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This new research sub-line, part of the Research Line/Department at Institute of Geosciences “Earth Dynamics and Earth Observation”, includes the activities of four previously existing research groups: (i) Space Geodesy,Gravimetry and Geomathematics, (ii) Palaeomagnetism, Rock Magnetism and Geomagnetic Modelling, (iii) Terrestrial and Planetary Magnetic Field and Aeronomy, and (iv)Gravimetry, Tides and Geodynamics. These four research groups, which are included on it to work together and cooperate during the next years, have been working until now independently and with very few cooperation between them. In short, it includes the study and modelling of the Earth’s (and others celestial bodies’) shape, gravity and magnetic fields, and their variations in time and space, using terrestrial and space integrated geodetic, gravimetric, geomagnetic and paleomagnetic data and advanced mathematical models and techniques.

Comunicación presntada a la 3ª Asamblea Hispano-Portuguesa de Geodesia y Geofísica = 3ª Assembleia Luso-Espanhola de Geodesia e Geofisica, celebrada en Valencia entre el 4 y el 8 de febrero de 2002., In this work, an analytical method based on the formulas by Mindlin (1936) is used to model the displacementfield and traction changes associated to the dynamic of a volcanic source. We summarized the set of analytical expressions of the displacement field due to a concentrated force and a center of dilation in a uniform halfspace. This kind of sources could be used to simulate the interaction of the magma intrusion mass with the hosting rack and the magma pressure change of the chamber due lo thermal effects or overfilling. This solution accounts for the effect of opposite signs for both types of sources. The dynamic of volcanic processes involves high strain and stress changes in the medium around the magma chamber. These local changes modify the regional tectonic stress field and can cause the failure of the rack containing the magma chamber. Modelling of such changes could be importantfor interpreting the evolution ofvolcanic unrests and the seismicity generated during unrests episodes.

Comunicación presntada a la 3ª Asamblea Hispano-Portuguesa de Geodesia y Geofísica = 3ª Assembleia Luso-Espanhola de Geodesia e Geofisica, celebrada en Valencia entre el 4 y el 8 de febrero de 2002., We have investigated the effects of the topography on the surface deformation and gravity changes caused by a magmatic infrusion in the Earth's crust. Considering axisymmetrical volcanoes and the varying depth methodology we show that topography has significant effecf on the magnitude of the predicted displacements and gravity changes. We see the reducfion of the magnitude close to the summit of the volcano. The topography effect is emphasized if we introduce the mass of the intrusion jointly with the dilation/compression of the magma chamber due to pressure change. Using the elastic-gravitational model introduced by Rundle (1980) that considers the interaciion of the intrusion mass with the ambient gravity field we show that neglecting the topographic effects may, in some cases, introduce an error greater than neglecting the ambient gravity field. We apply the described methodology to Mayon volcano, Philippines, to compute the gravity changes caused by an intrusion located in an elastic-gravitational halfspace. It can be seen that inversions based on spherical magma chamber model could gain accuracy by using varying elevation analytical solution. We show that, for inversions based on observed gravity changes, the amount of pressure or mass increment would be significantly underestimated and the depth of the chamber could be overestimated ifthe topography is not considered.

Comunicación presntada a la 3ª Asamblea Hispano-Portuguesa de Geodesia y Geofísica = 3ª Assembleia Luso-Espanhola de Geodesia e Geofisica, celebrada en Valencia entre el 4 y el 8 de febrero de 2002., Since September 1999 to December 2001 Indra Espacio and Spanish Volcanic Research Network (RIV) have been working together in the frame of DECIDE-VOLCANO project, funded by European Space Agency (ESA). The objective of this project was to demonstrate that satellite radar interferometry could be routinelly integrated in the operational volcano monitoring procedures as a complement to field collected data. For this purpose, the scenarios chosen in this project were the Canary Islands (Tenerife, Lanzarote y La Palma) and in a second stage, Ecuador (Tungurahua volcano and Galapagos islands, processing still on-going). Results obtained have been very different in every scenario: at Tenerife island we have found two deformations out of the usual monitoring areas and we have verified the results of no deformations previously obtained in Las Cañadas Caldera with ground surveys; at Lanzarote and La Palma islands we have not found any deformations greater than 3 cm.

