ABSTRACT. Recent studies have shown that urban ambient noise (UAN) decreased at many sites due to... more ABSTRACT. Recent studies have shown that urban ambient noise (UAN) decreased at many sites due to a slowdown in human activities brought by the SARS-CoV-2 (COVID-19) pandemic lockdowns. Such understanding is inferred from the historical record of the noise levels, which may also help us disambiguate noise sources as required for ambient noise tomography, microseismic and other seismic based studies. As UAN is site-specific, and its analysis enables passive situational awareness, therefore, in the present study, we analyzed the temporal variations in UAN before, during and after the social isolation in the metropolitan region of Lima, the capital of Peru, for the very first time. We used continuous waveforms recorded from February 1st to August 31st, 2020, at the Ñaña (NNA) broadband seismic station for the analysis. Results show the temporal changes occur in different frequency ranges; for example, at frequencies >1 Hz, significant changes in the mean daytime amplitudes are obser...
Data and models presented in the paper "Volcano-tectonic interactions at Sabancaya volcano, ... more Data and models presented in the paper "Volcano-tectonic interactions at Sabancaya volcano, Peru: Eruptions, magmatic inflation, moderate earthquakes, and fault creep". See file "README.txt" for detailed descriptions of each item.
We used a large set of satellite- (visible, infrared, and radar images from Planetscope, MODIS, V... more We used a large set of satellite- (visible, infrared, and radar images from Planetscope, MODIS, VIIRS, Sentinel2, Landsat 8, and Sentinel 1) and ground-based data (optical images, SO2 flux, shallow seismicity) to describe and characterize the activity of the Sabancaya volcano during the unrest and eruption phases that occurred between 2012 and 2020. The unrest phase (2012–2016) was characterized by increasing gas and thermal flux, sourced by a convective magma column rising along with the remnants of a buried plug still permeable to fluid flow. Conversely, a new conduit, adjacent to the previous one, fed the eruptive phase (2016–2020) which was instead characterized by a discontinuous extrusive activity, with phases of dome growth (at rates from 0.04 to 0.75 m3 s−1) and collapse. The extrusive activity was accompanied by fluctuating thermal anomalies (0.5–25 MW), by irregular SO2 degassing (700–7000 tons day−1), and by variable explosive activity (4–100 events d−1) producing repeate...
Asymmetrical structure, hydrothermal system and edifice stability: The case of Ubinas volcano, Pe... more Asymmetrical structure, hydrothermal system and edifice stability: The case of Ubinas volcano, Peru, revealed by geophysical surveys
Asymmetrical structure, hydrothermal system and edifice stability: The case of Ubinas volcano, Pe... more Asymmetrical structure, hydrothermal system and edifice stability: The case of Ubinas volcano, Peru, revealed by geophysical surveys
Journal of Volcanology and Geothermal Research, 2015
After 3 years of mild gases emissions, the Ubinas volcano entered in a new eruptive phase on Sept... more After 3 years of mild gases emissions, the Ubinas volcano entered in a new eruptive phase on September 2nd, 2013. The MIROVA system (a space-based volcanic hot-spot detection system), allowed us to detect in near real time the thermal emissions associated with the eruption and provided early evidence of magma extrusion within the deep summit crater. By combining IR data with plume height, sulfur emissions, hot spring temperatures and seismic activity, we interpret the thermal output detected over Ubinas in terms of extrusion rates associated to the eruption. We suggest that the 2013-2014 eruptive crisis can be subdivided into three main phases: (i) shallow magma intrusion inside the edifice, (ii) extrusion and growing of a lava plug at the bottom of the summit crater coupled with increasing explosive activity and finally, (iii) disruption of the lava plug and gradual decline of the explosive activity. The occurrence of the 8.2 Mw Iquique (Chile) earthquake (365 km away from Ubinas) on April 1st, 2014, may have perturbed most of the analyzed parameters, suggesting a prompt interaction with the ongoing volcanic activity. In particular, the analysis of thermal and seismic datasets shows that the earthquake may have promoted the most intense thermal and explosive phase that culminated in a major explosion on April 19th, 2014. These results reveal the efficiency of space-based thermal observations in detecting the extrusion of hot magma within deep volcanic craters and in tracking its evolution. We emphasize that, in combination with other geophysical and geochemical datasets, MIROVA is an essential tool for monitoring remote volcanoes with rather difficult accessibility, like those of the Andes that reach remarkably high altitudes.
