Geodetic evidence for continuing tectonic activity of the Carboneras fault (SE Spain)

The Carboneras fault zone (CFZ) is a prominent onshore offshore strike slip fault that forms part of the Eastern Betic Shear Zone (EBSZ), located in SE Spain. In this work, we show for the first time, the continuing tectonic ac- tivity of the CFZ and quantify its geodetic slip-rates using continuous and campaign GPS observations conducted during the last decade. We find that the left-lateral motion dominates the kinematics of the CFZ, with a strike slip rate of 1.3 ± 0.2 mm/yr along the N48° direction. The shortening component is significantly lower and poorly constrained. Recent onshore and offshore paleoseismic and geomorphic results across the CFZ suggest a mini- mum Late Pleistocene to present-day strike slip rate of 1.1 mm/yr. Considering the similarity of the geologic and geodetic slip rates measured at different points along the fault, the northern segment of the CFZ must have been slipping approximately at a constant rate during the Quaternary. Regarding the eastern Alpujarras fault zone corridor (AFZ), located to the north of the CFZ, our GPS measurements corroborate that this zone is ac- tive and exhibits a right-lateral motion. These opposite type strike slip motion across the AFZ and CFZ is a result of a push-type force due to Nubia and Eurasia plate convergence, which, in turn, causes the westward escape of the block bounded by these two fault zones

3D GPS velocity field and its implications on the present-day postorogenic deformation of the Western Alps and Pyrenees

We present a new 3D GPS velocity solution for 182 sites for the region encompassing the Western Alps, Pyrenees, and southern France. The velocity field is based on a Precise Point Positioning (PPP) solution, to which we apply a common-mode filter, defined by the 26 longest time series, in order to correct for network-wide biases (reference frame, unmodeled large scale processes, ¿). We show that processing parameters, such as troposphere delay modeling, can lead to systematic velocity variations of 0.1 - 0.5 mm/yr affecting both accuracy and precision, especially for short (< 5 yr) time series. A velocity convergence analysis shows that minimum time-series lengths of ~3 years and ~5.5 years are required to reach a velocity stability of 0.5 mm/yr in the horizontal and vertical components, respectively. On average, horizontal residual velocities show a stability of ~0.2 mm/yr in the Western Alps, Pyrenees, and southern France. The only significant horizontal strain rate signal is in the western Pyrenees with up to 4 x 10-9 yr-1 NNE-SSW extension, whereas no significant strain rates are detected in the Western Alps (< 1 x 10-9 yr-1). In contrast, we identify significant uplift rates up to 2 mm/yr in the Western Alps but not in the Pyrenees (0.1 ± 0.2 mm/yr). A correlation between site elevations and fast uplift rates in the northern part of the Western Alps, in the region of the Wurmian ice cap, suggests that part of this uplift is induced by postglacial rebound. The very slow uplift rates in the southern Western Alps and in the Pyrenees could be accounted for by erosion-induced rebound

Deformación cortical mediante GPS en el Este de la Cordillera Bética. Especial énfasis en el terremoto de Lorca.

