The assessment and management of landslide hazards and related risks have always been widely studied topics in the scientific community due to their destructive nature and the consequent socio-economic impacts. The occurrence of such events is strongly conditioned by both natural and anthropogenic factors and the definition of adequate prevention and mitigation measures is still a challenging task. One of the current challenges in the academic world is to provide reliable techniques able to forecast and monitor these phenomena in real-time, hence, reducing the adverse nature of their consequences. In order to achieve this objective, in the past decade, geophysical techniques have been integrated into multidisciplinary approaches to monitor slope instability as well as to design early warning monitoring systems. This Ph.D. project is directed towards the analysis, development, and experimentation with novel geophysical technologies and sensors for the monitoring of sites prone to slope stability issues. In detail, the research is focused on the analysis of ambient seismic noise to retrieve features that can provide valuable information concerning slope stability over time and thus, to support already existing technologies for geohazard monitoring. Among the available passive geophysical methods, three types of analysis were chosen due to their capability to yield the variation of the recorded signals' features over time: 1) spectral analysis; 2) polarization analysis; 3) monitoring of seismic wave velocity changes. These methodologies have been used to study the dynamic response of unstable rock blocks, both in terms of resonance frequencies and preferential vibrational directions, as well as to deduce whether ambient seismic noise allows retrieving information concerning the stability and water content of landslides. The combination of all these techniques aims to provide significant progress in the realization of an effective monitoring tool for slope stability phenomena. In addition, in this work, a low-cost seismometer (Raspberry Shake 3D) was tested through both laboratory and field experiments to assess whether it can be used for ambient seismic noise applications, thus, to perform long-term monitoring. Finally, this thesis was completed through the development of user-friendly software for organizing, visualizing, and processing seismic noise recordings and signals in general. The outcome of this work leads to the conclusion that seismic noise monitoring may be a reliable tool whose integration with standard geological/geotechnical techniques could improve our capabilities for landslide forecasting.
La valutazione e la gestione delle frane e dei rischi ad esse connessi sono argomenti da sempre studiati dalla comunità scientifica per via della natura distruttiva e delle conseguenze socioeconomiche di tali fenomeni. Il loro verificarsi è fortemente condizionato sia da fattori naturali sia da fattori antropici e la definizione di adeguate misure di prevenzione e mitigazione è tutt’oggi molto complessa. Una delle sfide attuali nel mondo scientifico è fornire tecniche affidabili in grado di prevedere e monitorare questi fenomeni in tempo reale, in maniera tale da ridurre al minimo le loro conseguenze. Per raggiungere questo obiettivo, nell'ultimo decennio, le tecniche geofisiche sono state integrate alle metodologie già esistenti al fine di studiare i pendii instabili, nonché per progettare sistemi di monitoraggio. Questo progetto di dottorato mira all'analisi, allo sviluppo e alla sperimentazione di nuove tecniche e sensori geofisici per il monitoraggio di siti soggetti a problemi di stabilità dei versanti. In dettaglio, la ricerca si focalizza sull’utilizzo del rumore sismico ambientale per ricavare informazioni che possano essere utilizzate a supporto delle tecnologie già esistenti per il monitoraggio del rischio idrogeologico. A tal fine, il rumore sismico è stato analizzato mediante: analisi spettrale, analisi di polarizzazione e monitoraggio delle variazioni di velocità delle onde sismiche. Queste metodologie sono state utilizzate per studiare la risposta dinamica di blocchi di roccia instabili, sia in termini di frequenze di risonanza che di direzioni di vibrazionali preferenziali, nonché per dedurre se il rumore sismico ambientale possa essere di valido supporto per lo studio della stabilità e del contenuto idrico delle frane. La combinazione di tutte queste tecniche mira a fornire progressi significativi nella realizzazione di un efficace strumento di monitoraggio della stabilità dei pendii. In questo lavoro è stato inoltre testato un sismometro a basso costo (Raspberry Shake 3D) sia attraverso esperimenti di laboratorio che mediante rilievi in sito con l’obbiettivo di valutare se può essere utilizzato per applicazioni di rumore sismico ambientale, quindi, per eseguire monitoraggi a lungo termine. Questo progetto di ricerca è stato infine completato mediante lo sviluppo di un software con interfaccia grafica che consente all’utente di organizzare, visualizzare ed elaborare le registrazioni del rumore sismico ambientale. I risultati di questo lavoro hanno portato a concludere che il monitoraggio del rumore sismico, integrato con le tradizionali tecniche geologiche e geotecniche, può migliorare la nostra capacità di prevedere il verificarsi degli eventi franosi.
Environmental applications of ambient seismic noise for monitoring sites with high hydrogeological risk
Taruselli, Marco
2020/2021
Abstract
The assessment and management of landslide hazards and related risks have always been widely studied topics in the scientific community due to their destructive nature and the consequent socio-economic impacts. The occurrence of such events is strongly conditioned by both natural and anthropogenic factors and the definition of adequate prevention and mitigation measures is still a challenging task. One of the current challenges in the academic world is to provide reliable techniques able to forecast and monitor these phenomena in real-time, hence, reducing the adverse nature of their consequences. In order to achieve this objective, in the past decade, geophysical techniques have been integrated into multidisciplinary approaches to monitor slope instability as well as to design early warning monitoring systems. This Ph.D. project is directed towards the analysis, development, and experimentation with novel geophysical technologies and sensors for the monitoring of sites prone to slope stability issues. In detail, the research is focused on the analysis of ambient seismic noise to retrieve features that can provide valuable information concerning slope stability over time and thus, to support already existing technologies for geohazard monitoring. Among the available passive geophysical methods, three types of analysis were chosen due to their capability to yield the variation of the recorded signals' features over time: 1) spectral analysis; 2) polarization analysis; 3) monitoring of seismic wave velocity changes. These methodologies have been used to study the dynamic response of unstable rock blocks, both in terms of resonance frequencies and preferential vibrational directions, as well as to deduce whether ambient seismic noise allows retrieving information concerning the stability and water content of landslides. The combination of all these techniques aims to provide significant progress in the realization of an effective monitoring tool for slope stability phenomena. In addition, in this work, a low-cost seismometer (Raspberry Shake 3D) was tested through both laboratory and field experiments to assess whether it can be used for ambient seismic noise applications, thus, to perform long-term monitoring. Finally, this thesis was completed through the development of user-friendly software for organizing, visualizing, and processing seismic noise recordings and signals in general. The outcome of this work leads to the conclusion that seismic noise monitoring may be a reliable tool whose integration with standard geological/geotechnical techniques could improve our capabilities for landslide forecasting.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/179042