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Clement Hibert - One of the best experts on this subject based on the ideXlab platform.
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spatio temporal evolution of Rockfall activity from 2007 to 2011 at the piton de la fournaise volcano inferred from seismic data
Journal of Volcanology and Geothermal Research, 2017Co-Authors: Gilles Grandjean, Clement Hibert, Anne Mangeney, Aline Peltier, Andrea Dimuro, Nikolai M Shapiro, Valerie Ferrazzini, Patrice Boissier, Virginie DurandAbstract:Abstract Seismic data have been used to catalog the location and volume of most of the Rockfalls that occurred at the Piton de la Fournaise volcano from May 2007, just after the major collapse of the Dolomieu summit crater floor, to May 2011. This catalog made it possible to compare the evolution of the number and volume of Rockfalls at a high temporal resolution and to investigate their links with eruptions, seismicity, deformations and rainfalls affecting the Piton de la Fournaise volcano. Results show that the purge of unstable areas created by the Dolomieu crater floor collapse occurred in two phases: a first phase, lasting three months, during which the intense Rockfall activity immediately following the collapse decreased abruptly and a second phase, lasting more than two years, during which the daily volume of the Rockfalls slowly decreased before reaching a steady state. A detailed study of 4 time periods, including 3 eruptive cycles, indicates that strong seismicity can increase the number of Rockfalls. Furthermore, when a dike reaches the surface at the summit of the central cone, giving birth to an eruption, the associated local forcing can in some cases increase the volume of Rockfalls, possibly by creating or expanding weak zones. In most cases, this is not observed for dike intrusions that do not reach the surface. The newly created weak zones are most often far from the eruptive fissures of the ongoing eruption, but close to the location of the next eruption. This suggests that these distant zones are also weakened at depth, thus creating preferred paths for future dikes propagating toward the surface. The impact of rainfall on Rockfall activity was also studied, given that La Reunion Island is subject to very intense rainfall events. Our results show that rainfall can in some cases trigger Rockfalls rapidly, with response times of less than a day, but not systematically, and no triggering rainfall threshold was found.
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slope instabilities in dolomieu crater reunion island from seismic signals to Rockfall characteristics
Journal of Geophysical Research, 2011Co-Authors: Clement Hibert, A. Mangeney, Gilles Grandjean, N M ShapiroAbstract:[1] The seismic signals of hundreds of Rockfalls within Dolomieu crater, Piton de la Fournaise volcano, Reunion Island, have been analyzed to investigate a possible link between physical Rockfall-generating processes and associated seismic signal features. Moreover, indirect observation of Rockfalls via the seismic signals they generate can provide useful data for studying volcanoes and the temporal variations of their structure. An increase in the number of Rockfall events and their volumes might be an indicator of structural weakness and deformation of the volcano associated with potential eruptive activity. The study focuses on a 10 month period following the 6 April 2007 crater floor collapse within Dolomieu crater, from May 2007 to February 2008. For granular flows a scaling law is revealed between seismic energy and signal duration. A semiempirical approach based on both analytical analysis and numerical simulation of these flows shows that a similar scaling law exists between the difference of potential energy computed for an event and its propagation times and also emphasizes the effect of local topography on this scaling law. Simulated and observed data were compared to evaluate the proportion of potential energy dissipated in the form of seismic waves and confirm a direct link between the seismic energy and potential energy of a given granular flow. The mean ratio of seismic to potential energy is of the order of 10−4, comparable to the range of values observed in previous studies. A simple method based on these ratios is proposed to estimate the volumes of Rockfalls from their seismic signal. Observed seismic energy and the frequency of Rockfalls decreased at the beginning of the studied period and reached a stable level in July, thus suggesting a postcollapse relaxation time of Dolomieu crater structure of about 2 months from seismic signal analysis, which is confirmed by deformation data. The total Rockfall volume over the study period is estimated to be 1.85 Mm3.
Donald B. Dingwell - One of the best experts on this subject based on the ideXlab platform.
