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[EN] Last week the Portuguese capital hosted the UN Ocean Conference which, with more than 7,000 attendees, sought to launch a new chapter of global action to protect the big blue, [ES] La semana pasada la capital portuguesa acogió a la UN Ocean Conference que, con más de 7.000 asistentes, buscaba impulsar un nuevo capítulo de acción mundial para proteger el planeta azul, [CAT] La setmana passada la capital portuguesa va acollir la UN Ocean Conference que, amb més de 7.000 assistents, buscava impulsar un nou capítol d’acció mundial per protegir el planeta blau

A primera hora de la tarde del 11 de marzo de 2011, un enorme terremoto de magnitud 9.0, el cuarto mayor registrado en la historia, agitó fuertemente la costa este de Japón, principalmente en la isla de Honshu. Pese a la formidable intensidad de la sacudida, que se prolongó durante seis minutos y liberó una energía de 500 megatones, los daños inmediatos fueron moderados gracias al modélico plan de prevención sísmica del país. Pero esa fue sólo la antesala del verdadero desastre. Unos 30 minutos después, el nivel del mar empezó a subir en el puerto de Miyako, ciudad de unos 50 000 habitantes situada 200 km al norte del epicentro. Las imágenes son hipnóticas. De entrada, nada parece particularmente grave. La subida, primero imperceptible y luego lenta, se prolonga durante varios minutos, arrastrando un número creciente de embarcaciones que golpean con fuerza los muros protectores del puerto, de 10 m de altura. Al otro lado del muro hay gente paseando que aparenta confianza y tranquilidad. Pero el nivel del agua sigue creciendo hasta que sobrepasa netamente los muros y la hipnosis da paso al estupor: una masa de agua oscura se precipita hacia el puerto y avanza tierra adentro, barriendo la ciudad y arrastrando embarcaciones, vehículos, edificaciones y todo lo que encuentra a su paso hasta unos 5 km de la costa. La devastación es absoluta

X Congreso Geológico de España, 5-7 de julio 2021, Vitoria-Gasteiz.-- 1 page, [EN] 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 (Martínez-Loriente et al., 2014). It is based on seismic velocity and density models along two regional wide-angle seismic transects, combined with previously available information. The integration of all this information allows defining the presence of 3 oceanic domains off SW-Iberia: (1) the SAP domain, made of oceanic crust generated during the first stages of slow seafloor spreading in the NE Central Atlantic (Early Jurassic) (Martínez-Loriente et al., 2014); (2) the GC domain, made of oceanic crust generated in the Alpine-Tethys spreading system between Iberia and Africa, which was coeval with the formation of the SAP domain and lasted up to the North Atlantic continental break-up (Late Jurassic); and (3) the Gorringe Bank (GB) domain, mainly made of rocks exhumed from the mantle with little synchronous magmatism, which formed during the first stages of North Atlantic opening. Our models suggest that the SAP and GC domains are separated by the Lineament South strike-slip fault, whereas the GC and GB domains appear to be limited by a deep thrust fault located at the center of the Horseshoe Abyssal Plain (Martínez-Loriente et al., 2014), [ES] Presentamos una nueva clasificación de dominios geológicos en el límite de placas África-Eurasia al suroeste de Iberia, junto con una reconstrucción geodinámica regional que abarca desde la extensión Mesozoica hasta la convergencia actual (Martínez-Loriente et al., 2014). Los resultados se basan en modelos de velocidad sísmica y densidad a lo largo de dos transectos regionales de gran ángulo, combinados con información previa disponible. La integración de toda la información nos permite definir 3 dominios oceánicos al suroeste de Iberia: (1) el dominio SAP, compuesto por corteza oceánica generada durante las primeras etapas de la extensión oceánica del NE Atlántico central (Martínez-Loriente et al., 2014); (2) el dominio GC, compuesto por corteza oceánica generada en el sistema extensivo Alpino-Tetis entre Iberia y África, que fue contemporáneo con la formación del dominio SAP y finalizó con la ruptura continental del Atlántico Norte (Jurásico tardío); y (3) el dominio del GB, compuesto principalmente de rocas exhumadas del manto con algo de magmatismo sincrónico, formado durante las primeras etapas de la apertura del Atlántico Norte. Los modelos sugieren que los dominios SAP y GC están separados por la falla en dirección Lineament South, mientras que los dominios de GC y GB parecen estar limitados por una falla inversa profunda ubicada en el centro de la llanura abisal de Horseshoe (Martínez-Loriente et al., 2014)

Challenge 9.-- Coordinators: José Pintado Valverde (IIM, CSIC), Ana Crespo Solana (IH-CCHS, CSIC).-- 20 pages, 4 figures., The Ocean has shaped human societies, providing resources and ways of communication, trade, exploration and expansion. Understanding the interactions with Society in the past and the present, is essential to tackle the challenges that face the future of the Ocean. With that aim, this chapter develops the consilience between Ocean Science, Social Sciences and Humanities, leading to the integration of diverse methodologies in an interdisciplinary framework. This holistic approach will be used to increase the knowledge and understanding of the interactions of the Oceans with Society by integrating digital and historical data, and natural and cultural heritage management and protection; connecting Ocean and Cultural Heritage Literacy to promote social change and citizen participation in research; developing interdisciplinary knowledge to base Governance and Management and to foster Sustainable Blue Economy, bridging Local and Indigenous Knowledge with Science-based knowledge

