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►Introduction : Le développement d’entreprises de recyclage des métaux comme la Société de Traitement Chimique des Métaux (STCM) participe à l’économie circulaire. Cependant, ces activités de recyclage ont durant plusieurs décennies également engendré des émissions de polluants dans l’environnement induisant une augmentation de sites pollués par les retombées atmosphériques de particules fines enrichies en métaux et métalloïdes. Par ailleurs, le ver de terre, organisme clé de l’écosystème sol, apparait comme un ingénieur physique et mécanique des sols, et fait désormais l’objet de nombreuses études environnementales. Pour cette étude, notre objectif était d’évaluer l’influence de la bioturbation des vers de terre sur la phytodisponibilité des métaux et les mécanismes en jeu en lien avec leur compartimentation, leur spéciation et leur écotoxicité. ►Mise en œuvre : Dans ce contexte, une expérience de 25 jours a été menée en microcosmes, avec ou sans vers de terre dans le sol et avec un gradient d’Eléments Traces Inorganiques (ETI) dû aux retombées des particules atmosphériques. L’influence de l’activité des vers de terre sur les transferts sol-plante des métaux a été étudiée au moyen de microcultures de laitues (dispositif RHIZOtests®) réalisées sur 3 conditions différentes de sols : sols non bioturbés (SNB), sols bioturbés (SB) et turricules (T, déjections des vers). Les concentrations en ETI dans les sols, les vers et les salades ont été mesurées et la bioaccessibilité gastrique humaine a été déterminée à partir du test in vitro BARGE. Par ailleurs, des analyses de spéciation chimique du plomb dans divers compartiments abiotiques (sols et turricules) et biotiques (divers organes du vers de terre) ont été réalisées par spectroscopie EXAFS au synchrotron de l’ESRF à Grenoble. ►Résultats & Discussions : L’activité des vers de terre n’est pas significativement impactée par les concentrations en ETI appliquées dans les sols. Mais, la bioturbation des vers augmente la concentration en ETI présents dans les feuilles de laitues (parties consommées par l’homme). La concentration en ETI dans les feuilles de salades peut augmenter avec l’activité des vers de terre, de plus de 45% et 36 % pour le Pb et le Zn respectivement. Généralement, dans les sols et les plantes, les concentrations mesurées en ETI pour les différentes conditions sont classées ainsi : SNB < SB et T. La bioaccessibilité gastrique humaine est fonction de la nature des ETI et augmente pour SB et T, dans le cas du Zn et du Cu notamment. Des changements de spéciation du plomb mettant en évidence l’effet des vers de terre sur le sol ont été observés par spectroscopie EXAFS, en comparant les sols SNB et T, et les tissus des vers de terre. La figure 1 présente les voies d’exposition des ETI pour les vers, et les mécanismes proposés pour expliquer l’augmentation de phytodisponibilité induite par la bioturbation. Figure 1. Voies d’exposition des vers de terre aux ETI et mécanismes potentiellement impliqués dans l’augmentation de phytodisponibilité du fait de la bioturbation. ►Conclusion : La bioturbation des vers de terre modifie le devenir des ETI dans les sols par des changements de spéciation pouvant augmenter la mobilité des métaux, et certainement aussi en raison de modifications de la distribution des matières organiques présentes dans le sol.

International audience; Le béton de ciment Portland est le premier matériau de construction dans le monde car il est facile à produire, résistant mécaniquement et a fait ses preuves de durabilité quand il était bien formulé par rapport à son exposition. Cependant, son impact environnemental est important du fait de l'utilisation de ciment Portland dont son constituant principal, le clinker, est grand consommateur d'énergie et fort contributeur en gaz à effet de serre. Des solutions permettant de diminuer les quantités de clinker sont donc recherchées dans le monde entier. L'Équateur est l'un des pays situés dans la ceinture de feu du Pacifique avec de très nombreux volcans. Or, les cendres volcaniques, présentes en quantité très importantes, sont connues pour améliorer les propriétés des matériaux cimentaires grâce à leur réactivité en milieu basique. Cependant, cette réactivité peut différer de manière notable selon les cendres utilisées. L'objectif de cet article est de qualifier plusieurs essais de laboratoire afin d'évaluer la réactivité de ces cendres volcaniques. Pour cela, 8 cendres, provenant de 4 volcans différents et broyées à la même finesse, ont été étudiées. Les essais pratiqués sont chimiques (essais Chapelle, analyse thermique sur pâtes ou mortiers hydratés), calorimétriques (suivi de la chaleur d'hydratation) ou mécaniques (essais sur mortiers de ciment ou de chaux à différentes échéances). Les résultats montrent une variabilité de réactivité selon le type d'essai pratiqué et le type de cendres. Les résultats obtenus confirment l'intérêt de ce type de matériau, présent à grande échelle, pour améliorer les performances des ciments en Equateur ou dans d'autres régions volcaniques, notamment sur le plan environnemental.

We investigate the relationship between the long-term (Quaternary) interplate coupling and the short-term geodetically derived interseismic coupling at the Central Ecuador subduction zone. At this nonaccretionary margin, the Cabo Pasado shelf promontory and coastal area are associated with two inter-plate geodetically locked patches. The deepest patch ruptured co-seismically during the Mw7.8-2016 Pedernales earthquake, while the shallowest underwent dominantly after-slip. Marine geophysical and chronostratigraphic data allow reconstructing the Quaternary tectonic evolution of the shelf promontory and substantiating variation of the long-term inter-plate coupling that led to the geodetically locked patches. Prior to ∼1.8 Ma, the outer-wedge inter-plate coupling was strong enough to activate trench-subparallel strike-slip faults. Then, between ∼1.8-0.79 Ma, shortening and uplift affected the shelf promontory, implying a locally increased inter-plate coupling. After a short, post-0.79 Ma period of subsidence, shortening and uplift resumed denoting a high inter-plate coupling that endured up to the present. The synchronicity of the structural evolution of the shelf promontory with the subduction chronology of two reliefs of the Carnegie Ridge crest suggests that the locked patches are caused by a geometrical resistance to subduction that propagates landward causing permanent deformation. In 2016, the deepest subducted relief localized stress accumulation and high seismic slip, while the shallowest relief, which is associated with a weakened outer-wedge, prevented updip rupture propagation. Thus, at nonaccretionary margins, active outer-wedge strike-slip faults might be considered a proxi of near-trench coupling, and subducted relief a cause of plate coupling but an obstacle to the tsunami genesis when the relief is shallow. Key Points A trench-parallel strike-slip fault and its earthquake-controlled fault scarps substantiate a pre-1.8 Ma, outer-wedge inter-plate coupling From 1.8 Ma, a robust shelf uplift caused by subducted reliefs highlights a long-term coupling that led to geodetically locked patches The shallowest subducted relief likely impeded the generation of a major tsunami during the Mw7.8, 2016 event Plain Language Summary The 2016-Ecuador earthquake ruptured a subduction fault segment previously locked for decades beneath the coastline. The rupture was arrested updip by another locked fault segment called locked patch, which instead slipped slowly. To understand the cause of the locked patches, their rupture behaviors, and whether the decadal fault locking and long-term subduction processes are related, we reconstructed the Quaternary tectonic evolution of the margin offshore Central Ecuador using geophysical data. We consider that tectonic deformation reflects the long-term inter-plate coupling, which is the ability of the fault to transfer long-term stress and strain to the margin. Prior to ∼1.8 Ma, a trench-subparallel fault accommodating lateral displacement indicates a shallow plate coupling, which increased locally between ∼1.8-0.79 Ma as shown by margin shortening. After a brief subsidence, shortening resumed, denoting a strong coupling that persisted until today in the form of the locked patches. Although many physical factors have been proposed to control plate coupling, here we find that the locked patches are caused by the subduction of two reliefs of a submarine ridge. Remarkably, in 2016, the deepest relief released high elastic strain, while the shallower relief, thrust under a weakened outer-margin, damped updip rupture propagation, impeding a significant tsunami.

