@booklet {Dagnino, title = {{Comparison of Objective Functionals in Seismic Full Waveform Inversion}}, year = {Submitted}, publisher = {European Association of Geoscientists and Engineers}, abstract = {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}, author = {Dagnino, D and Jiminez-Tejero, C E and Ranero, C{\'e}sar R and Sallares, Valenti} } @article {Biescas2016, title = {{Synthetic Modeling for an Acoustic Exploration System for Physical Oceanography}}, journal = {Journal of Atmospheric and Oceanic Technology}, volume = {33}, number = {1}, year = {2016}, pages = {191{\textendash}200}, publisher = {American Meteorological Society}, abstract = {AbstractMarine multichannel seismic (MCS) data, used to obtain structural reflection images of the earth?s subsurface, can also be used in physical oceanography exploration. This method provides vertical and lateral resolutions of O(10?100) m, covering the existing observational gap in oceanic exploration. All MCS data used so far in physical oceanography studies have been acquired using conventional seismic instrumentation originally designed for geological exploration. This work presents the proof of concept of an alternative MCS system that is better adapted to physical oceanography and has two goals: 1) to have an environmentally low-impact acoustic source to minimize any potential disturbance to marine life and 2) to be light and portable, thus being installed on midsize oceanographic vessels. The synthetic experiments simulate the main variables of the source, shooting, and streamer involved in the MCS technique. The proposed system utilizes a 5-s-long exponential chirp source of 208 dB relative to 1 ?Pa at 1 m with a frequency content of 20?100 Hz and a relatively short 500-m-long streamer with 100 channels. This study exemplifies through numerical simulations that the 5-s-long chirp source can reduce the peak of the pressure signal by 26 dB with respect to equivalent air gun?based sources by spreading the energy in time, greatly reducing the impact to marine life. Additionally, the proposed system could be transported and installed in midsize oceanographic vessels, opening new horizons in acoustic oceanography research.}, issn = {0739-0572}, doi = {10.1175/JTECH-D-15-0137.1}, url = {http://dx.doi.org/10.1175/JTECH-D-15-0137.1}, author = {Biescas, Berta and Ruddick, Barry and Kormann, Jean and Sallares, Valenti and Nedimovi{\'c}, Mladen R and Carniel, Sandro} } @article {Papadopoulos2014, title = {{Historical and pre-historical tsunamis in the Mediterranean and its connected seas: Geological signatures, generation mechanisms and coastal impacts}}, journal = {Marine Geology}, volume = {354}, year = {2014}, pages = {81{\textendash}109}, publisher = {Elsevier}, abstract = {The origin of tsunamis in the Mediterranean region and its connected seas, including the Marmara Sea, the Black Sea and the SW Iberian Margin in the NE Atlantic Ocean, is reviewed within the geological and seismotectonic settings of the region. A variety of historical documentary sources combined with evidence from onshore and offshore geological signatures, geomorphological imprints, observations from selected coastal archeological sites, as well as instrumental records, eyewitnesses accounts and pictorial material, clearly indicate that tsunami sources both seismic and non-seismic (e.g. volcanism, landslides) can be found in all the seas of the region with a variable tsunamigenic potential. Local, regional and basin-wide tsunamis have been documented. An improved map of 22 main tsunamigenic zones and their relative potential for tsunami generation is presented. From west to east, the most important tsunamigenic zones are situated offshore SW Iberia, in the North Algerian margin, in the Tyrrhenian Calabria and Messina Straits, in the western and eastern segments of the Hellenic Arc, in the Corinth Gulf of Central Greece, in the Levantine Sea offshore the Dead Sea Transform Fault and in the eastern side of the Marmara Sea. Important historical examples, including destructive tsunamis associated with large earthquakes, are presented. The mean recurrence of strong tsunamis in the several basins varies greatly but the highest event frequency (1/96. years) is observed in the east Mediterranean basin. For most of the historical events it is still unclear which was the causative seismic source and if the tsunami was caused by co-seismic slip, by earthquake-triggered submarine landslides or by a combination of