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Quantification of magma ascent rate through Rockfall monitoring at the growing/collapsing lava dome of Volcán de Colima, Mexico
Solid Earth, 2013Co-Authors: S. B. Mueller, N.r. Varley, U. Kueppers, Philippe Lesage, G. Reyes-dávila, Donald B. DingwellAbstract:The most recent eruptive phase of Volc'an de Colima, Mexico, started in 1998 and was characterized by dome growth with a variable effusion rate, interrupted intermittently by explosive eruptions. Between November 2009 and June 2011, activity at the dome was mostly limited to a lobe on the western side where it had previously started overflowing the crater rim, leading to the generation of Rockfall events. As a consequence of this, no significant increase in dome volume was perceivable and the rate of magma ascent, a crucial parameter for volcano monitoring and hazard assessment could no longer be quantified via measurements of the dome's dimensions. Here, we present alternative approaches to quantify the magma ascent rate. We estimate the volume of individual Rockfalls through the detailed analysis of sets of photographs (before and after individual Rockfall events). The relationship between volume and infrared images of the freshly exposed dome surface and the seismic signals related to the Rockfall events were then investigated. Larger Rockfall events exhibited a correlation between its previously estimated volume and the surface temperature of the freshly exposed dome surface, as well as the mean temperature of Rockfall mass distributed over the slope. We showed that for larger events, the volume of the Rockfall correlates with the maximum temperature of the newly exposed lava dome as well as a proxy for seismic energy. It was therefore possible to calibrate the seismic signals using the volumes estimated from photographs and the count of Rockfalls over a certain period was used to estimate the magma extrusion flux for the period investigated. Over the course of the measurement period, significant changes were observed in number of Rockfalls, Rockfall volume and hence averaged extrusion rate. The extrusion rate was not constant: it increased from 0.008±0.003 to 0.02±0.007m3 s−1 during 2010 and dropped down to 0.008±0.003m3 s−1 again in March 2011. In June 2011, magma extrusion had come to a halt. The methodology presented represents a reliable tool to constrain the growth rate of domes that are repeatedly affected by partial collapses. There is a good correlation between thermal and seismic energies and Rockfall volume. Thus it is possible to calibrate the seismic records associated with the Rockfalls (a continuous monitoring tool) to improve volcano monitoring at volcanoes with active dome growth.
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quantification of magma ascent rate through Rockfall monitoring at the growing collapsing lava dome of volcan de colima mexico
Solid Earth, 2013Co-Authors: S. B. Mueller, U. Kueppers, Philippe Lesage, Nick Varley, G Reyes A Davila, Donald B. DingwellAbstract:Abstract. The most recent eruptive phase of Volcan de Colima, Mexico, started in 1998 and was characterized by dome growth with a variable effusion rate, interrupted intermittently by explosive eruptions. Between November 2009 and June 2011, activity at the dome was mostly limited to a lobe on the western side where it had previously started overflowing the crater rim, leading to the generation of Rockfall events. As a consequence of this, no significant increase in dome volume was perceivable and the rate of magma ascent, a crucial parameter for volcano monitoring and hazard assessment could no longer be quantified via measurements of the dome's dimensions. Here, we present alternative approaches to quantify the magma ascent rate. We estimate the volume of individual Rockfalls through the detailed analysis of sets of photographs (before and after individual Rockfall events). The relationship between volume and infrared images of the freshly exposed dome surface and the seismic signals related to the Rockfall events were then investigated. Larger Rockfall events exhibited a correlation between its previously estimated volume and the surface temperature of the freshly exposed dome surface, as well as the mean temperature of Rockfall mass distributed over the slope. We showed that for larger events, the volume of the Rockfall correlates with the maximum temperature of the newly exposed lava dome as well as a proxy for seismic energy. It was therefore possible to calibrate the seismic signals using the volumes estimated from photographs and the count of Rockfalls over a certain period was used to estimate the magma extrusion flux for the period investigated. Over the course of the measurement period, significant changes were observed in number of Rockfalls, Rockfall volume and hence averaged extrusion rate. The extrusion rate was not constant: it increased from 0.008 ± 0.003 to 0.02 ± 0.007 m3 s−1 during 2010 and dropped down to 0.008 ± 0.003 m3 s−1 again in March 2011. In June 2011, magma extrusion had come to a halt. The methodology presented represents a reliable tool to constrain the growth rate of domes that are repeatedly affected by partial collapses. There is a good correlation between thermal and seismic energies and Rockfall volume. Thus it is possible to calibrate the seismic records associated with the Rockfalls (a continuous monitoring tool) to improve volcano monitoring at volcanoes with active dome growth.