Journal of Geophysical Research: Solid Earth, 2011
Most seismic eruption forerunners are described using Volcano-Tectonic earthquakes, seismic energ... more Most seismic eruption forerunners are described using Volcano-Tectonic earthquakes, seismic energy release, deformation rates or seismic noise analyses. Using the seismic data recorded at Ubinas volcano (Perú) between 2006 and 2008, we explore the time evolution of the Long Period (LP) seismicity rate prior to 143 explosions. We resolve an average acceleration of the LP rate above the background level during the 2-3 hours preceding the explosion onset. Such an average pattern, which emerges when stacking over LP time series, is robust and stable over all the 2006-2008 period, for which data is available. This accelerating pattern is also recovered when conditioning the LP rate on the occurrence of an other LP event, rather than on the explosion time. It supports a common mechanism for the generation of explosions and LP events, the magma conduit pressure increase being the most probable candidate. The average LP rate acceleration toward an explosion is highly significant prior to the higher energy explosions, supposedly the ones associated with the larger pressure increases. The dramatic decay of the LP activity following explosions, still reinforce the strong relationship between these two processes. We test and we quantify the retrospective forecasting power of these LP rate patterns to predict Ubinas explosions. The prediction quality of the forecasts (e.g. for 17% of alarm time, we predict 63% of Ubinas explosions, with 58% of false alarms) is evaluated using error diagrams. The prediction results are stable and the prediction algorithm validated, i.e. its performance is better than the random guess.
Present work studies the influence of the regional topography on the hydrothermal fluid flow patt... more Present work studies the influence of the regional topography on the hydrothermal fluid flow pattern in the subsurface of a volcanic complex. We discuss how the advective transfer of heat from a magmatic source is controlled by the regional topography for different values of the averaged permeability. For this purpose, we use a 2-D numerical model of coupled mass and heat transport and new data sets acquired at Ticsani and Ubinas, two andesitic volcanoes in Southern Peru which have typical topography, justifying this approach. A remarkable feature of these hydrothermal systems is their remote position not centered on the top of the edifice. It is evidenced by numerous hot springs located in more than 10 km distance from the top of each edifice. Upwelling of thermal water is also inferred from a positive self-potential anomaly at the summit of the both volcanoes, and by ground temperatures up to 37 • C observed at Ticsani. Our model results suggest that the regional topographic gradient is able to significantly divert the thermal water flow and can lead to an asymmetric emplacement of the hydrothermal system even considering a homogeneous permeability of the edifice. Inside the thermal flow, the hydraulic conductivity increases with the decrease of temperature-related viscosity, focusing the flow towards the surface and creating a hydrothermal zone at a large lateral distance from the heat source. The location and temperature of the hot springs together with the water table position given by self-potential data can be used to constrain the average permeability of the edifice, a key parameter influencing fluid flow and associated advective heat transfer in the direction opposite to the regional topographic gradient. Our study allows to explain the emplacement of the hydrothermal systems at volcanoes with asymmetric edifices or even the absence of a shallow hydrothermal system. These results can be generalized to the study of non-volcanic hydrothermal systems.
En: Congreso Peruano de Geologia, 17, Resumenes extendidos. Lima, PE, 12-15 octubre 2014, 4 p. Li... more En: Congreso Peruano de Geologia, 17, Resumenes extendidos. Lima, PE, 12-15 octubre 2014, 4 p. Lima:Sociedad Geologica del Peru.