both mechanisms. In pre-historical times, submarine volcanic eruptions (i.e. caldera collapse, massive pyroclastic flows, volcanogenic landslides) and large submarine landslides caused important tsunamis although little is known about their source mechanisms. We conclude that further investigation of the tsunami generation mechanisms is of primary importance in the Mediterranean region. Inputs from tsunami numerical modeling as well as from empirical discrimination criteria for characterizing tsunami sources have been proved particularly effective for recent, well-documented, aseismic landslide tsunamis (e.g., 1963 Corinth Gulf, 1979 C{\^O}te d{\textquoteright}Azur, 1999 Izmit Bay, 2002 Stromboli volcano). Since the tsunami generation mechanisms are controlled by a variety of factors, and given that the knowledge of past tsunami activity is the cornerstone for undertaking tsunami risk mitigation action, future interdisciplinary research efforts on past tsunamis are needed. {\textcopyright} 2014 Elsevier B.V.}, keywords = {Geological signatures, Historical tsunamis, Mediterranean region, Tsunami impact, Tsunami mechanisms}, issn = {00253227}, doi = {10.1016/j.margeo.2014.04.014}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84901663041\&partnerID=tZOtx3y1}, author = {Papadopoulos, Gerassimos A. and Gr{\'a}cia, Eul{\`a}lia and Urgeles, Roger and Sallares, Valenti and De Martini, Paolo Marco and Pantosti, Daniela and Gonz{\'a}lez, Mauricio and Yalciner, Ahmet C. and Mascle, Jean and Sakellariou, Dimitris and Salamon, Amos and Tinti, Stefano and Karastathis, Vassilis and Fokaefs, Anna and Camerlenghi, Angelo and Novikova, Tatyana and Papageorgiou, Antonia} } @article {Biescas2014, title = {{Recovery of temperature, salinity, and potential density from ocean reflectivity}}, journal = {Journal of Geophysical Research: Oceans}, volume = {119}, number = {5}, year = {2014}, pages = {3171{\textendash}3184}, publisher = {Blackwell Publishing Ltd}, abstract = {This work explores a method to recover temperature, salinity, and potential density of the ocean using acoustic reflectivity data and time and space coincident expendable bathythermographs (XBT). The acoustically derived (vertical frequency >10 Hz) and the XBT-derived (vertical frequency <10 Hz) impedances are summed in the time domain to form impedance profiles. Temperature (T) and salinity (S) are then calculated from impedance using the international thermodynamics equations of seawater (GSW TEOS-10) and an empirical T-S relation derived with neural networks; and finally potential density ($\rho$) is calculated from T and S. The main difference between this method and previous inversion works done from real multichannel seismic reflection (MCS) data recorded in the ocean, is that it inverts density and it does not consider this magnitude constant along the profile, either in vertical or lateral dimension. We successfully test this method on MCS data collected in the Gulf of Cadiz (NE Atlantic Ocean). T, S, and $\rho$ are inverted with accuracies of $δ$Tsd=0.1C, $δ$Ssd=0.09, and $δ$$\rho$sd=0.02kg/m 3. Inverted temperature anomalies reveal baroclinic thermohaline fronts with intrusions. The observations support a mix of thermohaline features created by both double-diffusive and isopycnal stirring mechanisms. Our results show that reflectivity is primarily caused by thermal gradients but acoustic reflectors are not isopycnal in all domains. Key Points Recovery of oceanic T, S, and potential density from acoustic reflectivity data Thermal anomalies observations at the Mediterranean tongue level Comparison between acoustic reflectors in the ocean and isopycnals {\textcopyright} 2014. American Geophysical Union. All Rights Reserved.}, keywords = {low-frequency acoustic oceanography, ocean reflectivity, Seismic oceanography, thermohaline fronts, thermohaline intrusions}, issn = {21699275}, doi = {10.1002/2013JC009662}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84902770570\&partnerID=tZOtx3y1}, author = {Biescas, Berta and Ruddick, Barry R. and Nedimovic, Mladen R. and Sallares, Valenti and Bornstein, Guillermo and Mojica, Jhon F.