Diseño de materiales virtuales y de blended learning para paliar el efecto de ajuste de presencialidad en los grados de la Facultad de Ciencias Matemáticas

Informe del proyecto de innovación docente para el diseño de una metodología b-learning en distintos grupos de las asignaturas de segundo curso del programa de grados de la Facultad de Matemáticas y desarrollo de materiales de autoaprendizaje y prácticas virtuales

Imaging the volcanic structures beneath Gran Canaria Island using new gravity data

From a new gravity data set that covers homogeneously the whole surface of Gran Canaria (Canary Islands, Spain) and marine gravity data in the nearest offshore, we have obtained a Bouguer anomaly gravity map of the island which improves the previous ones. Using these gravity anomalies, we have applied a gravity inversion approach to investigate the structures beneath the surface of Gran Canaria Island and derive a 3D gravity sources model. The geometry of structures with anomalous density values is constrained up to a depth of approximately 20,000 m below the sea level. The interpretation of the density model identified structures related to the different volcanic stages of Gran Canaria. Several deep-rooted high-density structures represent the intrusive bodies emplaced in the early formation of Gran Canaria and the magma plumbing system of the Miocene volcanic edifices. A low-density body in the center of the island may be associated with the syenitic core of the felsic central volcanic edifice (Tejeda Caldera). Shallow low-density structures identified fractures which acted as feeder dikes of monogenetic volcanoes during the rejuvenated stage. Finally, the NW-SE rift, which is the most important volcano-tectonic structure of Gran Canaria, has a characteristic gravimetric signature and represents a long-lived extensional fracture zone that has controlled the volcanic activity at least since the Miocene

Elaboración de una rúbrica para la evaluación de los TFG de la Facultad de Ciencias Matemáticas y e-portafolio para seguimiento de estudiantes

Fac. de Ciencias MatemáticasFALSEUCMsubmitte

Estudio metodológico del efecto oceánico indirecto y desarrollo de modelos de carga oceánica: aplicaciones geodésicas para la península Ibérica y Canarias

La marea oceánica origina una serie de efectos sobre la superficie terrestre que se engloban en lo que se conoce como Efecto Oceánico Indirecto (EOI). Dicho efecto se observa periódicamente en forma de variaciones de gravedad y deformaciones y afecta, por tanto, a observaciones geodésicas y geofísicas como son las realizadas con gravímetros, GPS, VLBI, etc. El objetivo principal de esta tesis es investigar el EOI, estudiando la metodología más apropiada que permita mejorar la exactitud en su determinación numérica. Para ello, se han estudiado los errores inherentes al propio cálculo con el fin de reducir sus consecuencias y se ha desarrollado un software, denominado ECOM, que permite determinar el EOI con gran exactitud. Los mayores errores en la determinación del EOI provienen de los modelos de marea oceánica. Así, para incrementar la exactitud en su evaluación, se ha abordado el desarrollo de estos modelos a escala regional mediante la técnica de asimilación de datos. Dicha técnica constituye una metodología eficaz que permite, mediante la combinación óptima de observaciones con un modelo hidrodinámico, obtener modelos de alta resolución que representan con gran exactitud la marea oceánica. De esta manera, en las zonas objeto de estudio, la Península Ibérica y el Archipiélago Canario, se han desarrollado dos modelos de marea oceánica de alta resolución (5’5’) para ocho constituyentes armónicos principales, denominados IBER01 y CIAM2, que permiten determinar con gran exactitud el EOI y corregir las medidas geodésicas correspondientes con una precisión al nivel del 1-1.5%. Para validar dichos modelos de carga, se han utilizado nuevas observaciones de marea terrestre gravimétrica en la Península Ibérica, norte de África y las Islas Canarias y, además, se han corregido con exactitud los respectivos modelos de marea gravimétrica y verificado los modelos terrestres DDW, para O1 y M2, con una exactitud entre 0,1% - 0,5%

