biodiversity and productivity, but they are also very fragile. The subaqueous dune field on the continental shelf off the Mar Menor exhibits sediment characteristics that favour the presence of maërl habitats. However, this seabed is altered by two kinds of disturbance: biogenic disturbance caused mainly by the feeding and burrowing activities of the sea urchin Spatangus purpureus, and anthropogenic disturbance caused by trawling activities.
Keywords: Bedforms, Habitat stability, Biodiversity conservation, Bioturbation, Trawling, Mediterranean
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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. Chap. 22. 135-141. DOI: 10.1007/978-3-319-33940-5_22. ISBN. 978-3-319-33938-2. (BibTeX: duran.etal.2017b)
Abstract: See
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
Keywords: Sorted bedforms, Bedform dynamics, Anthropogenic impact, Inner shelf, NW Mediterranean
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Durán R., Guillén J., Muñoz A. (2017)
Atlas of Bedforms in the Western Mediterranean. Ed. J. Guillén, J. Acosta, F.L. Chiocci, A. Palanques. Springer. Chap. 21. 127-133. DOI: 10.1007/978-3-319-33940-5_21. ISBN. 978-3-319-33938-2. (BibTeX: duran.etal.2017d)
Abstract: See
Multibeam echosounder data and sediment samples were used to characterize sorted bedforms on the inner shelf off Lloret and Tossa de Mar (NW Mediterranean Sea). The sorted bedforms are formed by a sequence of coarse-grained (coarse sand) and fine-grained (fine to medium sand) domains, with little topographic relief (up to 1 m). They exhibit elongated shapes and are oriented nearly perpendicular to the shoreline, at water depths ranging from 10 to 40 m. The sorted bedforms display lateral symmetry in backscatter and bathymetric relief with high backscatter centred on the bathymetric depression. They appear associated with elongated sand deposits fed by short, ephemeral streams that extend across-shelf over the infralittoral prograding wedge down to 40 m water depth. Sorted bedforms are better developed in deeper waters (20–40 m), probably due to stronger hydrodynamic conditions in the shallower sector of the shelf, which prevent the development or maintenance of these morphological features. The morphological evolution of these bedforms indicates that they are persistent features, showing small changes in their boundaries over a decadal timescale.
Keywords: Persistent sorted bedforms, Bedform evolution, Inner shelf, Ephemeral streams, NW Mediterranean
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Durán R., Guillén J., Rivera J., Muñoz A., Lobo F.J., Fernández-Salas L.M., Acosta J. (2017)
Atlas of Bedforms in the Western Mediterranean. Ed. J. Guillén, J. Acosta, F.L. Chiocci, A. Palanques. Springer. Chap. 29. 187-192. DOI: 10.1007/978-3-319-33940-5_29. ISBN. 978-3-319-33938-2. (BibTeX: duran.etal.2017f)
Abstract: See
Multibeam swath bathymetry, high-resolution seismic data and sediment samples were used to characterize a field of sand ridges and subaqueous dunes on the outer Murcia continental shelf (western Mediterranean Sea). Sand ridges are 1.5–3 m high and show a predominant E-W orientation oblique to the present-day shoreline. High-resolution seismic data reveal a backstepping stacking pattern of high-angle clinoforms dipping towards the southwest, interpreted as buried sand bodies. Subaqueous dunes have a mean height of 0.3 m and appear superimposed on the sand ridges showing a NW-SE orientation oblique to the ridges. They are composed of sandy sediments and display asymmetric morphology, with the lee side towards the southwest. Ridge and dune asymmetry and internal structure are indicative of long-term sediment transport towards the southwest. At present, dune migration rates deduced from repeated bathymetric surveys indicate that the dunes remain stationary or migrate at very low rates on a decadal scale.
Keywords: Sand ridges, Subaqueous dunes, Tideless continental shelf, Western Mediterranean sea
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Guerrero Q., Guillén J., Durán R., Urgeles R. (2017)
Atlas of Bedforms in the Western Mediterranean. Ed. J. Guillén, J. Acosta, F.L. Chiocci, A. Palanques. Springer. Chap. 15. 89-93. DOI: 10.1007/978-3-319-33940-5_15. ISBN. 978-3-319-33938-2. (BibTeX: guerrero.etal.2017a)
Abstract: See
High-resolution multibeam bathymetry, bottom sediment samples and time series of current intensities and directions were collected over a dune field in the Ebro Delta coastal area. Aerial photographs were used to analyse the morphological changes of the river mouth since 1946. The bathymetry show a ~6.4 km2 dune field located at a water depth of 6–15 m, with dunes of 1.3 m median height and 250 m median wavelength. The location of the dune field coincides partially with a former river mouth, an area that emerged in 1946. Onset of dune field development is believed to have started in the 1940s, when the Cape Tortosa river mouth was abandoned and the shoreline underwent a severe retreat. Currently, the recorded high-energy current events induced by northwesterly winds result in a dynamic seabed over the dunes, including ripple development, suggesting that the dune field is active mostly during these high-energy periods.