} } @article {Martinez-Loriente2014, title = {{Seismic and gravity constraints on the nature of the basement in the Africa-Eurasia plate boundary: New insights for the geodynamic evolution of the SW Iberian margin}}, journal = {Journal of Geophysical Research: Solid Earth}, volume = {119}, number = {1}, year = {2014}, month = {jan}, pages = {127{\textendash}149}, publisher = {Blackwell Publishing Ltd}, abstract = {We present a new classification of geological domains at the Africa-Eurasia plate boundary off SW Iberia, together with a regional geodynamic reconstruction spanning from the Mesozoic extension to the Neogene-to-present- day convergence. It is based on seismic velocity and density models along a new transect running from the Horseshoe to the Seine abyssal plains, which is combined with previously available geophysical models from the region. The basement velocity structure at the Seine Abyssal Plain indicates the presence of a highly heterogeneous, thin oceanic crust with local high-velocity anomalies possibly representing zones related to the presence of ultramafic rocks. The integration of this model with previous ones reveals the presence of three oceanic domains offshore SW Iberia: (1) the Seine Abyssal Plain domain, generated during the first stages of slow seafloor spreading in the NE Central Atlantic (Early Jurassic); (2) the Gulf of Cadiz domain, made of oceanic crust generated in the Alpine-Tethys spreading system between Iberia and Africa, which was coeval with the formation of the Seine Abyssal Plain domain and lasted up to the North Atlantic continental breakup (Late Jurassic); and (3) the Gorringe Bank domain, made of exhumed mantle rocks, which formed during the first stages of North Atlantic opening. Our models suggest that the Seine Abyssal Plain and Gulf of Cadiz domains are separated by the Lineament South strike-slip fault, whereas the Gulf of Cadiz and Gorringe Bank domains appear to be limited by a deep thrust fault located at the center of the Horseshoe Abyssal Plain. {\textcopyright}2013. American Geophysical Union. All Rights Reserved.}, keywords = {Central and North Atlantic kinematics, crustal nature, geological domains, gravity modeling, refraction and reflection traveltime tomography, wide-angle seismics}, issn = {21699313}, doi = {10.1002/2013JB010476}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84896782219\&partnerID=tZOtx3y1}, author = {Mart{\'\i}nez-Loriente, Sara and Sallares, Valenti and Gr{\'a}cia, Eul{\`a}lia and Bartolom{\'e}, Rafael and Da{\~n}obeitia, Juan Jos{\'e} and Zitellini, Nevio} } @booklet {Ranero2014, title = {{The Western Mediterranean Pairs of Basin and Arc Systems}}, year = {2014}, month = {feb}, publisher = {Sociedad Geol{\'o}gica de Espa{\~n}a}, abstract = {Ranero, C{\'e}sar R. ... et. al.{\textendash} VIII Congreso Geol{\'o}gico de Espa{\~n}a, 2012, Oviedo}, isbn = {http://hdl.handle.net/10261/92021}, url = {http://digital.csic.es/handle/10261/92021}, author = {Ranero, Cesar R. and Gr{\'a}cia, Eul{\`a}lia and Sallares, Valenti and Garcia, Xavier and Gallart Muset, Josep and Bartolom{\'e}, Rafael and Lo Iacono, Claudio and Martinez-Loriente, S. and Moreno, Ximena and Prada, Manel and Perea, Hector and Zitellini, N.} } @article {Martinez-Loriente2013, title = {{Active deformation in old oceanic lithosphere and significance for earthquake hazard: Seismic imaging of the Coral Patch Ridge area and neighboring abyssal plains (SW Iberian Margin)}}, journal = {Geochemistry, Geophysics, Geosystems}, volume = {14}, number = {7}, year = {2013}, month = {jul}, pages = {2206{\textendash}2231}, abstract = {Recently acquired high-resolution multichannel seismic profiles together with bathymetric and sub-bottom 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 Peninsula 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. Key Points New active structures have been mapped in the Coral Patch Ridge area The newly mapped faults are able to generate large magnitude earthquakes (Mw>7) These new structures may represent a significant earthquake and tsunami hazard {\textcopyright}2013. American Geophysical Union. All Rights Reserved.}, keywords = {blind thrusts, fault-bend folds, Iberia-Africa boundary, multichannel seismics, seismic hazard assessment, strike-slip faults}, issn = {15252027}, doi = {10.1002/ggge.20173}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84883575301\&partnerID=tZOtx3y1}, author = {Mart{\'\i}nez-Loriente, Sara and Gr{\'a}cia, Eul{\`a}lia and Bartolom{\'e}, Rafael and Sallares, Valenti and Connors, Christopher and Perea, Hector and Lo Iacono, Claudio and Klaeschen, Dirk and Terrinha, Pedro and Da{\~n}obeitia, Juan Jos{\'e} and Zitellini, Nevio} } @conference {BiescasGorriz2013, title = {{Inversion of density in the ocean from seismic reflection data}}, booktitle = {Proceedings of