Identification of snow avalanche release areas and flow characterization based on seismic data studies
[eng] The main objectives of this PhD thesis are the identification of the snow avalanche release areas and the snow avalanche flow regime characterization with the use of seismic data. We aim to search for new methods for conducting detailed studies of the seismic signal generated by snow avalanche...
| Autor: | |
|---|---|
| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2021 |
| País: | España |
| Institución: | Universidad de Barcelona |
| Repositorio: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/180200 |
| Acceso en línea: | https://hdl.handle.net/2445/180200 http://hdl.handle.net/10803/672460 |
| Access Level: | acceso abierto |
| Palabra clave: | Allaus Neu Sismologia Avalanches Snow Seismology |
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Identification of snow avalanche release areas and flow characterization based on seismic data studies |
| title |
Identification of snow avalanche release areas and flow characterization based on seismic data studies |
| spellingShingle |
Identification of snow avalanche release areas and flow characterization based on seismic data studies Roig-Lafon, Pere Allaus Neu Sismologia Avalanches Snow Seismology |
| title_short |
Identification of snow avalanche release areas and flow characterization based on seismic data studies |
| title_full |
Identification of snow avalanche release areas and flow characterization based on seismic data studies |
| title_fullStr |
Identification of snow avalanche release areas and flow characterization based on seismic data studies |
| title_full_unstemmed |
Identification of snow avalanche release areas and flow characterization based on seismic data studies |
| title_sort |
Identification of snow avalanche release areas and flow characterization based on seismic data studies |
| dc.creator.none.fl_str_mv |
Roig-Lafon, Pere |
| author |
Roig-Lafon, Pere |
| author_facet |
Roig-Lafon, Pere |
| author_role |
author |
| dc.contributor.none.fl_str_mv |
Suriñach Cornet, Emma Universitat de Barcelona. Departament de Dinàmica de la Terra i de l'Oceà |
| dc.subject.none.fl_str_mv |
Allaus Neu Sismologia Avalanches Snow Seismology |
| topic |
Allaus Neu Sismologia Avalanches Snow Seismology |
| description |
[eng] The main objectives of this PhD thesis are the identification of the snow avalanche release areas and the snow avalanche flow regime characterization with the use of seismic data. We aim to search for new methods for conducting detailed studies of the seismic signal generated by snow avalanches, considered as a moving seismic source. One of the main bases for achieving these objectives is to use widely tested seismological methods designed for the study of single seismic sources. In order to adapt them to a record of a moving source generating seismic vibrations (snow avalanches), we decided to apply windowing methods to the seismic signal so that the seismic signal could be processed in small portions. Over each time window of the seismic signal, we perform the study of ground particle motion polarization (3D) and obtain the frequency content information (Power Spectral Density). In the seismic signal produced by snow avalanches can be identified sections linked to the relative position of the avalanche front with respect to the position of the seismic sensor. The evolution of the total envelope of the seismic signal (At(t)) allows us to establish a criterion for the identification of the different sections based on the seismic signal amplitude. Furthermore, we are able to identify the moment when the snow avalanche mass starts to move (first vibrations generated by the avalanche) using an appropriate configuration of the STA/LTA algorithm adapted for our purposes. For each of the sections of the seismic signal, we apply a different methodology to obtain different information about the snow avalanche flow in each avalanche part. We seek to identify the snow avalanche release area by analysing the signal produced at the beginning of the snow avalanche mass movement (Signal Onset - SON). The study of the polarization of the ground particle motion (3D, ZNE coordinate system) makes it possible to identify the area where the first vibrations are generated, and by extension link it to the start of the snow avalanche mass movement. By analysing the seismic signal section corresponding to when the snow avalanche mass is flowing over the seismic sensor (Signal Over the sensor - SOV), we characterize the snow avalanche flow and identify the different regions in the snow avalanche body. The seismic signal is rotated to the QLT coordinate system in order to better link the information of the seismic signal to the flow progression direction. Work on this PhD thesis has also enabled us to establish a homogenization of the seismic data