A new ocean tide loading model in the Canary Islands region

A new high-resolution (1/12◦ ×l/12◦) regional ocean tide model for Canary Islands region (Spain), by assimilating TOPEX/Poseidon altimetry data and tide gauge measurements into a hydrodynamic model, is presented. This regional ocean tide model is also refined along all the coastlines in the Canary region, using automatic grid discretization and bilinear interpolation. The new ocean model obtained reveals differences in some areas when we compare it with global models. The results confirm that data assimilation for high resolution models improves the ocean tide estimation in complex areas as the Canarian Archipelago. Gravity tide measurements, which are available in two islands of the Canarian Archipelago, have been used to test the ocean tide model. In addition, a comparison of nine global ocean tide models, supplemented with the regional model, is done for the M2 and O1 tidal constituents. The tidal gravity residues reveal that, for the M2 wave, there exists a dependence of the global ocean tide model considered. In general, the agreement of the nine ocean models is rather similar, although TPXO.2 and SCHW displays the most discrepant results. Among the ocean tide models, which are in close agreement at both places for M2 and O1 tidal waves, no one of them give better results than other

The crustal structure of El Hierro (Canary Islands) from 3-D gravity inversion

El Hierro is the youngest and westernmost island of the Canarian Archipelago. Due to its singular and interesting characteristics, with extensive landsliding, studying its crustal structure can provide very useful information about its origin and evolution. With this aim, we use the gravity inversion methodology obtaining a crustal model of mass distribution. We performed a gravity survey of the entire island, completing the gravity anomaly map of this area with marine data from the United States Geological Survey. The calculated Bouguer gravity anomaly map was studied using a covariance analysis and the least squares technique. To obtain crustal information from these data, we used a 3D gravity inversion based on genetic algorithms (GA). Thus, our inversion technique aims to determine the geometry of the sources of the observed gravity field, upon a prismatic partition of the subsoil volume, and adopting a priori density contrast values. The results of this gravity study of El Hierro Island show the correlation of several volcanic structures with the distribution of the gravity field sources. The characteristic triple rift system of the island is associated with low-density areas, and the older volcanic stages with high-density structures. We also found differences among the structures related to the several landslides, which helped the island takes shape

Subsurface geometry and structural evolution of La Gomera island based on gravity data

We hereby present a new Bouguer gravity map of the La Gomera island (Canarian Archipelago), which is analysed and interpreted by means of a 3-dimensional inversion, in order to contribute to the knowledge of the structural setting of this volcanic island and its evolutionary history. A land gravity data set covering the whole island of La Gomera is used in combination with offshore measurements to achieve a better determination of the gravity field in areas near the coasts. The study of this map let us to shed some light on the hypothesis established about the volcanism of this island. Moreover, it shows the information that is hidden from a geological surface exploration, modelling deep sections of the crust in La Gomera, which have been unknown until now. A first interpretation of the Bouguer gravity anomaly is achieved from 1) the residual gravity map calculated by removing a regional component and 2) the total horizontal gradient of the gravity. These residual and derivative maps allow us to identify the horizontal location and borders of the shallowest gravity sources. This provides a useful tool to study the structures associated to the latest periods of the volcanism in the area. Moreover, the information so obtained supports the hypothesis about the migration of volcanic activity towards the south of the island. Subsequently, an inversion process is carried out looking for the 3D-modelisation of the sources of the observed gravity field, which provides a comprehensive view of the structures in volcanic environments. The inversion technique used is based on a genetic algorithm (GA) applied upon a prismatic partition of the subsoil volume, and adopting a priori values of density contrast (positive and negative). The main advantage of this method is that let us to model deep and shallow bodies which exhibit very different geometries and density contrasts. So, results indicate that this inversion strategy can be very effective for characterization of volcanic structures, improving the information from previous geologic and volcanologic studies. The inversion model obtained shows correlation between several sources of the gravity field and the volcanic units associated with the growth of La Gomera Island. The main gravity source of this model is associated with the oldest unit, called the Basal Complex. This unit corresponds to the first submarine growth stage and it is modelled as the most important and deepest high density structure. According to previous geological studies, the following edifice (Old Edifice) was also submarine in its initial phases, later being represented by a wide basaltic shield volcano. The original location and morphology of this Old Edifice is deduced from the distribution of positive density contrasts that appears in the model. Moreover, other gravity field sources are identified and associated to several feeding systems of this stage of the volcanism in La Gomera. The shallowest sections of the model let us recognise the distribution of light material inside the Vallehermoso caldera, surrounded by high density structures. This gives us some insight into the internal structure and morphology of the caldera, pointing to a vertical collapse origin followed by erosion and other destructive processes. Finally, other conclusions are obtained from the correlation found between the sources of the gravity field and the migration of the volcanic activity towards the southern area of the island