International audience; Since the VEI 4 eruption of November 2002, El Reventador volcano (Ecuador) has been the site of persistent open-vent activity characterized by frequent (hourly) Vulcanian-Strombolian explosions and occasional (every few years) effusion of lava flows. The conduit processes that sustain this continuous eruptive activity are still poorly understood. Here we combine high temporal resolution thermal infrared imaging with seismic recordings and DOAS-derived SO2 fluxes focusing on a period of Vulcanian-style activity on 22-23 February 2017. Thermal imagery captured the emission and ascent dynamics of 26 plumes during the observation period, including those fed by explosions and degassing episodes. While most explosions have associated seismic signals, a few are marked by the absence of measurable seismic activity. Degassing episodes also show very few associated seismic signals. Explosions and degassing events seem to follow a sequence that can be explained by changes in the conduit permeability associated with rapid (over time scales of minutes) rheological stiffening of magma in the uppermost portion of the conduit to reduce degassing efficiency. Periods of open-vent outgassing alternate with periods of conduit capping resulting in system pressurization and leading to Vulcanian explosions that reopen the conduit allowing outgassing to resume.; Desde la erupción VEI 4 de noviembre de 2002, el volcán El Reventador (Ecuador) ha sido protagonista de una actividad persistente en sistema abierto (open-vent) caracterizada por explosiones Vulcanianas — Estrombolianas frecuentes (en el orden de horas), y efusión de flujos de lava y piroclásticos ocasionales (en el orden de meses a años). Los procesos en el conducto que sustentan esta continua actividad eruptiva son aún poco conocidos. En este trabajo combinamos el análisis de imagen térmica infrarroja en alta resolución temporal con análisis de señales sísmicas y flujo de SO2 obtenido mediante DOAS, enfocándonos en el periodo de actividad tipo Vulcaniana ocurrida durante el 22 y 23 de febrero de 2017. Las imágenes térmicas registraron la dinámica de emisión y ascenso de 26 plumas durante el periodo de observación, incluyendo aquellas alimentadas por explosiones y episodios de desgasificación. Aunque la mayoría de las explosiones tienen señales sísmicas asociadas, unas pocas se caracterizan por la ausencia de actividad sísmica registrada en los sensores. Los periodos de desgasificación también presentan señales sísmicas asociadas muy pequeñas. Las explosiones y eventos de desgasificación parecen seguir una secuencia o ciclo que puede ser explicado por cambios en la permeabilidad del conducto asociados a una variación rápida (en la escala de minutos) de la rigidez del magma en la parte más somera del conducto, con lo que se limitaría la eficiencia de la desgasificación. La alternancia de periodos de desgasificación en conducto abierto con periodos de taponamiento del conducto da lugar a una presurización del sistema derivando en explosiones Vulcanianas que vuelven a abrir el conducto, lo que reanuda la secuencia con un nuevo proceso de desgasificación.

International audience; Summary In 1906, an earthquake with a magnitude estimated between Mw 8.4 and 8.8 occurred in the subduction zone along the coast of Ecuador and Colombia. This earthquake caused extensive damage on the coast but had a rather small impact on the capital city of Quito, situated 180 km away. At that time, the city of Quito extended over a small area with a few thousand inhabitants, while today it stretches over 40 km and has a population of over 3 million, with most of the city built without paraseismic regulations. The aim of this study is to obtain new insights on the impact that large earthquakes from the subduction zone would have on the city today. This question is crucial since we know that the city of Quito is prone to site effects and that the southern part of the city amplifies seismic waves at low frequencies, around 0.3-0.4 Hz (Laurendeau et al., 2017). In April 2016, an Mw 7.8 earthquake occurred on the subduction interface in the Pedernales area. This event was the first large earthquake in the city of Quito to be well recorded by 13 stations of the permanent accelerometric network (RENAC). In this study, we take advantage of this dataset (mainshock and large aftershock recordings) to (1) test an empirical Green's function blind simulation approach where the input stress drop is taken from a global catalog of source time functions, (2) compare the synthetic accelerograms and ground motion values we obtain for an Mw 7.8 earthquake with the actual recordings of the Pedernales earthquake, and then (3) simulate larger earthquakes of Mw 8.2 and Mw 8.5 from the subduction zone. For Mw 7.8 simulations, our approach allows a good reproduction of the ground motions in the whole frequency bands and properly takes into account site effects. For Mw 8.2 and Mw 8.5 simulations, we obtain for the stations in the southern part of the basin, larger values at low frequencies than the predicted motion given by Ground Motion Models (GMMs). These values, although high, should be supported by new or recent buildings if they are constructed respecting the building code that applies in Quito. Therefore, for this type of strong but distant earthquake, the seismic standards appear to be well suited and it is imperative to ensure that they are well considered in the design of the new buildings to be constructed, especially in the southern part of the expanding city.

International audience; Termites are key soil bioturbators in tropical ecosystems. Apart from mound nests constructed by some advanced lineages, most of the species use their faeces, oral secretions, debris, or soil aggregates to protect themselves from predators and desiccation when they go out to forage. Although this soil ‘sheeting’ is considered to play a key role in soil functioning, the properties of this termite-made material has been poorly studied. The few available data showed that sheeting properties are highly variable with positive, neutral or negative impacts on soil C and clay content, and consequently on soil aggregate stability. Therefore, the objective of this study was to determine the factors controlling the physical (particle size fractions and structural stability) and chemical (pH, electrical conductivity and carbon content) properties of soil sheeting produced by termite species encompassing all feeding and building categories using a dataset representative of an important diversity of biotopes coming from 21 countries from all continents colonized by termites. We showed that sheeting properties were explained by the properties of their environment, and especially by those of the bulk soil (linear relationships), followed in a lesser extent by the mean annual precipitation and biotope. Classic hypotheses related to termite feeding and building strategies were not hold by our analysis. However, the distinction of termites into fungus-growing and non-fungus growing species was useful when differentiating the impact of termites on soil electrical conductivity, C content, and structural stability. The large variability observed suggests the need to redefine termite functional groups based on their impacts on soil properties using a trait-based approach from morphological, anatomical and/or physiological traits.

co-auteur étranger; International audience; Tephra fallout hazard assessment is undertaken with probabilistic maps that rely on numerical models. Regarding maps production, the input parameters of the model (including atmospheric conditions), the physical approximations of the numerical simulations, and the probabilities of occurrence of different eruption types in specific time frames are among the most critical sources of uncertainty. We therefore present a tephra fallout hazard assessment study for two active volcanoes (Cotopaxi and Guagua Pichincha) in Ecuador. We utilize PLUME-MoM/HYSPLIT models, and a procedure for uncertainty quantification where: i) the uncertainty on eruptive source parameters and eruption type occurrence is quantified through expert elicitation; ii) we implement a new procedure for correlations between the different parameters, and iii) we use correction coeffients to take into account the uncertainty of the numerical model. Maps of exceedance probability given a deposit thickness threshold, and thickness maps given a robability of exceedence, are produced 1) for two eruptive scenarios (sub-plinian and Plinian) and 2) as a combination of these scenarios in case the next eruption will be sub-Plinian or Plinian. These maps are described according to the uncertainty distribution of eruption type occurrence probabilities, considering their 5th percentile, mean, and 95th percentile values. We finally present hazard curves describing exceeding probabilities in 10 sensitive sites within the city of Quito. Additional information includes the areal extent and the population potentially affected by different isolines of tephra accumulation. This work indicates that full uncertainty quantification helps in providing more robust scientific information, improving the hazard assessment reliability.

Tephra layers preserved in marine sediments are strong tools to study the frequency, magnitude and source of past major explosive eruptions. Thirty-seven volcanoes from the Ecuadorian and Colombian arc, in the northern Andes, experienced at least one eruption during the Holocene. The volcanic hazard is therefore particularly high for the populated areas of the Andes and in particular cases for the coastal region, and it is crucial to document such events to improve hazard assessment. The age and distribution of deposits from major Holocene eruptions have been studied in the Cordillera, but no descriptions of distal fallouts have been published. In this study we focused on 28 Holocene tephra layers recorded in marine sediment cores collected along the northern Ecuador - southern Colombia margin. New lithological, geochemical and isotope data together with 14C datings on foraminifers allow us to determine the age and volcanic source of marine tephra, and to propose a first land-sea correlation of distal tephra fallouts. We show that at least seven explosive eruptions from Guagua Pichincha, Atacazo-Ninahuilca, Cotopaxi, and Cerro Machín volcanoes left tephra deposits recorded in marine cores over 250 km away from their source. Volume estimates of emitted tephra range between 1.3 and 6.0 km3 for the 10th century Guagua Pichincha, ∼5 ka Atacazo-Ninahuilca, ∼6.7 and ∼7.9 ka Cotopaxi events, suggesting that they were eruptions of Volcanic Explosivity Index of 5. The distribution of these deposits also brings new constraints for a better evaluation of the volcanic hazard in Ecuador. Key Points We propose a first land-sea correlation of distal Holocene tephra off Ecuador based on 14C age and geochemical data Products from at least seven explosive Holocene eruptions in Ecuador and south Colombia reached the Pacific Ocean Volumes of tephra emitted by largest eruptions vary between 1.3 and 6.0 km3, suggesting they were VEI-5 eruptions Plain Language Summary During major explosive eruptions, large volumes of gases and tephra (lapilli and ash particles) are thrown into the atmosphere and can be spread by winds over hundreds of kilometers and more. Tephra fallouts can impact the population, infrastructures and climate. It is therefore essential to document the age and magnitude of past major eruptions to better assess the volcanic hazards. In this study we use the minerology, glass shard morphology, and the geochemical composition of tephra settled in marine sediments off Ecuador and Colombia to investigate their source. Thickness of tephra layers and radiocarbon ages performed on under- and over-lying marine fauna allow us to determine the age of the eruptions, whereas the distribution of tephra yields constraints on the volume of fallout deposits. We show that the largest explosive eruptions from Ecuadorian and Colombian volcanoes reached the Pacific Ocean with a recurrence rate of about 1.5 events per millennium over the past 8 kyr.