processing steps for studying snow avalanches. We automated these processes for all the data acquired in the Vallée de la Sionne test site between winter seasons 2013 and 2020, thereby creating a database consisting of more than 420 seismic events (source: automatic data acquisition system activations at VDLS). From all these events we managed to identify the snow avalanches and to test the procedures designed in this thesis for the release area identification and the flow characterization. Although the designed methods are subject to some limitations, we consider that the contribution to novel approaches for the study of the seismic signal produced by moving sources is proved. The release area identification has a very good success rate (78%) in a supervised application. The automated execution could be improved with a better isolation process for the seismic signal SON section. The method for the flow characterization provides new information regarding the interaction of the flow with the ground and with the snow cover. We consider that future studies in this direction may yield information about the snow avalanche basal friction as an indirect measurement. |
| publishDate |
2021 |
| dc.date.none.fl_str_mv |
2021 |
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info:eu-repo/semantics/doctoralThesis info:eu-repo/semantics/publishedVersion |
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doctoralThesis |
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publishedVersion |
| dc.identifier.none.fl_str_mv |
https://hdl.handle.net/2445/180200 http://hdl.handle.net/10803/672460 |
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https://hdl.handle.net/2445/180200 http://hdl.handle.net/10803/672460 |
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Inglés |
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Inglés |
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cc by-nc-sa (c) Roig-Lafon, Pere, 2021 http://creativecommons.org/licenses/by-nc-sa/3.0/es/ info:eu-repo/semantics/openAccess |
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cc by-nc-sa (c) Roig-Lafon, Pere, 2021 http://creativecommons.org/licenses/by-nc-sa/3.0/es/ |
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openAccess |
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application/pdf |
| dc.publisher.none.fl_str_mv |
Universitat de Barcelona |
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Universitat de Barcelona |
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Tesis Doctorals - Departament - Dinàmica de la Terra i de l'Oceà reponame:Dipòsit Digital de la UB instname:Universidad de Barcelona |
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Universidad de Barcelona |
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Dipòsit Digital de la UB |
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Dipòsit Digital de la UB |
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1869404307694026752 |
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Identification of snow avalanche release areas and flow characterization based on seismic data studiesRoig-Lafon, PereAllausNeuSismologiaAvalanchesSnowSeismology[eng] The main objectives of this PhD thesis are the identification of the snow avalanche release areas and the snow avalanche flow regime characterization with the use of seismic data. We aim to search for new methods for conducting detailed studies of the seismic signal generated by snow avalanches, considered as a moving seismic source. One of the main bases for achieving these objectives is to use widely tested seismological methods designed for the study of single seismic sources. In order to adapt them to a record of a moving source generating seismic vibrations (snow avalanches), we decided to apply windowing methods to the seismic signal so that the seismic signal could be processed in small portions. Over each time window of the seismic signal, we perform the study of ground particle motion polarization (3D) and obtain the frequency content information (Power Spectral Density). In the seismic signal produced by snow avalanches can be identified sections linked to the relative position of the avalanche front with respect to the position of the seismic sensor. The evolution of the total envelope of the seismic signal (At(t)) allows us to establish a criterion for the identification of the different sections based on the seismic signal amplitude. Furthermore, we are able to identify the moment when the snow avalanche mass starts to move (first vibrations generated by the avalanche) using an appropriate configuration of the STA/LTA algorithm adapted for our purposes. For each of the sections of the seismic signal, we apply a different methodology to obtain different information about the snow avalanche flow in each avalanche part. We seek to identify the snow avalanche release area by