Real Instituto Y Observatorio Of La Armada

San Fernando, Spain

Real Instituto Y Observatorio Of La Armada

San Fernando, Spain
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Bezada M.J.,University of Oregon | Humphreys E.D.,University of Oregon | Davila J.M.,Real Instituto Y Observatorio Of La Armada | Carbonell R.,CSIC - Institute of Earth Sciences Jaume Almera | And 3 more authors.
Geochemistry, Geophysics, Geosystems | Year: 2014

The elevation of the intracontinental Atlas Mountains of Morocco and surrounding regions requires a mantle component of buoyancy, and there is consensus that this buoyancy results from an abnormally thin lithosphere. Lithospheric delamination under the Atlas Mountains and thermal erosion caused by upwelling mantle have each been suggested as thinning mechanisms. We use seismic tomography to image the upper mantle of Morocco. Our imaging resolves the location and shape of lithospheric cavities and of delaminated lithosphere ∼400 km beneath the Middle Atlas. We propose discontinuous delamination of an intrinsically unstable Atlas lithosphere, enabled by the presence of anomalously hot mantle, as a mechanism for producing the imaged structures. The Atlas lithosphere was made unstable by a combination of tectonic shortening and eclogite loading during Mesozoic rifting and Cenozoic magmatism. The presence of hot mantle sourced from regional upwellings in northern Africa or the Canary Islands enhanced the instability of this lithosphere. Flow around the retreating Alboran slab focused upwelling mantle under the Middle Atlas, which we infer to be the site of the most recent delamination. The Atlas Mountains of Morocco stand as an example of large-scale lithospheric loss in a mildly contractional orogen. Key Points We image lithospheric cavities beneath the Middle Atlas and central HighAtlas We image the delaminated lithosphere of the Middle Atlas at ∼400 km depth We propose piecewise delamination of Atlas lithosphere © 2014. American Geophysical Union. All Rights Reserved.

Montojo F.J.,Real Instituto Y Observatorio Of La Armada | Lopez Moratalla T.,Real Instituto Y Observatorio Of La Armada
Advances in Space Research | Year: 2011

In the project titled "Astrometric Positioning of Geostationary Satellite" (PASAGE), carried out by the Real Instituto y Observatorio de la Armada (ROA), optical observation techniques were developed to allow satellites to be located in the geostationary ring with angular accuracies of up to a few tenths of an arcsec. These techniques do not necessarily require the use of large telescopes or especially dark areas, and furthermore, because optical observation is a passive method, they could be directly applicable to the detection and monitoring of passive objects such as space debris in the geostationary ring. By using single-station angular observations, geostationary satellite orbits with positional uncertainties below 350 m (2 sigma) were reconstructed using the Orbit Determination Tool Kit software, by Analytical Graphics, Inc. This software is used in collaboration with the Spanish Instituto Nacional de Técnica Aeroespacial. Orbit determination can be improved by taking into consideration the data from other stations, such as angular observations alone or together with ranging measurements to the satellite. Tests were carried out combining angular observations with the ranging measurements obtained from the Two-Way Satellite Time and Frequency Transfer technique that is used by ROA's Time Section to carry out time transfer with other laboratories. Results show a reduction of the 2 sigma uncertainty to less than 100 m. © 2010 COSPAR. Published by Elsevier Ltd. All rights reserved.

Villasenor A.,CSIC - Institute of Earth Sciences Jaume Almera | Chevrot S.,University Paul Sabatier | Harnafi M.,Mohammed V University | Gallart J.,CSIC - Institute of Earth Sciences Jaume Almera | And 5 more authors.
Tectonophysics | Year: 2015

New tomographic images of the upper mantle beneath the westernmost Mediterranean suggest that the evolution of the region experienced two subduction-related episodes. First subduction of oceanic and/or extended continental lithosphere, now located mainly beneath the Betics at depths greater than 400 km, took place on a NW-SE oriented subduction zone. This was followed by a slab-tear process that initiated in the east and propagated to the west, leading to westward slab rollback and possibly lower crustal delamination. The current position of the slab tear is located approximately at 4°W, and to the west of this location the subducted lithosphere is still attached to the surface along the Gibraltar Arc. Our new P-wave velocity model is able to image the attached subducted lithosphere as a narrow high-velocity body extending to shallow depths, coinciding with the region of maximum curvature of the Gibraltar Arc, the occurrence of intermediate-depth earthquakes, and anomalously thick crust. This thick crust has a large influence in the measured teleseismic travel time residuals and therefore in the obtained P-wave tomographic model. We show that removing the effects of the thick crust significantly improves the shallow images of the slab and therefore the interpretations based on the seismic structure. © 2015 Elsevier B.V.