3 pages, 2 figures, [EN] With the advent and gradual acceptance of plate tectonics from the 1960s onwards, it became clear that the Solid Earth is not a fixed and static framework but a dynamic and constantly evolving system that is governed by internal forces impacting on and shaping the surface in multiple ways. The opening and closure of the oceans, the formation of mountain ranges and the occurrence of earthquakes and volcanic eruptions are all a consequence of the constant interaction between tectonic plates. One of the most spectacular and outstanding manifestations of this interaction are earthquakes, which concentrate at the tectonic faults limiting the plates. The largest and most destructive ones occur at the megathrust fault of subduction zones, where the oceanic plates slide below the continental ones at a speed similar to that of fingernail growth. This sliding is not constant but episodic: the friction between the plates makes them couple, accumulating stresses over tens or hundreds of years until they suddenly slip and release the accumulated stresses in seconds or minutes as an earthquake. The amount of slip and its spatial distribution and depth determine the shaking intensity and the resulting ground deformation. […], [ES] A raíz del advenimiento y la gradual aceptación de la tectónica de placas a partir de los años 60 del siglo pasado, se constató que la tierra sólida no es un marco de referencia fijo y estático, sino un sistema dinámico y en constante evolución, gobernado por fuerzas internas que se expresan en superficie de múltiples formas. La apertura y cierre de los océanos, la formación de cordilleras, o los terremotos y volcanes, evidencian la interacción lenta pero constante entre las placas tectónicas. Una de las manifestaciones más espectaculares y notorias de esta interacción son los terremotos, que se concentran principalmente en las fallas tectónicas que limitan las placas. Los más grandes y destructivos tienen lugar en la denominada “falla de mega-cabalgamiento” de las zonas de subducción, donde las placas oceánicas se deslizan bajo las continentales a una velocidad similar a la que crecen las uñas. Este deslizamiento no es constante sino episódico: el rozamiento entre las placas hace que estas se acoplen acumulando esfuerzos durante decenas o centenares de años hasta que resbalan repentinamente liberándolos en segundos o minutos en forma de terremotos. La cantidad de deslizamiento, así como su distribución espacial y la profundidad, determinan la intensidad de las vibraciones y la deformación del terreno asociadas. […], [CAT] Arran de l’adveniment i la gradual acceptació de la tectònica de plaques a partir dels anys 60 del segle passat, es va constatar que la terra sòlida no és un marc de referència fixe i estàtic, sinó un sistema dinàmic i en constant evolució, governat per forces internes que s’expressen en superfície de múltiples formes. L’obertura i tancament dels oceans, la formació de serralades, o els terratrèmols i volcans, evidencien la interacció lenta però constant entre les plaques tectòniques. Una de les manifestacions més espectaculars i notòries d’aquesta interacció són els terratrèmols, que es concentren principalment a les falles tectòniques que limiten les plaques. Els més grans i destructius tenen lloc a la denominada “falla de mega-cavalcament” de les zones de subducció, on les plaques oceàniques llisquen sota les continentals a una velocitat similar a la que creixen les ungles. Aquest lliscament no és constant sinó episòdic: el fregament entre les plaques fa que aquestes s’acoblin acumulant esforços durant desenes o centenars d’anys fins que llisquen sobtadament alliberant-los en segons o minuts en forma de terratrèmols. La quantitat de lliscament, així com la seva distribució espacial i la profunditat determinen la intensitat de les vibracions i la deformació del terreny associades. […]

201 p. : 17 cm, The ocean is a fundamental element for the Earth and for the wellbeing of human societies. It influences weather and climate, impacting sectors such as marine ecosystems, economy, tourism, and human health. Urgent actions are demanded to help in understanding and managing the ocean in a multidisciplinary and integrated way. Here we present the major ocean research challenges for the next decade, CSIC contributions and leadership.

Some years ago, Helene Rozwadowski, a renowned historian of the oceans, entitled one of her books The Sea Knows No Boundaries ( 2002 ). It was a study of the ICES ( International Council for the Exploration of the Seas ), probably the first organization to identify the oceans as a transdisciplinary and collaborative research object. The sea knows no boundaries indeed, though it is a boundary object and it has some limits, since marine resources and biodiversity are today seriously threatened. Our blue planet is at risk. Throughout history, the sea has been many things and has played many different roles. Historically, the seas have located empires and business, networks of humans and commodities. Over the waters, chartered companies, spices or oil routes were established. The oceans have witnessed hundreds of conflicts, naval battles, and piratical encounters, but now it is time to rescue the ocean’s role as a common theatre and as a boundary object for international cooperation, for if the sea knows no boundaries, nor should oceanographic studies, maritime courses, hydrographic and bathymetric charts. Over the centuries, the oceans have been the school for collective endeavours for fishing, studying the fauna, transporting natural species, measuring the world or making astronomical observations. Furthermore, Spain has an historical background and a cultural heritage fully linked to the oceans, navigation and life on board. Numerous naturalists, sailors, astronomers, biologists, and oceanographers have participated in joint nautical undertakings. They have lived and worked on board of their floating laboratories, travelling academies, corvettes, frigates or oceanographic vessels. The sea knows no boundaries. It encircles and encompasses the world, as the Shield of Achilles reflected, as the first circumnavigation we are celebrating today demonstrated. All the oceans were connected. Common matters of different disciplines, collective concerns for humankind float on, navigate through and dive into the oceans. We may survey over its horizon, very likely, the future of our planet Earth. Keeping in mind this historical background, this challenge aims to develop consilience between Ocean Science, Social Sciences and Humanities, leading to the integration of diverse methodologies in an interdisciplinary framework. This holistic approach will be used to increase the knowledge and understanding on the interactions of the Oceans with Society in four main areas : Maritime Cultural Heritage, Ocean Literacy, Governance and Blue Economy, the four of them interconnected in a quadruple helix model.

20 pages, 3 figures, A marine hazard is a potentially damaging event, phenomenon or activity in the marine environment that may cause loss of human life, social and economic disruption or environmental degradation. In the last 30 years, natural and human-induced hazards have caused over 1.6 million victims and the economic losses average 300 thousand million dollars per year. Marine hazards are amongst the most devastating ones. Here we present the research challenges we face as a society to achieve a safer ocean whereby human communities and the environment are better protected from the most outstanding biological, climatic and geological threats. We advocate for the implementation of a multi-hazard research strategy with emphasis on trans-disciplinary collaboration, development of improved observational infrastructures and data-sharing platforms, multi-hazard warning and management, and effective transfer of information to stakeholders and authorities to enhance impact mitigation