Paleomagnetic studies undertaken in the Central Andes demonstrate that tectonic rotations are a k... more Paleomagnetic studies undertaken in the Central Andes demonstrate that tectonic rotations are a key feature of the deformation. Paleomagnetic results obtained in Mesozoic rocks (Roperch and Carlier, 1992; Macedo Sanchez, 1993) and Paleocene rocks (Macedo Sanchez, 1993) demonstrate counterclockwise rotations of Southern Peru larger than 30 degrees supporting the hypothesis of oroclinal bending of the Central Andes. However, the timing of the rotations remains poorly determined. In this study we present new paleomagnetic evidence for a late Paleogene counterclockwise rotation of Southern Peru.
Vulcanian explosions at Ubinas volcano, Peru produce Very Long Period (VLP) events. About 30 expl... more Vulcanian explosions at Ubinas volcano, Peru produce Very Long Period (VLP) events. About 30 explosions were recorded by an array of 7 broadband stations which that operated were installed for a 3 month period. The recorded VLP events have similar waveforms, suggesting a common source location and mechanism. We performed several moment tensor inversions on a stacked VLP signal. We first left all inversion parameters free in order to fix the more probable source position, which was found under the southern part of the caldera, 10 m below the crater. We then inverted the moment tensor assuming specific source geometries. Results suggest a crack geometry with a normal vector oriented N 15° E in the horizontal plane and 40° from the vertical axis. Introduction Ubinas stratovolcano (5672 m above sea level) is located 60 km east from Arequipa city in Peru. It is historically the most active volcano in Peru. During the last 450 years Ubinas erupted 23 times with a maximum Volcanic Explosiv...
En: Congreso Peruano de Geologia, 16, Resumenes extendidos. Lima, PE, 23-26 setiembre 2012, 5 p. ... more En: Congreso Peruano de Geologia, 16, Resumenes extendidos. Lima, PE, 23-26 setiembre 2012, 5 p. Lima:Sociedad Geologica del Peru.
ABSTRACT. Recent studies have shown that urban ambient noise (UAN) decreased at many sites due to... more ABSTRACT. Recent studies have shown that urban ambient noise (UAN) decreased at many sites due to a slowdown in human activities brought by the SARS-CoV-2 (COVID-19) pandemic lockdowns. Such understanding is inferred from the historical record of the noise levels, which may also help us disambiguate noise sources as required for ambient noise tomography, microseismic and other seismic based studies. As UAN is site-specific, and its analysis enables passive situational awareness, therefore, in the present study, we analyzed the temporal variations in UAN before, during and after the social isolation in the metropolitan region of Lima, the capital of Peru, for the very first time. We used continuous waveforms recorded from February 1st to August 31st, 2020, at the Ñaña (NNA) broadband seismic station for the analysis. Results show the temporal changes occur in different frequency ranges; for example, at frequencies >1 Hz, significant changes in the mean daytime amplitudes are obser...
Data and models presented in the paper "Volcano-tectonic interactions at Sabancaya volcano, ... more Data and models presented in the paper "Volcano-tectonic interactions at Sabancaya volcano, Peru: Eruptions, magmatic inflation, moderate earthquakes, and fault creep". See file "README.txt" for detailed descriptions of each item.
We used a large set of satellite- (visible, infrared, and radar images from Planetscope, MODIS, V... more We used a large set of satellite- (visible, infrared, and radar images from Planetscope, MODIS, VIIRS, Sentinel2, Landsat 8, and Sentinel 1) and ground-based data (optical images, SO2 flux, shallow seismicity) to describe and characterize the activity of the Sabancaya volcano during the unrest and eruption phases that occurred between 2012 and 2020. The unrest phase (2012–2016) was characterized by increasing gas and thermal flux, sourced by a convective magma column rising along with the remnants of a buried plug still permeable to fluid flow. Conversely, a new conduit, adjacent to the previous one, fed the eruptive phase (2016–2020) which was instead characterized by a discontinuous extrusive activity, with phases of dome growth (at rates from 0.04 to 0.75 m3 s−1) and collapse. The extrusive activity was accompanied by fluctuating thermal anomalies (0.5–25 MW), by irregular SO2 degassing (700–7000 tons day−1), and by variable explosive activity (4–100 events d−1) producing repeate...