Comunicación presntada a la 3ª Asamblea Hispano-Portuguesa de Geodesia y Geofísica = 3ª Assembleia Luso-Espanhola de Geodesia e Geofisica, celebrada en Valencia entre el 4 y el 8 de febrero de 2002., GPS techniques have demonstrated their usefulness in monitoring and detecting deformations, but a low cost-maximum gain technique such as InSAR must be found in order to assure the full surveillance of certain areas of interest. Two deformation areas have been detected using InSAR and two GPS geodetic campaigns have been designed to check these assessments. In this presentation we describe the results of two GPS campaigns conducted one year apart in Tenerife, Canary lslands, and designed to detect vertical movement. The results of these campaigns will provide future considerations about time span, number of points and general observation and documentation issues in order to obtain reliable results. We also describe in detail how the observation methodology and instrumentation were designed to avoid systematic errors in height and assure the necessary quality of the data.

Comunicación presntada a la 3ª Asamblea Hispano-Portuguesa de Geodesia y Geofísica = 3ª Assembleia Luso-Espanhola de Geodesia e Geofisica, celebrada en Valencia entre el 4 y el 8 de febrero de 2002., To define the most suitable volcano monitoring system is a particularly difficu/t task in the absence of recent activity. It must take into account not only the technical optimization of the monitoring systems, but also their economic and scientific profitability. Traditionally, observations of seismic, hydrologic, or fumarolic activity have proven useful. Since volcanic activity almost inevitably produces deformation and gravity changes before, during, between and after the events geodetic techniques are now included, in the light of the lA VCEJ's recommendations regarding routine monitoring. They are proving to be a powerful tool in the monitoring of volcanic activity detecting anomalies somefimes months or weeks before the magma jlow leads to earthquakes or other eruption precursors. Geodetic monitoring thus complements seismic monitoring by extending the study of volcanic phenomena from seconds to years and providing details on the growth of magma bodies within the volcano. Canary Islands, with a population of about 1.8 mil/ion people, are located less than /00 km from the African continent. They were formed on the continental rise and slope as independent structures. Despite being on a passive margin, they are a volcanic archipelago with a long-standing history of volcanic activity that began more than 40 m.y. ago. At least a dozen eruptions occurred on the islands ofLanzarote, Tenerife, and La Palma between /500 and 197 J. Several different types of volcanic manifestations, which follow a time pattern are to be seen on the Canary Islands. This is a typical case in which the volcanic monitoring system must be carefully designed. The system must be efficient, but must also make full use of existing facilities and have acceptable installation and running costs, in line with the current inactivity. In this presentation we described a proposal for the geodetic monitoring system in Canary lslands. This monitoring system has been develoloped with base on experimental results from different research projects and the application of theoretical analysis. This system makes used of terrestrial and space geodetic techniques.

Comunicación presntada a la 3ª Asamblea Hispano-Portuguesa de Geodesia y Geofísica = 3ª Assembleia Luso-Espanhola de Geodesia e Geofisica, celebrada en Valencia entre el 4 y el 8 de febrero de 2002., Observations of seismic, hydrologic or fumarolic activity have proven useful as reliable eruption precursors. In the last years, geodetic measurements are being used more extensively in active volcanoes because they have been shown to provide a reliable eruption precursor. Furthermore, ground deformation measurement techniques are attracting more attention, in particular with regard to pre-eruption ground displacement. The introduction of new geodetic techniques such as Global Positioning System (GPS) and Synthetic Aperture Radar Interferometry (SAR) can be highly useful in this context, because both techniques have pro ven to be a suitable tool for ground deformation monitoring of active volcanic areas. In this frame, it is possible to demonstrate the feas ibility of using space technologies for operational decision support demonstration at a volcanic risk scenario like Canary Islands. Particularly, the good existing coherence of volcanic areas makes them very proper for InSAR techniques application. By other hand, the theoretical and observational results of the analysis of sensibility of existing classical networks have made necessary the designing and observation of a GPS network in the island of Tenerife with a global coverage and monitoring purposes. This GPS network would be a complement and checking of InSAR observations performed in the island. The main objective of this job is defining and checking the applicability of a new geodetic monitoring system in Tenerife. In order to gel this, we make use of the existing facilities in the island and the new geodetic space techniques. We try to gel the possibility of detection of deformation at any part of the island. Therefore, the new system must be able to allow us the monitoring of any existing ground movement in the island.

Presented in the First Meeting of Special Study Group 4.176 (Models of temporal variations of the gravity field) of the International Association of Geodesy, We describe theoretical and computational methods developed by our group for the calculation of displacement, gravity and potential changes resulting from different sources (representing magma bodies and faults) in elastic-gravitational and viscoelastic-gravitationallayered media. The existing codes corresponding to the models are also presented with the information about how they can be obtained for scientific use. The results obtained and work currently in progress are also described in this paper., The subsurface deformation associated with earthquake faulting is modeled within a three-dimensional homogeneous half-space. It is found that at the boundary of ruptured fault, the strike slip faulting changes mainly the horizontal displacement field, shear stress; while dip slip events affect primarily both the vertical and horizontal components, normal stress. Yiscoelastic gravitational layered model was utilized for computing the postseismic displacement. The modeled postseismic subsurface uplift for five historical events match the geoid high found in the Himalayas. Such geoid residual may serve as a signature of historical events thus can be used to study the existence of seismic gaps.

