23 research outputs found
Ambient-noise tomography of the wider Vienna Basin region
We present a new 3-D shear-velocity model for the top 30âkm of the crust in the wider Vienna Basin region based on surface waves extracted from ambient-noise cross-correlations. We use continuous seismic records of 63 broad-band stations of the AlpArray project to retrieve interstation Greenâs functions from ambient-noise cross-correlations in the period range from 5 to 25 s. From these Greenâs functions, we measure Rayleigh group traveltimes, utilizing all four components of the cross-correlation tensor, which are associated with Rayleigh waves (ZZ, RR, RZ and ZR), to exploit multiple measurements per station pair. A set of selection criteria is applied to ensure that we use high-quality recordings of fundamental Rayleigh modes. We regionalize the interstation group velocities in a 5âkm Ă 5âkm grid with an average path density of âŒ20 paths per cell. From the resulting group-velocity maps, we extract local 1-D dispersion curves for each cell and invert all cells independently to retrieve the crustal shear-velocity structure of the study area. The resulting model provides a previously unachieved lateral resolution of seismic velocities in the region of âŒ15âkm. As major features, we image the Vienna Basin and Little Hungarian Plain as low-velocity anomalies, and the Bohemian Massif with high velocities. The edges of these features are marked with prominent velocity contrasts correlated with faults, such as the Alpine Front and Vienna Basin transfer fault system. The observed structures correlate well with surface geology, gravitational anomalies and the few known crystalline basement depths from boreholes. For depths larger than those reached by boreholes, the new model allows new insight into the complex structure of the Vienna Basin and surrounding areas, including deep low-velocity zones, which we image with previously unachieved detail. This model may be used in the future to interpret the deeper structures and tectonic evolution of the wider Vienna Basin region, evaluate natural resources, model wave propagation and improve earthquake locations, among others
Arrival angles of teleseismic fundamental mode Rayleigh waves across the AlpArray
The dense AlpArray network allows studying seismic wave propagation with high spatial resolution. Here we introduce an array approach to measure arrival angles of teleseismic Rayleigh waves. The approach combines the advantages of phase correlation as in the two-station method with array beamforming to obtain the phase-velocity vector. 20 earthquakes from the first two years of the AlpArray project are selected, and spatial patterns of arrival-angle deviations across the AlpArray are shown in maps, depending on period and earthquake location. The cause of these intriguing spatial patterns is discussed. A simple wave-propagation modelling example using an isolated anomaly and a Gaussian beam solution suggests that much of the complexity can be explained as a result of wave interference after passing a structural anomaly along the wave paths. This indicates that arrival-angle information constitutes useful additional information on the Earth structure, beyond what is currently used in inversions
Une partie de l'équipe intervenant dans la cave : température -54°C. Base Concordia, Antarctique
Une partie de l'équipe intervenant dans la cave : température -54°C. Base Concordia, Antarctiqu
Plateforme Instrumentale Sismologique de l'Eost
The realization of large-scale seismological projects within the framework of RĂ©sif has led to a significant increase in the fixed and mobile instrument fleets between 2016 and 2020 and has led to the emergence of the need for structures capable of testing, characterizing and calibrating all this instrumentation. This requires infrastructures such as a dedicated seismological pillar, a test room and specific expertise. The Pise service (Eost Instrumental Seismological Platform) was born in 2016 in Strasbourg to meet this need. Initially, Pise developed a series of standardised procedures for absolute and relative calibrations for wired systems (dissociated sensor and digitizer). For example, the use of a vibrating table and the analysis of the response by injecting a signal into the calibration coil of the sensor allow the complete calculation of the transfer function. Subsequently, the purchase of a much larger number of nodes without a calibration coil necessitated the development of strictly relative calibrations. Thus, Pise is able to characterize their responses when they are simultaneously arranged around the reference sensor, but also to estimate their detection threshold (self-noise). The picture shows the calibration operation of a series of nodes in the Eost park. Pise is a tool of the RLBP action of RĂ©sif research infrastructure, dedicated to the observation and understanding of the internal Earth structure and dynamics. RĂ©sif is based on observation networks of high technological level, composed of seismological, geodetic and gravimetric instruments deployed in a dense way on the whole French territory. The data collected allow to study with a high spatio-temporal resolution the ground deformation, the superficial and deep structures, the