Resumen de articulo presentado en 2nd Alexander von Humboldt Conference on "The Role of Geop... more Resumen de articulo presentado en 2nd Alexander von Humboldt Conference on "The Role of Geophysics in Natural Disaster Prevention", 05 – 09 March 2007, Lima, Peru. Disponible en: EGU Topical Conference Series.
We document the impact of irrigation on the triggering of rockfalls and landslides in the valleys... more We document the impact of irrigation on the triggering of rockfalls and landslides in the valleys of the western coast of Peru, based on a series of remote sensing optical images. We first process Digital Elevation models from 1978 and 2016 using KH9 spy satellite and SPOT6 images, and show elevation changes caused by very large landslides. We then quantify the motion of these large landslides over the period 2013-2017 by processing of time-series of displacement from Sentinel-2 and Landsat-8 images. Those landslides present long periods of quiescence followed by short periods of rapid activity. We show that the landslide activity is triggered by rockfalls from the valley walls. The time-series of landslide motion reveal a dynamic poro-elastic effect due to the seismic shaking produced by rockfalls. Those landslides affect the fertile valleys floors, leading to the destruction of villages and crops, inducing an accelerate loss of traditional agriculture fields. ∗Speaker sciencesconf...
In areas where both earthquakes and precipitations can influence the kinematic of landslides, a c... more In areas where both earthquakes and precipitations can influence the kinematic of landslides, a combination of these two forcings, enhancing the impact that each one of them would have had separately, has already been observed . However, we are still missing quantitative observation with in-situ measurements in order to better understand the mechanisms at the origin of this combined effect. In order to fill this lack, we monitored for almost three years the activity of a slow-moving landslide, Maca, located in the Colca Valley, Peru. This landslide is very interesting for its location, being subject to both seasonal precipitation with rainfall only between December and April and earthquakes with magnitude ranging from 3 to 8. The monitoring of the landslide, based on GPS measurements and soil rigidity variations, thanks to the ambient seismic noise correlation method, allows us to go further in the understanding of the mechanisms impacting the landslide kinematic.
En: Congreso Peruano de Geologia, 16, Resumenes extendidos. Lima, PE, 23-26 setiembre 2012, 4 p. ... more En: Congreso Peruano de Geologia, 16, Resumenes extendidos. Lima, PE, 23-26 setiembre 2012, 4 p. Lima:Sociedad Geologica del Peru.
En: XIII Congreso Latinoamericano de Geologia y XIV Congreso Peruano de Geologia, 16, Resumenes e... more En: XIII Congreso Latinoamericano de Geologia y XIV Congreso Peruano de Geologia, 16, Resumenes extendidos. Lima, PE, 29 setiembre - 3 octubre, 2008, 6 p.
In tectonically active mountain belts, landslides contribute significantly to erosion. Statistica... more In tectonically active mountain belts, landslides contribute significantly to erosion. Statistical analysis of regional inventories of earthquake-triggered-landslides after large earthquakes (Mw > 5.5) reveal a complex interaction between seismic shaking, landslide material, and rainfall. However, the contributions of each component have never been quantified due to a lack of in-situ data for active landslides. We exploited a 3-year geodetic and seismic dataset for a slow-moving landslide in Peru affected by local earthquakes and seasonal rainfalls. Here we show that in combination, they cause greater landslide motion than either force alone. We also show the rigidity of the landslide's bulk clearly decreasing during Ml ≥ 5 earthquakes. The recovery is affected by rainfall and small earthquakes (Ml < 3.6), which prevent the soil from healing, highlighting the importance of the timing between forcings. These new quantitative insights into the mechanics of landslides open new perspectives for the study of the mass balance of earthquakes.
