Seismic Attenuation Analysis using Lg waves and Ambient Noise Recordings: Application to the Iberian Peninsula and Morocco

In this thesis I have carried out a comprehensive study of the attenuation properties of the Earth´s crust of the Iberia-Morocco region (IMR). I have investigated the crustal attenuation by means of the quality factor Q, which is inversely proportional to attenuation, using both earthquakes and nois...

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Detalles Bibliográficos
Autor: Noriega, R.
Tipo de recurso: tesis doctoral
Estado:Versión publicada
Fecha de publicación:2016
País:España
Institución:Consejo Superior de Investigaciones Científicas (CSIC)
Repositorio:DIGITAL.CSIC. Repositorio Institucional del CSIC
OAI Identifier:oai:digital.csic.es:10261/149605
Acceso en línea:http://hdl.handle.net/10261/149605
Access Level:acceso abierto
Palabra clave:Seismic prospecting
Seismology
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spelling Seismic Attenuation Analysis using Lg waves and Ambient Noise Recordings: Application to the Iberian Peninsula and MoroccoNoriega, R.Seismic prospectingSeismologyIn this thesis I have carried out a comprehensive study of the attenuation properties of the Earth´s crust of the Iberia-Morocco region (IMR). I have investigated the crustal attenuation by means of the quality factor Q, which is inversely proportional to attenuation, using both earthquakes and noise-derived measurements. In order to fulfill the thesis objectives a large dataset including earthquake waveforms and seismic noise records has been used. Three different traditional earthquake methods have been implemented to estimate Q in the IMR: the two-station (TS) method, the coda normalization (CN) method and the spectral amplitude decay (SAD) method. For the estimation of Q, these approaches measure the spectral amplitude of the Lg wave (direct and coda) of regional events. Among all the methods evaluated, the TS method allows imaging the spatial variation of the Lg wave attenuation in the Iberian Peninsula whereas the CN and the SAD methods only estimate average attenuation values as well as its frequency dependence. For the Iberian Peninsula, high Lg Q values are observed in the stable Iberian Massif in western Iberia, while lower values are mainly found in the Pyrenean Range and in eastern and southern Iberia. For Morocco, the CN and the SAD methods produce similar results, indicating that the Lg Q models are robust to differences in the methodologies. The frequency-dependent Q estimates represent an average attenuation across a broad region of different structural domains and correlate well with areas of moderate seismicity. Additionally, I have studied the Lg propagation efficiency across the IMR. Results reflect an inefficient or even blocked propagation across the Gulf of Cádiz and for most paths crossing the western Alboran basin. The continental crust of the Iberian Peninsula and Morocco shows efficient Lg propagation. I have also investigated the potential of using ambient noise measurements to retrieve information about the anelastic structure of the Earth´s crust. Since noise preprocessing techniques modify the amplitude of the recovered empirical Green function of the medium, additional tests have to be done in order to verify the reliability of the attenuation results obtained. In this regard, I have carefully examined the influence of the distribution of noise sources and receivers on Q estimates. Azimuthally and spatially averaged Q values derived from noise recordings were further compared with earthquake attenuation measurements. Results reveal that the average Q estimates are in concordance with previous long-period surface-wave measurements from earthquakes in the central part of the Iberian Peninsula. Accurate Q estimates are also found in Morocco. I would like to emphasize that this thesis presents new contributions and improvements to the knowledge of the attenuation structure of the IMR. The first regional map that images the lateral variation of the Lg Q has been estimated for the Iberian Peninsula improving the spatial resolution of earlier studies.Programa Consolider-INGENIO 2010 TOPOIBERIA (CSD2006-00041 y proyecto Repsol CO-DOSPeer ReviewedUniversidad de BarcelonaJurado, Maria JoséVillaseñor, AntonioRepsolConsejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72]2017201720162017info:eu-repo/semantics/doctoralThesishttp://purl.org/coar/resource_type/c_db06Publisher's versioninfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/10261/149605reponame:DIGITAL.CSIC. Repositorio Institucional del CSICinstname:Consejo Superior de Investigaciones Científicas (CSIC)InglésSíinfo:eu-repo/semantics/openAccessoai:digital.csic.es:10261/1496052026-05-22T06:33:51Z
dc.title.none.fl_str_mv Seismic Attenuation Analysis using Lg waves and Ambient Noise Recordings: Application to the Iberian Peninsula and Morocco
title Seismic Attenuation Analysis using Lg waves and Ambient Noise Recordings: Application to the Iberian Peninsula and Morocco
spellingShingle Seismic Attenuation Analysis using Lg waves and Ambient Noise Recordings: Application to the Iberian Peninsula and Morocco
Noriega, R.