3 pages, 2 figures, [EN] The oceans are essential for life on Earth. They sustain ecosystems, stabilize the climatic system and provide resources that make Earth habitable for humankind. However, human activity is causing rapid global changes that affect the ocean’s health and productivity, understood as the resilience to stay within certain boundaries. Global warming, changing weather patterns, sea level rise, ocean acidification and extreme weather events are disrupting the economies of coastal countries and having a profound effect on people’s daily lives. Along with the invasion of anthropic structures on the coastline, marine pollution and overfishing, these environmental stressors alter marine populations, harm ecosystems and threaten biodiversity. Moreover, oceans are the sources of devastating natural hazards that hit the coasts episodically, causing huge human and economic losses. […], [ES] Los océanos son fundamentales para la vida en la Tierra. Ellos sostienen los ecosistemas, estabilizan el sistema climático y proporcionan los recursos que hacen de la Tierra un planeta habitable para la humanidad. Sin embargo, la actividad humana está provocando rápidos cambios globales que afectan la salud de los océanos, entendida como su resiliencia para mantenerse dentro de ciertos límites. El calentamiento global, las fluctuaciones climáticas, el aumento del nivel del mar, la acidificación de los océanos y los eventos climáticos extremos perturban las economías de los países costeros y afectan la vida cotidiana de sus habitantes. A estos factores de estrés ambiental se le añaden la invasión de estructuras antrópicas en el litoral, la contaminación marina y la sobrepesca, que alteran las poblaciones marinas, dañan los ecosistemas y amenazan la biodiversidad. Además, los océanos están sujetos a diversos riesgos naturales, que golpean episódicamente las costas causando enormes pérdidas humanas y económicas. […], [CAT] Els oceans són fonamentals per a la vida a la Terra. Ells sostenen els ecosistemes, estabilitzen el sistema climàtic i proporcionen els recursos que fan que la Terra sigui habitable per a la humanitat. Tanmateix, l’activitat humana està provocant ràpids canvis globals que afecten la salut dels oceans, entesa com a resiliència per a mantenir-se dins d’uns certs límits. L’escalfament global, les alteracions dels patrons climàtics, la pujada del nivell del mar, l’acidificació dels oceans i els fenòmens meteorològics puntuals i extrems, pertorben les economies dels països costaners i afecten la vida quotidiana dels seus habitants. A aquests factors d’estrès ambiental se li afegeixen la invasió d’estructures antròpiques en el litoral, la contaminació marina i la sobrepesca, que alteren les poblacions marines, perjudiquen el funcionament dels ecosistemes i amenacen la biodiversitat. A més, els oceans estan subjectes a diversos riscos naturals, que colpegen episòdicament les costes causant enormes pèrdues humanes i econòmiques. […]

El jurat, format per Isabel Cacho, Frederic Bartumeus, Francisco J. Doblas, Josep Peñuelas i Silvia Acinas acorda per unanimitat atorgar el premi de ciències ambientals i de la Terra al treball d’investigació científica Upper-plate rigidity determines depth-varying rupture behaviour of megathrust earthquakes dels autors Valentí Sallarès i César R. Ranero, de l’Institut de Ciències del Mar de Barcelona (CSIC) i ICREA, publicat a la revista Nature el 2019. Aquest treball proposa un nou model amb un canvi de paradigma en considerar l’elasticitat dels materials en el comportament dels terratrèmols, de manera que es millora substancialment la previsió de tsunamis

Se puede descifrar el comportamiento de los grandes terremotos en función de la profundidad y estimar su potencial para generar tsunamis de forma más precisa. Un estudio liderado por investigadores del Consejo Superior de Investigaciones Científicas (CSIC) ha desarrollado un modelo que permite predecir características clave de los terremotos así como cuantificar su peligrosidad y su potencial para generar tsunamis. El estudio, elaborado por científicos del Instituto de Ciencias del Mar, se publica en la revista Nature. [...]

The ocean is a fundamental element for the Earth and for the wellbeing of human societies. It influences weather and climate, impacting sectors such as marine ecosystems, economy, tourism, and human health. Urgent actions are demanded to help in understanding and managing the ocean in a multidisciplinary and integrated way. Here we present the major ocean research challenges for the next decades, CSIC leadership and resources needed.

Chapter 8., Oceans are no longer inaccessible places for data acquisition. High-throughput technological advances applied to marine sciences (from genes to global current patterns) are generating Big Data sets at unprecedented rates. How to manage, store, analyse, useand transform this data deluge into knowledge is now a fundamental challenge for ocean sciences. Artificial Intelligence and Machine Learning are the most promising and exciting approaches addressing this challenge. These technologies are directly applicable to many data analysis problems and major challenges in the study of the ocean microbiome, ocean observation and forecasting, animal biology, ecology and conservation, resource management, and marine geosciences. We are only at the beginning of an era when machines are able to solve complex tasks that, until today, have required human expertise. We envision that the combination of ocean Big Data and Artificial Intelligence will provide the means for ground-breaking advances in our understanding of ocean functioning.

American Geophysical Union (AGU) Fall Meeting, 9-13 December 2019, San Francisco, Over the last decades researchers have emphasized on the important role that elastic properties - particularly rigidity - and structural features play in the ¿anomalous¿ shallow rupture of tsunami earthquakes. Yet, we have little understanding on the depth-distribution of such properties and how they influence the rupture of these particular events. Here, we focus on the rupture zone of the 1992 Nicaragua tsunami earthquake (Mw ~7). This event occurred ~20 km down-dip of the megathrust interface but it released large seismic moment near the trench, triggering a devastating tsunami. We analyze the elastic and structural properties of the rupture area from a set of 2D coincident wide-angle (WAS) and multichannel seismic (MCS) lines acquired across and along the rupture area of the 1992 event. We have jointly inverted refracted and reflected travel-times (TT) from both WAS and MCS data to derive P-wave velocity (Vp) information of the overriding plate and the geometry of the megathrust. Combining MCS TTs of reflected arrivals at the megathrust with the ensemble of WAS TTs allowed to enhance the tomographic resolution of our results. This way, we are able to retrieve small-scale topographic variations of the plate interface that would have been omitted with the inversion of WAS TT alone. From Vp we derive other elastic parameters namely, density, S-wave velocity and rigidity using well-established empirical relationships. The results obtained from two parallel sections across the megathrust show that, despite minor local variations, the down-dip distribution of megathrust elastic properties does not present significant variations, sharing a similar trend with depth. The depth-dependence of these properties is consistent with the along-dip distribution of megathrust elastic properties inferred from many other subduction zones of the Pacific, Indonesia, and the Caribbean. We finally use the inferred down-dip distribution of rigidity to compute the slip and the rupture time of the 1992 event. The results agree remarkably well with the estimates of rupture times derived from the inversion of surface waves spectra of the event. These results demonstrate that the along-dip variation of rigidity in the plate interface is key in the up-dip rupture of megathrust earthquakes, particularly, that of tsunami earthquakes