Resumen: En este trabajo se presenta el campo de deformación cortical en el Este de la Cordillera Bética, basado en observaciones de la red GPS CuaTeNeo. Esta red geodésica no permanente, se estableció en 1996 con el objetivo de cuantificar las deformaciones tectónicas actuales del SE de las Béticas. La red está formada por 15 monumentos estables distribuidos entre Murcia y Almería y ha sido observada en cinco ocasiones (1997, 2002, 2006, 2009 y 2011). Los resultados obtenidos muestran en general un campo de velocidades no superior a los 2 mm/a y con una dirección similar a la convergencia entre las placas Eurasiática y Nubia. Las estaciones situadas en el interior presentan velocidades de menor magnitud. El campo de deformación cortical obtenido muestra que de las fallas de la Zona de Cizalla de las Béticas Orientales permanecen activas. El mecanismo focal del terremoto de Mw5.1 ocurrido en Lorca el 11/05/2011, atribuido a la Falla Alhama de Murcia, muestra una componente inversa y de desgarre, de acuerdo con la deformación cortical detectada a través de las observaciones de GPS. Ha sido posible detectar un salto co-sísmico debido al terremoto en la estación continua LORC de ~5mm hacia el Norte. Palabras clave: GPS, terremotos, neotectónica, Béticas. Abstract: In this communication is presented the updated crustal deformation field in the Eastern Betics, based on GPS observations of the CuaTeNeo network. This non-permanent network was established in 1996 to quantify the current tectonic deformation of the SE Betics. The network consist of 15 stable monuments distributed between Murcia and Almeria and were observed five times (1997, 2002, 2006, 2009 and 2011). In general, the results show a velocity field lower than 2 mm/yr with a similar trend to the Eurasia and Nubia plate convergence. Stations located to the inland exhibit lower velocity vector. The crustal deformation field shows evidences of active faults of the Eastern Betic Shear Zone. The focal mechanism calculated for the May 11th 2011 earthquake in Lorca, attributed to the Alhama de Murcia Fault, shows reverse and sinistral components, in accordance to the crustal deformation detected by GPS. Co-seismic offset of ~5mm to the North was detected due to the earthquake in the continuous GPS LORC station. Key words: GPS, earthquakes, neotectonics, Betics

GPS studies of active deformation in the Pyrenees

The Pyrenees mountain belt, which separates the Iberian Peninsula from the rest of the European continent, is part of the AlpineHimalayan orogenic belt, formed as a result of a collision between the African and Eurasian Plates. Although the instrumental seismicity in the Pyrenees is moderate, in the past centuries a number of destructive earthquakes have occurred, which could indicate continuing tectonic activity of the area. We analyse GPS observations spanning 3.5 yr from 35 continuous stations in the Pyrenees region and find significant on-going extension perpendicular to the range at 2.5 ± 0.5 nstrain yr1, with the possibility of higher strain rates concentrated in the westernmost part of the range. This finding is in agreement with the predominantly normal faulting focal mechanisms of earthquakes that occur in the area and suggests a recurrence time for magnitude 6.5 earthquakes of 22002500 yr

Crustal deformation in eastern Betics from CuaTeNeo GPS network

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 2 mm/yr near the coast to 0.5 mm/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 ± 0.3 mm/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

Minerales supergénicos de Hg de Almadén: Una forma natural de fijar mercurio

Como es conocido, la zona de Almadén constituye uno de los reservorios de mercurio más importantes del mundo (Higueras et al., 2006)

Topo-Iberia Project: CGPS crustal velocity field in the Iberian Peninsula and Morocco

A new continuous GPS network was installed under the umbrella of a research project called 'Geociencias en Iberia: Estudios integrados de topografı´a y evolución 4D (Topo-Iberia)', to improve understanding of kinematic behavior of the Iberian Peninsula region. Here we present a velocity field based on the analysis of the 4 years of data from 25 stations constituting the network, which were analyzed by three different analysis groups contributing to the project. Different geodetic software packages (GIPSY-OASIS, Bernese and GAMIT) as well as different approaches were used to estimate rates of present day crustal deformation in the Iberian Peninsula and Morocco. In order to ensure the consistency of the velocity fields determined by the three groups, the velocities obtained by each analysis center were transformed into a common Eurasia Reference Frame. After that, the strain rate field was calculated. The results put in evidence more prominent residual motions in Morocco and southernmost part of the Iberian Peninsula. In particular, the dilatation and shear strain rates reach their maximum values in the Central Betics and northern Alboran Sea. A small region of high shear strain rate is observed in the east-central part of the peninsula and another deformation focus is located around the Strait of Gibraltar and the Gulf of Cadiz

COVID-19 symptoms at hospital admission vary with age and sex: results from the ISARIC prospective multinational observational study