Asymmetrical structure, hydrothermal system and edifice stability: The case of Ubinas volcano, Pe... more Asymmetrical structure, hydrothermal system and edifice stability: The case of Ubinas volcano, Peru, revealed by geophysical surveys
Asymmetrical structure, hydrothermal system and edifice stability: The case of Ubinas volcano, Pe... more Asymmetrical structure, hydrothermal system and edifice stability: The case of Ubinas volcano, Peru, revealed by geophysical surveys
Journal of Volcanology and Geothermal Research, 2015
After 3 years of mild gases emissions, the Ubinas volcano entered in a new eruptive phase on Sept... more After 3 years of mild gases emissions, the Ubinas volcano entered in a new eruptive phase on September 2nd, 2013. The MIROVA system (a space-based volcanic hot-spot detection system), allowed us to detect in near real time the thermal emissions associated with the eruption and provided early evidence of magma extrusion within the deep summit crater. By combining IR data with plume height, sulfur emissions, hot spring temperatures and seismic activity, we interpret the thermal output detected over Ubinas in terms of extrusion rates associated to the eruption. We suggest that the 2013-2014 eruptive crisis can be subdivided into three main phases: (i) shallow magma intrusion inside the edifice, (ii) extrusion and growing of a lava plug at the bottom of the summit crater coupled with increasing explosive activity and finally, (iii) disruption of the lava plug and gradual decline of the explosive activity. The occurrence of the 8.2 Mw Iquique (Chile) earthquake (365 km away from Ubinas) on April 1st, 2014, may have perturbed most of the analyzed parameters, suggesting a prompt interaction with the ongoing volcanic activity. In particular, the analysis of thermal and seismic datasets shows that the earthquake may have promoted the most intense thermal and explosive phase that culminated in a major explosion on April 19th, 2014. These results reveal the efficiency of space-based thermal observations in detecting the extrusion of hot magma within deep volcanic craters and in tracking its evolution. We emphasize that, in combination with other geophysical and geochemical datasets, MIROVA is an essential tool for monitoring remote volcanoes with rather difficult accessibility, like those of the Andes that reach remarkably high altitudes.
Journal of Geophysical Research: Solid Earth, 2011
Most seismic eruption forerunners are described using Volcano-Tectonic earthquakes, seismic energ... more Most seismic eruption forerunners are described using Volcano-Tectonic earthquakes, seismic energy release, deformation rates or seismic noise analyses. Using the seismic data recorded at Ubinas volcano (Perú) between 2006 and 2008, we explore the time evolution of the Long Period (LP) seismicity rate prior to 143 explosions. We resolve an average acceleration of the LP rate above the background level during the 2-3 hours preceding the explosion onset. Such an average pattern, which emerges when stacking over LP time series, is robust and stable over all the 2006-2008 period, for which data is available. This accelerating pattern is also recovered when conditioning the LP rate on the occurrence of an other LP event, rather than on the explosion time. It supports a common mechanism for the generation of explosions and LP events, the magma conduit pressure increase being the most probable candidate. The average LP rate acceleration toward an explosion is highly significant prior to the higher energy explosions, supposedly the ones associated with the larger pressure increases. The dramatic decay of the LP activity following explosions, still reinforce the strong relationship between these two processes. We test and we quantify the retrospective forecasting power of these LP rate patterns to predict Ubinas explosions. The prediction quality of the forecasts (e.g. for 17% of alarm time, we predict 63% of Ubinas explosions, with 58% of false alarms) is evaluated using error diagrams. The prediction results are stable and the prediction algorithm validated, i.e. its performance is better than the random guess.