El esfuerzo en la corteza debido a la marea terrestre es del orden de 0.03 bares, siendo pocos órdenes de magnitud menor que los esfuerzos que causan los terremotos y las erupciones volcánicas. No obstante, es posible que en determinadas circunstancias puedan disparar ciertos eventos sísmicos. Se han realizado gran número de investigaciones buscando correlaciones entre la generación de terremotos y la amplitud y fase de la marea. Pero mientras que algunos investigadores han aportado resultados estadísticos significativos, otros han obtenido resultados negativos, lo que hace que ésta sea todavía un área de controversia.

Data from heat flow and gramivetric tides are at our disposal in the island of Lanzarote (Canary Islands); its formation is known and, in addition to it, a model of its. crust which provides us with its thicknes is at our disposal. When studying the relationship among these parameters, a disagreement with the results obtained from previous studies is observed; those studies show a clear relationship between positive anomalies in the cosine component of the M2 and 01 waves of the gravimetric tide harmonic development and high values of heat flow; while the heat flow values determined in the island are abnormally high, the cosine components of the residues for these waves, determined by observation, have no abnormal values, and in the case of M2 wave, a negative value. On the other hand, the measured heat flow values are as expected, once the island crust thickness and its recent volcanic activity have been seen.

Since 1988, under the exislinq collaboralion belween the Instituto de Astronomía y Geodesia, the Observaloire Royale de Belgique and the European Center for Geodynamics and Seismology,lhermal measuremenls have be en made in the geodynamlc slalion Cueva de los Verdes (Lanzarole, Canary Islands), that have been used lo check the quality oí the sensors used as well the thermal slablllly of the laboralory. Several experiments have been performed:measuremenls oí vertical and horizontal thermal profiles, continuous records of the temperature In different points of rock and continuos record of the ambient temperature of the laboratory. The measures of the temperature profiles have been made in three observation campaings, the results of which we pr:~ent here. We have achieved precisions in the range of 10 oC. We have found a vertical gradient O.03oC/m in the profile temperature. The long and short period variations of rock and ambient temperature have been studied. The results of the harmonic analysis of those temperatures are presented here.

The Lanzarote underground laboratory. - High precision thermal measurements in the volcanic tube of "La Corona" (Lanzarote). - Structural gravimetric model of Lanzarote island.

The Lanzarote underground laboratory. - High precision thermal measurements in the volcanic tube of "La Corona" (Lanzarote). - Structural gravimetric model of Lanzarote island.

Comunicación presentada en la “VI Asamblea Nacional de Geodesia y Geofísica”, Madrid, 1988., En el marco de los proyectos de investigación que sobre Mareas Terrestres y Geodinámica en las Islas Canarias desarrolla el Instituto de Astronomía y Geodesia, se ha instalado en el interior del túnel volcánico del Volcán de la Corona en Lanzarote, en la zona llamada Cueva de los Verdes, una estación Geodinámica. Uno de los sensores,ya en funcionamiento desde mayo de 1987, es un gravimetro LaCoste Romberg mod. G modificado como instrumento de masa estática (Van Ruymbeke, 1985) con registro continuo, sobre sistema analógico, de las variaciones de la gravedad. En este trabajo se presentan los primeros resultados obtenidos y se discuten dichos resúltados teniendo en cuenta las singularidades de Lanzarote, isla con volcanismo reciente, con fuertes anomalías térmicas, con corteza no continental, etc. y del lugar de emplazamiento de la estación a menos de 3 km de la costa y por consiguiente con una importante infuencia oceánica.

Publicado también en "Proceedings", X International Symposium on Earth Tides., A general discusion about the normalization of gravimeters in the Iberian Gravity Tide Profile. - An European Tidal Gravity Profile over a 30º Latitude difference (Kevo - Bruxelles - Madrid). - Ocean tides in the nearby of the Iberian Peninsula. Part I: M2 Iberia Map. - Ocean tides in the nearby of the Iberian Peninsula. Part II: S2 Iberia map.