Keywords: Subaqueous dune field development, Coastal retreat, Deltaic area, Present-day dynamics
Guillén J., Acosta J., Chiocci F.L., Palanques A. (2017)
Atlas of Bedforms in the Western Mediterranean. Ed. J. Guillén, J. Acosta, F.L. Chiocci, A. Palanques. Springer. 1-307. DOI: 10.1007/978-3-319-33940-5. ISBN. 978-3-319-33938-2. (BibTeX: guillen.etal.2017a)
Abstract: See
This atlas illustrates the characteristics of present-day bedforms, from the shoreline to deep-sea environments, and it also includes short reviews of the main mechanisms that generate such bedforms. The atlas is aimed at the research community, in addition to students, the public at large and companies with interests in the marine environment. The book is divided into seven sections composed of a number of short chapters: 1) bedform analysis and the main physical processes, 2) bedforms in the coastal zone, 3) bedforms on prodeltas and sorted bedforms, 4) bedforms on the continental shelf, 5) bedforms and benthos, 6) bedforms in submarine canyons and 7) slope and deep-sea bedforms. This atlas offers a comprehensive, though not exhaustive, view of the diversity of bedforms and associated processes and of the morphological and temporal scales in the enclosed tideless western Mediterranean Sea.
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Lo Iacono C., Guillén J. (2017)
Atlas of Bedforms in the Western Mediterranean. Ed. J. Guillén, J. Acosta, F.L. Chiocci, A. Palanques. Springer. Chap. 20. 121-126. DOI: 10.1007/978-3-319-33940-5_20. ISBN. 978-3-319-33938-2. (BibTeX: loiacono.guillen.2017a)
Abstract: See
The analysis of sidescan sonar data and sediment samples around the Egadi Islands, on the NW Sicilian margin (southern Tyrrhenian), revealed the existence of two main sorted bedform fields. Sorted bedforms were mapped along the shelf sectors of the Marettimo and Favignana Islands, organized on elongated patches almost perpendicular to the coastline for a depth range of 15–50 m. Sediment sampling revealed that the bedforms are composed of sandy sediments lying over coarse sandy, gravelly and pebbly substrates. We assessed the long-term stability of the sorted bedforms, which could be related to along-shore transverse bottom currents associated with exceptional storms coming from the NE.
Keywords: Sorted bedforms, Inner shelf, Sidescan sonar, Egadi insular margin, Tyrrhenian sea
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Mas J., Franco I., Demestre M., Guillén J., J. Murcia F, Ruiz J.M. (2017)
Atlas of Bedforms in the Western Mediterranean. Ed. J. Guillén, J. Acosta, F.L. Chiocci, A. Palanques. Springer. Chap. 31. 199-206. DOI: 10.1007/978-3-319-33940-5_31. ISBN. 978-3-319-33938-2. (BibTeX: mas.etal.2017b)
Abstract: See
Benthic communities on shallow sedimentary bottoms in the western Mediterranean can play a crucial role in the development, maintenance and evolution of bedforms. This chapter presents an overview of the most characteristic benthic communities in shallow waters classified by the type of substrate: coarse bottoms, sandy bottoms and fine-grained bottoms. Examples from the Murcia continental shelf are provided to illustrate the main communities, giving special emphasis to the seagrass beds (some of them endemic to the Mediterranean) and the scarce maërl community, both with high biodiversity and ecological value.