Background: The ISARIC prospective multinational observational study is the largest cohort of hospitalized patients with COVID-19. We present relationships of age, sex, and nationality to presenting symptoms. Methods: International, prospective observational study of 60 109 hospitalized symptomatic patients with laboratory-confirmed COVID-19 recruited from 43 countries between 30 January and 3 August 2020. Logistic regression was performed to evaluate relationships of age and sex to published COVID-19 case definitions and the most commonly reported symptoms. Results: ‘Typical’ symptoms of fever (69%), cough (68%) and shortness of breath (66%) were the most commonly reported. 92% of patients experienced at least one of these. Prevalence of typical symptoms was greatest in 30- to 60-year-olds (respectively 80, 79, 69%; at least one 95%). They were reported less frequently in children (≤ 18 years: 69, 48, 23; 85%), older adults (≥ 70 years: 61, 62, 65; 90%), and women (66, 66, 64; 90%; vs. men 71, 70, 67; 93%, each P &lt; 0.001). The most common atypical presentations under 60 years of age were nausea and vomiting and abdominal pain, and over 60 years was confusion. Regression models showed significant differences in symptoms with sex, age and country. Interpretation: This international collaboration has allowed us to report reliable symptom data from the largest cohort of patients admitted to hospital with COVID-19. Adults over 60 and children admitted to hospital with COVID-19 are less likely to present with typical symptoms. Nausea and vomiting are common atypical presentations under 30 years. Confusion is a frequent atypical presentation of COVID-19 in adults over 60 years. Women are less likely to experience typical symptoms than men

Estudios de la deformación cortical de la península ibérica mediante observaciones GPS

