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Détermination non-linéaire des paramètres hypocentraux et structuraux : application à la sismicité intracontinentale du Massif armoricain

Abstract : The most widely used inversion schemes to determine local or regional earthquake sources (epicenter, depth and origin time), are based on iterative linearized least-squares algorithms and strongly depend on an a priori knowledge. We introduce a joint structure-source determination approach for one or several events. This procedure manages to get away from dependence on an initial solution and minimizes the influence of poorly known seismic velocity structure used for calculating the propagation time. The exploration relies on parallel Markov chain Monte Carlo techniques, which sample models within a broad range of parameters, distributed according to the posterior distributions. The arrival time uncertainties of direct and refracted waves on the Mohorovičić discontinuity, defined by hand-picking, are fully exploited by Bayesian inference and lead the nonlinear determination. The analysis of covariances between parameters and the projections of the structure parameter variations on the source parameter space provide information about the influence of the seismic network geometry (sparse and/or azimuthally inhomogeneous), or an inappropriate velocity structure. This procedure is applied to the moderate and diffuse local seismicity of the Armorican Massif (western France), an extensive outcrop of the Variscan basement, which crustal structure is apprehended with large uncertainties. The accurate location of 350 earthquakes, with a set of more than 7,000 onset time of seismic-waves recorded by permanent and temporary networks between 2011 and 2013, sheds new light on the seismicity and the structure of the Armorican Massif.
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https://tel.archives-ouvertes.fr/tel-01396016
Contributor : Méric Haugmard Connect in order to contact the contributor
Submitted on : Wednesday, March 8, 2017 - 12:18:39 PM
Last modification on : Sunday, November 27, 2022 - 3:02:09 PM
Long-term archiving on: : Friday, June 9, 2017 - 1:46:51 PM

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  • HAL Id : tel-01396016, version 1

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Méric Haugmard. Détermination non-linéaire des paramètres hypocentraux et structuraux : application à la sismicité intracontinentale du Massif armoricain. Géophysique [physics.geo-ph]. Université Bretagne Loire, 2016. Français. ⟨NNT : ⟩. ⟨tel-01396016⟩

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