Present work studies the influence of the regional topography on the hydrothermal fluid flow patt... more Present work studies the influence of the regional topography on the hydrothermal fluid flow pattern in the subsurface of a volcanic complex. We discuss how the advective transfer of heat from a magmatic source is controlled by the regional topography for different values of the averaged permeability. For this purpose, we use a 2-D numerical model of coupled mass and heat transport and new data sets acquired at Ticsani and Ubinas, two andesitic volcanoes in Southern Peru which have typical topography, justifying this approach. A remarkable feature of these hydrothermal systems is their remote position not centered on the top of the edifice. It is evidenced by numerous hot springs located in more than 10 km distance from the top of each edifice. Upwelling of thermal water is also inferred from a positive self-potential anomaly at the summit of the both volcanoes, and by ground temperatures up to 37 • C observed at Ticsani. Our model results suggest that the regional topographic gradient is able to significantly divert the thermal water flow and can lead to an asymmetric emplacement of the hydrothermal system even considering a homogeneous permeability of the edifice. Inside the thermal flow, the hydraulic conductivity increases with the decrease of temperature-related viscosity, focusing the flow towards the surface and creating a hydrothermal zone at a large lateral distance from the heat source. The location and temperature of the hot springs together with the water table position given by self-potential data can be used to constrain the average permeability of the edifice, a key parameter influencing fluid flow and associated advective heat transfer in the direction opposite to the regional topographic gradient. Our study allows to explain the emplacement of the hydrothermal systems at volcanoes with asymmetric edifices or even the absence of a shallow hydrothermal system. These results can be generalized to the study of non-volcanic hydrothermal systems.
En: Congreso Peruano de Geologia, 17, Resumenes extendidos. Lima, PE, 12-15 octubre 2014, 4 p. Li... more En: Congreso Peruano de Geologia, 17, Resumenes extendidos. Lima, PE, 12-15 octubre 2014, 4 p. Lima:Sociedad Geologica del Peru.
Paleomagnetic studies undertaken in the Central Andes demonstrate that tectonic rotations are a k... more Paleomagnetic studies undertaken in the Central Andes demonstrate that tectonic rotations are a key feature of the deformation. Paleomagnetic results obtained in Mesozoic rocks (Roperch and Carlier, 1992; Macedo Sanchez, 1993) and Paleocene rocks (Macedo Sanchez, 1993) demonstrate counterclockwise rotations of Southern Peru larger than 30 degrees supporting the hypothesis of oroclinal bending of the Central Andes. However, the timing of the rotations remains poorly determined. In this study we present new paleomagnetic evidence for a late Paleogene counterclockwise rotation of Southern Peru.
Vulcanian explosions at Ubinas volcano, Peru produce Very Long Period (VLP) events. About 30 expl... more Vulcanian explosions at Ubinas volcano, Peru produce Very Long Period (VLP) events. About 30 explosions were recorded by an array of 7 broadband stations which that operated were installed for a 3 month period. The recorded VLP events have similar waveforms, suggesting a common source location and mechanism. We performed several moment tensor inversions on a stacked VLP signal. We first left all inversion parameters free in order to fix the more probable source position, which was found under the southern part of the caldera, 10 m below the crater. We then inverted the moment tensor assuming specific source geometries. Results suggest a crack geometry with a normal vector oriented N 15° E in the horizontal plane and 40° from the vertical axis. Introduction Ubinas stratovolcano (5672 m above sea level) is located 60 km east from Arequipa city in Peru. It is historically the most active volcano in Peru. During the last 450 years Ubinas erupted 23 times with a maximum Volcanic Explosiv...
En: Congreso Peruano de Geologia, 16, Resumenes extendidos. Lima, PE, 23-26 setiembre 2012, 5 p. ... more En: Congreso Peruano de Geologia, 16, Resumenes extendidos. Lima, PE, 23-26 setiembre 2012, 5 p. Lima:Sociedad Geologica del Peru.
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