[spa] La península ibérica representa el extremo más occidental del cinturón orogénico Alpino-Himalayo y está caracterizada por la colisión entre la placa africana (Nubia) y la euroasiática. La convergencia entre estas dos placas tiene una orientación oblicua (~NW-SE) respecto al límite de placas con una tasa de aproximadamente 5 mm/año. La sismicidad actual en la península ibérica está concentrada principalmente en la cordillera Bética y en los Pirineos. Esta sismicidad implica la presencia de esfuerzos corticales causados por el movimiento de las placas tectónicas y/o deformaciones corticales locales que se pueden analizar utilizando la metodología de la geodesia espacial, y en particular con las observaciones GPS. Ambas zonas, aunque con regímenes tectónicos muy dispares, han sido analizadas en este estudio a partir de observaciones GPS. Las técnicas de geodesia espaciales aplicadas al estudio de la deformación cortical en combinación con la modelización numérica nos han permitido abordar los objetivos principales de la tesis: determinar el campo de velocidades GPS para los Pirineos y las Béticas, y configurar un modelo de bloques que explique la cinemática del límite de placas entre África y Eurásica en la región Ibero-Magrebí. Los nuevos datos de la red GPS del proyecto Topo-Iberia, en el cual se enmarca la tesis, han sido incorporados en ambas áreas de estudio. Para el estudio de la deformación activa de los Pirineos se han analizado 3,5 años de observaciones GPS de 35 estaciones continuas en la región. Se ha encontrado una extensión activa significativa perpendicular a la cordillera de 2,5±0,5 nstrain/año, con una posible tasa de deformación más elevada concentrada en la parte más occidental de la cordillera. Los resultados obtenidos están de acuerdo con los mecanismos focales predominantemente normales que ocurren en la zona y sugieren un intervalo de recurrencia de 2.200-2.500 años para un terremoto de magnitud 6,5. Se sugiere que la extensión obtenida en este estudio probablemente es debida al rebote isostático producido por el levantamiento y erosión de la cordillera y/o por un proceso de relajación causada por colapsos gravitacionales. Para la modelización numérica de la cinemática del límite de placas de la región Ibero-Magrebí se ha obtenido el campo de velocidades GPS a partir de los campos de velocidades existentes en la región. Se ha construido un modelo de bloques elástico a partir del campo de velocidades obtenido que describe la geodinámica de la zona y muestra que la deformación principal ocurre en el dominio Bético-Rif-Alborán. El modelo propuesto consta de 5 bloques: dos bloques que representan las placas africana y euroasiática respectivamente, un bloque que engloba el Rif y el mar de Alborán, otro bloque con las Béticas Centrales y Orientales, y un bloque con las Béticas más Orientales. Según el modelo propuesto las principales zonas de deformación, correspondientes a las fallas que definen los bloques propuestos por el modelo, son: 1) la falla que se extienden desde el Golfo de Cádiz hasta las Béticas Orientales con orientación aproximadamente E-W caracterizada por un movimiento dextral; 2) las fallas que corresponden a la zona de cizalla Trans-Alboran con orientación NE-SW, caracterizada por un movimiento sinistro con una pequeña componente extensiva; 3) las fallas del sur del Rif y norte de Argelia con comportamiento transpresivo, y 4) la falla que se alinea con las fallas pliocenas y cuaternarias paralelas a la línea de costa andaluza con comportamiento dextral. Basándonos en los resultados obtenidos en esta tesis, proponemos que las velocidades GPS podrían estar justificadas por la subducción aún activa hacia el este bajo el estrecho de Gibraltar de una slab y un roll-back asociado que provocaría la extensión del back-arc, situado en las Béticas Orientales.[eng] Himalayan orogenic belt and is characterized by the collision between the Africa and Nubia plates. The convergence between these plates has a ~NW-SE orientation, oblique to the plate boundary, with a rate of 5 mm/yr. The seismicity of the Iberian Peninsula is mainly concentrated in the Betics and Pyrenees mountain ranges. This seismicity indicates the presence of crustal stresses, which cause the plate tectonics movement and/or local crustal deformations, which could be analyzed using space geodetic techniques, particularly using GPS observations. The main goals of the given thesis include the determination of the GPS velocity field of the Pyrenees and Betic mountain belts and, the development of a new elastic block model that explains the kinematics of the plate boundary in the Iberian-Maghrebian region. These objectives were achieved using the methodology of space geodesy applied to crustal deformation studies, and using three-dimensional numerical modeling techniques. The data of a new GPS network installed as part of the Topo-Iberia project was included in the study of the Pyrenees and the Ibero-Maghrebian region. In order to analyze the present day crustal deformations in the Pyrenees, we analyze data from 35 continuous stations located within the mountain range, spanning 3.5-year period. Our results indicate a presence of statistically significant ongoing extension of 2.5±0.5 nstrain/yr perpendicular to the main axis of the Pyrenees, with the possibility of higher strain rates concentrated in the westernmost part of the range. This finding is in agreement with the predominantly normal faulting focal mechanisms of earthquakes that occur in the area. Using the GPS measured extension rates, we estimate that the recurrence time for magnitude 6.5 earthquakes equals 2200–2500 yr. We suggest that the extension obtained in this study could be the result of an isostatic rebound produced by the uplift and erosion of the mountain range or a process of relaxation caused by gravitational collapse, or both. To study the kinematics of the plate boundary in the Iberian-Maghrebian region, we estimated the velocity field from the combination of all of the published GPS velocities, including the velocity estimates form the Topo-Iberia network. We design a new elastic block model from the velocity field, which explains the geodynamic behavior of this complex plate boundary. The model shows that the principal deformation are concentrate at the Betic-Rif-Alboran domain. The proposed model consists in 5 blocks: two blocks that represents the African and Eurasian plates, a block which includes the Rif and the Alboran sea, a block with the Central and Eastern Betics, and finally a block with the easternmost part of the Betics range. The principal faults which separate blocks are: 1) a right-lateral behavior of the fault with E-W orientation from Gulf of Cadiz to the eastern Betics; 2) the system of faults of Trans-Alboran Shear Zone with a NE-SW orientation has a left-lateral movement with a low extensional component; 3) the transpresive behavior of the Rif and north Argelia faults; 4) the parallel to the Andalusian coast faults have a right lateral movement. Based on the model results, we suggest that GPS velocities support a geodynamic model that supports a continued active slab subduction beneath the Strait of Gibraltar, with a consequent back-arc extension in the eastern Betics