New deep multichannel seismic reflection images from the Alboran Basin: The TOPOMED-GASSIS dataset

European Geosciences Union General Assembly 2015 (EGU2015), 12-17 April 2015, Vienna, Austria.-- 1 pageThe Alboran Basin (Western Mediterranean) is located between the Iberian Peninsula and Africa. Along this basin runs the diffuse plate boundary between Iberia and Africa. In order to improve the knowledge of the lithospheric structure in this region, the TOPOMED-GASSIS cruise took place during October 2011 on board the RV Sarmiento de Gamboa. During this cruise, the new deep multichannel seismic acquisition system was used for the first time. The equipment used were two high volume G-gun arrays (2000 psi / 2500 psi) and up to 6 km long Sercel multichannel digital streamer (408 / 480 active channels) towed behind the vessel. The results correspond to a series of multichannel seismic profiles with unprecedented quality, which allows us to apply state of the art processing and imaging techniques to obtain the deep tectonic structure of the plate boundary while keeping a good resolution in the sedimentary infill of the basin. A complete processing sequence has been used in order to increase the signal to noise ratio, including deconvolution, multiple attenuation and time migration. A high-quality deep penetration dataset has been acquired using the new instrumentation allowing to image the whole basin at a crustal scale. The results are high-quality sections for interpretation through frequency preservation, effective multiple attenuation and velocity analysis. Moreover, we will carry out Pre-Stack Depth Migration algorithms to selected profiles, in order to obtain the real geometry of the structures at depthPeer Reviewe

First AUV and ROV investigation of seismogenic faults in the Alboran Sea (Western Meditarranean)

In May-June 2015 we carried out the SHAKE cruise on board the RV “Sarmiento de Gamboa” the first in situ investigation using state-of-the-art underwater vehicles, the AUVs “AsterX” and “IdefX” (IFREMER, France) and the ROV “Max Rover” (HCMR, Greece). Here we present how these vehicles helped us to achieve our main goals to survey active seismogenic faults and associated structures of the Eastern Alboran Sea (Western Mediterranean).Peer Reviewe

Quaternary active tectonic structures in the offshore Bajo Segura basin (SE Iberian Peninsula Mediterranean Sea).

The Bajo Segura fault zone (BSFZ) is the northern terminal splay of the Eastern Betic shear zone (EBSZ), a large left-lateral strike-slip fault system of sigmoid geometry stretching more than 450 km from Alicante to Almería. The BSFZ extends from the onshore Bajo Segura basin further into the Mediterranean Sea and shows a moderate instrumental seismic activity characterized by small earthquakes. Nevertheless, the zone was affected by large historical earthquakes of which the largest was the 1829 Torrevieja earthquake (IEMS98 X). The onshore area of the BSFZ is marked by active transpressive structures (faults and folds), whereas the offshore area has been scarcely explored from the tectonic point of view. During the EVENT-SHELF cruise, a total of 10 high-resolution single-channel seismic sparker profiles were obtained along and across the offshore Bajo Segura basin. Analysis of these profiles resulted in (a) the identification of 6 Quaternary seismo-stratigraphic units bounded by five horizons corresponding to regional erosional surfaces related to global sea level lowstands; and (b) the mapping of the active sub-seafloor structures and their correlation with those described onshore. Moreover, the results suggest that the Bajo Segura blind thrust fault or the Torrevieja left-lateral strike-slip fault, with prolongation offshore, could be considered as the source of the 1829 Torrevieja earthquake. These data improve our understanding of present deformation along the BSFZ and provide new insights into the seismic hazard in the area

Technological and infrastructure collaborative seismic research in Western Mexico