Made available in DSpace on 2022-04-28T19:51:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-01-01 This paper investigates the secrecy performance of a power splitting-based simultaneous wireless information and power transfer cooperative relay network in the presence of an eavesdropper. The relay is considered to operate in full-duplex (FD) mode to perform both energy harvesting and information decoding simultaneously. To accomplish that, the relay is assumed to employ two rechargeable batteries, which switch between power supplying mode and charging mode at each transmission block. We also assume that the self-interference inherent of the FD mode is not completely suppressed. Therefore, it is assumed that, after some stages of passive and active self-interference cancellation, there is still a residual self-interference (RSI). A portion of this RSI (remaining after passive cancellation) is recycled for energy harvesting. In order to improve the system secrecy performance, it is considered that the relay can split its transmit power to send the information signal and to emit a jamming signal to degrade the eavesdropper's channel. The secrecy performance is evaluated in terms of the secrecy outage probability and the optimal secrecy throughput. Tight-approximate and asymptotic expressions are obtained for the secrecy outage probability, and the particle swarm optimization method is employed for addressing the secrecy throughput optimization problem. From numerical results, we show that the secrecy performance can be increased depending on the self-energy recycling channel condition. Finally, our derived expressions are validated via Monte Carlo simulations. São Paulo State University (UNESP) Campus of São João da Boa Vista, São João da Boa Vista Departamento de Electrónica Telecomunicaciones y Redes de Información Escuela Politécnica Nacional (EPN) Centre for Wireless Communications (CWC) University of Oulu São Paulo State University (UNESP) Campus of São João da Boa Vista, São João da Boa Vista

We study the existence of global weak solutions of a nonlinear transport-diffusion equation with a fractional derivative in the time variable and under some extra hypotheses, we also study some regularity properties for this type of solutions. In the system considered here, the diffusion operator is given by a fractional Laplacian and the nonlinear drift is assumed to be divergence free and it is assumed to satisfy some general stability and boundedness properties in Lebesgue spaces.

International audience; Study regionThe upper part of the Guayllabamba and Napo basins (78.2 ° W, 0.3 °S; 18,500 km2) in the equatorial Andes, which are vulnerable to stress on the ecosystem services.Study focusThis paper analyses the diurnal cycle of precipitation over a transect from the Andes to the Amazon. The diurnal cycle is estimated as the diurnal distribution of precipitation for 2014–2019 using records from 80 stations. Cluster analysis performed on the diurnal cycle estimates depicts the spatial association between the diurnal and seasonal cycles of precipitation.New hydrological insightsA northwest-southeast spatial variation in the diurnal and seasonal cycles is identified with four groups of stations. In the western part, the seasonal cycles of Groups 1 and 2 are bimodal with precipitation maxima in the March-April and October-November seasons and a short drier season in July-August. In the eastern part, Group 3 also presents bimodality, but a weaker seasonal cycle. Conversely, Group 4 is unimodal with a peak in June. Distinct diurnal cycles are observed in both drier and wetter seasons of Groups 1–3; no marked diurnal cycle is observed in Group 4. Groups 3 and 4 are the most spatially heterogeneous, with an exceptional horizontal variation of 330 mm/yr/km. The analysis of these variations provides insight into the atmospheric dynamics driving precipitation in this zone, and may help to better optimize the water supply system.

International audience; Extensional faults are often observed along subduction zones as a response of a margincollapse. However, their role remain underestimated within the structural evolution offorearc systems. In southern Ecuador, the oblique subduction of the Nazca Platebeneath South America led to the formation of the Cretaceous-Miocene NW-SEChongón-Colonche Cordillera surrounded by Eocene-to-recent sedimentary basins.This region, generally interpreted as an onshore-offshore compressional forearc,interferes with the active tectonic escape of the North Andean Sliver and the opening ofthe Gulf of Guayaquil.Herein, we explore fault distribution and kinematics along the onshore-offshore SantaElena Peninsula using academic and industrial 2D seismic profiles calibrated with wellsand field data. Polyphase trench-parallel and NW-SE-trending, >20km-long normalfaults are observed cross-cutting the former Chongón-Colonche thrust wedge. Faultsare either steep and oceanward-dipping along the trench, or low-angle continentward-dipping through the platform where they likely reactivate former thrusts. Wespecifically observe repeated extensional pulses during Eocene, Miocene and Plio-Pleistocene times, separated by inversion periods, and shaping the geometry of variousforearc basins. In the Late Pleistocene, normal faults are also associated with upliftedmarine terraces.We interpret normal faulting as an overlap of long-term and short-term processes, suchas the subduction of bathymetric asperities, underplating and/or variations ofconvergence velocity, and more recently the North Andean Sliver escape. NW-SEextensional structures dissect the overall thrust wedge through the Cenozoic and arecombined with N-S to NW-SE active faults over the Quaternary. This polyphase settingshows eastward-stacked accretionary wedges with thrusts reactivated as normal faults,suggesting that pervasive inheritance processes take place continuously. This project ispart of the ANR MARACAS (ANR-18-CE31-0022, MARine terraces along the northernAndean Coast as a proxy for seismic hazard ASsessment).

National audience; Along the Ecuadorian convergent margin, the onshore Manabí sedimentary forearcbasin is bounded to the east by the foothills of the Andes, while to the north and west, itis limited by the Canandé and Jama fault systems. The fault systems limit basementblocks resulting from the fragmentation of an oceanic plateau topped by island arcs,which were accreted against the continental margin during the Late Cretaceous toEocene times. From the interpretation of 2D seismic reflection profiles we identify thesyn- and post-accretionary tectonic phases recorded in the Manabí basin area. Werecognize 9 seismic units (S1 to S9) above the acoustic basement (Ub) separated by 9unconformities (U1 to U9), which were dated by the correlation with the Ricaurte-1well and regional stratigraphy.Seismic units S1-S2 (Late Cretaceous to Eocene) onlap irregular basement topographyinterpreted as inheritance of eroded island arcs prior to accretion. S1 is deformedby low angle NE-dipping thrust faults, which were sealed by regional unconformity U1.This unconformity is tentatively dated ~75 Ma and correlated with an early stage ofcollision. Then, E-dipping reverse faults were developed in the foothills of the Andesand are associated to an erosional and sedimentary hiatus (U2, Early-Middle Eocene),marking the last stage of accretion. The development of the modern forearc basin ismarked by S3 deposition (Oligocene), which extends beyond the current edges of thebasin. Then the overlying S4 depocenter (Early Miocene) migrated eastward as a resultof the higher subsidence and depositional rates associated to the orogenic buildingeffects of the Andean reliefs. An extensional stage is evidenced by a fan shape of S5(17.8 -15.9 Ma) against the Jama fault. After U5 (top dated 15.9 Ma) and up to U8 (~5Ma), a sedimentary platform was built by NW sedimentary progradation, thus markinga remarkable change in the mode of basin filling. The Coastal Cordillera uplifts during aPliocene compressional stage (post S8) marked by a antiform development along theJama fault system, and the uplift of the footwall block of the Canandé fault.Synchronously, Santo Domingo fan developed at the foot of the Andes causing theeastward down flexing of flat erosional surface U9. This stage coincides with the arrivalin subduction of the Carnegie ridge.

International audience; The recent development of a national seismic broadband network in Ecuador enables us to determine a comprehensive catalog of earthquake focal mechanisms at the country-scale. Using a waveform inversion technique accounting for the spatially variable seismic velocity structure across the country, we provide location, depth, focal mechanism and seismic moment for 282 earthquakes during the 2009–2015 period. Our results are consistent with source parameter determinations at the global scale for the largest events, and increase the number of waveform-based focal mechanism solutions by a factor of two. Our new catalog provides additional constraints on the active deformation processes in Ecuador. Along the Ecuador margin, we find a correlation between the focal mechanisms and the strength of interseismic locking at the subduction interface derived from GPS measurements: thrust earthquakes predominate in Northern Ecuador where interseismic locking is high, while the low-to-moderate locking in Central and Southern Ecuador results in variable fault plane orientations. Focal mechanisms for crustal earthquakes are consistent with the principal axis of strain rate field derived from GPS data and with the location of the main active faults. Our catalog helps to determine the earthquake type to be expected in each of the seismic zones that have recently been proposed for probabilistic seismic hazard assessment.

Monitoring precipitation in mountainous areas using traditional tipping-bucket rain gauges (TPB) has become challenging in sites with strong variations of air temperature and wind speed (Ws). The drop size distributions (DSD), amount, and precipitation-type of a Parsivel OTT2 disdrometer installed at 4730 m above sea level (close to the 0 °C isotherm) in the glacier foreland of the Antisana volcano in Ecuador are used to analyze the precipitation type. To correct the DSDs, we removed spurious particles and shifted fall velocities such that the mean value matches with the fall velocity–diameter relationship of rain, snow, graupel, and hail. Solid (SP) and liquid precipitation (LP) were identified through −1 and 3 °C thresholds and then grouped into low, medium, and high Ws categories by k-means approach. Changes in DSDs were tracked using concentration spectra and particle’s contribution by diameter and fall velocity. Thus, variations of concentration/dispersion and removed hydrometeors were linked with Ws changes. Corrected precipitation, assuming constant density (1 g cm−3), gives reliable results for LP with respect to measurements at TPB and overestimates SP measured in disdrometer. Therefore, corrected precipitation varying density models achieved fewer differences. These results are the first insight toward the understating of precipitation microphysics in a high-altitude site of the tropical Andes.