8th International Symposiumon Andean Geodynamics (ISAG), 24-26 September 2019, Quito, Ecuador.-- 1 page, Great subduction earthquakes occur along the seismogenic zone of the megathrust, a fault segment that is mechanically coupled so that seismic rupture can propagate. Numerous factors, including the rheology and structure of the plates, shear stress distribution, fluids pressure, or thermal structure, size and width of the coupled zone, have been proposed to play a role to determine and dynamic behavior of the rupture. These factors are conditioned, in turn, by the properties of the rocks undergoing deformation during seismic rupture and by the fault geometry and roughness. While the information on the 3D velocity field and on inter-plate geometry can potentially be extracted from travel-times of active seismic data, the experiments that are appropriate to define these parameters are scarce. Additionally, most 3D travel-time tomography codes use only first arrivals to define the velocity field, so that they do not provide information on the megathrust geometry. Here we combine for the first time ever wide-angle seismic data with a joint refraction and reflection travel-time tomography code [tomo3d, Meléndez et al., 2015], to retrieve a 3D velocity model of margin and the geometry of the inter-plate boundary with unprecedented detail. In particular, we use data acquired in the French project ¿Esmeraldas¿ offshore NE Ecuador/SE Colombia in 2005. Our model, which builds on a previous one obtained by first arrival tomography [Garcia-Cano et al., 2014], goes from the surface to 18-20 km depth, covering a substantial part of the seismogenic zone. This region, where the Nazca plate plunges beneath South America, has produced remarkable examples of variable earthquake rupture behavior. The entire ~500 km-long segment ruptured during the great tsunamigenic earthquake of 1906 (Mw = 8.8), and it was ruptured again by three smaller events, directly adjacent to one another, in 1942 (Mw = 7.8), 1958 (Mw = 7.7) and 1979 (Mw = 8.2) [Kanamori and McNally, 1982]. According to our results, the inter-plate boundary where these earthquakes took place is of variable dip and rough, spotted by 2-3 km-high and 10-15 km-wide features that resemble subducting seamounts. The velocity of the overriding plate just above the inter-plate boundary is strongly heterogeneous, showing velocity-derived rock rigidity variations of up to 30-40% both along- and across-strike. The presence of inter-plate relief and velocity changes is confirmed by parameter uncertainty analysis and data sensitivity tests. Interestingly, the sharpest velocity contrasts appear to follow the limits between crustal blocks of different origin and composition that, according to previous work, could correspond to crustal-scale faults acting as barriers during earthquake propagation [Collot et al., 2004]. The combined effect of a rough inter-plate boundary and heterogeneous elastic properties on earthquake rupture remains to be tested by dynamic rupture models

4th Fault2SHA Workshop, Fault Complex Interaction: Characterization and Integration into Seismic Hazard Assessment (SHA), 3-5 June 2019, Barcelona, 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 two regional wide-angle seismic transects, combined with previously available information. The seismic velocity and density structure at the Seine Abyssal Plain (SAP) and the internal Gulf of Cadiz (GC) indicates the presence of a highly heterogeneous oceanic crust, 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 3 oceanic domains off SW Iberia: (1) the SAP domain, generated during the first stages of slow seafloor spreading in the NE Central Atlantic (Early Jurassic); (2) the GC domain, made of oceanic crust generated in the Alpine-Tethys spreading system between Iberia and Africa, which was coeval with the formation of the SAP domain and lasted up to the North Atlantic continental break-up (Late Jurassic); and (3) the Gorringe Bank (GB) domain, mainly made of rocks exhumed from the mantle with little synchronous magmatism, which formed during the first stages of North Atlantic opening. Our models suggest that the SAP and GC domains are separated by the Lineament South strike-slip fault, whereas the GC and GB domains appear to be limited by a deep thrust fault located at the center of the Horseshoe Abyssal Plain. The formation and evolution of these 3 domains during the Mesozoic is key to understand the sequence of events that occurred during the first stages of opening of the Northern Atlantic

European Geosciences Union (EGU) General Assembly, 7-12 April 2019, Vienna, Austria.-- 1 page, We present seismic data collected in summer 2018 of the structure of the opening of the central Atlantic in NW Africa, and the west Iberia Mesozoic rift basins and rifted margins. We obtained crustal-scale seismic images collected with a large tuned source and a 6-km-long streamer, and new coincident wide-angle seismic data with ~10-km-spaced OBSs. Our cross-sections were collected in transects in regions where previous work from the 1980 to mid 1990's collected some of the most emblematic geophysical cross-sections. New images of the Galicia Interior Basin (GIB) display prominent thinning at the basin center with an asymmetric tectonic and crustal structure, indicating that extension stopped when the basin was in the latest phase before break up. The basin is characterized by large-scale normal faults that are laterally bounded by transfer fault structures. New Vp models from the Iberia abyssal plain indicate that the crustal structure is more complex than models with lower resolution -widely used in geological interpretations- have inferred. The new data preliminarily supports that the exhumed mantle may contain magmatic bodies and that continental break up may have occurred before mantle exhumation. Comparison of observations from Iberia and Tagus Abyssal Plains display the transition from exhumed mantle to the oceanic crust across the J-anomaly ridge, providing data of on the interaction between magma and tectonics. Seismic images from NW Africa display a rather different structure, with upper Triassic evaporite diapirs extruding from fault-blocks of highly-extended possibly continental crust, with Early Jurassic (drilled) synrift deposits in tilted blocks. Here, a rather abrupt continental slope is followed by a deep-water basin underlain by perhaps as much as 100 km of highly-extended continental crust

European Geosciences Union (EGU) General Assembly, 7-12 April 2019, Vienna, Austria.-- 1 page, Deformation by bending of incoming oceanic plates prior to subduction was noted soon after the beginning of the Plate Tectonics revolution 50 years ago, however the observations available at the time did not permit any detailed scrutiny. It is only since 15 years ago that we begun to realize the intensity of the processes that modify oceanic plates at subduction trenches, and the potential implications for a broad range of subduction-related phenomena. Albeit the limited number of dedicated studies in the world subduction system, a growing body of observations supports that the physical and chemical nature of oceanic lithosphere created at spreading centres is profoundly modified during their passage of the outer rise and trench. Yet, there is neither consensus for conceptual models of the processes at work, nor robust global averages of the intensity of those changes. To understand the structure and nature of subducting slabs and the implications for material recycling and mantle evolution we need to further study the variability of those processes with new experiments and novel methods. It is likely that as methods improve and research intensifies we will serendipitously discover new still unreported features and phenomena. However, the available data are currently enough to warrant the proposal that the intensity of the physical and chemical modifications imply that incoming plates at subduction trenches are a class of geodynamic setting in their own that requires to be understood to unravel the earth evolution in terms of material and volatiles