In February and March 2014, Spanish, Mexican and British scientists and technicians explored the western margin of Mexico, a region with a high occurrence of large earthquakes (> Mw = 7.5) and tsunami generation, on board the British Royal Research Ship James Cook. This successful joint cruise, named TSUJAL, was made possible thanks to a cooperative agreement between NERC and CSIC as part of the Ocean Facilities Exchange Group (OFEG), a major forum of European oceanographic institutions for the exchange of ship time, equipment and personnel. A dense geophysical data set was acquired using for the first time 6 km length seismic streamer facilities from Spain’s Consejo Superior de Investigaciones Cientificas (CSIC), usually operating in the Spanish RV Sarmiento de Gamboa, onboard the British RRS James Cook by solving all mechanical, electrical and electronic problems. The RRS James Cook in turn provides the seismic source and the acoustic, hullmounted echosounder operated by the British Natural Environment Research Council (NERC). Multiscale seismic and echosounder images unravel the subduction geometry, nature of the crust, and evidence faults and mass wasting processes. The data are crucial to estimating fault seismic parameters, and these parameters are critical to carrying out seismic hazard in Mexico, especially when considering largemagnitude earthquakes (Mw 8.0), and to constrain tsunami models.Peer Reviewe

The module for ocean observatory data analysis of EMSO

The European Multidisciplinary Seafloor and water-column Observatory (EMSO) is a large-scale, distributed, Marine Research Infrastructure (RI). EMSO consists of ocean observation systems for long-term, high-resolution, (near) real-time monitoring of environmental processes including natural hazards, climate change, and marine ecosystems. EMSO observatory nodes are at key sites around Europe, from the Arctic to the Atlantic, through the Mediterranean, to the Black Sea. To analyse the EMSO data, we develop the Module for Ocean Observatory Data Analysis (MOODA). MOODA is a software with a Graphical User Interface (GUI) developed for scientists. The software helps to facilitate data access (mainly off-line) for further analysis by the scientific community. Some of the features the MOODA offers are: (1) Direct data access with complex query capabilities; (2) Data filtering methods based on metadata information; (3) Complex visualization tools; (4) Summary reports of the validated data generated from a specific query, including event annotations; (5) Specific data analysis tools for different scientific disciplines; (6) The system will be designed to be open, adaptable and scalable allowing future contributions from researchers and developers from all the disciplines associated to the EMSO observatories. The code is written in Python, and it is available on GitHub. MOODA aims to make informative plots as a central part of exploring and understanding data.Postprint (published version

OGC SWE-based Data Acquisition System Development for EGIM on EMSODEV EU Project

The EMSODEV[1] (European Multidisciplinary Seafloor and water column Observatory DEVelopment) is an EU project whose general objective is to set up the full implementation and operation of the EMSO distributed Research Infrastructure (RI), through the development, testing and deployment of an EMSO Generic Instrument Module (EGIM). This research infrastructure will provide accurate records on marine environmental changes from distributed local nodes around Europe. These observations are critical to respond accurately to the social and scientific challenges such as climate change, changes in marine ecosystems, and marine hazards. In this paper we present the design and development of the EGIM data acquisition system. EGIM is able to operate on any EMSO node, mooring line, sea bed station, cabled or non-cabled and surface buoy. In fact a central function of EGIM within the EMSO infrastructure is to have a number of ocean locations where the same set of core variables are measured homogeneously: using the same hardware, same sensor references, same qualification methods, same calibration methods, same data format and access, and same maintenance procedures.Peer ReviewedPostprint (published version

Data acquisition system development for EGIM on EMSODEV EU Project

The EMSODEV1 (European Multidisciplinary Seafloor and water-- column Observatory DEVelopment) is a UE project whose general objective is to set up the full implementation and operation of the EMSO distributed Research Infrastructure (RI), through the development, testing and deployment of an EMSO Generic Instrument Module (EGIM). The EGIM module will measure various ocean parameters in a long-term consistent, accurate and comparable manner. These measurements are critical to respond accurately to the social and scientific challenges such as climate change, changes in marine ecosystems, and marine hazards. Here we present the current status of the EGIM data acquisition system development.Peer ReviewedPostprint (published version

La Zona de Falla del Bajo Segura: cabalgamiento activo “ciego” en la Cordillera Bética oriental