Hydrogeology in the Andes cordillera reflects its complex geological history. In most cases, groundwater flows through fractures and faults that compartmentalize the volcanic material, and through the primary porosity of the volcano-sedimentary material. The volcanic mineral context and geothermal environment mark the groundwater chemistry, especially in the high concentrations of specific trace elements. This study focuses on the complex system of the Tumbaco – Cumbayá – Los Chillos aquifer, in the vicinity of the Ilaló volcano near Quito (Ecuador). Hydrodynamic, geochemical and isotopic tools were used to assess the chemical characteristics of water and its origin, identify the recharge areas, and estimate the transit time of water using simple methods and scarce data. Results revealed two distinct aquifers, one in the volcanic cone located in the center of the study area, and the other in the volcano-sedimentary series of the Tumbaco – Cumbayá – Los Chillos valley. The volcanic aquifer is characterized by a high mineralization, a recharge zone between 2400 m asl and 3100 m asl, and radiocarbon concentrations lower than 20 pmc. The volcano-sedimentary aquifer seems to behave as a partly disconnected system, between the north and the south of Ilaló volcano, and also with a great heterogeneity, maybe due to the presence of lenses of volcanic ash. It has an intermediate mineralization, a mean recharge zone between 2,300 and 2,700 m asl, and 14C activities between 45.4 and 87.4 pmc in apparent contradiction with the hydrodynamic mass balance.

International audience; Correlations between marine distal ash layers and continental proximal volcanic deposits constitute a strong tool to investigate the eruptive chronology of an active volcanic arc, to constrain the detailed stratigraphy of the marine sediments, as well as help constraining the magnitude of some large explosive eruptions.In the Andean Northern Volcanic Zone (NVZ), Ecuadorian Holocene major explosive eruptions have been widely documented over the past 30 years, and a large geochemical and geochronological database is available. However, the dispersion of distal volcanic products associated with these events is poorly known, and investigation of offshore tephra fallout deposits appears essential to clarify the recurrence, magnitude, and impact of past major explosive eruptions, and thus better define the volcanic hazards.We present for the first time chemical and morphological features of 30 Holocene tephra layers sampled in marine cores off the Ecuadorian coast during the Amadeus and Atacames cruises. Tephra layers are mainly composed of glass shards visible to the naked eye (~50-150 µm) with some calcareous nannofossils, foraminifera and diatoms. We present new geochemical data obtained on these tephra layers and compare different analysis techniques applied on such material. Major and trace element contents were measured on single glass shards by electron microprobe and LA-ICP-MS (Laser Ablation Inductively Coupled Plasma Mass Spectrometry), respectively, and compared to bulk whole-rock measurements performed by ICP-AES (Atomic Emission Spectrometry). Pb isotopic composition was analyzed by MC-ICP-MS (MultiCollector ICP-MS). Comparison of the chemical and isotopic signature of marine tephra with data acquired on land allows us to correlate some historic events, but also highlights eruptions that do not seem to have been described otherwise.Finally, land-sea correlations of tephra fallout deposits will also provide temporal constraints to marine seismic records, constrain the age of the tectonic structures of the basin, and possibly better define the recurrence of paleoearthquakes in this region where the seismic hazard is particularly high.

Mineral-hosted melt inclusions have become an important source of information on magmatic processes. As the number of melt inclusion studies increases, so does the need to establish recommended practice guidelines for collecting and reporting melt inclusion data. These guidelines are intended to ensure certain quality criteria are met and to achieve consistency among published melt inclusion data in order to maximize their utility in the future. Indeed, with the improvement of analytical techniques, new processes affecting melt inclusions are identified. It is thus critical to be able to reprocess any previously published data, such that reporting the raw data is one of the first “recommended practices” for authors and a publication-criteria that reviewers should be sensitive to. Our guidelines start with melt inclusion selection, which is a critical first step, and then continue on to melt inclusion preparation and analysis, covering the entire field of methods applicable to melt inclusions. Dedication In March of 2000, a melt inclusion workshop was held at the Chateau de Sassenage in Grenoble and a companion issue of Chemical Geology entitled “Melt Inclusions at the Millennium” was published. Erik Hauri was heavily involved with the meeting and contributed two landmark papers to the topical issue of Chemical Geology on the use of secondary ion mass spectrometry to analyze volatiles in melt inclusions. When the melt inclusion community re-convened at Woods Hole Oceanographic Institution (WHOI) in August of 2018, we were saddened that Erik was unable to join us due to his failing health. Less than a month later came the devastating news of his passing at only 52 years of age. In recognition of his incredible contributions to science in general and to the in situ analysis of melt inclusions in particular, the participants and organizers of the WHOI melt inclusion workshop dedicate this collegial paper to Erik Hauri, our colleague, mentor and friend. Thank you Erik.

International audience; Repeating earthquakes repeatedly rupture the same seismic asperity and are strongly linked to aseismic slip. Here, we study the repeating aftershocks of the April 16, 2016 MW 7.8 Pedernales earthquake in Ecuador, which generated a large amount of afterslip. Using temporary and permanent stations, we correlate waveforms from a one‐year catalog of aftershocks. We sort events with a minimum correlation coefficient of 0.95 into preliminary families, which are then expanded using template‐matching to include events from April 2015 to June 2017. In total, 376 repeaters are classified into 62 families of 4–15 events. They are relocated, first using manual picks, and then using a double difference method. We find repeating earthquakes during the whole period, occurring primarily within large aftershock clusters on the edges of the areas of largest afterslip release. Their recurrence times, shortened by the mainshock, subsequently increase following an Omori‐type law, providing a timeframe for the afterslip's deceleration. Although they are linked temporally to the afterslip, repeater‐derived estimates of slip differ significantly from GPS‐based models. Combined with the fact that repeaters appear more spatially correlated with the afterslip gradient than with the afterslip maxima, we suggest that stress accumulation at the edge of the afterslip may guide repeater behavior.

We use 40 continuous GPS stations in Ecuador to quantify 3 years of the post-seismic deformation that followed the Mw 7.8 April 16 Pedernales earthquake. We perform a kinematic inversion solving for the daily slip along the subduction to retrieve the afterslip evolution through time and space.Rolandone et al. (2018) had found that the afterslip during the first 30 days following the earthquake was abnormally large and rapid, mainly developing at discrete patches north and south updip of the co-seismic rupture. We find that large slip and slip rate continue at both location, decreasing through time. However, models suggest that modulations of slip rate occur within those areas, with episods of slip acceleration sometimes associated with the occurrence of moderate size aftershocks. Aside these patches, afterslip developed updip the co-seismic rupture between the patches and downdip of the coseismic rupture, with little slip occurring within the co-seismic rupture.The overall model confirms a model of a seismic asperity encompassed in a subduction interface releasing stress through aseismic processes. However, some areas experiencing afterslip appear to be locked before the earthquake. Furthermore, those areas experienced SSE before the earthquake and during the afterslip period, raising the question of the friction parameter controlling their behavior.In terms of moment, the amount of afterslip after 3 years is equivalent to 90% of the moment released by the Pedernales earthquake. This observation highlights that aseismic slip has an important contribution to the balance of slip during the earthquake cycle along the central Ecuador segment. This observation strengthens the proposed hypothesis of earthquake an super-cycle in central Ecuador (Nocquet et al., 2017), by confirming that the occurrence of three successive major earthquakes within 110 years exceeds the moment accumulation as derived from a decade of interseismic coupling models spanning a decade before the 2016 earthquake.

International audience; Network users usually need a third party validation to prove that they are who they claim to be. Authentication systems mostly assume the existence of a Trusted Third Party (TTP) in the form of a Certificate Authority (CA) or as an authentication server. However, relying on a TTP implies that users do not directly manage their identities, but delegate this role to a third party. This intrinsic issue can generate trust concerns (e.g., identity theft), as well as privacy concerns towards the third party. The main objective of this research is to present an autonomous and independent solution where users can store their self created credentials without depending on TTPs. To this aim, the use of an TTP autonomous and independent network is needed, where users can manage and assess their identities themselves. In this paper, we propose the framework called Three Blockchains Identity Management with Elliptic Curve Cryptography (3BI-ECC). With our proposed framework, the users' identities are self-generated and validated by their owners. Moreover, it allows the users to customize the information they want to share with third parties.

co-auteur étranger; International audience; The monitoring of the frequency, intensity/magnitude and dynamics of explosive events at volcanoes in a state of unrest is key to surveying and forecasting their activity. Thermal and visual video observations of eruptive phenomena, and their correlation with data from deformation and seismic networks, are often limited by technical constraints including lack of time synchronisation, data volumes and power consumption. Several solutions are currently available and here we present an instrument designed for the permanent and real-time observation of volcanic explosive events in the visible and thermal infrared wavelengths, the output of which can be fully synchronised with ancillary monitoring data. Our system (VIGIA: visual and infrared ground-based imagery analyser) follows an edge computing approach whereby information is processed on-site, and periodic reports are sent to the local observatory and the system “decides” when to acquire high-temporal resolution data so as to capture key explosive events. As a permanent installation, VIGIA enables the continuous, long-term and time-synchronised observation of volcanic activity while reducing power consumption and data volumes. We suggest that VIGIA-style instruments could provide useful scientific and monitoring information, and provide here the key details of the components, assembly, and code so that observatories can replicate the system and build their own VIGIA at minimal cost. We use the Reventador volcano, in Ecuador, as a case study to present the capabilities of the instrument.