The large slow-moving landslide of Maca is located in the upper Colca valley (southern Peru), a r... more The large slow-moving landslide of Maca is located in the upper Colca valley (southern Peru), a region characterized by a well pronounced rainy period, and intense and recurrent sustained seismicity. The landslide, developed in deep lacustrine deposits, has recently accelerated, threatening the Maca village. This work aims at understanding the rupture mechanism and the causes of the recent landslide reactivation/acceleration. We present a multidisciplinary characterization of the Maca landslide that includes: (i) geological and morphological mapping in the field; (ii) remote sensing analysis using an historical aerial photograph of 1955 and the Pléiades satellite images (2013); (iii) global positioning system (GPS) including time-series of surveys over 13 years, and continuous measurements over 14 months; (iv) a geophysical campaign with deep electrical resistivity tomography profiles acquired across the landslide mass. Our study shows that this 60 Mm 3 landslide, which can be classified as a clay/silt compound landslide, moved by 15 m between 2001 and 2014 with a large inter-annual velocity variation (up to a factor of 500) depending on the rainfall intensity. We suggest that these dramatic changes in velocity are the result of the combination of a threshold mechanism and the short intense rainy season in Peru. This study reveals three main driving factors acting at different timescales: (i) over several decades, the river course has significantly changed, causing the Maca landslide reactivation in the 1980s due to the erosion of its toe; (ii) at the year scale, a minimum amount of rainfall is required to trigger the motion and this amount controls the landslide velocity; (iii) transient changes in slide velocity may occur anytime due to earthquakes. This study particularly highlights the non-linear behaviour of the motion with rainfall.
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.
El pueblo de Maca y alrededores durante los últimos años viene siendo afectado de manera recurren... more El pueblo de Maca y alrededores durante los últimos años viene siendo afectado de manera recurrente por procesos de movimientos en masa y actividad sísmica. Estos fenómenos están afectando viviendas, áreas de cultivos (andenes), canales y reservorios, así como infraestructura vial vital para el desplazamiento de la población local y la actividad turística. El Instituto Geológico Minero y Metalúrgico (INGEMMET) y el Instituto de Investigación Para el Desarrollo de Francia (IRD), vienen realizando en Maca, estudios geológicos, geofísicos e hidrogeológicos, la evaluación y zonificación de los peligros geológicos y el monitoreo instrumental de estos fenómenos. Presentamos en este estudio el mapa geológico a nivel de detalle de Maca, el mapa geomorfológicos y de procesos activos, el mapa hidrogeológico, el mapa de susceptibilidad a movimientos en masa y un mapa con recomendaciones de propuestas de intervención. Los movimientos en masa tienen lugar en áreas donde afloran depositos de aval...
We document the first time series of a landslide reactivation by an earthquake using continuous G... more We document the first time series of a landslide reactivation by an earthquake using continuous GPS measurements over the Maca landslide (Peru). Our survey shows a coseismic response of the landslide of about 2 cm, followed by a relaxation period of 5 weeks during which postseismic slip is 3 times greater than the coseismic displacement itself. Our results confirm the coseismic activation of landslides and provide the first observation of a postseismic displacement. These observations are consistent with a mechanical model where slip on the landslide basal interface is governed by rate and state friction, analogous to the mechanics of creeping tectonic faults, opening new perspectives to study the mechanics of landslides and active faults.
Vulcanian explosions at Ubinas volcano, Peru, produce Very Long Period (VLP) events. About 30 exp... 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 that 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 N15°E in the horizontal plane and 40° from the vertical axis.
Journal of Geophysical Research: Earth Surface, 2019
In mountainous environments, slow-moving landslides (velocities <100 m/yr) are a major concern fo... more In mountainous environments, slow-moving landslides (velocities <100 m/yr) are a major concern for local populations. Rainfall is often the dominant forcing, and often result in major changes in kinematics which can mask smaller signals related to internal forcings. We focus here on a major (> 40 Mm 3) slow-moving landslide in the desert of southern Peru, and take advantage of this arid environment to study the internal processes affecting landslide kinematics. We first estimate the ground displacement from timeseries analysis of Landsat-8 images, spanning a 5.7 year period. Systematic artifacts in the optical time-series are shown to correlate with topography, as well as vary seasonally. We apply a novel procedure for correcting these artifacts, which significantly reduces noise in the resulting time-series, thereby allowing us to precisely resolve landslide displacements. We find landslide velocities of up to 35 m/yr, with complex non-linear interannual pattern, including a period of rapid acceleration. We validate our optically-derived time-series using GNSS field measurements, and find uncertainties (RMSE) on the moving mass of 1.12 to 1.55 m. Sudden acceleration of the landslide body after March 2016 may originate from a mass collapse due to retrogression of the headscarp. By coupling sparse 3D GNSS measurements with dense 2D optical time-series data, we show that the headscarp retrogression acts like a wedge, resulting in domino-like tilting of the downward blocks, and accelerates basal sliding over two years. These observations reveal that the dynamics of this retrogressive landslide are predominantly controlled by sediment supply, and that succession of retrogressive and advancing motions is a self entrainment process.