Martos Y.M.,University of Granada | Catalan M.,Real Instituto Y Observatorio Of La Armada | Galindo-Zaldivar J.,University of Granada | Maldonado A.,University of Granada | Bohoyo F.,Instituto Geologico Y Minero Of Espana
Global and Planetary Change | Year: 2014

Analysis of a new regional compilation of magnetic anomalies from marine, aeromagnetic and satellite data reveals the main structural/tectonic elements of the Scotia Arc. The most relevant magnetic anomaly in the continental crust, the Pacific Margin Anomaly (PMA), is related to composite magmatic arc batholiths. It was emplaced by subduction processes along the Pacific continental margin of the Antarctic Peninsula and can be followed within the continental blocks of the South Scotia Ridge and South America. Four representative magnetic profiles also show the structure in depth, and allow us to characterize the main crustal elements of the region. The new compilation and models improve our knowledge of the Scotia Arc's development. The PMA is seen to have a roughly W-E orientation, decreasing in intensity eastwards from the Pacific Margin of the Antarctic Peninsula, and extending towards the South Scotia Ridge to Discovery Bank and even to Herdman Bank. However, the identification of the PMA in the North Scotia Ridge is uncertain, since the magnetic anomalies and the modeled profiles do not support the presence of an important batholithic body. This setting can be attributed to the kinematics of subduction, almost orthogonal to the Pacific margin of the Antarctic Peninsula and oblique along the South American margin. Based on the new magnetic anomaly map, magnetic modeling, and the continuity of the PMA along the Antarctic Peninsula and South Scotia Ridge, we propose a reconstruction of the initial distribution of the main continental blocks in the initial stages during the Cretaceous. The anomalies identified in the northern Scotia Sea are probably related to local basic and/or intermediate igneous rocks intruded in pull-apart basins that developed in the South America-Antarctica plate boundary deformation zone during the initial stages of South Atlantic Ocean and Weddell Sea spreading. © 2014 Elsevier B.V. All rights reserved.

Catalan M.,Real Instituto Y Observatorio Of La Armada | Galindo-Zaldivar J.,Instituto Andaluz Of Ciencias Of La Tierra Csic Ugr | Galindo-Zaldivar J.,University of Granada | Davila J.M.,Real Instituto Y Observatorio Of La Armada | And 4 more authors.
Tectonophysics | Year: 2013

Bransfield Basin, a 500-km-long and 100-km-wide extensional structure with a well-marked NE-SW orientation, is considered a back-arc basin developed since the Pliocene and associated with subduction of the former Phoenix Plate below the South Shetland Islands Block. Extension also occurs in this area as a consequence of the end of the sinistral fault zone that deforms the South Scotia Ridge. On the basis of potential field data from marine cruises, we provide new magnetic and Bouguer gravity maps of the area at sea level. We have characterized the central magnetic anomaly by using Euler deconvolution method, spectral analysis and forward modeling obtaining a thin (1.5. km) and shallow (4. km b.s.l.) layer, and a low total magnetization (2.6. A/m). The forward modeling was constrained on basis of previous seismic refraction studies. Our models show two situations. The first presents a uniform density values along the entire crust in the basin. This would be compatible with rifting in a more advanced stage, or even an oceanic crust in its earliest stages, while the second would support the existence of a stretched, thinned and altered crust through the injection of volcanic material. In the light of these models, analysis of the new potential field maps presented in this work and information from previous studies we consider that the Central Bransfield Basin is in a rifting in its latest stages or presents an incipient oceanic crust formed by recent oceanic spreading. © 2012 Elsevier B.V.

Martos Y.M.,University of Granada | Galindo-Zaldivar J.,University of Granada | Catalan M.,Real Instituto Y Observatorio Of La Armada | Bohoyo F.,Instituto Geologico Y Minero Of Espana | Maldonado A.,University of Granada
Geophysical Research Letters | Year: 2014

The Drake Passage is considered a gateway for oceanic and asthenospheric flows since its opening, entailing widespread consequences for climate and plate tectonics, respectively. Both the surface and the 50 km upward continued Bouguer anomaly maps of the Scotia Sea and surrounding areas, based on Gravity Recovery and Climate Experiment gravity satellite data, improve our knowledge of deep lithospheric structures and the asthenosphere. We show that the West Scotia Sea is likely to be underlain by an anomalously low-density upper mantle. Gravity data are compatible with variable lithospheric thicknesses related to asthenospheric currents. The new data suggest that the development of the Shackleton Fracture Zone since the middle Miocene was probably a main factor that determined the evolution of the eastward Pacific mantle flows and the extinction of the West Scotia Sea oceanic spreading around 6 Ma ago. Deep lithospheric roots are likely to divert asthenospheric currents around them, flowing eastward through Drake Passage. Key Points Pacific mantle outflow is still present through the Drake Passage The Shackleton Fracture Zone modified asthenospheric flow patterns A redistribution of mantle flow may have caused West Scotia Ridge extinction ©2013. American Geophysical Union. All Rights Reserved.