Seismic prospecting
Seismology
title_short Seismic Attenuation Analysis using Lg waves and Ambient Noise Recordings: Application to the Iberian Peninsula and Morocco
title_full Seismic Attenuation Analysis using Lg waves and Ambient Noise Recordings: Application to the Iberian Peninsula and Morocco
title_fullStr Seismic Attenuation Analysis using Lg waves and Ambient Noise Recordings: Application to the Iberian Peninsula and Morocco
title_full_unstemmed Seismic Attenuation Analysis using Lg waves and Ambient Noise Recordings: Application to the Iberian Peninsula and Morocco
title_sort Seismic Attenuation Analysis using Lg waves and Ambient Noise Recordings: Application to the Iberian Peninsula and Morocco
dc.creator.none.fl_str_mv Noriega, R.
author Noriega, R.
author_facet Noriega, R.
author_role author
dc.contributor.none.fl_str_mv Jurado, Maria José
Villaseñor, Antonio
Repsol
Consejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72]
dc.subject.none.fl_str_mv Seismic prospecting
Seismology
topic Seismic prospecting
Seismology
description In this thesis I have carried out a comprehensive study of the attenuation properties of the Earth´s crust of the Iberia-Morocco region (IMR). I have investigated the crustal attenuation by means of the quality factor Q, which is inversely proportional to attenuation, using both earthquakes and noise-derived measurements. In order to fulfill the thesis objectives a large dataset including earthquake waveforms and seismic noise records has been used. Three different traditional earthquake methods have been implemented to estimate Q in the IMR: the two-station (TS) method, the coda normalization (CN) method and the spectral amplitude decay (SAD) method. For the estimation of Q, these approaches measure the spectral amplitude of the Lg wave (direct and coda) of regional events. Among all the methods evaluated, the TS method allows imaging the spatial variation of the Lg wave attenuation in the Iberian Peninsula whereas the CN and the SAD methods only estimate average attenuation values as well as its frequency dependence. For the Iberian Peninsula, high Lg Q values are observed in the stable Iberian Massif in western Iberia, while lower values are mainly found in the Pyrenean Range and in eastern and southern Iberia. For Morocco, the CN and the SAD methods produce similar results, indicating that the Lg Q models are robust to differences in the methodologies. The frequency-dependent Q estimates represent an average attenuation across a broad region of different structural domains and correlate well with areas of moderate seismicity. Additionally, I have studied the Lg propagation efficiency across the IMR. Results reflect an inefficient or even blocked propagation across the Gulf of Cádiz and for most paths crossing the western Alboran basin. The continental crust of the Iberian Peninsula and Morocco shows efficient Lg propagation. I have also investigated the potential of using ambient noise measurements to retrieve information about the anelastic structure of the Earth´s crust. Since noise preprocessing techniques modify the amplitude of the recovered empirical Green function of the medium, additional tests have to be done in order to verify the reliability of the attenuation results obtained. In this regard, I have carefully examined the influence of the distribution of noise sources and receivers on Q estimates. Azimuthally and spatially averaged Q values derived from noise recordings were further compared with earthquake attenuation measurements. Results reveal that the average Q estimates are in concordance with previous long-period surface-wave measurements from earthquakes in the central part of the Iberian Peninsula. Accurate Q estimates are also found in Morocco. I would like to emphasize that this thesis presents new contributions and improvements to the knowledge of the attenuation structure of the IMR. The first regional map that images the lateral variation of the Lg Q has been estimated for the Iberian Peninsula improving the spatial resolution of earlier studies.
publishDate 2016
dc.date.none.fl_str_mv 2016
2017
2017
2017
dc.type.none.fl_str_mv info:eu-repo/semantics/doctoralThesis
http://purl.org/coar/resource_type/c_db06
Publisher's version
info:eu-repo/semantics/publishedVersion
format doctoralThesis
status_str publishedVersion
dc.identifier.none.fl_str_mv http://hdl.handle.net/10261/149605
url http://hdl.handle.net/10261/149605
dc.language.none.fl_str_mv Inglés
language_invalid_str_mv Inglés
dc.relation.none.fl_str_mv Sí
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
eu_rights_str_mv openAccess
dc.publisher.none.fl_str_mv Universidad de Barcelona
publisher.none.fl_str_mv Universidad de Barcelona
dc.source.none.fl_str_mv reponame:DIGITAL.CSIC. Repositorio Institucional del CSIC
instname:Consejo Superior de Investigaciones Científicas (CSIC)
instname_str Consejo Superior de Investigaciones Científicas (CSIC)
reponame_str DIGITAL.CSIC. Repositorio Institucional del CSIC
collection DIGITAL.CSIC. Repositorio Institucional del CSIC
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repository.mail.fl_str_mv
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