Resumen de articulo presentado en 2nd Alexander von Humboldt Conference on "The Role of Geop... more Resumen de articulo presentado en 2nd Alexander von Humboldt Conference on "The Role of Geophysics in Natural Disaster Prevention", 05 – 09 March 2007, Lima, Peru. Disponible en: EGU Topical Conference Series.
We document the impact of irrigation on the triggering of rockfalls and landslides in the valleys... more We document the impact of irrigation on the triggering of rockfalls and landslides in the valleys of the western coast of Peru, based on a series of remote sensing optical images. We first process Digital Elevation models from 1978 and 2016 using KH9 spy satellite and SPOT6 images, and show elevation changes caused by very large landslides. We then quantify the motion of these large landslides over the period 2013-2017 by processing of time-series of displacement from Sentinel-2 and Landsat-8 images. Those landslides present long periods of quiescence followed by short periods of rapid activity. We show that the landslide activity is triggered by rockfalls from the valley walls. The time-series of landslide motion reveal a dynamic poro-elastic effect due to the seismic shaking produced by rockfalls. Those landslides affect the fertile valleys floors, leading to the destruction of villages and crops, inducing an accelerate loss of traditional agriculture fields. ∗Speaker sciencesconf...
In areas where both earthquakes and precipitations can influence the kinematic of landslides, a c... more In areas where both earthquakes and precipitations can influence the kinematic of landslides, a combination of these two forcings, enhancing the impact that each one of them would have had separately, has already been observed . However, we are still missing quantitative observation with in-situ measurements in order to better understand the mechanisms at the origin of this combined effect. In order to fill this lack, we monitored for almost three years the activity of a slow-moving landslide, Maca, located in the Colca Valley, Peru. This landslide is very interesting for its location, being subject to both seasonal precipitation with rainfall only between December and April and earthquakes with magnitude ranging from 3 to 8. The monitoring of the landslide, based on GPS measurements and soil rigidity variations, thanks to the ambient seismic noise correlation method, allows us to go further in the understanding of the mechanisms impacting the landslide kinematic.
En: Congreso Peruano de Geologia, 16, Resumenes extendidos. Lima, PE, 23-26 setiembre 2012, 4 p. ... more En: Congreso Peruano de Geologia, 16, Resumenes extendidos. Lima, PE, 23-26 setiembre 2012, 4 p. Lima:Sociedad Geologica del Peru.
En: XIII Congreso Latinoamericano de Geologia y XIV Congreso Peruano de Geologia, 16, Resumenes e... more En: XIII Congreso Latinoamericano de Geologia y XIV Congreso Peruano de Geologia, 16, Resumenes extendidos. Lima, PE, 29 setiembre - 3 octubre, 2008, 6 p.
In tectonically active mountain belts, landslides contribute significantly to erosion. Statistica... more In tectonically active mountain belts, landslides contribute significantly to erosion. Statistical analysis of regional inventories of earthquake-triggered-landslides after large earthquakes (Mw > 5.5) reveal a complex interaction between seismic shaking, landslide material, and rainfall. However, the contributions of each component have never been quantified due to a lack of in-situ data for active landslides. We exploited a 3-year geodetic and seismic dataset for a slow-moving landslide in Peru affected by local earthquakes and seasonal rainfalls. Here we show that in combination, they cause greater landslide motion than either force alone. We also show the rigidity of the landslide's bulk clearly decreasing during Ml ≥ 5 earthquakes. The recovery is affected by rainfall and small earthquakes (Ml < 3.6), which prevent the soil from healing, highlighting the importance of the timing between forcings. These new quantitative insights into the mechanics of landslides open new perspectives for the study of the mass balance of earthquakes.