S. B. Mueller - One of the best experts on this subject based on the ideXlab platform.
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Quantification of magma ascent rate through Rockfall monitoring at the growing/collapsing lava dome of Volcán de Colima, Mexico
Solid Earth, 2013Co-Authors: S. B. Mueller, N.r. Varley, U. Kueppers, Philippe Lesage, G. Reyes-dávila, Donald B. DingwellAbstract:The most recent eruptive phase of Volc'an de Colima, Mexico, started in 1998 and was characterized by dome growth with a variable effusion rate, interrupted intermittently by explosive eruptions. Between November 2009 and June 2011, activity at the dome was mostly limited to a lobe on the western side where it had previously started overflowing the crater rim, leading to the generation of Rockfall events. As a consequence of this, no significant increase in dome volume was perceivable and the rate of magma ascent, a crucial parameter for volcano monitoring and hazard assessment could no longer be quantified via measurements of the dome's dimensions. Here, we present alternative approaches to quantify the magma ascent rate. We estimate the volume of individual Rockfalls through the detailed analysis of sets of photographs (before and after individual Rockfall events). The relationship between volume and infrared images of the freshly exposed dome surface and the seismic signals related to the Rockfall events were then investigated. Larger Rockfall events exhibited a correlation between its previously estimated volume and the surface temperature of the freshly exposed dome surface, as well as the mean temperature of Rockfall mass distributed over the slope. We showed that for larger events, the volume of the Rockfall correlates with the maximum temperature of the newly exposed lava dome as well as a proxy for seismic energy. It was therefore possible to calibrate the seismic signals using the volumes estimated from photographs and the count of Rockfalls over a certain period was used to estimate the magma extrusion flux for the period investigated. Over the course of the measurement period, significant changes were observed in number of Rockfalls, Rockfall volume and hence averaged extrusion rate. The extrusion rate was not constant: it increased from 0.008±0.003 to 0.02±0.007m3 s−1 during 2010 and dropped down to 0.008±0.003m3 s−1 again in March 2011. In June 2011, magma extrusion had come to a halt. The methodology presented represents a reliable tool to constrain the growth rate of domes that are repeatedly affected by partial collapses. There is a good correlation between thermal and seismic energies and Rockfall volume. Thus it is possible to calibrate the seismic records associated with the Rockfalls (a continuous monitoring tool) to improve volcano monitoring at volcanoes with active dome growth.
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quantification of magma ascent rate through Rockfall monitoring at the growing collapsing lava dome of volcan de colima mexico
Solid Earth, 2013Co-Authors: S. B. Mueller, U. Kueppers, Philippe Lesage, Nick Varley, G Reyes A Davila, Donald B. DingwellAbstract:Abstract. The most recent eruptive phase of Volcan de Colima, Mexico, started in 1998 and was characterized by dome growth with a variable effusion rate, interrupted intermittently by explosive eruptions. Between November 2009 and June 2011, activity at the dome was mostly limited to a lobe on the western side where it had previously started overflowing the crater rim, leading to the generation of Rockfall events. As a consequence of this, no significant increase in dome volume was perceivable and the rate of magma ascent, a crucial parameter for volcano monitoring and hazard assessment could no longer be quantified via measurements of the dome's dimensions. Here, we present alternative approaches to quantify the magma ascent rate. We estimate the volume of individual Rockfalls through the detailed analysis of sets of photographs (before and after individual Rockfall events). The relationship between volume and infrared images of the freshly exposed dome surface and the seismic signals related to the Rockfall events were then investigated. Larger Rockfall events exhibited a correlation between its previously estimated volume and the surface temperature of the freshly exposed dome surface, as well as the mean temperature of Rockfall mass distributed over the slope. We showed that for larger events, the volume of the Rockfall correlates with the maximum temperature of the newly exposed lava dome as well as a proxy for seismic energy. It was therefore possible to calibrate the seismic signals using the volumes estimated from photographs and the count of Rockfalls over a certain period was used to estimate the magma extrusion flux for the period investigated. Over the course of the measurement period, significant changes were observed in number of Rockfalls, Rockfall volume and hence averaged extrusion rate. The extrusion rate was not constant: it increased from 0.008 ± 0.003 to 0.02 ± 0.007 m3 s−1 during 2010 and dropped down to 0.008 ± 0.003 m3 s−1 again in March 2011. In June 2011, magma extrusion had come to a halt. The methodology presented represents a reliable tool to constrain the growth rate of domes that are repeatedly affected by partial collapses. There is a good correlation between thermal and seismic energies and Rockfall volume. Thus it is possible to calibrate the seismic records associated with the Rockfalls (a continuous monitoring tool) to improve volcano monitoring at volcanoes with active dome growth.
