Configuration of geological domains and geodynamic evolution of the Africa-Eurasia plate boundary off SW Iberia revisited based on seismic velocity and density models

European Geosciences Union General Assembly 2015 (EGU2015), 12-17 April 2015, Vienna, Austria.-- 1 pageWe present a new classification of geological (basement) domains at the Africa-Eurasia plate boundary offshore 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 two regional wide- angle seismic transects, one running NW-SE from the Tagus to the Seine abyssal plains, and the other running N-S from S Portugal to the Seine Abyssal Plain, combined with previously available information. The seismic velocity and density structure at the Seine Abyssal Plain and the internal Gulf of Cadiz indicates the presence of a highly heterogeneous oceanic crust, similar to that described in ultra-slow spreading centers, whereas in the Horseshoe and Tagus abyssal plains, the basement structure resembles that of exhumed mantle sections identified in the Northern Atlantic margin. The integration of all this new information allows defining the presence of three oceanic domains off SW Iberia: (1) the Seine Abyssal Plain domain, generated during the first stages of slow seafloor spreading in the NE segment of the 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 break-up (Late Jurassic); and (3) the Gorringe Bank domain, mainly made of rocks exhumed from the mantle with little synchronous magmatism, which formed during the first stages of North Atlantic opening (Early Cretaceous). 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, which coincides with the seismicity cluster nucleated in the middle of the plain that shows moment tensor solutions of reverse faulting at depths of 40–60 km. The formation and evolution of these three domains during the Mesozoic is key to understand the sequence of events that occurred during the first stages of opening of the Northern Atlantic and its connection and interplay with the Western Mediterranean basinPeer Reviewe

Processing and interpretation of multichannel seismic reflection data ( SWIN-06 cruise): from the horsehoe to seine abyssal plains (Gulf of Cadiz)

Martech 2007 International Workshop on Marine Technology, 15-16 november 2007, Vilanova i la Geltrú, Spain.-- 2 pages, 1 figureThe authors acknowledge the support of the SWIM project (REN2002-11234- E-MAR), National project EVENT (CGL 2006-12861-C02-02) and the EU-NEAREST project (Ref. 037110)Peer reviewe

Acoustic and seismic imaging of the Adra Fault (NE Alboran Sea): in search of the source of the 1910 Adra earthquake

13 pages, 7 figures, 1 tableRecently acquired swath-bathymetry data and high-resolution seismic reflection profiles offshore Adra (Almería, Spain) reveal the surficial expression of a NW–SE trending 20 km-long fault, which we termed the Adra Fault. Seismic imaging across the structure depicts a sub-vertical fault reaching the seafloor surface and slightly dipping to the NE showing an along-axis structural variability. Our new data suggest normal displacement of the uppermost units with probably a lateral component. Radiocarbon dating of a gravity core located in the area indicates that seafloor sediments are of Holocene age, suggesting present-day tectonic activity. The NE Alboran Sea area is characterized by significant low-magnitude earthquakes and by historical records of moderate magnitude, such as the Mw = 6.1 1910 Adra Earthquake. The location, dimension and kinematics of the Adra Fault agree with the fault solution and magnitude of the 1910 Adra Earthquake, whose moment tensor analysis indicates normal-dextral motion. The fault seismic parameters indicate that the Adra Fault is a potential source of large magnitude (Mw ≤ 6.5) earthquakes, which represents an unreported seismic hazard for the neighbouring coastal areasThe authors acknowledge the support of the Spanish Ministry of Science and Innovation (MICINN) through National Projects IMPULS (REN2003-05996MAR), EVENT (CGL2006-12861-C02-02) and SHAKE (CGL2011-30005-C02-02); Acciones Complementarias EVENT-SHELF (CTM 2008-03346-E/MAR) and SPARKER (CTM 2008-03208-E/MAR) and the ESF TopoEurope TOPOMED project (CGL2008-03474-E/BTE). We thank the captain, crew, scientific party and technical staff of the UTM-CSIC on board the Spanish R/V “Hesperides” and R/V “García del Cid” during the IMPULS and EVENT-SHELF cruises, respectively. We thank Fabrizio Pepe (Univ. Palermo) for his assistance in using the Geotrace software.We thank guest editor Hans Nelson, Carlos Marín Lechado and an anonymous referee for constructive comments and reviews. This work has been carried out within Grup de Recerca de la Generalitat de Catalunya B-CSI (2009 SGR 146)Peer reviewe

Characterizing active faults and associated mass transport deposits in the South Iberian Margin (Alboran Sean and Gulf of Cadiz): on-fault and off-fault paleoseismic evidence

During the last years we have carried out successive high-resolution marine geological and geophysical surveys to investigate the seismic potential of the slow-moving seismogenic faults from the South Iberian Margin. Based on ,ultiscale acoustic mapping, sub-seafloor seismic imaging and dating methods we have characterized submarine fault systems with unprecedented resolution. We present primary paleoseismic evidence obtained by direct investigations of selected faults from theMediterranean Sea (i.e. Carboneras Fault, Bajo Segura Fault, Adra Fault) and the external part of the Gulf of Cadiz (i.e. Marques de Pombal Fault, Horseshoe Fault, Coral Patch Ridge Fault and SWIM lineaments). The obtained fault seismic parameters suggest that these faults are active and capable of generating large magnitude (Mw > 6) seismic events, representing an earthquake and tsunami hazard for the surrounding coastal areas. Secondary paleoseismic evidence in the SW Iberian Margin (based on landslides and turbidite deposits) yields a regional recurrence rate of large magnitude earthquake of 1800 - 2000 years