Trabajo presentado en el XI International Symposium on Earth Tides, Helsinki, 1989., Since 1987, and as part of the research project that the I.A.G. is carrying out in the Canary Islands, records are obtained of gravimetric and ocean tides, pressure, temperature, etc. on the island of Lanzarote. The structural and geodynamic features of the island make our observations especially interesting because they may help to further research of the possible correlations of responses to tidal forces and other parameters such as crust structure and thickness, geothermic anomalies, etc. In this paper, we present the results obtained until now and a preliminary appraisal is given of these results in view of various previous hypotheses.

Comunicación presentada en la “VI Asamblea Nacional de Geodesia y Geofísica”, Madrid, 1988., Como se expuso en otra comunicación, se ha desarrollado un modelo digital topográfico de la Isla de Tenerife, una de cuyas aplicaciones es el cálculo de la corrección topográfica de las observaciones grav~métricas efectuadas en la Caldera del Teide y en zonas próximas. El método clásico, que utiliza ábacos a cuyos compartimentos deben asignarse altitudes medias a partir de la cartografía existente, resulta enormemente lento, penoso y no exento de posibles errores personales. Para obtener mayor precisión el modelo d í gí t al de la Isla obtenido a partir del 50.000 del Servicio Geográfico del Ejército, se ha suplementado en la zona de la Caldera con el 25.000 de dicha zona. Se presenta en esta comunicación el método y los resultados obtenidos, para la corrección topográfica, y la comparación de dichos resultados con los que se calculan a partir de emplear el método de Hammer en la primera campaña de observación. Como conclusión podemos decir que las anomalías obtenidas a partir del calculo automático, basado en el modelo digital, son del mismo orden de magnitud que las que se obtuvieron por el método del ábaco pero con la enorme ventaja de ganancia en tiempo y disminución de errores personales

Comunicación presentada en la sesión científica de la Real Academia de Ciencias Exactas, Físicas y Naturales, celebrada el día 4 de mayo de 1988. Publicada a su vez en la revista de la "Real Academia de Ciencias Exactas, Físicas y Naturales de Madrid"., En el presente trabajo se recogen los primeros resultados que, tanto en mareas gravimétricas como en mareas oceánicas, se han obtenido con los sensores instalados por el Instituto de Astronomía y Geodesia en la zona norte de la Isla de Lanzarote. En la introducción se hace una breve descripción de los objetivos de las instalaciones y del estado actual de las mismas., A new geodynamic station was instalated by the Instituto de Astronomía y Geodesia in Lanzarote Island. In this work the first results of the analysis of gravity tidal variations and tide-gauge are presented.

Comunicación presentada en la “VI Asamblea Nacional de Geodesia y Geofísica”, Madrid, 1988., Dentro del proyecto de investigación geodésica y geofísica desarrollado por el Instituto de Astronomía y Geodesia en Canarias, se ha instalado en el lago formado por la intersección del túnel volcánico del volcán de la Corona, con el océano, un mareógrafo de presión con registro analógico y digital cuyo objetivo científico es por un lado el estudio del nivel del mar como parámetro de interés para la auscultación del riesgo volcánico y por otro la evaluación del efecto oceanico de carga como corrección a ser tenida en cuenta para las observaciones gravinlétricas , clinométricas y extensométricas previstas en la Cueva de los Verdes. Los registros obtenidos, de una gran calidad al estar desprovistos de efectos perturbadores de corto periodo tales como oleajes y vientos, han sido analizados armónicamente y se han obtenido los principales armónicos del potencial perturbador. La comparación de estos resultados con los obteni dos por otros mareógrafos costeros nos permiten conocer los retardos producidos por la estructura del propio túnel en su desarrollo submarino.

Comunicación presentada en la “VI Asamblea Nacional de Geodesia y Geofísica”, Madrid, 1988., En esta comunicaclon se hace una síntesis de la génesis, estado actual y planes de futuro en el complejo Geodinámico de la "Cueva de los Verdes" - Jameos del Agua cuya instalación se inició en 1986 y que recientemente ha comenzado la etapa de observaciones.

Trabajo presentado en el XI International Symposium on Earth Tides, Helsinki, 1989, Both in the stations of the "Valle de los Caidos", near Madrid, and in the "Cueva de los Verdes", in Lanzarote, Canary Islands, two sets of data acquisition equipment have been set up that allow for the registration of all the information produced in both stations. Taking into account the special features of both locations, the two systems respond to different building principIes, but their services are mainly similar. In this communication we give a description of both sets of equipment and present the results obtained.