European Geosciences Union (EGU) General Assembly, 7-12 April 2019, Vienna, Austria.-- 1 page, When continents break apart, continental crust and lithosphere is stretched until break-up occurs and seafloor spreading forms new oceanic basins. However, at settings with low magma supply the area between the oceanic and continental domain is a wide transition zone (COT) rather than a sharp boundary. This end-member type of margin has been defined as non-volcanic or magma-poor margin and type-examples are the Iberia Abyssal Plain and the conjugated Newfoundland margin. Yet, at both margins, the structure of the COT and the onset of seafloor spreading are poorly defined with available data and a matter of long debate. For instance, some authors suggested that a prominent magnetic anomaly ¿ called the J-anomaly ¿ is not marking an age-isochron, but is mimicking the onset of oceanic crust and hence seafloor spreading. Others have proposed that the COT is actually ultra-slow seafloor spreading before the J-anomaly. Here, we present results from a new seismic refraction and wide-angle profile shot in September of 2018 aboard the Spanish research vessel Sarmiento de Gamboa in the Iberia Abyssal Plain about 20 km to the south of seismic line IAM9. Thirty ocean-bottom-seismometers and hydrophones spaced at 10-12 km intervals recorded seismic shots fired along the 360 km long profile P3. The line is roughly centred at the J-anomaly, revealing the nature of crust and lithosphere on either side. Seismic travel time data were inverted to yield the P-wave seismic velocity (Vp) structure using a least-square damped tomographic inversion procedure. To assess the nature of basement, we used two features derived from the seismic velocity structure: (i) average Vp within 4 km below basement and (ii) maximum P-wave speed in the same depth range. Results show that the J-anomaly marks indeed a major change in lithology. Thus, to the west, sedimentary cover is in the order of 2 km and average crustal velocity ranges from >6 km/s to 6.7 km/s, with a maximum velocity of 6.6 to 7.5 km/s and maximum velocity ranges from 7.0 to 8.1 km/s. Therefore, the domain to the east of the J-anomaly seems to be dominated by serpentinized mantle as previously proposed, but the structure is more complex than the image obtained in previous sparser data sets. The domain of serpentinized mantle may include some bodies of magmatic crust and thus could either be interpreted as domain of un-roofed mantle, which had been affected by some magmatic activity as observed in the Tyrrhenian Sea or it may represent ultra-slow spreading lithosphere as observed in the Cayman Trough. The domain west of J may indicate magmatic crust, though it shows notable differences when compared to normal oceanic crust. The new higher resolution data set challenges the concepts built in numerous publications based on lower resolution geophysical images

American Geophysical Union (AGU) Fall Meeting, 9-13 December 2019, San Francisco, The Gulf of Lions margin is located in the West Mediterranean Sea and opened as a back-arc basin from the end of Eocene to the Miocene. Previous studies of this area modelled and interpreted seismic data to explain the geological processes that lead to the formation of this margin. These works show the presence of a particular continent-ocean transition zone (COT) where crustal velocity structure is atypical. The objective of this study is to use advanced joint refraction and reflection tomography (TTT) tools to obtain higher-resolution models that allow (1) characterizing the nature of the crust along the Gulf of Lions margin, and (2) defining the structure of the margin, especially in the COT zone. We present a new velocity model obtained using a joint TTT of two different active-source seismic data sets: ocean bottom seismic (OBS) data and long-streamer data (MSC data). OBS-derived images show the Vp structure of the crust and uppermost mantle and the geometry of the Moho along the basin axis. Additionally, the long-streamer tomographic image shows the Vp structure of the post-rift section in detail, providing insights into basin-scale processes that occurred after lithospheric extension. The joint TTT allows us to invert the main geological horizons of the margin identified in the OBS and MCS images and, for the first time in this area, also to jointly invert the geological horizons present and identified in both data sets. Our results show a Vp velocity model that display three distinct domains. Domain I shows a structure that corresponds to thin continental crust. Here the crust thins from 15 to 5 km by a system of normal faults. The upper crust has Vp between 5 to 6 km/s and the lower crust with velocities ranging from ~6.0 km/s to ~7.5 km/s. The lithospheric mantle has a velocity around 8.0 km/s along the entire modeled profile. Domain II, which is interpreted as the COT zone, displays a well-delimited lens-shaped body with high crustal velocities (6.0-7.5 km/s). In the central part of the Domain II, where the lens-shaped body is thickest, its top coincides with the top of the basement. The Domain III is characterized by a 4-km thickness crust and velocities ranging from 5.5 to 6 km/s. Based on their markedly different Vp distribution, we argue that Domain II and Domain III might be not genetically linked

American Geophysical Union Fall Meeting, 10-14 December 2018, Washington D.C., Adjoint-state full waveform inversion (FWI) is an HPC technique that potentially allows extracting models of the rocks elastic properties with a resolution that is higher than that of almost any other geophysical method. Despite its potential, FWI suffers from a number of issues that makes it challenging to be applied to most types of field data. One of the main problems is the high non-linearity, which makes the solution strongly dependent on the initial model selected. In particular, for the commonly-used L2-norm objective function, successful FWI requires initial models that allow reproducing seismograms differing by less than half a period from the recorded ones. A typical solution is applying arrival travel-time tomography (TTT) in a first stage and use the resulting model as initial one for FWI. However, this approach does not work when the original data lack low frequencies and have only short offsets, as it occurs with streamer data in deep water settings, so that there are no first arrival refractions in the original recordings. In this work, we present a number of solutions that allow overcoming these issues and apply FWI to short-offset streamer data lacking low frequencies. These include (1) the wave equation downward continuation (DC) of the streamer data followed by joint refraction and reflection TTT to obtain a suitable starting model for FWI, and (2) using robust, instantaneous phase-based functions instead of the typical L2-norm to compare simulated and recorded data. We show that both approaches allow successful application of FWI to limited-offset data (4 Hz, typically present in field data recordings. In particular, we present field data examples showing that the combination of DC, joint refraction and reflection TTT, and FWI, allows obtaining accurate high-resolution velocity models using data acquired with a 480 channel, 6 km-long streamer in a >2 km deep water layer, starting FWI at a frequency as high as 8 Hz. The obtained FWI velocity model allows identifying a number of geologically meaningful details, as a high-velocity salt layer interbedded within sediments, which can not be identified otherwise