Meetings on Acoustics}, volume = {19}, year = {2013}, pages = {005009{\textendash}005009}, abstract = {Previous works in seismic oceanography explain that acoustic reflections are primarily associated with temperature vertical variations, so seismic images in the ocean can be interpreted as thermal contrasts maps. Temperature and salinity are the physical properties that describe structures in the ocean. However, the main physical parameter that controls oceans dynamics is the density and, since the ocean is a compressible fluid, potential density is the property that determines the stability, mixing and mesoscale motions of the particles. We have inverted oceanic impedance from seismic data and then derived density and potential density surfaces from the oceanic impedance. Results of the inverted potential density have been compared with seismic reflectors to show the relation between isopycnals and reflectors. We have also compare the seismic profiles of the GO Survey with the space-coincident CTDs and space and time-coincident XBTs to understand the nature of the reflectivity and its relation with the potential density in the ocean. {\textcopyright} 2013 Acoustical Society of America.}, issn = {1939800X}, doi = {10.1121/1.4798967}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84878986220\&partnerID=tZOtx3y1}, author = {Biescas Gorriz, Berta and Ruddick, Barry R. and Sallares, Valenti} } @article {Sallares2013a, title = {{Overriding plate structure of the Nicaragua convergent margin: Relationship to the seismogenic zone of the 1992 tsunami earthquake}}, journal = {Geochemistry, Geophysics, Geosystems}, volume = {14}, number = {9}, year = {2013}, month = {sep}, pages = {3436{\textendash}3461}, abstract = {We present 2-D seismic velocity models and coincident multichannel seismic reflection images of the overriding plate and the inter-plate boundary of the Nicaragua convergent margin along two wide-angle seismic profiles parallel and normal to the trench acquired in the rupture area of the 1992 tsunami earthquake. The trench-perpendicular profile runs over a seamount subducting under the margin slope, at the location where seismological observations predict large coseismic slip. Along this profile, the igneous basement shows increasing velocity both with depth and away from the trench, reflecting a progressive decrease in upper-plate rock degree of fracturing. Upper mantle-like velocities are obtained at \~{}10 km depth beneath the fore-arc Sandino basin, indicating a shallow mantle wedge. A mismatch of the inter-plate reflector in the velocity models and along coincident multichannel seismic profiles under the slope is best explained by \~{}15\% velocity anisotropy, probably caused by subvertical open fractures that may be related to fluid paths feeding known seafloor seepage sites. The presence of a shallow, partially serpentinized mantle wedge, and the fracture-related anisotropy are supported by gravity analysis of velocity-derived density models. The downdip limit of inter-plate seismicity occurs near the tip of the inferred mantle wedge, suggesting that seismicity could be controlled by the presence of serpentinite group minerals at the fault gouge. Near the trench, the inferred local increase of normal stress produced by the subducting seamount in the plate boundary may have made this fault segment unstable during earthquake rupture, which could explain its tsunamigenic character. {\textcopyright} 2013. American Geophysical Union. All Rights Reserved.}, keywords = {Convergent margin, travel time tomography, tsunami earthquake, wide-angle seismics}, issn = {15252027}, doi = {10.1002/ggge.20214}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84886671506\&partnerID=tZOtx3y1}, author = {Sallares, Valenti and Mel{\'e}ndez, Adri{\`a} and Prada, Manuel and Ranero, Cesar R. and McIntosh, Kirk and Grevemeyer, Ingo} } @booklet {Martinez-Loriente2013a, title = {{Pre-stack depth migration seismic imaging of the Coral Patch Ridge and adjacent Horseshoe and Seine Abyssal Plains (Gulf of Cadiz): tectonic implications}}, year = {2013}, month = {apr}, publisher = {Universidad de Oviedo}, abstract = {Peer Reviewed}, url = {http://digital.csic.es/handle/10261/75234}, author = {Martinez-Loriente, S. and Gr{\'a}cia, Eul{\`a}lia and Bartolom{\'e}, Rafael and Klaeschen, D. and Vizcaino, A. and Sallares, Valenti and Da{\~n}obeitia, Juan Jos{\'e} and Zitellini, N.