Juanjo Dañobeitia

Crustal transition between continental and oceanic domains along the North Iberian Margin from wide angle seismic and gravity data

Deep crustal features of the transition between the North Iberian mainland and the Bay of Biscay are constrained from new wide-angle seismic and gravity data. Velocity-depth models are derived from far-offset recordings onshore of two N-S marine profiles, complemented with new refraction data inland and tested against models that fit the gravity anomalies. Important lateral variations are inferred along the North Iberian margin. In the western transect, a Variscan crust is documented from the mainland across the continental shelf, and a rapid crustal thinning beneath the slope marks the transition to the oceanic domain. The eastern transect shows an outstanding crustal thickening beneath the coastline (Moho depths around 50 km) and a gradual thinning across the shelf. Differences are related to the V-shape of the Bay of Biscay that causes a W-E transition along the margin, from a short-lived oceanic subduction to continental collision during the Tertiary oblique convergence between Europe and Iberia.

On the TT-Transform and Its Diagonal Elements

The TT-transform stands for time-time transform and has been derived as an inverse Fourier transform of the time-frequency S-transform. Up to date, only the diagonal of the TT-transform has been used for signal characterization. We show here an alternative and simplified derivation of the TT-transform which enables a better understanding of this transform. In particular, we demonstrate that the diagonal elements of the TT-transform represent a simple frequency filtered version of the original signal and, thus, that little additional information is gained through the TT-transform.

Evidence for active strike-slip faulting along the Eurasia-Africa convergence zone: Implications for seismic hazard in the southwest Iberian margin

New seismic imaging and seismotectonic data from the southwest Iberian margin, the site of the present-day boundary between the European and African plates, reveal that active strike slip is occurring along two prominent lineaments that have recently been mapped using multibeam bathymetry. Multichannel seismic and subbottom profiler images acquired across the lineaments show seafloor displacements and active faulting to depths of at least 10 km and of a minimum length of 150 km. Seismic moment tensors show predominantly WNW–ESE right-lateral strike-slip motion, i.e., oblique to the direction of plate convergence. Estimates of earthquake source depths close to the fault planes indicate upper mantle (i.e., depths of 40–60 km) seismogenesis, implying the presence of old, thick, and brittle lithosphere. The estimated fault seismic parameters indicate that the faults are capable of generating great magnitude (Mw ≥ 8.0) earthquakes. Such large events raise the concomitant possibility of slope failures that have the potential to trigger tsunamis. Consequently, our findings identify an unreported earthquake and tsunami hazard for the Iberian and north African coastal areas.

Expedition gathers new data on crust beneath Mexican West Coast

During the spring of 1996, scientists explored the North American plate boundary of southern Mexico and the Gulf of California through the Crustal Offshore Research Transect by Extensive Seismic Profiling (CORTES-P96) experiment (Figure la). Through dense sampling of the plates, the new data provides images that unravel the style of deformation along and across the subduction zone and in the Gulf interior, the dimensions of the accretionary prism, and the geometry of the subduction zone, which is well constrained by the reflection and refraction records. The subduction process along the south coast of Mexico, in spite of the high seismic risk that it represents, is poorly constrained due to the lack of high-resolution data. This project is aimed at resolving the crustal architecture in a zone of confronted plates.

Local earthquakes seismic tomography in the Betic Cordillera (southern Spain)

Abstract A crustal tomographic image, from the surface down to 35 km depth beneath the Betic Cordillera (southern Spain), is obtained using data on local earthquakes recorded at stations from the National and Andalusian Seismic Networks. The velocity structure and the hypocentre locations are derived from the inversion of P first arrival times, using an iterative simultaneous inversion method. The reliability of the results is assessed using different control parameters. The inverted velocity field in the uppermost layers shows a significant lateral variability which reflects most of the large-scale geological features of the Betic Cordillera. Well determined local surface anomalies allow to constrain the location and geometry of the most prominent Neogene sedimentary basins. The upper crust is well resolved throughout the whole region, and is characterized by relatively high velocities in the Internal Betics and in the South Iberian Massif and lower velocities within the External Betics. A relatively well constrained event cluster displays a NNE–SSW trend, and outlines the contact zone between the Internal and the External domains. The middle and lower crustal levels show reliable results beneath the central part of the Betic Cordillera. High averaged velocities are obtained within the South Iberian and the Alboran domains, in contrast to a relatively low velocity anomaly which characterizes the boundary between them. These findings support the hypothesis of the lack of well differentiated crustal levels below the contact zone, while crustal layering is better defined beneath the Alboran and the Iberian domains.