Congresso congiunto Società Geologica Italiana (SGI) - Società Italiana di Mineralogia e Petrologia (SIMP), Geosciences for the environment, natural hazards and cultural heritage, 12-14 September 2018, Catania.-- 1 page, The Tyrrhenian back-arc basin is a Neogenic basin that opened in response to the E-SE-ward retreat of the subducting Ionian slab under the Apennine chain. To date a large bibliography is available for this basin (Moeller et al., 2014), but un updated morpho-structural map which takes into account the latest multibeam and multichannel seismic data sets is still lacking. Indeed, the structural maps of the entire Tyrrhenian date back to ‘80/’90. In this work, we present a new morpho-tectonic map of the entire Tyrrhenian basin, from slopes to abyssal plains. This map results from the analysis of 65 multichannel seismic profiles, several sparker profiles and 200-m-grid cell size bathymetry data. All data were georeferenced and interpreted together using the kingdom package (HIS Markit). In detail, the data sets used are composed by the: CROP profiles acquired in the ’90; MS profiles acquired by the OGS during the ’60/’80 (http://snap.ogs.trieste.it/); SITHERE profiles acquired for the site survey of IODP leg 107; MEDOC profiles acquired in 2010; and ISTEGE profiles acquired in the 2010. IODP/DSDP wells (Leg 107 and 42A) and crustal velocity information (Prada et al., 2014, 2015; 2018) were used for the seismo-stratigraphic calibration allowing the mapping of three main units: pre-Messinian; Messinian including evaporites; and Plio-Quaternary. This information allowed to constrain the age of faults activity. Our work results highlight a basin dominated by extension locally overprinted by compression or by transcurrent-motion fault systems. In the western Tyrrhenian, the extension was mostly accommodated by large listric faults forming deep and elongated sedimentary basins. In its eastern (Campania) and southern (Sicily-Calabria) margins the stretching was mainly accomplished through normal faults forming irregular and smaller basins. Furthermore, the central Magnaghi/Vavilov abyssal plain is confined by normal faults that bound the magmatic crust and exhumed mantle rocks (Prada et al., 2016) to continental blocks of the Sardinia-Campania conjugate margins. The Marsili abyssal plain instead is surrounded by fewer, not well expressed, normal faults and, to north and to south, by lithospheric faults (STEP fault)

Congresso congiunto Società Geologica Italiana (SGI) - Società Italiana di Mineralogia e Petrologia (SIMP), Geosciences for the environment, natural hazards and cultural heritage, 12-14 September 2018, Catania.-- 1 page, The main object of the Proposal 927-pre: “ TyrrhenIan Magmatism & Mantle Exhumation” (TIME) is the understanding of the relationship between the exhumed mantle rocks and the overlying basalts sampled in the Tyrrhenian Basin during the previous ODP Leg 107 (Kastens et al 1988).The scientific objectives of the proposal include studying the kinematics of the opening, the nature and timing of associated magmatism and the geochemistry and deformation of the exhumed mantle section.The proposal resulted from the outcome of the MagellanPlus Workshop “TyrrhenIan Magmatism & Mantle Exhumation” (TIME) sponsored by IODP and ECORD. The workshop was held in the Institute of Marine Science (ISMAR) of the National Council of the Italian Research (CNR) in Bologna on June 5-7, 2017. The proposal 927-pre was submitted on October. 2017 and received the recommendation for the development into a full proposal by the IODP STEP Panel on February 2018.The database used to conceive the drilling project is possibly one of the best available from a rifted basin. The basement of the Tyrrhenian basin has been dredged at highs and drilled in several campaigns, and the stratigraphy is reasonably well known from three previous drilling expeditions, DSDP leg 13, DSPD leg 42 and the ODP leg 107 It is available a full-coverage, high-resolution, multibeam bathymetry of the basin as well as a large data set of vintage and modern 2D MCS reflection profiles and seven regional wide-angle seismic profiles crossing the main geological domains (Moeller et al 2014; Prada et al 2016, 2018)

36th General Assembly of the European Seismological Commission (ESC), 2-7 September 2018, Valletta, Malta.-- 2 pages

18 International SEISMIX Symposium, Seismology between the Poles, 17-22 June 2018, Cracow, Poland.-- 1 page, We present preliminary results from the application of TOMO3D [Meléndez et al., 2015] to the modelling of wide-angle seismic data set acquired at the convergent margin of Ecuador and Colombia in 2005, in the framework the ESMERALDAS project. The offshore data were recorded on 23 OBS with the oceanographic R/V L'Atalante in a cruise leaded by IRD-Géosciences Azur and funded by French agencies. These data were complemented by onshore recordings of the airgun shots in a network of 31 landstations. The aim of this survey was gathering 3-D information on the nature and structure of the margin at the rupture area of the 1906 and 1958 seismic events in order to increase the present geological knowledge derived from existing 2-D experiments, and to extract possible seismological implications. The results prove useful for the on-going study of this subduction zone, the characterisation of the North Andean margin, and the associated seismic activity. Refraction traveltime picks from this data set were previously modelled by García-Cano et al. [2014] using FAST. For the new tomographic inversion with TOMO3D we added ~20,000 reflection picks, corresponding to the interplate boundary, to the ~200,000 refraction picks already available. In a first step, we limited the model to the marine area containing all OBS, which has the best ray coverage and resolution of the experiment. Comparison between the resulting 3D velocity models shows that the general structures and the major geological features defined by the isovelocity contours are rather similar, indicating that TOMO3D is capable of producing sound results for the velocity distributions of the overriding and underthrusting plates, and thus that it is a valuable tool for crustal-scale investigation. The main geological features interpreted from the 3-D velocity model are a low vertical velocity gradient that characterises the weak, highly fractured outer margin wedge, which is related to the trenchward limit of the rupture area and the tsunami excitation, and the low-velocity zone in the overriding plate just above the interplate boundary and below the continental slope. Furthermore, the sedimentary thickness both on the oceanic crust and on the continental shelf can be estimated, and two high velocity anomalies are observed: one in the continental crust and another in the subducting plate, which seems to indicate a thin oceanic crust. The thickness of the oceanic crust and its dip angle are discussed assuming that it is limited between the 4 km/s and 7.5 km/s isovelocity contours. Our inversion of reflected data associated to the interplate boundary allows us to define a 2-D geometry model of this reflective discontinuity as well as the physical properties just above it, and to correlate them with characteristics of the seismogenic zone. This new information contributes to the general understanding of the margin, in particular regarding its seismological behaviour and the characterization of the oceanic plate