International audience; The degradation of Schottky Barrier Diodes (SBDs) with a Gated Edge Termination (GET) under on-state stress conditions is studied for a 650 V GaN-on-Si technology. Reliability metric techniques previously used in MOS-HEMTs are applied in this work due to a similar MIS gate stack architecture in GET-SBDs. Here, the density of traps is analyzed in GET structures where the dielectric is either Si 3 N 4 (nitride-based) or a stack of Al 2 O 3 /SiO 2 (oxide-based). Statistical analysis across two wafers indicates some systematic differences in turn-on voltage degradation depending on wafer location, likely caused by process-related variations. Under 1000 s stress time and ON-state voltage, the number of trapped charges in nitride-based dielectric devices keeps increasing. This suggests an ongoing dielectric degradation. On the other hand, Al 2 O 3 /SiO 2 dielectric devices with an Al-based interfacial layer (IL) exhibit less process-induced variability across the wafer along with a lower density of trapped charges compared with nitride-based dielectric diodes under the same stress conditions suggesting better reliability and process improvement.

The North Andean Sliver (hereinafter NAS) lies at the northwestern end of the South American plate (hereinafter SOAM). This extensive area exhibits a complex deformation process controlled by the interactions of Nazca, Caribbean, South America plates, and Panama block, producing crustal seismicity, arc-continental collision, and subduction processes. Previous models based on partial GPS data sets have estimated the NAS kinematics as a single rigid block moving towards northeast at 8-10 mm/yr (Nocquet et al. 2014, Mora-Paez et al 2019). By contrary, geologic interpretations as well as seismotectonic data propose more complex kinematic models based on the interaction of several blocks (Audemard et al 2014, Alvarado et al 2016). Here, we present an updated and most extensive interseismic horizontal velocity field derived from continuous and episodic GPS data between 1994 and 2019 that encompasses the whole North Andean Sliver. We then interpret it, developing a kinematic elastic block model in order to simultaneously estimate rigid block rotations, consistent slip rates at faults and the spatial distribution of interseismic coupling at the Nazca/NAS megathrust interface. Our model is not constrained either by a priori information derived from geologic slip rates or by a priori information of creeping faults. In contrast with previous simplest models, our model will allow us to estimate the degree of slip partitioning more precisely along the NAZCA/SOAM convergence as well as an improved model of interseismic coupling. We will discuss our coupling distribution with respect to previous models, and our block geometry quantifying the goodness of fit, resolution, and considering its consistency with geological interpretations.

International audience; In this work, we are studying the effect of the technology scaling for different full-wave rectifier topologies using the Cross-Coupled Differential Drive (CCDD) strategy to implement a multiplier. For a conventional CCDD scaling from 90nm to 32nm, the PCE and VCE are maintained the same while a large degradation of the dynamic range and sensitivity are observed. This effect could be slightly limited by using a self-body bias CCDD topology. However, the use of TFET enables to avoid this degradation and provide a large VCE and output voltage for input voltage lower than 300mV. To extend this VCE for input voltage > 300mV, we use a CCDD topology increasing the loading drive capability. Interestingly, this resulted not only on increasing the output voltage for large Vin but also demonstrated larger PCE than expected for this topology.

International audience

Since cacao beans accumulate Cd in high levels and restrictions have been imposed on safe levels of chocolate consumption, concern about whether or not cacao trees store other toxic elements seems to be inevitable. Following a previous study in Ecuador examining Cd content in five cacao varieties collected in pristine areas and in places impacted by oil activities, we present here the concentrations of 11 trace elements (TEs) (As, Ba, Co, Cu, Cr, Mo, Mn, Ni, Pb, V and Zn) in soils, cacao tissues (leaves, pod husks, beans) and cocoa liquor (CL). Several TEs showed concentrations in topsoils above the Ecuadorian limits, and may have a mixed natural and anthropogenic origin. Ba and Mo concentrations in cacao tissues are slightly higher than those reported in other surveys, but this was not the case for toxic elements (As and Pb). TE contents are lower in CL, than in beans, except for Pb and Co, but no risk was identified for human health. Compared with control areas, Enrichment Factors were below 2 in impacted areas, except for Ba. Transfer factors (from soils to cacao) indicated that cacao does not accumulate TEs. A positive correlation was found between Cd and Zn in topsoils and cacao tissues for the CCN-51 variety, and between Cd and Ni for the Nacional variety. Identifying patterns of TE distribution and potential interactions in order to explain plant internal mechanisms, which is also dependent on the cacao variety, is a difficult task and needs further research.

International audience; The Billecocha plateau (4000 m a.s.l.) lies in the high elevation Ecuadorian Andes volcanic arc. It overhangs by 2000 m above the interandean valley. Both the plateau and surrounding volcanoes are heavily affected by active faulting characterized by straight, sharp and discontinuous scarps within a 6 km wide and 24 km long corridor. Contrasting interpretations have been proposed to explain the expression at surface of the so-called Billecocha fault system (BFS), from normal faulting related to postglacial elastic rebound or gravitational processes, to right-lateral faulting compatible with the North-Andean Sliver tectonic regime. The instrumental seismicity recorded around the BFS is low, however, a M~7 earthquake heavily struck the region in 1868.With the aim to discuss the kinematic and coseismic nature of the encountered deformations as well as the seismogenic character of the BFS, we performed (1) morphological analysis to map and quantify evidence of active faulting and (2) paleoseismological investigations across the longer segment of the fault system. In three trenches, we show that surface deformations are at least partly coseismic in origin during the Holocene with a minor lateral component, the last paleoseismic event being compatible in date with the 1868 earthquake. In addition, some of the enlightened paleoseismic events could have occurred in relationship with volcanic eruptions of the surrounding volcanoes.While field evidence of reverse and strike slip faulting suggests that regional tectonics could be involved, the geomorphological signature of the BFS at the mountain scale, as seen on the digital surface model, can partly be related to the development of deep seated gravitational deformations, hence suggesting an interaction between boundary (i.e. tectonic, volcanic) and body forces (i.e. gravity, post-glacial rebound). Further studies are however mandatory to better address the influence of each process at the BFS, in particular geodetic and seismological surveys.Given the available data, we suggest that the BFS could actually correspond to the distributed surface expression of the tectonic reactivation of the inherited Pujilí suture, enhanced by gravitational phenomenon. In this light, paleoearthquakes identified along the BFS may help evidencing the recurrence of major events in the region. However, it also imply that surface deformations along the BFS shall not be used without a careful and more detailed field work to derive fault slip rates for seismic hazard calculations.

Along the Western Cordillera of Ecuador, fault-bounded ophiolites derived from the Late Cretaceous Caribbean Large Igneous Province (CLIP) have provided key petrotectonic indicators that outline the nature and the mechanism of continental growth in this region. However, most of the forearc basement across Western Ecuador is buried under sediments impairing its crustal structure understanding. Here, we propose a first crustal model throughout the spectral analysis of gravity and aeromagnetic data, constrained by observations made both at the surface and at the subsurface. Three main geophysical domains, within the North Andean Sliver in Western Ecuador, have been defined based on spectral analysis and augmented by 2D forward models. An outer domain, characterized by magnetic anomalies associated with mafic rocks, coincides with evidence of a split intraoceanic arc system. An inner domain is governed by long-wavelength mid to deep crust-sourced gravity and magnetic anomalies possibly evidencing the root of a paleoisland arc and the residuum of a partial melting event with subsequent associated serpentinization, the latest possibly associated with an obduction process during the middle Eocene-Oligocene. In addition, our model supports the presence of a lithospheric vertical tear fault, herein the southern suture domain, inherited from an oblique arc-continent interaction. Our interpretation also brings new insights and constraints on the early geodynamic evolution of the Ecuadorian forearc and provides evidence on the structural style and preservation potential of the forearc basement, most likely the roots of a mature island arc built within an oceanic plateau.

International audience; Most of the authentication protocols assume the existence of a Trusted Third Party (TTP) in the form of a Certificate Authority or as an authentication server. The main objective of this research is to present an autonomous solution where users could store their credentials, without depending on TTPs. For this, the use of an autonomous network is imperative, where users could use their uniqueness in order to identify themselves. We propose the framework “Three Blockchains Identity Management with Elliptic Curve Cryptography (3BI-ECC)”. Our proposed framework is a decentralize identity management system where users’ identities are self-generated.

