Development of numerical methods to determine the litospheic structure combining geopetential, litosthatic and heat transport equations. Application to the Gibraltar arc system

Detailed modelling of the present-day lithospheric structure is of paramount importance to understand the evolution of the Earth in the context of plate tectonics. The objectives of this thesis are twofold: the development of numerical methods to determine the lithospheric structure combining geopotential, lithostatic and heat transport equations, and the application of these methods to the study area, the Gibraltar Arc System region (GAS). The final product should be a useful 3D tool to analyse the lithosphere integrating, in a consistent manner, the thermal field, elevation, geoid and gravity anomalies, and SHF. In this sense, four main goals are: 1) Development of a numerical code to compute Bouguer anomalies from publicly available satellite-derived free air data in both continental and marine areas. 2) Development of a 1D method to calculate a first order lithospheric structure using elevation and geoid anomaly as input data. 3) Development of a 3D interactive code to perform lithospheric forward modelling, integrating SHF, gravity and geoid anomalies, and elevation. 4) Obtain a 3D image of the lithosphere geometry over the study region independent from seismic tomography in order to improve our knowledge of the deep, present day, lithospheric structure of the GAS region, and discuss the different geodynamic models proposed to explain its origin. FA2BOUG is a FORTRAN 90 code to compute Bouguer anomaly specially intended to work with global elevation and free air data bases (Chapter 3). The program is designed to calculate in both continental and oceanic areas. Chapter 4 deals with a method based on the combination of elevation and geoid anomaly data that allows for a rapid calculation of the crustal and lithospheric thickness over large regions under the assumption of local isostasy, thermal steady state, linear vertical density gradient for the crust, and temperature dependent mantle density. Chapter 5 presents GEO3Dmod, a computer program intended to perform interactive 3D lithospheric forward modelling, integrating SHF, elevation, gravity anomaly and geoid anomaly. The program consists of two modules. The first one (GEO3Dmod) resolves the direct problem, i.e. given a lithospheric model (a set of layers with different properties), it calculates the 3D thermal and density structure of the lithosphere and the associated geophysical observables. The second one (GEO3Dmod_INTF) is a graphical interface designed to visualize and modify the lithospheric st