18 International SEISMIX Symposium, Seismology between the Poles, 17-22 June 2018, Cracow, Poland.-- 1 page, Adjoint-state FWI is in terms of resolution the most powerful existing tomographic method. It has become a well-established inversion method thanks to the efforts made by both industry and academy (Virieux and Operto, 2009). The main strength of the technique is that it allows obtaining unprecedented high resolution images of the subsurface of the Earth. In the last years we have developed our own FWI code called 2D3DA-FWI as a reference to the 2D and 3D acoustic FWI (Dagnino et al. 2014, Jimenez et al. 2015, Dagnino et al. 2016). Now, we applied this code to invert a 66 km-wide and 3 kmdeep Vp model. This shallow part displays the deep Sandino basin, filled by a sediment pile of variable thickness, which is folded and bent by the tectonic activity associated to the convergence between the subducting Cocos plate and the continent. Below the sediments, the basement is located at a variable depth between 200m and 2.5km depth. The details of its inner structure, the lithology of the geological domains, and the geometry and location of the main faults, which reflect the coupling between the subducting and overriding plates, are unknown. To better define all this details we have applied an adjoint-state FWI using the streamer data acquired in this region to obtain a higher resolution Vp model. To achieve this goal we have processed the multi-channel seismic data, applying data processing sequences designed by our group (Dagnino et al. 2017), and we have generated an initial model using a first arrival travel time tomography code based on a previously obtained one (Sallares et al., 2013)

18 International SEISMIX Symposium, Seismology between the Poles, 17-22 June 2018, Cracow, Poland.-- 1 page, Subduction zones are known to be key in shaping the lithospheric structure of the Earth, and consequently its surface. The dehydration of ultramafic products from the subducted oceanic lithosphere triggers the hydration of the overlying mantle wedge, resulting in the production of hydrous flush melting, and the consequent formation of new crustal material at the volcanic arc. However, the evolution of processes such as crustal construction and mantle hydration are still poorly constrained mainly because of the lack of observations from young subduction settings. In this study, we focus on the Plio-Quaternary Calabrian subduction system, located in the Central Mediterranean. This subduction zone is the result of the same slab rollback process that shaped back-arc basins in the Western Mediterranean and is characterized by the subduction of the Ionian Lithosphere under Calabria. To date, there is limited understanding of its shallow crustal structure and the transition between lithospheric domains (e.g. Arc - back-arc) due to the lack of dedicated active-source experiments. Here, we present the 2D P-wave velocity structure of the entire subduction system from travel-time tomography of wide-angle seismic data. The data were recorded during the CHIANTI amphibious experiment in 2015 along a ~600 kmlong transect that extends from the Tyrrhenian back-arc domain to the fore-arc in the Ionian Sea, across Calabria. In the back-arc system, OBS sections lack PmP-like arrivals and the velocity structure of the model shows a continuous and strong vertical velocity gradient of ~1 s-1. These results together with previous tomographic models, analysis of Vp/Vs and basement rock sampling strongly supports the exhumation of the mantle along ~300 km long section in the back-arc region. The back-arc region is also characterized by large volcanic edifices that were emplaced soon after the exhumation of the mantle. The transition between back-arc and Calabria is marked by a steep Moho geometry that shallows from SE to NW, revealing a dramatic crustal thinning along the N Calabrian margin. The lower crust of the margin has localized Vp of ~7 km/s under the submarine volcanic arc. The vertical velocity structure of this young arc (< 2Ma) reveals a thin and mafic crust, suggesting that crustal growth by magmatic addition is still at an early stage in the Calabrian volcanic arc, and that little crustal felsic-to-mafic differentiation has occurred as opposed to older well-established volcanic arcs in the Pacific. SE Calabria, the model shows a strong horizontal velocity gradient that is interpreted as the backstop of the subduction. In the Ionian, a 3-5 km thick sedimentary wedge thickens towards the NW. The frontal part of the wedge shows sub-vertical low-velocity anomalies indicating the presence of fluid-saturated large thrusts faults

Inciativa Ibérica para el Estudio de las Fallas Activas, Tercera Reunión Ibérica sobre Fallas Activas y Paleosismología IBERFAULT 2018 - Third Iberian Meeting on Active Faults and Paleoseismology, 11-13 June 2018, Alicante, Spain.-- 4 pages, 4 figures, The Gulf of Cadiz is located at the SW Iberian Margin and hosts the African-Eurasian plate boundary. This is one of the most seismogenic areas in Western Europe, where historical and instrumental earthquakes occurred, ranging from Mw 6 to 8.5, and some of them triggered destructive tsunamis. The ICM-CSIC team keeps investigating the Gulf of Cadiz area since more than 15 years, carrying out multiscale bathymetric, high-resolution to deep seismic and sampling surveys. The active structures in the Gulf of Cadiz can be classified in two main families: The WNW-ESE dextral strike-slip faults and the NE-SW thrusts faults. The orientation of these faults is compatible with the current plate convergence in the region. The largest active strike-slip faults are: -the Lineament South and the Lineament North that may generate earthquakes up to Mw 8; while the active NE-SW thrust faults, the Marquês de Pombal, the Horseshoe and the Coral Patch Ridge faults can individually generate earthquakes up to Mw7.8