We propose a theoretical model of a non-local dipersive-dissipative equation which contains as a particular case a large class of non-local PDE's arising from stratified flows. Within this fairly general framework, we study the spatial behavior of solutions proving some sharp pointwise and averaged decay properties as well as some pointwise grow properties.

Based on new geological data and the analysis of a 4 m spatial resolution Digital Elevation Model (DEM), we provide a detailed and comprehensive description of section of the Chingual Cosanga Pallatanga Puna Fault System, a major active fault system in Ecuador. This work allows estimating new slip rates and large earthquakes parameters (displacement, recurrence) along a similar to 100 km-long section of the continental-scale dextral shear zone that accommodates the extrusion of the North Andean Sliver with respect to the South America continental Plate. We focus on the NE-SW Pallatanga strike-slip fault zone and related contractional and transcurrent features that extend to the north in the Inter-Andean valley and the Cordillera Real, respectively. The detailed analysis of the available DEM allowed mapping a series of lineaments at the regional scale and along the entire fault system. Field studies on key areas show valley deflections, aligned and elongated hills of Tertiary or Quaternary sediments, as well as faulted Holocene deposits and even preserved coseismic free-face ruptures in some places. Such morphological anomalies strongly suggest that those landscape scars represent long-living (Holocene to historical times) earthquake faults. Altogether, these new data confirm that very large crustal earthquakes (M similar to 7.5) have been generated along the fault system, probably during multiple segment ruptures. This conclusion agrees with reports of large earthquakes during historical times (post-1532 CE) in 1698, 1797, and 1949. They all occurred in the vicinity of the Pallatanga fault, causing catastrophic effects on environmental and cultural features. Based on new sample dating of both soils and volcanic series, we infer that the NE-SW dextral Pallatanga fault slips at rates ranging from similar to 2 to 6 mm/yr for southern and central strands of the studied area, respectively. Further north, surface faulting is distributed and the deformation appears to be partitioned between sub-meridian fault-related folds (similar to 2 mm/yr) and NE-SW strike-slip fault(s), like the similar to 1 mm/yr Pisayambo Fault that ruptured the surface in 2010. All this information offers the opportunity to size the earthquake sources for further seismic hazard analyses.

Displacement waveforms derived from Global Navigation Satellite System (GNSS) data have become more commonly used by seismologists in the past 15 yrs. Unlike strong‐motion accelerometer recordings that are affected by baseline offsets during very strong shaking, GNSS data record displacement with fidelity down to 0 Hz. Unfortunately, fully processed GNSS waveform data are still scarce because of limited public availability and the highly technical nature of GNSS processing. In an effort to further the use and adoption of high‐rate (HR) GNSS for earthquake seismology, ground‐motion studies, and structural monitoring applications, we describe and make available a database of fully curated HR‐GNSS displacement waveforms for significant earthquakes. We include data from HR‐GNSS networks at near‐source to regional distances (1–1000 km) for 29 earthquakes between Mw 6.0 and 9.0 worldwide. As a demonstration of the utility of this dataset, we model the magnitude scaling properties of peak ground displacements (PGDs) for these events. In addition to tripling the number of earthquakes used in previous PGD scaling studies, the number of data points over a range of distances and magnitudes is dramatically increased. The data are made available as a compressed archive with the article. The authors thank Ronni Grapenthin and Valerie Sahakian for helpful discussions on the peak ground displacement (PGD) scaling law and residuals. This work was funded by the Gordon and Betty Moore Foundation through Grant GBMF3024 to University of California (UC) Berkeley and the U.S. Geological Survey Grants G16AC00348 and G17AC00346 to UC Berkeley. Work was also done under Grant 41674033 from the National Science Foundation of China. Scripps Orbit and Permanent Array Center (SOPAC) work was funded by NASA Grants NNH17ZDA001N, NNX16AM04A and NNX17AD99G and National Science Foundation (NSF) Grant EAR-1400. The authors thank the Geospatial Information Authority of Japan for operation and maintenance of the GEONET Global Positioning System (GPS) network whose data are used in this study. The authors gratefully acknowledge all the personnel from Servicio Sismologico Nacional (SSN), Servicio de Geodesia Satelital (SGS) and UNAVCO Inc. for GPS station maintenance, data acquisition, IT support and data distribution. The authors acknowledge the New Zealand GeoNet project and its sponsors EQC, GNS Science, and LINZ, for providing data used in this study.

International audience; The 2015 reactivation of the Cotopaxi volcano urges us to understand the complex eruptive dynamics of Cotopaxi for better management of a potential major crisis in the near future. Cotopaxi has commonly transitioned from andesitic eruptions of strombolian style (lava flows and scoria ballistics) or nuées ardentes (pyroclastic flows and ash falls) to highly explosive rhyolitic ignimbrites (pumiceous pyroclastic flows), which entail drastically different risks. To better interpret geophysical and geochemical signals, Cotopaxi magma storage conditions were determined via existing phase-equilibrium experiments that used starting materials chemically close to the Cotopaxi andesites and rhyolites. The results suggest that Cotopaxi's most mafic andesites (last erupted products) can be stored over a large range of depth from ~7 km to ≥16 km below the summit (pressure from ~200 to ≥400 MPa), 1000 °C, NNO +2, and contain 4.5–6.0±0.7 wt% H2O dissolved in the melt in equilibrium with ~30–40% phenocrysts of plagioclase, two pyroxenes, and Fe-Ti oxides. These mafic andesites sometimes evolve towards more silicic andesites by cooling to 950 °C. Rhyolitic magmas are stored at 200–300 MPa (i.e. ~7–11 km below the summit), 750 °C, NNO +2, and contain ~6–8 wt% H2O dissolved in a nearly aphyric melt (

This study investigated a new direction for improving the decision making of populations at risk in the context of uncertain environmental events, such as volcanic hazards. According to the risk as feelings theory and dual process models, situations with certain outcomes do not necessarily require the use of affect heuristics (e.g., experienced feelings, anticipated emotions) as valid information in the decision-making process. In the case of difficult decisions with moral dilemmas, certainty could even improve decisions. Thus, using an ecological design with various scenarios depicting upcoming volcanic hazards, we examined whether reducing the uncertainty of lethal threat by conveying certainty in an information campaign could influence decision making and promote a better quality of choice (correct application of the recommendations from the competent authorities). We focused specifically on two populations composed of local people living in the vicinity of an active volcano (Tungurahua volcano, Ecuador) and local scientists. We also examined whether a difficult decision involving a moral dilemma (e.g., leaving people behind so as not to jeopardize one's own life) potentiated this effect, compared to a less difficult situation without a dilemma. We demonstrated that, for local people facing a moral dilemma (difficult decision), the reduction of uncertainty of lethal threat involved a better application of the actual recommendations. These outcomes provided perspectives on improving the applications of the recommendations among local populations at risk in the context of a real risk exposure.

Along the Ecuadorian margin, the North Andean Sliver is moving in the northeastward direction due to the oblique subduction of the Nazca plate. The opening of the gulf of Guayaquil is a consequence of this motion. Two principal models compete to explain the opening. One proposes an opening achieved essentially with strike-slip motion along a single major fault through the gulf, the other with a combination of strike-slip and normal faulting on both sides of the gulf. The consequences in term of seismic hazard are very different. A single strike-slip fault model could imply a long fault segment capable of generating large magnitude events. In contrast, a multi-segments composite fault system will give conditions for producing small to medium size earthquakes. The southern Ecuador subduction zone is characterized by the absence of large historical earthquake. Data from the historical and instrumental seismicity for magnitude above 4 show the forearc has a high level of moderate seismic activity within and around the gulf that connects to the crustal seismic activity of the volcanic arc. In contrast, the forearc elsewhere shows very little or no seismic activity between the marine forearc zone and the volcanic arc. Regional and global CMTS data show a large number of mechanisms within the gulf that do not line up on a simple straight fault system. We present new earthquake data from the recently upgraded national seismic network of Ecuador. They provide the first image of SW-NE trending crustal faults stretching in the central part of the gulf and running eastward south of the Puna island. The main seismic belt appears to be discontinuous, made of short length segments with variable trends. The variety of focal solutions also indicates complex faulting. As the shape of this seismic belt is in good agreement with the orientation of the GPS velocity vectors, this new fault zone is readily interpreted as the southernmost segment of the actual NAS boundary. Others seismic clusters are observed parallel to the northern coast of the gulf, indicating active structures eventually accommodating the North-South opening of the gulf through normal faulting. b-value analysis of the main seismic belt seismicity shows high b value (>1) indicating either highly fractured or heterogeneous medium, or/and low stress level within the gulf of Guayaquil. This is again in agreement with a multi-segmented faulting system and also with the lack of large magnitude event in the historical seismic data. A cross-section for the entire seismic belt shows a depth extend of the crustal seismic activity down to 30 km which confirms the seismic belt to be a sliver boundary.

Local regularity results are obtained for the MHD equations using as global framework the setting of parabolic Morrey spaces. Indeed, by assuming some local boundedness assumptions (in the sense of parabolic Morrey spaces) for weak solutions of the MHD equations it is possible to obtain a gain of regularity for such solutions in the general setting of the Serrin regularity theory. This is the first step of a wider program that aims to study both local and partial regularity theories for the MHD equations.