Gilles Grandjean - One of the best experts on this subject based on the ideXlab platform.
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spatio temporal evolution of Rockfall activity from 2007 to 2011 at the piton de la fournaise volcano inferred from seismic data
Journal of Volcanology and Geothermal Research, 2017Co-Authors: Gilles Grandjean, Clement Hibert, Anne Mangeney, Aline Peltier, Andrea Dimuro, Nikolai M Shapiro, Valerie Ferrazzini, Patrice Boissier, Virginie DurandAbstract:Abstract Seismic data have been used to catalog the location and volume of most of the Rockfalls that occurred at the Piton de la Fournaise volcano from May 2007, just after the major collapse of the Dolomieu summit crater floor, to May 2011. This catalog made it possible to compare the evolution of the number and volume of Rockfalls at a high temporal resolution and to investigate their links with eruptions, seismicity, deformations and rainfalls affecting the Piton de la Fournaise volcano. Results show that the purge of unstable areas created by the Dolomieu crater floor collapse occurred in two phases: a first phase, lasting three months, during which the intense Rockfall activity immediately following the collapse decreased abruptly and a second phase, lasting more than two years, during which the daily volume of the Rockfalls slowly decreased before reaching a steady state. A detailed study of 4 time periods, including 3 eruptive cycles, indicates that strong seismicity can increase the number of Rockfalls. Furthermore, when a dike reaches the surface at the summit of the central cone, giving birth to an eruption, the associated local forcing can in some cases increase the volume of Rockfalls, possibly by creating or expanding weak zones. In most cases, this is not observed for dike intrusions that do not reach the surface. The newly created weak zones are most often far from the eruptive fissures of the ongoing eruption, but close to the location of the next eruption. This suggests that these distant zones are also weakened at depth, thus creating preferred paths for future dikes propagating toward the surface. The impact of rainfall on Rockfall activity was also studied, given that La Reunion Island is subject to very intense rainfall events. Our results show that rainfall can in some cases trigger Rockfalls rapidly, with response times of less than a day, but not systematically, and no triggering rainfall threshold was found.
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Automated identification, location, and volume estimation of Rockfalls at Piton de la Fournaise volcano
Journal of Geophysical Research: Earth Surface, 2014Co-Authors: C. Hibert, A. Mangeney, Gilles Grandjean, C. Baillard, D. Rivet, N. Shapiro, C. Satriano, A. Maggi, P. Boissier, V. FerrazziniAbstract:Since the collapse of the Dolomieu crater floor at Piton de la Fournaise Volcano (la Réunion) in 2007, hundreds of seismic signals generated by Rockfalls have been recorded daily at the Observatoire Volcanologique du Piton de la Fournaise (OVPF). To study Rockfall activity over a long period of time, automated methods are required to process the available continuous seismic records. We present a set of automated methods designed to identify, locate, and estimate the volume of Rockfalls from their seismic signals. The method used to automatically discriminate seismic signals generated by Rockfalls from other common events recorded at OVPF is based on fuzzy sets and has a success rate of 92%. A kurtosis-based automated picking method makes it possible to precisely pick the onset time and the final time of the Rockfall-generated seismic signals. We present methods to determine Rockfall locations based on these accurate pickings and a surface-wave propagation model computed for each station using a Fast Marching Method. These methods have successfully located directly observed Rockfalls with an accuracy of about 100 m. They also make it possible to compute the seismic energy generated by Rockfalls, which is then used to retrieve their volume. The methods developed were applied to a data set of 12,422 Rockfalls that occurred over a period extending from the collapse of the Dolomieu crater floor in April 2007 to the end of the UnderVolc project in May 2011 to identify the most hazardous areas of the Piton de la Fournaise volcano summit.