Muinos J.L.,Real Instituto Y Observatorio Of La Armada | Evans D.W.,Institute of Astronomy
Astronomische Nachrichten | Year: 2014

CMC15 is the last of the series "Carlsberg Meridian Catalogue, La Palma" and comprises all the observations made between March 1999 and March 2011 with the Carlsberg Automatic Meridian Circle in El Roque de los Muchachos Observatory on the island of La Palma (Spain). The catalogues CMC12, CMC13, and CMC14 are superseded by this one. It contains more than 122 million observations of right ascension, declination, and magnitude of stars in the magnitude range of 9m < r′ < 17m and declination range of -40° < δ < +50°. The catalogue internal errors in astrometry are below 30 mas in both coordinates for stars brighter than r′ = 13, reaching 60 mas for r′ = 16. The internal magnitude error is below 0.020 mag for stars brighter than r′ = 13, and about 0.090 mag for r′ = 16. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Echeverria A.,University of Barcelona | Khazaradze G.,University of Barcelona | Asensio E.,University of Barcelona | Garate J.,Real Instituto Y Observatorio Of La Armada | And 2 more authors.
Tectonophysics | Year: 2013

The eastern Betic Cordillera, Spain, is the most seismically active area within the Iberian Peninsula. We present a Global Positioning System (GPS)-derived horizontal crustal deformation obtained from five occupations of the CuaTeNeo GPS network (1997, 2002, 2006, 2009 and 2011) that clearly shows continuing tectonic activity in the SE Betics. The most prominent feature of the GPS velocity field is the NW oriented motion of the majority of the stations at rates ranging from 2mm/yr near the coast to 0.5mm/yr inland. This type of deformation indicates that the main driving force responsible for the observed velocities is related to the on-going convergence between Nubia and Eurasia plates. The calculated deformation field shows evidence for localized deformation related to active faults within the area. Most of the deformation is concentrated on the Alhama de Murcia fault, the source of the 2011 Lorca earthquake (Mw 5.2). We estimate a reverse-sinistral geodetic slip rate of 1.5±0.3mm/yr for this fault. Our crustal deformation field and analyses are important contributions to estimating seismic hazard for the eastern Betics, since it is the first time crustal deformation rates at this scale are presented. © 2013 Elsevier B.V.

Esteban H.,Real Instituto Y Observatorio Of La Armada | Palacio J.,Real Instituto Y Observatorio Of La Armada | Galindo F.J.,Real Instituto Y Observatorio Of La Armada | Feldmann T.,Physikalisch - Technische Bundesanstalt | And 2 more authors.
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control | Year: 2010

The calibration of time transfer links is mandatory in the context of international collaboration for the realization of International Atomic Time. In this paper, we present the results of the calibration of the GPS time transfer link between the Real Instituto y Observatorio de la Armada (ROA) and the Physikalisch-Technische Bundesanstalt (PTB) by means of a traveling geodetic-type GPS receiver and an evaluation of the achieved type A and B uncertainty. The time transfer results were achieved by using CA, P3, and also carrier phase PPP comparison techniques. We finally use these results to re-calibrate the two-way satellite time and frequency transfer (TWSTFT) link between ROA and PTB, using one month of data. We show that a TWSTFT link can be calibrated by means of GPS time comparisons with an uncertainty below 2 ns, and that potentially even sub-nanosecond uncertainty can be achieved. This is a novel and cost-effective approach compared with the more common calibration using a traveling TWSTFT station. © 2006 IEEE.

Catalan M.,Real Instituto Y Observatorio Of La Armada | Martin-Davila J.,Real Instituto Y Observatorio Of La Armada
Geologica Acta | Year: 2013

A more complete crustal perspective of the northernmost part of the Venezuela Basin is provided by data from an international public database processed with new geomagnetic models (CM4) together with data from aeromagnetic surveys and from a recent marine cruise in areas offshore Puerto Rico and the Dominican Republic. The magnetic anomaly map set off three main domains: the North Atlantic plate, a narrow zone extending from the Dominican Republic to Puerto Rico-Virgin Islands, and the North Caribbean Plate. We focused mainly on the latter, applying the Euler deconvolution algorithm in the Venezuela Basin. Shallow and middle depth sources (located between 2km and 12km) are inferred to be the dominant sources (85%), while deep sources are located mostly in the Venezuela Basin, and scarcely appear in the Beata and Aves Ridges. We performed 2D+1/2 modeling on an eastwest transect, using Bouguer gravity and magnetic anomaly data to derive a more detailed crustal description of the northern part of the Venezuela Basin. The model suggests that in the Caribbean crust, long wavelengths (>200km) are controlled by variations in crustal thickness, whereas the intermediate ones (50-100km) are mainly controlled by variations in their magnetic properties. It also suggests the presence of a local anomalous body located in the east-west transect, between 487km and 560km, displaying a remarkable positive magnetization contrast (0.3 SI) with regard to the rest of the basin. This body shows a slight increase in density (3010kg/m3), and extends from the bottom of the UCL (Underplate Cumulate Layer) to a depth of 7.5km. We correlate it with the volcanic wedge reported by Driscoll and Diebold (1998).

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