} } @article {Sallares2013, title = {{Seismic evidence of exhumed mantle rock basement at the Gorringe Bank and the adjacent Horseshoe and Tagus abyssal plains (SW Iberia)}}, journal = {Earth and Planetary Science Letters}, volume = {365}, year = {2013}, month = {mar}, pages = {120{\textendash}131}, abstract = {The Gorringe Bank is a gigantic seamount that separates the Horseshoe and Tagus abyssal plains offshore SW Iberia, in a zone that hosts the convergent boundary between the Africa and Eurasia plates. Although the region has been the focus of numerous investigations since the early 1970s, the lack of appropriate geophysical data makes the nature of the basement, and thus the origin of the structures, still debated. In this work, we present combined P-wave seismic velocity and gravity models along a transect that crosses the Gorringe Bank from the Tagus to the Horseshoe abyssal plains. The P-wave velocity structure of the basement is similar in the Tagus and Horseshoe plains. It shows a 2.5-3.0. km-thick top layer with a velocity gradient twice stronger than oceanic Layer 2 and an abrupt change to an underlying layer with a five-fold weaker gradient. Velocity and density is lower beneath the Gorringe Bank probably due to enhanced fracturing, that have led to rock disaggregation in the sediment-starved northern flank. In contrast to previous velocity models of this region, there is no evidence of a sharp crust-mantle boundary in any of the record sections. The modelling results indicate that the sediment overlays directly serpentinite rock, exhumed from the mantle with a degree of serpentinization decreasing from a maximum of 70-80\% under the top of Gorringe Bank to less than 5\% at a depth of \~{}20. km. We propose that the three domains were originally part of a single serpentine rock band, of nature and possibly origin similar to the Iberia Abyssal Plain ocean-continent transition, which was probably generated during the earliest phase of the North Atlantic opening that followed continental crust breakup (Early Cretaceous). During the Miocene, the NW-SE trending Eurasia-Africa convergence resulted in thrusting of the southeastern segment of the exhumed serpentinite band over the northwestern one, forming the Gorringe Bank. The local deformation associated to plate convergence and uplift could have promoted pervasive rock fracturing of the overriding plate, leading eventually to rock disaggregation in the northern flank of the GB, which could be now a potential source of rock avalanches and tsunamis. {\textcopyright} 2013 Elsevier B.V.}, keywords = {Gravity modelling, Mantle exhumation, North Atlantic margin, Travel-time tomography, wide-angle seismics}, issn = {0012821X}, doi = {10.1016/j.epsl.2013.01.021}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84874491076\&partnerID=tZOtx3y1}, author = {Sallares, Valenti and Mart{\'\i}nez-Loriente, Sara and Prada, Manel and Gr{\'a}cia, Eul{\`a}lia and Ranero, C{\'e}sar and Gutscher, Marc-Andr{\'e} and Bartolom{\'e}, Rafael and Gailler, Audrey and Da{\~n}obeitia, Juan Jos{\'e} and Zitellini, Nevio} } @booklet {Sallares, title = {{Active faulting and slope failure in the Iberian margins: towards offshore geohazard mitigation}}, year = {2011}, publisher = {International Commission for the Scientific Exploration of the Mediterranean Sea}, abstract = {12 pages, 7 figures.}, url = {http://digital.csic.es/handle/10261/57350}, author = {Sallares, Valenti and Gr{\'a}cia, Eul{\`a}lia and Urgeles, Roger} } @article {Manchuel2011, title = {{New insights on the interseismic active deformation along the North Ecuadorian-South Colombian (NESC) margin}}, journal = {Tectonics}, volume = {30}, number = {4}, year = {2011}, month = {aug}, pages = {n/a{\textendash}n/a}, abstract = {The North Ecuadorian-South Colombian subduction zone was the site of the 1906 Mw 8.8 megathrust earthquake. This main shock was followed by three large events in 1942, 1958, and 1979 whose rupture zones were located within the 500 km long 1906 rupture area. A combined onshore and offshore temporary seismic network covering from the trench to the Andes was deployed during 3 months in the area of large earthquakes, in order to obtain a detailed knowledge of the seismic background activity. Resulting earthquakes location and mechanisms bring new insights on interseismic active deformation distribution in the three main tectonic units of the margin, namely, the Interplate Seismogenic Zone, the fore-arc region which is part of the North Andean Block and the downgoing oceanic Nazca plate. The