A tribute to Marie Tharp: Mapping the seafloor of back-arc basins, mid-ocean ridges, continental margins and plate boundaries

European Geosciences Union (EGU) General Assembly 2020, 4-8 May 2020Marie Tharp (1920-2006) was a pioneer of modern oceanography. She was an American geologist and oceanographic cartographer who, together with his husband Bruce Heezen, generated the first bathymetric map of the Atlantic Ocean floor. Tharp's work revealed the detailed topography and geological landscape of the seafloor. Her work revealed the presence of a continuous rift valley along the Mid-Atlantic Ridge axis, causing a paradigm in earth sciences that led to the acceptance of plate tectonics and continental drift theories. Piecing maps together in the late 1940s and early 1950s, Marie and his partner Bruce Heezen discovered the 75.000 km underwater ridge bounding around the globe. By this finding, they laid the conclusion from geophysical data that the seafloor spreads from mid-ocean ridges and that continents are in motion with respect to one another¿a revolutionary geological theory at that time. Many years later, satellite images demonstrate that Tharp¿s maps were accurate. In this contribution, we focus on detailed bathymetric maps collected from year 1992 to today, which include bathymetric maps from diverse parts of the world. For instance, we will show a) Back-arc basins (i.e. the Bransfield Basin, Antarctica; and the North Fiji Basin, SW Pacific); b) Mid-ocean ridges and fracture zones (i.e. the MAR at the South of Azores, the MAR at the Oceanographer-Hayes, and the St. Paul Fracture Zone at the Equator), and c) Active tectonic structures from the Gulf of Cadiz and Alboran Sea, located at the Africa-Eurasia plate boundary (Gibraltar Arc). Regarding this last area, we will characterize the seafloor expression of the fault systems, as well as the subsurface structure of the faults in the Gulf of Cadiz and Alboran Sea. This zone is characterized by a moderate seismicity, mainly reverse and strike-slip focal mechanisms; although large historical (AD1755, AD1829) and instrumental earthquakes or large/great magnitude also occurred, such as the earthquakes of 1969, 1994, 2004 and 2016. In addition, the Gulf of Cadiz-Alboran Sea area is compartmentalized in different crustal domains, bounded by active strike-slip fault systems. We adopted a multi-scale approach, including morphological analysis of shipboard multibeam bathymetry, near-bottom bathymetry obtained with Autonomous Underwater Vehicles (AUVs) at a resolution of 1-2 m, and medium to deep penetration multi-channel seismic (MCS) data. Finally, we will also show a couple of videos from recent marine cruises in the Gibraltar Arc (SHAKE-2015 and INSIGHT-2018), both using state-of-the-art high-resolution marine technologie

Tectonic evolution, geomorphology and influence of bottom currents along a large submarine canyon system: The São Vicente Canyon (SW Iberian margin)

A multi-scale dataset consisting of multi-beam echo-sounder, 2D multi-channel seismic and sidescan sonar (TOBI) data allows us to identify a large variety of morphologies originating from sedimentary and tectonic processes along the São Vicente Canyon (SVC), which is the largest submarine canyon developed in the external part of the Gulf of Cadiz. The SVC is located in one of the most seismogenic areas of Western Europe. The convergence between the Eurasian and African plates has controlled the formation and evolution of the canyon. The SVC is tectonically controlled by three main thrust faults: the Marquês de Pombal Fault, the São Vicente Fault and the Horseshoe Fault. No major rivers feed sediment to the canyon head, but the main sediment source is related to the dismantling of canyon flanks and the MOW (Mediterranean Overflow Water). This current contributes sediments by two different processes: a) conturites deposition at the head and flanks of the SVC that periodically fail into the canyon; and b) the coarser-grained and denser sediment of the MOW might be trapped at the head of the canyon and could develops into hyperpycnal flows. The SVC is characterized by retrogressive erosion being submarine landslide deposits and scars the main seafloor morphologies. The tectonic and stratigraphic interpretation of seismic profiles indicate that the SVC is a clear example of a diachronous and segmented canyon developed since the Late Miocene in an area of present-day active plate tectonics. This study investigates the interaction between active tectonics, the dynamics of submarine canyons and the resulting geomorphologies

Using ultra-high resolution methodologies to imaging active submarine faults: The STRENGTH 2023 cruise in the Alboran sea