Multichannel seismic image of the crustal thinning at the NE Iberian Margin combining normal and wide angle reflection data

The seismic image of the Moho at the transition from the NE Iberian Peninsula to the Western Mediterranean Sea is investigated using coincident steep and wide-angle reflection data merged into a single stacked and migrated section. The multichannel analysis of onshore/offshore large-aperture data provides new insight on the deep structure in areas where the steep sections lack penetration, and reveals that the crust undergoes a strong but continuous thinning along the flanks of the Valencia trough. The combined seismic image indicates that almost half of the continental crust (14–15 km) is lost in less than 60 km horizontal distance.

From ESONET multidisciplinary scientific community to EMSO novel European research infrastructure for ocean observation

Environmental and climate changes are crucial challenges for sustainable living because of their significant impact on the Earth system and the important consequences for natural resources. Oceans have a primary role in these changes as they regulate heat flux, greenhouse gases and climate whilst harboring many different life forms and resources. Understanding processes in the marine environment is of paramount importance for any prediction of short-, intermediate- and long-term global change.

Automatic Segmentation of Multi-Beam Data for Predictive Mapping of Benthic Habitats on the Chella Seamount (North-Eastern Alboran Sea, Western Mediterranean)

A reliable and objective classification method has been produced for the differentiation of benthic habitats in the seamount regions of the North-Eastern Alboran Sea. Acoustic backscatter and depth measurements from multi-beam data are automatically fused and then classified using video transects of known cold-water coral ecosystems as ground-truth. Results of the classification reveal the locations of potentially similar habitats in the region, and could be used as a base map for the planning of future scientific campaigns in the area.

The EMSO-ERIC Pan-European Consortium: data benefits and lessons learned as the legal entity forms

The European Multidisciplinary Seafloor and water-column Observatory (EMSO) European Research Infrastructure Consortium (ERIC) provides power, communications, sensors, and data infrastructure for continuous, high-resolution, (near-)real-time, interactive ocean observations across a multidisciplinary and interdisciplinary range of research areas including biology, geology, chemistry, physics, engineering, and computer science, from polar to subtropical environments, through the water column down to the abyss. Eleven deep-sea and four shallow nodes span from the Arctic through the Atlantic and Mediterranean, to the Black Sea. Coordination among the consortium nodes is being strengthened through the EMSOdev project (H2020), which will produce the EMSO Generic Instrument Module (EGIM). Early installations are now being upgraded, for example, at the Ligurian, Ionian, Azores, and Porcupine Abyssal Plain (PAP) nodes. Significant findings have been flowing in over the years; for example, high-frequency surface and subsurface water-column measurements of the PAP node show an increase in seawater pCO2 (from 339 μatm in 2003 to 353 μatm in 2011) with little variability in the mean air-sea CO2 flux. In the Central Eastern Atlantic, the Oceanic Platform of the Canary Islands open-ocean canary node (aka ESTOC station) has a long-standing time series on water column physical, biogeochemical, and acidification processes that have contributed to the assessment efforts of the Intergovernmental Panel on Climate Change (IPCC). EMSO not only brings together countries and disciplines but also allows the pooling of resources and coordination to assemble harmonized data into a comprehensive regional ocean picture, which will then be made available to researchers and stakeholders worldwide on an open and interoperable access basis.

Characterization of turbulent regimes derived from high resolution CTD profiles. potential application to continuous profiling systems

The present study proposes a new method for estimating mixing parameters from continuous CTD profiling data processing. The method is mainly oriented to the continuous profiling systems that can be installed in permanent observatories. The method could be particularly useful in studies of biologicalphysical interactions at small scale, because it overcomes some of the limitations of the eddy diffusivity concept when dealing with the complex vertical pattern of biological and chemical tracers. The proposed method obtains empirically the coefficients of the transilient matrix, this being the discrete descriptor used in non-local mixing closure.