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slope instabilities in dolomieu crater reunion island from seismic signals to Rockfall characteristics
Journal of Geophysical Research, 2011Co-Authors: Clement Hibert, A. Mangeney, Gilles Grandjean, N M ShapiroAbstract:[1] The seismic signals of hundreds of Rockfalls within Dolomieu crater, Piton de la Fournaise volcano, Reunion Island, have been analyzed to investigate a possible link between physical Rockfall-generating processes and associated seismic signal features. Moreover, indirect observation of Rockfalls via the seismic signals they generate can provide useful data for studying volcanoes and the temporal variations of their structure. An increase in the number of Rockfall events and their volumes might be an indicator of structural weakness and deformation of the volcano associated with potential eruptive activity. The study focuses on a 10 month period following the 6 April 2007 crater floor collapse within Dolomieu crater, from May 2007 to February 2008. For granular flows a scaling law is revealed between seismic energy and signal duration. A semiempirical approach based on both analytical analysis and numerical simulation of these flows shows that a similar scaling law exists between the difference of potential energy computed for an event and its propagation times and also emphasizes the effect of local topography on this scaling law. Simulated and observed data were compared to evaluate the proportion of potential energy dissipated in the form of seismic waves and confirm a direct link between the seismic energy and potential energy of a given granular flow. The mean ratio of seismic to potential energy is of the order of 10−4, comparable to the range of values observed in previous studies. A simple method based on these ratios is proposed to estimate the volumes of Rockfalls from their seismic signal. Observed seismic energy and the frequency of Rockfalls decreased at the beginning of the studied period and reached a stable level in July, thus suggesting a postcollapse relaxation time of Dolomieu crater structure of about 2 months from seismic signal analysis, which is confirmed by deformation data. The total Rockfall volume over the study period is estimated to be 1.85 Mm3.
Virginie Durand - One of the best experts on this subject based on the ideXlab platform.
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spatio temporal evolution of Rockfall activity from 2007 to 2011 at the piton de la fournaise volcano inferred from seismic data
Journal of Volcanology and Geothermal Research, 2017Co-Authors: Gilles Grandjean, Clement Hibert, Anne Mangeney, Aline Peltier, Andrea Dimuro, Nikolai M Shapiro, Valerie Ferrazzini, Patrice Boissier, Virginie DurandAbstract:Abstract Seismic data have been used to catalog the location and volume of most of the Rockfalls that occurred at the Piton de la Fournaise volcano from May 2007, just after the major collapse of the Dolomieu summit crater floor, to May 2011. This catalog made it possible to compare the evolution of the number and volume of Rockfalls at a high temporal resolution and to investigate their links with eruptions, seismicity, deformations and rainfalls affecting the Piton de la Fournaise volcano. Results show that the purge of unstable areas created by the Dolomieu crater floor collapse occurred in two phases: a first phase, lasting three months, during which the intense Rockfall activity immediately following the collapse decreased abruptly and a second phase, lasting more than two years, during which the daily volume of the Rockfalls slowly decreased before reaching a steady state. A detailed study of 4 time periods, including 3 eruptive cycles, indicates that strong seismicity can increase the number of Rockfalls. Furthermore, when a dike reaches the surface at the summit of the central cone, giving birth to an eruption, the associated local forcing can in some cases increase the volume of Rockfalls, possibly by creating or expanding weak zones. In most cases, this is not observed for dike intrusions that do not reach the surface. The newly created weak zones are most often far from the eruptive fissures of the ongoing eruption, but close to the location of the next eruption. This suggests that these distant zones are also weakened at depth, thus creating preferred paths for future dikes propagating toward the surface. The impact of rainfall on Rockfall activity was also studied, given that La Reunion Island is subject to very intense rainfall events. Our results show that rainfall can in some cases trigger Rockfalls rapidly, with response times of less than a day, but not systematically, and no triggering rainfall threshold was found.