18 International SEISMIX Symposium, Seismology between the Poles, 17-22 June 2018, Cracow, Poland.-- 1 page, Here we present a high-resolution P-wave velocity model of the sedimentary cover and the uppermost basement until ~3 km depth obtained by applying adjoint-state full-waveform inversion (FWI) to a Multichannel Seismic (MCS) data set acquired with a 6 km-long streamer of 480 channels. The MCS profile was acquired in the Alboran Sea (SE Iberia), in the framework of the TOPOMED-2011 experiment. The inherent non-linearity of FWI for short-offset, band-limited seismic data as this one, was circumvented by using a reference velocity model obtained by travel-time tomography. Given the water depth in excess of ~2 km and the short acquisition offset, refractions are not visible as first arrivals in the original shot gathers. To solve this issue, we applied a data processing/modelling sequence consisting of three steps: (1) data re-datuming (i.e. downward continuation, DC) by back-propagation of the recorded seismograms to the seafloor using a numerical solver of the wave equation; (2) joint refraction (first arrival) and reflection (top of basement) travel-time tomography of the DC shot/receiver gathers; and (3) FWI of the original shot gathers using the model obtained by travel-time tomography as initial reference. FWI is performed using specific data and gradient preconditioning techniques to concentrate model updates in the regions where the gradient is more reliable. A multi-scale strategy adding low to high frequencies sequentially is followed to reduce the risk of converging to a local minimum and add details progressively to the model. The source wavelet is also inverted and updated in each inversion step. We show that FWI provides reliable and accurate results starting at frequencies as high as ~6 Hz, because the initial model has the low wavenumber information needed to avoid cycle-skypping. The final velocity model shows a number of geologically meaningful details that cannot be identified in the initial model. For instance, a volcano-like structure is observed in the central part of the profile, also a strong velocity contrast that accurately follows the shape and geometry of the top of the basement, and steeply dipping anomalies that correspond to normal faults can be seen at the flanks of the basin. In addition, a 200-300 m thick, high-velocity layer embedded within the sediments that likely correspond to salt deposited during the Messinian crises is clearly imaged. The two-way-time transformed velocity model has an excellent match with time-migrated MCS image: velocity changes nicely follow major reflectivity contrasts and fault locations, which further validates the inversion result. The results confirm that the combination of DC and joint refraction and reflection travel-time inversion provides models that are accurate enough to apply FWI to relatively short offset streamer data starting at realistic field data frequencies

European Geosciences Union (EGU) General Assembly 2018, 8-13 April 2018, Vienna, Austria.-- 1 page, In this work we present a 2D time-domain, adjoint-state acoustic full-waveform inversion to retrieve high-resolution models of ocean physical parameters such as sound speed, temperature and salinity. The proposed method is first described and then applied to pre-stack multi-channel seismic (MCS) data acquired in the Gulf of Cadiz (SW Iberia) in 2007 in the framework of the Geophysical Oceanography project. The inversion strategy flow includes specifically-designed data pre-conditioning for acoustic noise reduction, followed by the inversion of sound speed in the shotgather domain. We show that the final sound speed model has a horizontal resolution of∼70m, which is two orders of magnitude better than that of the initial model constructed with coincident eXpend-able Bathy Thermograph (XBT) data, and close to the theoretical resolution of O (λ). Temperature (T) and salinity(S) are retrieved with the same lateral resolution as sound speed by combining the inverted sound speed model with the thermodynamic equation of seawater and a local, depth-dependent T-S relation derived from regional conductivity-temperature-depth (CTD) measurements of the National Oceanic and Atmospheric Administration database. The comparison of the inverted T and S models with XBT and CTD casts deployed simultaneously to the MCS acquisition shows that the thermohaline contrasts are resolved with an accuracy of0.18oCfor temperatureand0.08PSUfor salinity. The combination of oceanographic and MCS data into a common, pseudo-automatic inversion scheme allows to quantitatively resolve submeso-scale features that ought to be incorporated into larger-scale ocean models of ocean’s structure and circulation

American Geophysical Union Fall Meeting, 10-14 December 2018, Washington D.C., The seismogenic zone of megathrust faults at subduction zones hosts the largest earthquakes on Earth. These events are particularly hazardous and destructive, because the upper limit of the seismogenic zone lies offshore, so that coseismic deformation can affect the seafloor and generate tsunamis. Large tsunamis are typically caused by large and giant earthquakes of magnitude >8, but some remarkable exceptions exist. One of them is tsunami earthquakes, which generate anomalously large tsunamis for their size (typically M~7-7.5). Additional anomalous characteristics of tsunami earthquakes are a rupture concentrating in the shallowmost portion of the megathrust, a large discrepancy between their surface wave and moment magnitudes, a long source duration, and a marked depletion in high frequency content. In this work, we first examine a number of P-wave seismic velocity models of Circum-Pacific subduction zones to get the average depth variation of elastic properties above the inter-plate boundary. Then, we analyze the potential effect of the observed depth trends on different earthquake rupture characteristics including coseismic slip, source duration, moment rate spectrum, and surface wave magnitude. We show that the effect is substantial for all the computed variables, particularly in the shallowmost megathrust, indicating that this can be an important factor to explain the anomalous behavior of tsunami earthquakes as compared to deeper, regular events

European Geosciences Union (EGU) General Assembly 2018, 8-13 April 2018, Vienna, Austria.-- 1 page, We present seismic of the opening of the Tyrrhenian basin. Previous work with extensive wide-angle seismic data crossing the basin in 7 transects (collected in 2010 and 2015) provide P-wave velocity models that support the presence of oceanic-like magmatism after an abrupt breakup in a backarc spreading setting. However the magmatic phase stopped and was followed by a phase of mantle exhumation constrained by P and S wave velocity models, and groundtruth by an existing ODP drill samples. The wide-angle data indicates that mantle exhumation has occurred in several episodes through time and that mantle rocks floors most of the Vavilov and Marsilli sub-basins of the Tyrrhenian basin. We show that in the Vavilov basin mantle exhumation was largely accomplished by largescale detachment faulting producing the well-know core-complex geometry, similar to structures described in slow & ultra-slow spreading centers. However, detailed stratigraphic information calibrated with drilling information provides accurate constrained rates of opening. The stratigraphy supports that mantle exhumation (after backarc seafloor-spreading stopped) opened at fast rates comparable to the East Pacific Rise, a mid ocean ridge where magmatism is robust, core complexes have not been observed, and mantle exhumation has not been described. We propose that small-scale pre-existing mantle heterogeneities may condition the deformation style, melt production and thus the architecture of the continent ocean transition at rifted continental margins