interplate seismic activity presents along strike variations, suggesting that the seismicity and the associated stress buildup along the plate interface depend on the time elapsed since the last large earthquakes. According to our results, the updip and downdip limits of the seismogenic zone appear to be located at 12 and 30 km depth, respectively. Shallow to intermediate depth seismicity indicates a slab dip angle of ≈25{\textdegree}. North of the Carnegie Ridge, the Wadati-Benioff plane is defined beneath the fore arc down to ≈100 km depth. Facing the ridge, the Wadati-Benioff plane extends beneath the Andes, down to ≈140 km depth. This observation conflicts with the hypothesis of the presence of a flat slab at a depth of 100 km facing the ridge. In the overlying fore-arc region, the crustal seismicity occurs down to 40 km depth and is mainly concentrated in a roughly NW-SE 100 km wide stripe stretching from the coast, at about 1{\textdegree}N, to the Andes. The location of this active deformation stripe coincides with observed tectonic segmentation of the coastal domain as evidenced by the presence of an uplifting segment to the south and a subsiding segment to the north of the stripe. It also corresponds to a ≈30{\textdegree} change in the trend of the Andes, suggesting that the curvature of the volcanic arc might play an important role in the deformation of the fore-arc region. Copyright 2011 by the American Geophysical Union.}, issn = {02787407}, doi = {10.1029/2010TC002757}, url = {http://doi.wiley.com/10.1029/2010TC002757 http://www.scopus.com/inward/record.url?eid=2-s2.0-79960929640\&partnerID=tZOtx3y1}, author = {Manchuel, Kevin and R{\'e}gnier, Marc and B{\'e}thoux, Nicole and Font, Yvonne and Sallares, Valenti and D{\'\i}az, Jordi and Yepes, Hugo} } @article {Sallares2011, title = {{Seismic evidence for the presence of Jurassic oceanic crust in the central Gulf of Cadiz (SW Iberian margin)}}, journal = {Earth and Planetary Science Letters}, volume = {311}, number = {1-2}, year = {2011}, month = {nov}, pages = {112{\textendash}123}, abstract = {We investigate the crustal structure of the SW Iberian margin along a 340. km-long refraction and wide-angle reflection seismic profile crossing from the central Gulf of Cadiz to the Variscan continental margin in the Algarve, Southern Portugal. The seismic velocity and crustal geometry model obtained by joint refraction and reflection travel-time inversion reveal three distinct crustal domains: the 28-30. km-thick Variscan crust in the north, a 60. km-wide transition zone offshore, where the crust abruptly thins \~{}. 20. km, and finally a \~{}. 7. km-thick and \~{}. 150. km-wide crustal section that appears to be oceanic in nature. The oceanic crust is overlain by a 1-3. km-thick section of Mesozoic to Eocene sediments, with an additional 3-4. km of low-velocity, unconsolidated sediments on top belonging to the Miocene age, Gulf of Cadiz imbricated wedge. The sharp transition between continental and oceanic crust is best explained by an initial rifting setting as a transform margin during the Early Jurassic that followed the continental break-up in the Central Atlantic. The narrow oceanic basin would have formed during an oblique rifting and seafloor spreading episode between Iberia and Africa that started shortly thereafter (Bajocian) and lasted up to the initiation of oceanic spreading in the North Atlantic at the Tithonian (late Jurassic-earliest Cretaceous). The velocity model displays four wide, prominent, south-dipping low-velocity anomalies, which seem to be related with the presence of crustal-scale faults previously identified in the area, some of which could well be extensional faults generated during this rifting episode. We propose that this oceanic plate segment is the last remnant of an oceanic corridor that once connected the Alpine-Tethys with the Atlantic ocean, so it is, in turn, one of the oldest oceanic crustal fragments currently preserved on Earth. The presence of oceanic crust in the central Gulf of Cadiz is consistent with geodynamic models suggesting the existence of a narrow, westward retreating oceanic slab beneath the Gibraltar arc-Alboran basin system. {\textcopyright} 2011 Elsevier B.V.