The large slow-moving landslide of Maca is located in the upper Colca valley (southern Peru), a r... more The large slow-moving landslide of Maca is located in the upper Colca valley (southern Peru), a region characterized by a well pronounced rainy period, and intense and recurrent sustained seismicity. The landslide, developed in deep lacustrine deposits, has recently accelerated, threatening the Maca village. This work aims at understanding the rupture mechanism and the causes of the recent landslide reactivation/acceleration. We present a multidisciplinary characterization of the Maca landslide that includes: (i) geological and morphological mapping in the field; (ii) remote sensing analysis using an historical aerial photograph of 1955 and the Pléiades satellite images (2013); (iii) global positioning system (GPS) including time-series of surveys over 13 years, and continuous measurements over 14 months; (iv) a geophysical campaign with deep electrical resistivity tomography profiles acquired across the landslide mass. Our study shows that this 60 Mm 3 landslide, which can be classified as a clay/silt compound landslide, moved by 15 m between 2001 and 2014 with a large inter-annual velocity variation (up to a factor of 500) depending on the rainfall intensity. We suggest that these dramatic changes in velocity are the result of the combination of a threshold mechanism and the short intense rainy season in Peru. This study reveals three main driving factors acting at different timescales: (i) over several decades, the river course has significantly changed, causing the Maca landslide reactivation in the 1980s due to the erosion of its toe; (ii) at the year scale, a minimum amount of rainfall is required to trigger the motion and this amount controls the landslide velocity; (iii) transient changes in slide velocity may occur anytime due to earthquakes. This study particularly highlights the non-linear behaviour of the motion with rainfall.
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.
El pueblo de Maca y alrededores durante los últimos años viene siendo afectado de manera recurren... more El pueblo de Maca y alrededores durante los últimos años viene siendo afectado de manera recurrente por procesos de movimientos en masa y actividad sísmica. Estos fenómenos están afectando viviendas, áreas de cultivos (andenes), canales y reservorios, así como infraestructura vial vital para el desplazamiento de la población local y la actividad turística. El Instituto Geológico Minero y Metalúrgico (INGEMMET) y el Instituto de Investigación Para el Desarrollo de Francia (IRD), vienen realizando en Maca, estudios geológicos, geofísicos e hidrogeológicos, la evaluación y zonificación de los peligros geológicos y el monitoreo instrumental de estos fenómenos. Presentamos en este estudio el mapa geológico a nivel de detalle de Maca, el mapa geomorfológicos y de procesos activos, el mapa hidrogeológico, el mapa de susceptibilidad a movimientos en masa y un mapa con recomendaciones de propuestas de intervención. Los movimientos en masa tienen lugar en áreas donde afloran depositos de aval...
We document the first time series of a landslide reactivation by an earthquake using continuous G... more We document the first time series of a landslide reactivation by an earthquake using continuous GPS measurements over the Maca landslide (Peru). Our survey shows a coseismic response of the landslide of about 2 cm, followed by a relaxation period of 5 weeks during which postseismic slip is 3 times greater than the coseismic displacement itself. Our results confirm the coseismic activation of landslides and provide the first observation of a postseismic displacement. These observations are consistent with a mechanical model where slip on the landslide basal interface is governed by rate and state friction, analogous to the mechanics of creeping tectonic faults, opening new perspectives to study the mechanics of landslides and active faults.
Vulcanian explosions at Ubinas volcano, Peru, produce Very Long Period (VLP) events. About 30 exp... 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 that 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 N15°E in the horizontal plane and 40° from the vertical axis.
Journal of Geophysical Research: Earth Surface, 2019
In mountainous environments, slow-moving landslides (velocities <100 m/yr) are a major concern fo... more In mountainous environments, slow-moving landslides (velocities <100 m/yr) are a major concern for local populations. Rainfall is often the dominant forcing, and often result in major changes in kinematics which can mask smaller signals related to internal forcings. We focus here on a major (> 40 Mm 3) slow-moving landslide in the desert of southern Peru, and take advantage of this arid environment to study the internal processes affecting landslide kinematics. We first estimate the ground displacement from timeseries analysis of Landsat-8 images, spanning a 5.7 year period. Systematic artifacts in the optical time-series are shown to correlate with topography, as well as vary seasonally. We apply a novel procedure for correcting these artifacts, which significantly reduces noise in the resulting time-series, thereby allowing us to precisely resolve landslide displacements. We find landslide velocities of up to 35 m/yr, with complex non-linear interannual pattern, including a period of rapid acceleration. We validate our optically-derived time-series using GNSS field measurements, and find uncertainties (RMSE) on the moving mass of 1.12 to 1.55 m. Sudden acceleration of the landslide body after March 2016 may originate from a mass collapse due to retrogression of the headscarp. By coupling sparse 3D GNSS measurements with dense 2D optical time-series data, we show that the headscarp retrogression acts like a wedge, resulting in domino-like tilting of the downward blocks, and accelerates basal sliding over two years. These observations reveal that the dynamics of this retrogressive landslide are predominantly controlled by sediment supply, and that succession of retrogressive and advancing motions is a self entrainment process.
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