Tilt observations in the normal mode frequency band at the Geodynamic Observatory Cueva de los Verdes, Lanzarote

We have conducted observations with the aid of a seismo-tiltmeter station, which is based on the Ostrovsky pendulum and installed at the Geodynamic Observatory Cueva de los Verdes at Lanzarote Island since 1995. In this station the signal is separated into two frequency bands – tidal tilts (from 0 to 5 mHz) and ground oscillations in the frequency range of free Earth’s normal modes (from 0.2 to 5 mHz). The later band, called accelerometer channel, has additional amplification. We analyzed the background records in the frequency range of Earth’s free oscillations from August 2000 to September 2001, as well as, Earth’s normal modes after strong earthquakes. We found several distinctive persistent peaks in the spectra of background oscillations. Both amplitudes of distinguished peaks and noises have seasonal variations. We found that spectra of background oscillations are different in the frequency interval between 1.4 and 2.5 mHz for North- South and East-West components

Verifying the body tide at the Canary Islands using tidal gravimetry observations

Gravity tide records from El Hierro, Tenerife and Lanzarote Islands (Canarian Archipelago) have been analyzed and compared to the theoretical body tide model (DDW) of Dehant el al. (1999). The use of more stringent criterion of tidal analysis using VAV program allowed us to reduce the error bars by a factor of two of the gravimetric factors at Tenerife and Lanzarote compared with previous published values. Also, the calibration values have been revisited at those sites. Precise ocean tide loading (OTL) corrections based on up-to-date global ocean models and improved regional ocean model have been obtained for the main tidal harmonics O1, K1, M2, S2.We also point out the importance of using the most accurate coastline definition for OTL calculations in the Canaries. The remaining observational errors depend on the accuracy of the calibration of the gravimeters and/or on the length of the observed data series. Finally, the comparison of the tidal observations with the theoretical body tide models has been done with an accuracy level of 0.1% at El Hierro, 0.4% at Tenerife and 0.5% at Lanzarote

Exploring deformation scenarios in Timanfaya volcanic area (Lanzarote, Canary Islands) from GNSS and ground based geodetic observations

We report on a detailed geodetic continuous monitoring in Timanfaya volcanic area (TVA), where the most intense geothermal anomalies of Lanzarote Island are located. We analyze about three years of GNSS data collected on a small network of five permanent stations, one of which at TVA, deployed on the island, and nearly 20 years of tiltmeter and strainmeter records acquired at Los Camelleros site settled in the facilities of the Geodynamics Laboratory of Lanzarote within TVA. This study is intended to contribute to understanding the active tectonics on Lanzarote Island and its origin, mainly in TVA. After characterizing and filtering out the seasonal periodicities related to “non-tectonic” sources from the geodetic records, a tentative ground deformation field is reconstructed through the analysis of both tilt, strain records and the time evolution of the baselines ranging the GNSS stations. The joint interpretation of the collected geodetic data show that the area of the strongest geothermal anomaly in TVA is currently undergoing a SE trending relative displacement at a rate of about 3 mm/year. This area even experiences a significant subsidence with a maximum rate of about 6 mm/year. Moreover, we examine the possible relation between the observed deformations and atmospheric effects by modelling the response functions of temperature and rain recorded in the laboratory. Finally, from the retrieval of the deformation patterns and the joint analysis of geodetic and environmental observations, we propose a qualitative model of the interplaying role between the hydrological systems and the geothermal anomalies. Namely, we explain the detected time correlation between rainfall and ground deformation because of the enhancement of the thermal transfer from the underground heat source driven by the infiltration of meteoric water.Depto. de Física de la Tierra y AstrofísicaFac. de Ciencias MatemáticasTRUEpu