The heterogeneous seafloor topography of the Nazca Plate as it enters the Ecuador subduction zone provides an opportunity to document the influence of seafloor roughness on slip behavior and megathrust rupture. The 2016 M$_{w}$ 7.8 Pedernales Ecuador earthquake was followed by a rich and active postseismic sequence. An internationally coordinated rapid response effort installed a temporary seismic network to densify coastal stations of the permanent Ecuadorian national seismic network. A combination of 82 onshore short and intermediate period and broadband seismic stations and six ocean bottom seismometers recorded the postseismic Pedernales sequence for over a year after the mainshock. A robust earthquake catalog combined with calibrated relocations for a subset of magnitude ≥4 earthquakes shows pronounced spatial and temporal clustering. A range of slip behavior accommodates postseismic deformation including earthquakes, slow slip events, and earthquake swarms. Models of plate coupling and the consistency of earthquake clustering and slip behavior through multiple seismic cycles reveal a segmented subduction zone primarily controlled by subducted seafloor topography, accreted terranes, and inherited structure. The 2016 Pedernales mainshock triggered moderate to strong earthquakes (5 ≤ M ≤ 7) and earthquake swarms north of the mainshock rupture close to the epicenter of the 1906M$_{w}$ 8.8 earthquake and in the segment of the subduction zone that ruptured in 1958 in a M$_{w}$ 7.7 earthquake.

International audience; Forearc basins have developed along accretionary and nonaccretionary convergent margins. Here, we investigate the evolution of an offshore nonaccretionary-type forearc basin that has developed along the Ecuadorian convergent margin. We used 2D-Multichannel Seismic Reflection profiles to recognize five seismic units overlying the acoustic basement. The units were dated by correlation with wells and regional stratigraphy. They recorded the structural evolution of the margin into North, Central-North and Central-South margin segments identified from Gravity Free Air Anomalies. Intersegment transition zones accommodated deformation related to the margin segmentation, contributing to the development of shelf forearc depocenters. An offshore forearc basin (subunit L1a) developed on accreted oceanic terranes during the middle-to-late Eocene. The basin was affected by normal faulting during the Oligocene to early-middle Miocene (subunit L1b). This extension stage initiated during the rifting and oblique subduction of the Farallon plate beneath the Ecuador margin. The basin underwent an early-middle Miocene uplift outlined by unconformity U1 potentially associated with the subduction of the young Nazca plate, in a less oblique plate convergence environment. During the early-Pliocene, the Central-South margin segment individualized by uplift during the formation of unconformity U2. The Manta anticline, which developed in the intersegment transition zone, accommodated the segmentation. This event is associated with the arrival of the Carnegie ridge in the subduction. The North segment individualized by uplift during the Pliocene early-Pleistocene formation of the Pedernales structural high, which may coincide with a reactivation of the Canandé fault. Synchronously, unit L3 sediment recorded the subsidence of the Central-North segment, and strike-slip tectonics in the area of the Jama-Bahía depocenter. A mosaic of middle-to-late Pleistocene unit L5 depocenters that alternate with uplifted zones along the shelf likely recorded the subduction of the topographically irregular Carnegie ridge. The study provides a remarkable example of the evolution of a non-accretionary-type forearc basin.

SUMMARYThe Ecuadorian convergent margin has experienced many large mega-thrust earthquakes in the past century, beginning with a 1906 event that propagated along as much as 500 km of the plate interface. Many subsections of the 1906 rupture area have subsequently produced Mw ≥ 7.7 events, culminating in the 16 April 2016, Mw 7.8 Pedernales earthquake. Interestingly, no large historic events Mw ≥ 7.7 appear to have propagated southward of ∼1°S, which coincides with the subduction of the Carnegie Ridge. We combine data from temporary seismic stations deployed following the Pedernales earthquake with data recorded by the permanent stations of the Ecuadorian national seismic network to discern the velocity structure of the Ecuadorian forearc and Cordillera using ambient noise tomography. Ambient noise tomography extracts Vsv information from the ambient noise wavefield and provides detailed constraints on velocity structures in the crust and upper mantle. In the upper 10 km of the Ecuadorian forearc, we see evidence of the deepest portions of the sedimentary basins in the region, the Progreso and Manabí basins. At depths below 30 km, we observe a sharp delineation between accreted fast forearc terranes and the thick crust of the Ecuadorian Andes. At depths ∼20 km, we see a strong fast velocity anomaly that coincides with the subducting Carnegie Ridge as well as the southern boundary of large mega-thrust earthquakes. Our observations raise the possibility that upper-plate structure, in addition to the subducting Carnegie Ridge, plays a role in the large event segmentation seen along the Ecuadorian margin.

SUMMARYThe Ecuadorian forearc is a complex region of accreted terranes with a history of large megathrust earthquakes. Most recently, a Mw 7.8 megathrust earthquake ruptured the plate boundary offshore of Pedernales, Ecuador on 16 April 2016. Following this event, an international collaboration arranged by the Instituto Geofisico at the Escuela Politécnica Nacional mobilized a rapid deployment of 65 seismic instruments along the Ecuadorian forearc. We combine this new seismic data set with 14 permanent stations from the Ecuadorian national network to better understand how variations in crustal structure relate to regional seismic hazards along the margin. Here, we present receiver function adaptive common conversion point stacks and a shear velocity model derived from the joint inversion of receiver functions and surface wave dispersion data obtained through ambient noise cross-correlations for the upper 50 km of the forearc. Beneath the forearc crust, we observe an eastward dipping slow velocity anomaly we interpret as subducting oceanic crust, which shallows near the projected centre of the subducting Carnegie Ridge. We also observe a strong shallow positive conversion in the Ecuadorian forearc near the Borbon Basin indicating a major discontinuity at a depth of ∼7 km. This conversion is not ubiquitous and may be the top of the accreted terranes. We also observe significant north–south changes in shear wave velocity. The velocity changes indicate variations in the accreted terranes and may indicate an increased amount of hydration beneath the Manabí Basin. This change in structure also correlates geographically with the southern rupture limit of multiple high magnitude megathrust earthquakes. The earthquake record along the Ecuadorian trench shows that no event with a Mw >7.4 has ruptured south of ∼0.5°S in southern Ecuador or northern Peru. Our observations, along with previous studies, suggest that variations in the forearc crustal structure and subducting oceanic crust may influance the occurrence and spatial distribution of high magnitude seismicity in the region.

Co-auteur étranger; International audience; New K-Ar ages obtained on juvenile pumice glass shards indicate that the Chalupas ignimbrite, one of the main Pleistocene tephra markers of the Ecuadorian arc, was emplaced at 216 ± 5 ka. Morphology and major and trace element contents of the glass shards are similar to those of ash layers from deep-sea cores and allow correlation between continental deposits and marine tephra layers. Based on biostratigraphy and δ18O data, the age models of these cores support our K-Ar age. Fine ashes from the Chalupas eruption column have been found about 1000 km away from the source caldera, and the estimated deposit volume of both ignimbrite and co-ignimbrite deposits ranges from 200 to 265 km3. This suggests that the Chalupas event could have been strong enough to reach the stratosphere and inject large amount of SO2 in both hemispheres, possibly impacting global temperatures. In addition, the age of the Chalupas ignimbrite obtained here could provide a new radiometric constraint for the age of isotope stage 7 recorded in orbitally-tuned δ18O deep-sea cores. This study highlights the relevance of K-Ar dating applied to small glass shards from massive ignimbrite deposits, and the potential that it represents to improve risk assessments in volcanic zones where dating crystals is not possible. Finally, detailed tephrochronology of deep-sea cores and correlation between marine ash-layers and continental volcanic deposits constitute a strong tool to investigate the eruptive history of an active volcanic arc whose proximal products have been eroded or deeply buried by younger deposit sequences

SUMMARY Quito, the capital city of Ecuador hosting ∼2 million inhabitants, lies on the hanging wall of a ∼60-km-long reverse fault offsetting the Inter-Andean Valley in the northern Andes. Such an active fault poses a significant risk, enhanced by the high density of population and overall poor building construction quality. Here, we constrain the present-day strain accumulation associated with the Quito fault with new Global Positioning System (GPS) data and Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) analysis. Far field GPS data indicate 3–5 mm yr–1 of horizontal shortening accommodated across the fault system. In the central segment of the fault, both GPS and PS-InSAR results highlight a sharp velocity gradient, which attests for creep taking place along the shallowest portion of the fault. Smoother velocity gradients observed along the other segments indicate that the amount of shallow creep decreases north and south of the central segment. 2-D elastic models using GPS horizontal velocity indicate very shallow (

Co-auteur étranger; International audience; In the northern Andes, the Ecuadorian arc presents a large number of Quaternary volcanoes, spread over a rather restricted area. The origin of this volcanic clustering is not well understood, and only a few chronological data older than the Holocene are available in northern Ecuador to document the arc development stages. In this study, we present new K-Ar ages obtained on lava flow and pumice samples for Cushnirumi, Mojanda, Fuya Fuya, Imbabura, Cubilche, and Cusín volcanoes, located about 40 km north of Quito, the Ecuador's capital city. Our results show that the volcanic activity in the northern part of the Ecuadorian arc started at least at ~ 1 Ma and that construction of volcanoes mainly occurred during the last 500 ka. Together with the radiometric data, numerical reconstructions of the paleomorphology of the volcanoes are used to estimate the volume of emitted magmas and the amount of eroded material in order to quantify their eruptive and erosion rates. Emission rates of Ecuadorian volcanoes range between < 0.2 and 3.6 ± 2.1 km3/kyr. Highest rates are obtained for volcanoes constructed over time periods shorter than 100 kyr by sporadic eruptive pulses, whereas lowest rates are calculated over longer periods that include quiescence phases. Erosion rates range between 0.02 ± 0.01 and 0.14 ± 0.09 km3/kyr and highlight that volcanic edifices whose activity ended recently are rapidly dismantled by physicochemical processes. Finally, the spatial distribution of Quaternary volcanoes as well as the spatio-temporal evolution of lava geochemistry may reflect the progressive influence of the Carnegie Ridge at depth.