Keywords: Bedforms, Coastal zone, Benthic communities, Maërl, Posidonia meadows, “Soft” and “hard” bottoms
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Ribó M., Durán R., Puig P., Van Rooij D., Guillén J. (2017)
Atlas of Bedforms in the Western Mediterranean. Ed. J. Guillén, J. Acosta, F.L. Chiocci, A. Palanques. Springer. Chap. 40. 259-264. DOI: 10.1007/978-3-319-33940-5_40. ISBN. 978-3-319-33938-2. (BibTeX: ribo.etal.2017a)
Abstract: See
Recently acquired swath bathymetry and seismic datasets on the Gulf of Roses continental slope revealed the presence of large sediment waves that have developed between ~200 and ~400 m water depth. Geometric parameters were computed from the multibeam dataset and the obtained results showed mean sediment wave lengths of ~2000 m and maximum heights of ~60 m. The analysis of seismic profiles showed the general architecture of the Late Quaternary deposits over the Gulf of Roses outer shelf and slope. The outer continental shelf is characterized by morphological erosional features affecting the upper part of the most recent seismic unit. Over the continental slope five main unconformity-bounded seismic units are differentiated, with sediment waves developed in all of them. The sediment waves observed over the continental slope are presumably generated by bottom currents intensified during major dense shelf water cascading events flowing downslope at an oblique angle with respect to the main bathymetry.
Keywords: Sediment waves, Continental slope, NW Mediterranean sea, Dense shelf water cascading
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Ribó M., Puig P., Muñóz A., Lo Iacono C., Masqué P., Palanques A., Acosta J., Guillén J., Gómez Ballesteros M. (2017)
Atlas of Bedforms in the Western Mediterranean. Ed. J. Guillén, J. Acosta, F.L. Chiocci, A. Palanques. Springer. Chap. 41. 265-271. DOI: 10.1007/978-3-319-33940-5_41. ISBN. 978-3-319-33938-2. (BibTeX: ribo.etal.2017c)
Abstract: See
Recently acquired swath bathymetry, high-resolution seismic profiles and bottom sediment samples have revealed the presence of large-scale fine-grained sediment waves over the Gulf of Valencia continental slope. Like many other deep-water sediment waves, these features were previously attributed to gravitational slope failure related to creep-like deformation, and have now been reinterpreted as sediment wave fields extending from 250 m depth to the continental rise at ~850 m depth. Sediment wave lengths range between 500 and 1000 m and maximum wave heights of up to 50 m are found on the upper slope, decreasing downslope to a minimum height of 2 m. Seismic profiles showed continuous internal reflectors and several sediment wave packages were differentiated, being thicker on the crest of each wave and thinner on the downslope flank, indicating that these sediment waves are upslope-migrating. The sediment wave formation process was inferred from contemporary hydrodynamic observations, and internal wave activity is suggested to be the most probable mechanism for the sediment transport and deposition and subsequent maintenance of the sediment waves over the Gulf of Valencia continental slope.
Keywords: Sediment waves, Continental slope, Gulf of valencia, Internal waves
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Simarro G., Guillén J., Puig P., Ribó M., Lo Iacono C., Palanques A., Muñoz A., Durán R., Acosta J. (2017)
Atlas of Bedforms in the Western Mediterranean. Ed. J. Guillén, J. Acosta, F.L. Chiocci, A. Palanques. Springer. Chap. 27. 173-177. DOI: 10.1007/978-3-319-33940-5_27. ISBN. 978-3-319-33938-2. (BibTeX: simarro.etal.2017c)
Abstract: See
A sand ridge field with crests oriented NE–SW (52°) located between 55 and 85 m water depth on the Valencia continental shelf (Spain) was mapped with multibeam swath bathymetry and characterized with high-resolution seismic reflection profiling and sediment sampling. Boundary layer hydrodynamic and suspended sediment concentration measurements conducted over a sand ridge at 66 m depth showed evidence of wave and current sediment resuspension during a major storm event. It is argued that these sand ridges developed in a shallow environment and there is no evidence of present-day ridge migration or morphological degradation.
Keywords: Bedforms, Sand ridge, Sediment resuspension, Continental shelf
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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)
Abstract: See
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.
Keywords: 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)
Abstract: See
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)
Abstract: See
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)
Abstract: See
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.
Keywords: 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)
Abstract: See
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)
Abstract: See
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
Keywords: 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)
Abstract: See
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.
Keywords: 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)
Abstract: See
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.
Keywords: 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)
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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)
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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)
Abstract: See
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.
Keywords: 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)
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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)
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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)
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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
Keywords: 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)
Abstract: See
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.
Keywords: 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)
Abstract: See
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.
Keywords: 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)
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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.
Keywords: 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)
Abstract: See
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.
Keywords: 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)
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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)
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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.
Keywords: 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)
Abstract: See
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)
Abstract: See
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)
Abstract: See
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”.
Keywords: 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)
Abstract: See
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)
Abstract: See
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.
Keywords: hyperspectral attenuation spectra, particle size distribution, hierarchical cluster analysis, multidimensional scaling