}, keywords = {Geodynamic evolution, Jurassic oceanic crust, Refraction and reflection travel-time tomography, SW Iberian margin, Uncertainty analysis, wide-angle seismics}, issn = {0012821X}, doi = {10.1016/j.epsl.2011.09.003}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-81155155560\&partnerID=tZOtx3y1}, author = {Sallares, Valenti and Gailler, Audrey and Gutscher, Marc-Andr{\'e} and Graindorge, David and Bartolom{\'e}, Rafael and Gr{\'a}cia, Eul{\`a}lia and D{\'\i}az, Jordi and Da{\~n}obeitia, Juan Jos{\'e} and Zitellini, Nevio} } @article {Biescas2010, title = {{Seismic imaging of staircase layers below the Mediterranean Undercurrent}}, journal = {Deep Sea Research Part I: Oceanographic Research Papers}, volume = {57}, number = {10}, year = {2010}, month = {oct}, pages = {1345{\textendash}1353}, abstract = {Seismic images of staircase layers at the bottom of the Mediterranean Undercurrent with a lateral coherence up to 50. km and a horizontal resolution of \~{}10m are presented. The images show clearly the interaction between these staircase layers and other flow structures such as meddies, seamounts and internal waves. The staircase layers were imaged during two different surveys that used different sound sources. Comparison between seismic images and historical oceanographic observations illustrates the importance of using a seismic source adapted to the vertical scale of the oceanographic target to be imaged. Wavelengths larger than the size of the staircase structure distort the image in the vertical. For optimal imaging, deconvolution of the data is required. {\textcopyright} 2010 Elsevier Ltd.}, keywords = {Boundary mixing, Gulf of Cadiz, Meddy, Mediterranean Undercurrent, Seismic oceanography, Thermohaline staircase layers}, issn = {09670637}, doi = {10.1016/j.dsr.2010.07.001}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-77956879722\&partnerID=tZOtx3y1}, author = {Biescas, Berta and Armi, Larry and Sallares, Valenti and Gr{\'a}cia, Eul{\`a}lia} } @article {Kormann2010, title = {{Synthetic modelling of acoustical propagation applied to seismic oceanography experiments}}, journal = {Geophysical Research Letters}, volume = {37}, number = {6}, year = {2010}, month = {mar}, pages = {n/a{\textendash}n/a}, abstract = {Recent work shows that multichannel seismic (MCS) systems provide detailed information on the oceans{\textquoteright} finestructure. The aim of this paper is to analyze if high order numerical algorithms are suitable to accurately model the extremely weak wavefield scattered by the oceans{\textquoteright} finestructures. For this purpose, we generate synthetic shot records along a coincident seismic and oceanographic profile acquired across a Mediterranean salt lens in the Gulf of Cadiz. We apply a 2D finite-difference time-domain propagation model, together with second-order Complex Frequency Shifted Perfectly Matched Layers at the numerical boundaries, using as reference a realistic sound speed map with the lateral resolution of the seismic data. We show that our numerical propagator creates an acoustical image of the ocean finestructures including the salt lens that reproduces with outstanding detail the real acquired one. Copyright {\textcopyright} 2010 by the American Geophysical Union.}, issn = {00948276}, doi = {10.1029/2009GL041763}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-77949835265\&partnerID=tZOtx3y1}, author = {Kormann, Jean and Cobo, Pedro and Biescas, Berta and Sallares, Valenti and Papenberg, Cord and Recuero, Manuel and Carbonell, Ram{\'o}n} } @article {Buske2009, title = {{Imaging and inversion {\textemdash} Introduction}}, journal = {GEOPHYSICS}, volume = {74}, number = {6}, year = {2009}, month = {nov}, pages = {WCA1{\textendash}WCA4}, issn = {0016-8033}, doi = {10.1190/1.3256872}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84861190134\&partnerID=tZOtx3y1}, author = {Buske, Stefan and Lecomte, Isabelle and Nemeth, Tamas and Operto, St{\'e}phane and Sallares, Valenti} } @article {Kormann2009, title = {{Modelling Seismic Oceanography Experiments by Using First- and Second-Order Complex Frequency Shifted Perfectly Matched Layers}}, journal = {Acta Acustica united with Acustica}, volume = {95}, number = {6}, year = {2009}, month = {nov}, pages = {1104{\textendash}1111}, abstract = {This work investigates the ability of modelling seismic oceanography experiments by using underwater acoustic propagation equations. Seismic oceanography tries to retrieve the fine structure of the ocean water masses by processing the acoustic waves reflected in the low-contrast interfaces of fronts, eddies, internal waves or thermohaline intrusions. Since the reflectivity of such interfaces is of order 10-3-10-4, the absorption capability of the numerical boundaries becomes crucial. Complex Frequency Shifted offers a better alternative to classical Perfectly Matched Layer formulation, but has not yet been extended to acoustic equations. Here, first- and second-order Complex Frequency Shifted Perfectly Matched Layers equations are proposed which can provide reflection coefficients of order 10-5. Therefore, a numerical Finite-Difference Time-Domain (FDTD) scheme combined with the proposed CFS-PML equations is able to model such experiments. {\textcopyright} S. Hirzel Verlag {\textperiodcentered} EAA.