8th International Colloquium on Historical Earthquakes, Palaeo- Macroseismology and Seismotectonics, Past earthquakes and advances in seismology for informed risk decision-making, 17-20 September 2023, Lixouri, Kefalonia Island, Greece.-- 4 pages, 2 figuresGreat earthquakes and the possibility to generate destructive tsunamis are geohazards of key societal concern, as they may impact world economies, disturb submarine structures and affect coastal areas with the associated risk for local populations (Bilham, 2010). We still have in our mind catastrophic episodes, such as the giant events of the Sumatra earthquake and tsunami in 2004 in the Indian Ocean of magnitude (Mw) 8.7, and the Tohoku-Oki earthquake and tsunami in 2011 in the northwest of Japan, of magnitude (Mw) 9.0-9.1. Nevertheless, seismic events of moderate to large magnitude (Mw 6-7.3) in areas of low to moderate tectonic deformation, and with long recurrence intervals, such as the Alboran Sea in the Western Mediterranean, might also have a significant effect. Accordingly, during the last decades there has been an expansion of paleoseismology to marine areas, both on-fault and off-fault investigations (Pantosti et al., 2011; Perea et al., 2021a). [...]This research was supported by the grant STRENGTH (PID2019-104668RB-I00) funded by MCIN/AEI/10.13039/501100011033. This project acknowledges the „Severo Ochoa Centre of Excellence‟ accreditation (CEX2019-000928-S), the grant UNrIDDLE (2018-T1/AMB-11039) “Atracción de Talento Investigador” call 2018 funded by Comunidad de Madrid and the Ocean Facilities Exchange Group (OFEG) for allowing us to use the AUV “AsterX” from IFREMERPeer reviewe

Estratigrafia i estructura de la part externa del Golf de Cadis basades en dades de sísmica de reflexió multicanal migrades en profunditat pre-stack

Trabajo presentado por Sara Martínez Loriente para obtener el Diploma de Estudios Avanzados del programa de doctorado Exploració, Anàlisi i Modelització de Conques i Sistemes Orogènics de la Universitat de Barcelona (UB), realizado bajo la dirección de la Dra. Eulàlia Gràcia, el Dr. Rafael Bartolomé y el Dr. Valentí Sallarès de la Unitat de Tecnologia Marina (UTM-CSIC).-- 67 page

Caracterització geofísica i geològica de les estructures actives i la natura del basament en el límit de plaques Euràsia-Àfrica (Marge SO d’Ibèria): Implicacions per la geodinàmica regional i per l’avaluació de la perillositat sísmica

Memoria de tesis doctoral presentada por Sara Martínez Loriente para optar al grado de Doctora por la Universitat de Barcelona (UB), realizada bajo la dirección de la Dra. Eulàlia Gràcia Mont y del Dr. Valentí Sallarès Casas del Institut de Ciències del Mar (ICM-CSIC).-- 334 pagesIn this PhD Thesis I present a new interpretation of: 1) active structures implicating old oceanic lithosphere; 2) the nature of the basement; and 3) the distribution of the basement domains and the geodynamic reconstruction of the SW Iberian margin, a region that hosts the slow convergent boundary between the African and Eurasian plates. This interpretation is based on new geophysical data acquired, processed and modeled in the framework of this PhD work. The main findings of my study are the following ones: [...]The author of the thesis benefited from a four-year JAE Pre-Doc fellowship from CSIC between 2008 and 2012. The author also benefied from a European Transnational Access SALVADORE program of the EU (RITA-CT-2004–505322) to do a short stay carried out at the Department of Geodynamics of IFM-GEOMAR, Kiel (Germany) in 2007 (5 weeks). Within the framework of the JAE Pre-Doc, the author was granted with two short stays at the following foreign institutions: the Department of Geology of the National Institute of Water and Atmospheric Research (NIWA), Wellington (New Zealand) in 2010 (5.5 months), and the Istituto di Scienze Marine (ISMAR) of the Consiglio Nazionale delle Ricerche (CNR), Bologna (Italia) in 2011 (5 weeks). The data used in this work was acquired and interpreted within the framework of the ESF EuroMargins SWIM project (01-LEG-EMA09F and REN2002–11234E-MAR) and the Complementary Action NEAREST-SEIS (CGL2006-27098-E/ BTE) of the Spanish Ministry of Science and Innovation (MICINN) as part of the FP6 EU-funded NEAREST Project (# 037110). In addition, different parts of the work have also been supported by the MICINN through National Projects EVENT (CGL2006–12861-C02-02), SHAKE (CGL2011–30005-C02-02), ESF TopoEurope TOPOMED project (CGL2008–03474-E/BTE), MEDOC (CTM2007-66179-C02-02/MAR), and POSEIDON (CTM2010-21569), and Acción Complementaria NEAREST-CORE (CTM2008-04938-E/MAR). The Spanish Ministry of Science and Education (MEC) through the Management Committee of Research Vessels (COCSABO) allocated ship-time on the national large scale facility RV Hesperides, allowing to carry out the marine cruises SWIM (June 2006, PI: E. Gràcia) and NEAREST-SEIS (October 2008, PI: V. Sallarès), from which most of the data presented in this thesis have been acquiredPeer Reviewe

Per què és important haver descobert l'epicentre del terratrèmol que va destruir Lisboa a finals del segle divuit?

Uns investigadors catalans han descobert el lloc exacte on es va produir. La troballa de l'epicentre servirà per adoptar mesures de prevenció si hi hagués un sisme semblantPeer reviewe