Scientific and Technological Research of the Barcelona CSI

Geophysical measurements of physical properties of the Earth and their integration with geological data is the optimal methodology to study geological processes. The Barcelona-CSI develops geophysical & geological methods and instrumentation to study a range of geological processes

Methodological Development:

The group investigates how to improve modelling and inversion tools and to develop new ones for seismic and electromagnetic (EM) data. A priority is to develop 2- and 3-D full waveform inversion codes of seismic data, because they yield much improved information compared to current travel time inversions. The group also develops algorithms for processing, and 2- and 3-D modelling of EM data. An imminent goal is simultaneous inversion of seismic and EM data. Those methods are applied to a range of topics that require imaging subsurface structures and to determine material distribution based of physical properties (e.g. P & S wave velocities, resistivity, attenuation etc.). These methods are suited to monitor fluid (water, hydrocarbons or CO₂) movement across rock volumes, to estimate fluid overpressures, or to map tectonic structures like faults.

Technological Development:

The Barcelona-CSI works to develop geological and geophysical instrumentation. Members of the group in collaboration with technicians of the Marine Technology Unit have developed, built and installed in the Research Vessels Hespérides and Sarmiento de Gamboa a new Kullemberg-type piston corer, designed to collect 10-15 meter sediment cores of wide diameter, high-quality and large-volume. The group also develops geophysical instruments. A notable effort is the design of an Ocean Bottom Seismometer (OBS) in collaboration with the Catalan Polytechnic University (UPC). Currently, 8 to 10 instruments are being built in a collaborative project with industry, aiming at marketing them.

Research on Geological Processes:

Work at Barcelona-CSI covers a broad range of geological processes. Research is carried out mainly using seismic data that are integrated with other data sets like multi-beam bathymetry, side-scan sonar, potential field, core samples, etc. Most work is offshore, often collected with cruises lead by group members. Onshore field work is less common.

Work is largely focused in three broad research areas encompassing the following topics:

I) Tectonic and fluid and material transfer processes at subduction zones: Studies of processes originating from interactions of subducting and overriding plates. Some work focuses on deformation, and associated processes of the oceanic plate during bending prior to subduction. This deformation causes a profound mechanical and chemical modification of the plate creating large-scale bending-related faulting and massive water percolation causing serpentinization of the upper mantle. The chemically-stored water is transported into the subduction zone and released by metamorphism, promoting intraslab earthquakes, mantle-wedge melting and arc volcanism. Complementary studies investigate tectonics and hydro-geological systems of convergent margins of subduction zones. One of the areas of interest is the active Cascadia Margin, characterized by abundant gas hydrates, and where the ODP Leg 204 was carried out (participation of E. Gràcia). Gas hydrate research has important implications for its economical potential, geological hazards arising from its destabilization and its impact on climate change. We focused on hydrate distribution, migration and diagenetic processes on the basis of sedimentological, physical properties and geochemical characterization of gas hydrate-rich sediments. Current work is now focused on the subduction zones of Central America and Chile in collaboration with IFM-Geomar (Kiel, Germany), the German Geological Survey (BGR, Germany) and University of Texas (USA).

II) Earthquake genesis, paleoseismology and geohazards: The group leads several complementary earthquake projects. Ongoing leadership continues towards the realization of a tens-of-million project to drill the plate boundary in Costa Rica to study the earthquake cycle. The drill proposal (537, www.iodp.org/597), with C.R. Ranero as a PI, is approved at the Integrated Ocean Drilling Program (IODP) and the first leg has occurred in April 2011. Drilling is accompanied by a multimillion 3D seismic cruise funded by NSF (PI: N. Bangs, Uni. Texas, C.R. Ranero collaborator) taking place in April-May 2011. Processing worth about two millions is provided by Repsol through collaboration with C.R. Ranero. E. Gràcia leads studies to characterize active faults that potentially generate large earthquakes and associated tsunamis. In particular, paleoseismological studies (onshore-offshore on-fault approach and turbidite paleoseismology) have been carried out in the Gulf of Cadiz and Alboran Sea. The goal is to determine the geometry, fault segmentation, slip rate and recurrence period, and potential earthquake magnitude for a given fault. These parameters allow us to estimate the seismic hazard and are fundamental for earthquake and tsunami risk assessment. Geo-hazards related to submarine slope stability is a recently initiated line of research at the group, which implied the implementation of a new geotechnical laboratory led by R. Urgeles.

III) Formation of Sedimentary Basins, Rifted Continental Margins, and Mid Ocean Ridges: We focus on processes governing deformation of the lithosphere during extension and related mantle melting. Current projects study the South China Sea, Tyrrhenian Basin, Alborán Basin, Atlantic Moroccan margin, Gulf of California, conjugate Iberia-Newfoundland and Antarctica-Australia margins and Mid- Atlantic Ridge. Work is based on seismic images, wide-angle seismic velocity models, and tectonic interpretation. Analyses restore structure to understand the evolution of deformation through time. Models include constraints from rheology, extension rate, etc., to understand thermal history and sediment facies. These studies are underway in several projects of C.R. Ranero, in collaboration with V. Sallarès and R. Bartolomé and external collaborators from Royal Holloway (London Univ., UK), IFM-Geomar (Germany), BGR (Germany), Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS, Bologna, Italy), Geoscience Australia and Adelaide University (Australia).