}, issn = {16101928}, doi = {10.3813/AAA.918242}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-77149123321\&partnerID=tZOtx3y1}, author = {Kormann, Jean and Cobo, Pedro and Recuero, Manuel and Biescas, Berta and Sallares, Valenti} } @booklet {Martinez-Loriente2009, title = {{Wide-angle reflection and refraction seismic profile from the outer part of the gulf of Cadiz: nearest-seis cruise}}, journal = {Instrumentation ViewPoint}, number = {8}, year = {2009}, pages = {49}, publisher = {Universitat Polit{\`e}cnica de Catalunya}, abstract = {We will explain the first interpretations from a marine refraction and wideangle reflection seismic profile acquired in the outer part of the Gulf of Cadiz in November 2008, in the framework of the NEAREST-SEIS cruise}, keywords = {Tecnolog{\'\i}a industrial. Tecnolog{\'\i}a mec{\'a}nica, Tecnolog{\'\i}as}, issn = {1886-4864}, url = {http://dialnet.unirioja.es/servlet/articulo?codigo=3202467\&info=resumen\&idioma=ENG}, author = {Mart{\'\i}nez-Loriente, Sara and Sallares, Valenti and Bartolom{\'e}, Rafael and Gr{\`a}cia i Mont, Eulalia} } @book {Sallares2007, title = {{Special Paper 430: Plates, Plumes and Planetary Processes}}, series = {Special Paper of the Geological Society of America}, volume = {430}, year = {2007}, pages = {507{\textendash}524}, publisher = {Geological Society of America}, organization = {Geological Society of America}, abstract = {At present there is no single "unified theory" capable of explaining the variety of geological, geophysical, and geochemical observations that characterize what is generically known as hotspot magmatism. An increasing number of geophysical and geo- chemical observations disagree with the predictions of the conventional thermal plume model, in which excess melting is due mainly to high mantle temperatures. Other parameters such as the presence of water or the composition of the mantle source have been shown to be as important as temperature in controlling the structure and physical properties of the igneous crust. In this article we first emphasize the importance of doing proper velocity and density modeling, including comprehensive uncertainty analysis, to determine how well resolved the geophysical parameters actually are. We show that in some cases the contribution of velocity-derived lateral crustal density variations can be sufficiently significant to account for the observed gravity and topography anomalies without calling for noticeable mantle density contrasts. Next we show that the comparison of crustal geometry obtained along age-progressive volcanic tracks enables temporal variations of the hotspot-ridge distance to be estimated. Finally we use a 2-D mantle melting model to illustrate the effect of different mantle melting parameters on the resulting crustal structure. The tests made indicate that it is difficult to find a plausible combination of mantle temperature, upwelling rate, melt productivity, and thickness of the melting zone to explain either the high-velocity, un- derplated bodies frequently described at midplate settings or the lack of a positive crustal thickness-velocity (H-Vp) correlation found at igneous provinces originated on-ridge. We suggest that the main parameter controlling the generation of volcanic underplating is the presence of a lithospheric lid limiting the extent of the mantle melting zone, whereas the H-Vp anticorrelation can be related to the presence of a major element heterogeneity, such as eclogite derived from recycled oceanic lithosphere, in the mantle source. {\textcopyright} 2007 The Geological Society of America.}, keywords = {Crustal structure, Density, Mantle melting parameters, Seismic velocity}, isbn = {978-0-8137-2430-0}, issn = {00721077}, doi = {10.1130/978-0-8137-2430-0}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-75749138216\&partnerID=tZOtx3y1}, author = {Sallares, Valenti and Calahorrano, Alcinoe} }