Comunicaciones presentadas en la sesión científica de la Real Academia de Ciencias Exactas, Físicas y Naturales, celebrada el día 4 de mayo de 1988. Publicadas a su vez en la revista de la "Real Academia de Ciencias Exactas, Físicas y Naturales de Madrid"., Influencia del modelo troposférico en la solución de un experimento de Radio Interferometría Geodésica. - Estudio de las deformaciones en zonas volcánicas activas con redes geodésicas: aplicación a la red del Teide. - La estación geodinámica de la Cueva de los Verdes (Lanzarote): primeros resultados de las experiencias realizadas. - Obtención de un modelo de densidad de la Caldera del Teide.

Data acquisition systems in the "Valle de los Caídos" and "Cueva de los Verdes" stations. - Structural and oceanic effects in the gravimetric tides observations in Lanzarote (Canary Islands). - Least square prediction applied to gravimetric tides in Europe.

Comunicaciones presentadas en la "VI Asamblea Nacional de Geodesia y Geofísica", Madrid, 1988., Estación geodinámica del complejo Jameos del Agua - Cueva de los Verdes (Lanzarote): objetivos científicos y estado actual de las instalaciones. - Estudio térmico de una zona de la Cueva de los Verdes (Lanzarote). - Las variaciones periódicas de la gravedad observadas en el tunel volcánico de la Cueva de los Verdes (Lanzarote). - Instalación, observación y análisis de los primeros meses de registro del mareógrafo de presión instalado en el lago de Jameos del Agua (Lanzarote).

Comunicaciones presentadas en la "VI Asamblea Nacional de Geodesia y Geofísica", Madrid, 1988., Modelo topográfico digital de la isla de Tenerife. - Modelo estructural de densidades de la Caldera del Teide obtenido a partir de observaciones gravimétricas. - Cálculo de la corrección topográfica a las observaciones gravimétricas en la Caldera del Teide obtenidas a partir del modelo topográfico digital de la isla de Tenerife.

Land subsidence associated with overexploitation of aquifers is a hazard that commonly affects large areas worldwide. The Lorca area, located in southeast Spain, has undergone one of the highest subsidence rates in Europe as a direct consequence of long-term aquifer exploitation. Previous studies carried out on the region assumed that the ground deformation retrieved from satellite radar interferometry corresponds only to vertical displacement. Here we report, for the first time, the two- and three-dimensional displacement field over the study area using synthetic aperture radar (SAR) data from Sentinel-1A images and Global Navigation Satellite System (GNSS) observations. By modeling this displacement, we provide new insights on the spatial and temporal evolution of the subsidence processes and on the main governing mechanisms. Additionally, we also demonstrate the importance of knowing both the vertical and horizontal components of the displacement to properly characterize similar hazards. Based on these results, we propose some general guidelines for the sustainable management and monitoring of land subsidence related to anthropogenic activities. Introduction, The research has been supported by the Spanish Ministry of Economy and Competitiveness research projects ESP2013-47780-557 C2-1-R and TEC2017-85244-C2-2-P. It is a contribution to the Moncloa Campus of International Excellence.

El objetivo de esta memoria es el estudio de la influencia del campo gravitatorio y la topografía del terreno en el modelado e interpretación de deformaciones y variaciones de gravedad. Tras realizar una introducción de los modelos empleados habitualmente en la interpretación de deformaciones y variaciones de gravedad, se describe brevemente el modelo elástico-gravitatorio. Mediante este modelo se pueden calcular de forma simultánea desplazamientos y variaciones de gravedad. El análisis dimensional de sus ecuaciones muestra la importancia de incluir el campo gravitatorio en el modelado. La consecuencia principal que se extrae de este análisis es que para la interpretación conjunta de deformaciones y variaciones de gravedad mediante modelos de deformación es necesario tener en cuenta tanto la masa de la intrusión como su interacción con el campo gravitatorio que se simula mediante el acoplamiento de las ecuaciones. Mediante un análisis similar se observa cómo el efecto del acoplamiento elástico-gravitatorio se ve enmascarado por el de la topografía del terreno. Por ello, se desarrolla un modelo elástico tridimensional que permite considerar el efecto de la topografía en el cálculo de deformaciones y variaciones de gravedad. Este modelo se resuelve numéricamente mediante el método indirecto de elementos en la frontera. El efecto de la topografía disminuye la magnitud de los desplazamientos y variaciones de gravedad y produce cambios de patrón con respecto a una solución obtenida sobre un semiespacio plano. Por tanto, posee fuertes implicaciones en la determinación de parámetros de fuente mediante la inversión de datos de observación. Así, para finalizar, invirtiendo los desplazamientos y variaciones de gravedad observados en el volcán Mayon (Filipinas) mediante un algoritmo genético, se muestra la variación que experimentan los parámetros de la fuente al tener en cuenta el efecto topográfico.