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Ondelettes continues en Sciences de la Terre - méthodes et applications -

Abstract : This work is devoted to the development of processing methods of Earth and Planetary Sciences data. Because geophysical and geological signals are, by nature, characterised by complex dynamics, non-stationarity and/or multi-scale behaviour, their analysis could be considerably improved by the use of non-stationary methods. So, we propose to use methods based on the mathematical formalism of the wavelet transform. Presented and illustrated on various synthetic and natural examples, local and multi-scale wavelets properties offer many advantages in respect to classical signal analysis methods (Fourier Transform, Windowed Fourier Transform ...). In particular, the one- or two- dimensional developed techniques transform the information into a “space-scale” representation revealing the complex dynamics, the multi-scale behaviour and/or the interactions within the investigated system. Requiring any hypothesis on the nature of the analysed signal, these techniques are general-purpose and allow the recognition of the processes acting on various systems. - Applied to the study of relative geomagnetic paleointensity, the re-inspection of magnetic records from Ocean Drilling Program (ODP) Site 983, characterised by significant components close to the Earth orbital parameters (eccentricity, obliquity, precession), suggested that the orbital frequencies embedded in the paleointensity record are the expression of lithologic variations, and probably not a characteristic of the geodynamo itself, and confirmed the representativity of the paleointensity record and its usefulness to be correlated to other records. - In the frame of seismic monitoring, we have developed an automatic seismic phase picking algorithm. Used as band-pass filters intrinsically well localised in time and frequency, wavelets allow quasi real time picking of local and teleseismic events, rejecting uncertain picks and noise. - Based on methodological developments related with the investigation of two-dimensional galaxies fields and fractures fields, we have developed a new method which applied to the study of mineral organisation of magmatic rock sections enabled us to detect and quantify in terms of size, shape, orientation and spatial distribution the different levels of mineral organisation, and consequently to better define the dynamical history of the plutons. - Applied to the the spatial distribution of seismic events the 1980 Arudy earthquake sequence (M=5.1, Western Pyrennes), 2D anisotropic wavelets allowed identification of the possible active rupture planes which combined with available focal mechanisms and geological and geomorphological markers leaded to propose and validate a local tectonic model which takes the form of a horse tail termination of an E-W sub-vertical dextral strike-slip fault.
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https://tel.archives-ouvertes.fr/tel-00007019
Contributor : Philippe Gaillot <>
Submitted on : Sunday, October 3, 2004 - 11:30:45 AM
Last modification on : Friday, January 10, 2020 - 9:09:03 PM
Long-term archiving on: : Wednesday, November 23, 2016 - 5:10:13 PM

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  • HAL Id : tel-00007019, version 1

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Philippe Gaillot. Ondelettes continues en Sciences de la Terre - méthodes et applications -. Traitement du signal et de l'image [eess.SP]. Université Paul Sabatier - Toulouse III, 2000. Français. ⟨tel-00007019⟩

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