analysing the signal produced at the beginning of the snow avalanche mass movement (Signal Onset - SON). The study of the polarization of the ground particle motion (3D, ZNE coordinate system) makes it possible to identify the area where the first vibrations are generated, and by extension link it to the start of the snow avalanche mass movement. By analysing the seismic signal section corresponding to when the snow avalanche mass is flowing over the seismic sensor (Signal Over the sensor - SOV), we characterize the snow avalanche flow and identify the different regions in the snow avalanche body. The seismic signal is rotated to the QLT coordinate system in order to better link the information of the seismic signal to the flow progression direction. Work on this PhD thesis has also enabled us to establish a homogenization of the seismic data processing steps for studying snow avalanches. We automated these processes for all the data acquired in the Vallée de la Sionne test site between winter seasons 2013 and 2020, thereby creating a database consisting of more than 420 seismic events (source: automatic data acquisition system activations at VDLS). From all these events we managed to identify the snow avalanches and to test the procedures designed in this thesis for the release area identification and the flow characterization. Although the designed methods are subject to some limitations, we consider that the contribution to novel approaches for the study of the seismic signal produced by moving sources is proved. The release area identification has a very good success rate (78%) in a supervised application. The automated execution could be improved with a better isolation process for the seismic signal SON section. The method for the flow characterization provides new information regarding the interaction of the flow with the ground and with the snow cover. We consider that future studies in this direction may yield information about the snow avalanche basal friction as an indirect measurement.[cat] En aquesta tesi els objectius principals són la identificació de les zones d’alliberament d’allaus de neu i la caracterització del seu tipus de flux a partir de l’ús de dades sísmiques. Perseguim noves maneres de realitzar una caracterització detallada del senyal sísmic generat per allaus de neu. Ens basem en l’ús de mètodes sismològics àmpliament provats per a l'estudi de fonts sísmiques puntuals. Per tal de poder implementar aquests mètodes al registre sísmic d’una font sísmica en moviment (allaus de neu), utilitzem procediments de tractament del senyal en finestres de temps. En cada finestra del senyal sísmic, realitzem l’estudi de la polarització del moviment de la partícula (3D) i n’obtenim la informació del contingut en freqüències. L’evolució de l’evolvent total del senyal sísmic (At(t)), ens permet establir un criteri per a la identificació de diferents seccions en el senyal, relacionades amb la posició relativa de l’allau respecte el sensor sísmic. També podem identificar l’instant en què s’inicia el moviment de l’allau mitjançant una configuració adequada de l’algorisme STA/LTA. En cadascuna d’aquestes seccions hi apliquem una metodologia diferent per tal d’obtenir informació específica. Amb l'estudi de la polarització del moviment de la partícula sísmica en l’anàlisi del senyal sísmic produït per l’inici del moviment de l’allau de neu (secció SON), és possible identificar l'àrea des d'on es generen les primeres vibracions (78% de taxa d’èxit). Analitzant el senyal sísmic corresponent al pas de l’allau per sobre el sensor sísmic (secció SOV), caracteritzem el tipus de flux i identifiquem les regions en el cos de l’allau a partir de l’evolució del moviment de la partícula sísmica i l’evolució del contingut en freqüències. L'elaboració d'aquesta tesi també ens ha portat a homogeneïtzar i automatitzat els passos en el processament de dades sísmiques per a l’estudi de les allaus, creant una base de dades amb més de 420 esdeveniments sísmics al lloc experimental de Vallée de la Sionne (2013-2020). Tot i que trobem algunes limitacions, considerem que queda demostrada la contribució en nous enfocaments per a l’estudi del senyal sísmic produït per fonts sísmiques en moviment.Universitat de BarcelonaSuriñach Cornet, EmmaUniversitat de Barcelona. Departament de Dinàmica de la Terra i de l'Oceà2021info:eu-repo/semantics/doctoralThesisinfo:eu-repo/semantics/publishedVersionapplication/pdfhttps://hdl.handle.net/2445/180200http://hdl.handle.net/10803/672460Tesis Doctorals - Departament - Dinàmica de la Terra i de l'Oceàreponame:Dipòsit Digital de la UBinstname:Universidad de BarcelonaIngléscc by-nc-sa (c) Roig-Lafon, Pere, 2021http://creativecommons.org/licenses/by-nc-sa/3.0/es/info:eu-repo/semantics/openAccessoai:diposit.ub.edu:2445/1802002026-05-27T06:46:51Z |
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15,300719 |