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Badal, J.
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Badal, J.
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- PublicationOpen AccessA proper methodology aimed at surface wave tomography(1997-01)
; ; ; ;Sabadell, F. J.; Civil Engineering School, Polytechnic, University of Cataluña, Barcelona, Spain ;Serón, F. J.; Department of System Engineering and Computer Sciences, CPS, University of Zaragoza, Zaragoza, Spain ;Badal, J.; Department of Theoretical Physics and Geophysics, University of Zaragoza, Zaragoza, Spain; ; When applying a methodology for obtaining the 3D shear-wave velocity structure of a medium from surface wave dispersion data, the problem must be considered with caution since one inverts path-averaged velocities and the use of any inversion method entails some drawbacks such as lack of uniqueness, unwarranted stability and constraints affecting the data. In order to avoid the application of consecutive inversions and to overcome these drawbacks, we propose alternative mapping methods, for example spatial prediction methods, or else the use of an algorithm that, from a mathematical viewpoint, can be understood through the application of the orthogonal projection theorem onto convex sets (POCS). Among the first ones, we try inverse weighted distance interpolation. The POCS algorithm we have used discretises a second order differential equation for the velocity field with boundary conditions. All these imaging techniques aimed at volumetric modelling and the visualisation of data are discussed, and finally we show some results based on ray path velocities obtained previously by inversion of phase and group velocities of Rayleigh waves propagating across the Iberian peninsula.135 393 - PublicationOpen AccessPreliminary objective regionalization of the Mediterranean basin derived from surface-wave tomography(1997-01)
; ; ; ; ; ;Martínez, M. D.; Departament de F¡sica Aplicada, Universitat Politècnica de Catalunya, ETSAB, Barcelona, Spain ;Lana, X.; Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya, ETSEIB, Barcelona, Spain ;Badal, J.; Departamento de Física Teórica-Geof¡sica, Universidad de Zaragoza, Zaragoza, Spain ;Canas, J. A.; Departament d'Enginyeria del Terreny, Universitat Politècnica de Catalunya, ETSECCPB, Barcelona, Spain ;Pujades, L.; Departament d'Enginyeria del Terreny, Universitat Politècnica de Catalunya, ETSECCPB, Barcelona, Spain; ; ; ; An objective regionalization of the Mediterranean basin is derived from a tomographic study based on the fundamental mode of Rayleigh waves. The database is formed by seismic wavetrains recorded at very-broadband stations belonging to MedNet and other cooperative stations, located in the Mediterranean area. The data treatment consists of application of spectral filtering techniques aimed to determine path-averaged group velocities, computation of local group velocity maps for some periods and classification of the studied area in several homogeneous regions according to Principal Component Analysis (PCA) and Average Linkage (AL) algorithms. Finally, the group velocity dispersion curves representing each homogeneous region are compared and possible correlation between these regions and seismotectonic and structural characteristics are discussed.119 254