The Bajo Segura Fault Zone, located at the NE end of the Eastern Betic Shear Zone, has been the site of some of the most intense seismic activity on the Iberian Peninsula in the historical and instrumental time periods. This structure is an active blind fault that does not show any surface rupture. It is characterised by a set of ENE-WSW trending blind thrust faults that offset the Triassic basement and cause active folding of the Upper Miocene-Quaternary sedimentary cover. The main active structures of this fault zone are two ENE-WSW striking reverse blind faults, the Torremendo and the Bajo Segura Faults, and several secondary NW-SE striking dextral faults (San Miguel de Salinas, Torrevieja and Guardamar Faults). These structures continue offshore to the east. From geological, geomorphological and geodetic data, we obtain fault slip rates between 0.2 and 0.4 mm/yr, whereas other authors have proposed higher values ranging between 0.75 and 1 mm/yr. The fault zone can generate earthquakes with maximum estimated magnitudes (Mw) from 6.6 to 7.1 and has approximate recurrence intervals between 4.500 and 21.500 years.La Zona de Falla del Bajo Segura, localizada en el extremo NE de la Zona de Cizalla de la Bética Oriental, es una de las estructuras tectónicas de la Península Ibérica con mayor actividad sísmica asociada durante el periodo histórico e instrumental. Es una zona de falla ciega, sin ruptura en superficie, caracterizada por varios pliegues que deforman las rocas sedimentarias de edad Mioceno Superior a Cuaternario. Su traza principal tiene varios segmentos aproximadamente paralelos entre sí de dirección ENE-WSW entre los que destacan la Falla del Bajo Segura y la Falla de Torremendo. Además, tiene asociadas varias fallas de transferencia dextrorsas de dirección NW-SE (San Miguel de Salinas, Torrevieja y Guardamar). Estas fallas ENE-WSW y NW-SE tienen su continuidad hacia el este, en el Mar Mediterráneo. Algunos marcadores geológicos y geomorfológicos junto con un perfil de nivelación de alta precisión, han permitido obtener tasas de desplazamiento que varían entre 0.2 y 0.4 mm/año, aunque otros autores han propuesto valores más altos de entre 0.75 y 1 mm/año. A partir de estas tasas de desplazamiento y de la cartografía de la zona de falla, se estima que la máxima magnitud Mw varía entre 6.6 y 7.1 con periodos de recurrencia aproximados entre 4.500 y 21.500 años.Financial support for this work was provided by the research projects CGL2011-30153-C02-02, FASEGEO (CGL2009-09726), EVENT (CGL 2006-12861-C02-02) and SHAKE (CGL 2011-30005-C02-02) and Acciones Complementarias EVENT-SHELF (CTM 2008-03346-E/MAR) and SPARKER (CTM 2008-03208-E/MAR)

Estructura y evolución tectónica del sector oriental del margen continental cantábrico: resultados de los perfiles de sísmica multicanal MARCONI

El Golfo de Vizcaya se formó durante el Cretácico como consecuencia de la apertura del Océano Atlántico. La convergencia entre las placas Euroasiática e Ibérica durante el Cenozoico dio lugar al levantamiento de la cordillera pirenaico-cantábrica y al cierre parcial del Golfo de Vizcaya. La mayor parte de esta deformación tiene lugar en el margen Noribérico, haciendo de este área un lugar único para estudiar los estadios iniciales de la deformación de un margen pasivo. En el verano de 2003, el experimento sísmico MARCONI permitió adquirir 11 perfiles de sísmica de reflexión vertical profunda utilizando el buque Hespérides, lo que ha proporcionado una nueva imagen 3D de la estructura cortical del sector SE del Golfo de Vizcaya. Los datos muestran que la estructura de este margen se caracteriza por una espesa secuencia de sedimentos meso-cenozoicos (hasta 4 s TWT, hasta > 6 km) parcialmente deformada por cabalgamiento y pliegues asociados, vergentes al N. Se han diferenciado tres conjuntos sedimentarios separados por discordancias que se corresponden con las secuencias alpinas pre-, sin- y postectónicas. Los datos sísmicos muestran también la existencia de cuencas mesozoicas con evidencias de inversión tectónica y la existencia de fallas y estructuras laterales coincidiendo con los importantes cañones submarinos de dirección aproximada N-S. Teniendo tambien en cuenta otros datos geofísicos, la estructura general del sector SE del Golfo de Vizcaya se ha interpretado como una corteza continental adelgazada o transicional deslizada hacia el S por debajo del extremadamente abrupto y muy deformado talud continental Noribérico