International audience; Over the past few years, we have seen the emergence of a wide range of banking archi-tectures, technologies, and applications made possible by the significant improvements in hardware, software, and networking technologies. Nowadays, innovative solutions are being developed by banks to leverage the benefits of blockchain, to improve their business agility and performance, and to make their business operations more efficient and secure. However, there are still cases where regular access to Internet is impossible or unreliable due to saturated networks or harsh environments, hence limiting the deployment of typical blockchain based solutions. In this context, an approach using a new connec-tivity technology is needed in order to increase mobile Internet services for any device to reach nearly 95% of the world population, instantly, simply by drawing on existing mobile phone networks, with no additional infrastructure development. We aim to give the user full bank access from their device, even if the device is not a smart one, using ordinary mobile phone networks. However, providing efficient and secure communications over lossy and low bandwidth networks remains a challenge. The main objective of this paper will be to design an end-to-end and low overhead secure solution for the communications between mobile devices and their corresponding remote application servers that using blockchain via ordinary mobile networks.

International audience; In active subduction zones, the sum of the deformation over many seismic cycles accounts for the long-term cumulated deformation of the forearc. Along the Andean coast, several studies have suggested a correlation between the seismic segmentation of the megathrust and the morpho-tectonic segmentation of the forearc. Large megathrust earthquakes tend to occur on highly coupled patches in the seismogenic zone right beneath forearc basins. These basins are often framed in between coastal peninsulas, identified as seismic barriers that impede seismic ruptures propagation. On the contrary, strong coastal uplifts are observed in peninsula areas where the slip along the plate interface is mostly achieved by creeping. These observations suggest a counter-intuitive relationship between megathrust earthquakes, interseismic coupling, and permanent deformations in the upper plate (Saillard et al., 2017). At first order, the permanent deformation recorded in the coastal zone is linked to the seismic behavior on the megathrust whose along-strike variation seems stable through times. We plan to use these observations to resolve the inverse problem: characterization of upper plate Quaternary deformations and active structures distribution would then allow for assessing the margin segmentation, rupture lengths and seismic hazard. Hence the MARACAS program newly funded by the French National Research Agency will address these issues. It proposes to develop an innovative approach to assess seismic hazard in subduction zone that would take into account the survey of the long-term deformation of the upper plate to better identify multicycles margin segmentation. Here, we introduce the MARACAS program scientific question, objectives and potential impacts. Major objectives of the program are 1) to identify the conditions of vertical crustal motions along the plate boundary; 2) to evaluate the lateral impact of seismic ruptures on forearc deformation in weakly coupled segments below peninsulas; and 3) to determine whether the correlation between the seismic segmentation and the morpho-tectonic segmentation is fortuitous or long-lasting.

International audience; Temporary seismic networks installed in urban areas provide a powerful tool for investigating the shal-low geological structure and assess the seismic hazard using seismic interferometry. Quito, the capital of Ecuador, is located in a high seismic zone, placed at 200 km from the Pacific sub-duction zone and surrounded by crustal-faults prone to generate significant earthquakes. The city has been built on a basin, on the hanging wall of a system of active reverse faults. The high population density (around 3 million inhabitants), together with the lack of planning in most of its buildings, make Quito a metropolis with a high seismic risk. In Quito, the filling of the basin has been described as volcano-sedimentary sequences consisting of lavas, lahars, lacustrine and pyroclastic deposits. However, the thickness of the in-fill material, its spa-tial arrangement, and the deep structure of the basin remain poorly known. Between May 2016 and July 2018, 20 broad- and mid-band seismological stations were deployed pro-gressively throughout the city in an irregular array to record ambient seismic noise to investigate the upper-most geological structure of the basin. Here, we present the results of ambient noise cross-correlations of simultaneous operating seismic stations to retrieve inter-stations surface waves Green's functions in the frequency band 0.1 - 2 Hz. Careful analyses of day-night variations in noise spectral power have been done to select optimal time windows for the cross-correlations. Rayleigh and Love phase- velocity dispersion curves were inverted to obtain shear wave velocity profiles throughout the city. Love wave trains traveling in the longitudinal direction of the basin (NNE-SSW) are much clearer than Rayleigh wave trains. The surface waves Green’s functions and their inversions mark a clear difference in the structure of the basin between the northern and southern parts. At the north, we detect the seismic basement at a depth of about 500 meters whereas at the south it appears much deeper around 1300 meters. This strong difference could be the main explanation for the low-frequency amplification (at 0.3 Hz) highlighted in the southern part of the basin on the recording of earthquakes (the April 2016, Mw 7.8 Pedernales earthquake being an example) and by the analysis of spectral ratios (Laurendeau et al., 2017).

We launched an array of nine freely floating submarine seismometers near the Galápagos islands, which remained operational for about two years. P and PKP waves from regional and teleseismic earthquakes were observed for a range of magnitudes. The signal-to-noise ratio is strongly influenced by the weather conditions and this determines the lowest magnitudes that can be observed. Waves from deep earthquakes are easier to pick, but the S/N ratio can be enhanced through filtering and the data cover earthquakes from all depths. We measured 580 arrival times for different raypaths. We show that even such a limited number of data gives a significant increase in resolution for the oceanic upper mantle. This is the first time an array of floating seismometers is used in seismic tomography to improve the resolution significantly where otherwise no seismic information is available. We show that the Galápagos Archipelago is underlain by a deep (about 1900 km) 200–300 km wide plume of high temperature, with a heat flux very much larger than predicted from its swell bathymetry. The decrease of the plume temperature anomaly towards the surface indicates that the Earth’s mantle has a subadiabatic temperature gradient.

Co-auteur étranger; International audience; Continental arc lavas display geochemical signatures that reflect both mantle metasomatism by slab fluids or melts and extensive differentiation of magmas within crustal reservoirs. The relative effect of source and crustal processes are difficult to disentangle based on whole-rock compositions. This issue is critical in Ecuador where volcanism occurs through a thick continental crust (>50 km). This study reconstructs the history of melts feeding the Guagua Pichincha volcano, Western Cordillera, by analysing the Pb isotope composition and major-trace element content of individual minerals (33 amphiboles, 4 orthopyroxenes and 18 plagioclases) hosted in two dacite samples. It uses a low-blank wet-chemistry method for precise analysis of Pb amounts as low as 150 pg.Early crystallized, high-Al amphiboles with Al2O3 ≥ 9.8 wt% and Eu/Eu* > 0.7 have the lowest and most heterogeneous 206Pb/204Pb (18.816–18.999), whereas plagioclases have the highest and most homogeneous 206Pb/204Pb (19.003–19.023). Low-Al amphiboles and orthopyroxenes display intermediate compositions and variability (18.934–19.007). The 206Pb/204Pb ratio correlates negatively with Eu/Eu* in amphiboles and orthopyroxenes, which indicates that the Guagua Pichincha magmas assimilate radiogenic Pb within the stability field of plagioclase (i.e. in the upper crust). The radiogenic ankaramites of the Guaranda unit, an accreted ocean terrain making the basement of the Western Cordillera, are the most suitable contaminant. If this is correct, the 206Pb/204Pb increase from the two most primitive amphiboles to their respective host rocks requires ca. 20% crustal assimilation, which is higher than previous estimates in the Northern Volcanic Zone but similar to those inferred for Central Andean mafic lavas. The two most primitive amphiboles with no significant Eu anomaly record the composition of melts before plagioclase crystallization. These deep melts have contrasted 206Pb/204Pb ratios (18.816–18.879) and contents of fluid mobile elements (Li, Cu, Rb, Pb) that probably reflect the input of different slab components to the mantle wedge. Melts in equilibrium with the two most primitive amphiboles of the Guagua Pichincha volcano are enriched in incompatible elements, but depleted in fluid mobile elements compared to the olivine-hosted melt inclusions of the older Rucu Pichincha volcano. This supports previous inferences based on whole-rock data that the mantle source of the Pichincha Volcanic Complex has changed through time.

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