seismicity at the local and global scale and the natural hazards, especially seismic, on the French territory. RĂ©sif integrates with European (EPOS - European Plate Observing System) and worldwide instruments that allow to image the interior of the Earth as a whole and to study many natural phenomena.La reÌalisation de projets sismologiques dâenvergure dans le cadre de RĂ©sif a entraĂźnĂ© une augmentation importante des parcs dâinstruments fixes et mobiles entre 2016 et 2020 et a fait eÌmerger le besoin de structures capables de tester, caracteÌriser et eÌtalonner lâensemble de cette instrumentation. Cela requiĂšre des infrastructures telles quâun pilier sismologique deÌdieÌ, une salle de tests et des expertises speÌcifiques. Le service Pise (Plateforme Instrumentale Sismologique de lâEost) est nĂ© en 2016 Ă Strasbourg pour rĂ©pondre Ă ce besoin. Dans un premier temps, Pise a deÌveloppeÌ une seÌrie de proceÌdures normaliseÌes dâeÌtalonnages absolus et relatifs pour les systeÌmes caÌbleÌs (capteur et numeÌriseur dissocieÌs). Par exemple, l'usage d'une table vibrante et l'analyse de la rĂ©ponse par injection d'un signal dans la bobine de calibration du capteur permettent le calcul complet de la fonction de transfert. Par la suite, lâachat des nodes en nombre bien plus important, et ne disposant pas de bobine de calibration, a nĂ©cessitĂ© la mise au point dâĂ©talonnages strictement relatifs. Ainsi, Pise est capable de caractĂ©riser leurs rĂ©ponses lorsquâils sont disposĂ©s simultanĂ©ment autour du capteur de rĂ©fĂ©rence, mais aussi dâestimer leur seuil de dĂ©tection (self-noise). La photo montre la plateforme instrumentale de lâEost avec, au premier plan, le pilier supportant des capteurs en cours de test. Pise est un outil de l'action RLBP (RĂ©seau large bande permanent) de l'infrastructure de recherche RĂ©sif, dĂ©diĂ©e Ă lâobservation et la comprĂ©hension de la structure et de la dynamique Terre interne. RĂ©sif se base sur des rĂ©seaux dâobservation de haut niveau technologique, composĂ©s dâinstruments sismologiques, gĂ©odĂ©siques et gravimĂ©triques dĂ©ployĂ©s de maniĂšre dense sur tout le territoire français. Les donnĂ©es recueillies permettent dâĂ©tudier avec une haute rĂ©solution spatio-temporelle la dĂ©formation du sol, les structures superficielles et profondes, la sismicitĂ© Ă lâĂ©chelle locale et globale et les alĂ©as naturels, et plus particuliĂšrement sismiques, sur le territoire français. RĂ©sif sâintĂšgre aux dispositifs europĂ©ens (EPOS - European Plate Observing System) et mondiaux dâinstruments permettant dâimager lâintĂ©rieur de la Terre dans sa globalitĂ© et dâĂ©tudier de nombreux phĂ©nomĂšnes naturels
Installation d'une station sismologique large bande Ă Charmoille (Doubs)
Installation d'une station sismologique large bande Ă Charmoille (Doubs
Nodes en cours de test sur la plateforme Instrumentale Sismologique de l'Eost
The realization of large-scale seismological projects within the framework of RĂ©sif has led to a significant increase in the fixed and mobile instrument fleets between 2016 and 2020 and has led to the emergence of the need for structures capable of testing, characterizing and calibrating all this instrumentation. This requires infrastructures such as a dedicated seismological pillar, a test room and specific expertise. The Pise service (Eost Instrumental Seismological Platform) was born in 2016 in Strasbourg to meet this need. Initially, Pise developed a series of standardised procedures for absolute and relative calibrations for wired systems (dissociated sensor and digitizer). For example, the use of a vibrating table and the analysis of the response by injecting a signal into the calibration coil of the sensor allow the complete calculation of the transfer function. Subsequently, the purchase of a much larger number of nodes without a calibration coil necessitated the development of strictly relative calibrations. Thus, Pise is able to characterize their responses when they are simultaneously arranged around the reference sensor, but also to estimate their detection threshold (self-noise). The picture shows the calibration operation of a series of nodes in the Eost park. Pise is a tool of the RLBP actin of RĂ©sif research infrastructure, dedicated to the observation and understanding of the internal Earth structure and dynamics. RĂ©sif is based on observation networks of high technological level, composed of seismological, geodetic and gravimetric instruments deployed in a dense way on the whole French territory. The data collected allow to study with a high spatio-temporal resolution the ground deformation, the superficial and deep structures, the seismicity at the local and global scale and the natural hazards, especially seismic, on the French territory. RĂ©sif integrates with European (EPOS - European Plate Observing System) and worldwide instruments that allow to image the interior of the Earth as a whole and to study many natural phenomena.La reÌalisation de projets sismologiques dâenvergure dans le cadre de RĂ©sif a entraĂźnĂ© une augmentation importante des parcs dâinstruments fixes et mobiles entre 2016 et 2020 et a fait eÌmerger le besoin de structures capables de tester, caracteÌriser et eÌtalonner lâensemble de cette instrumentation. Cela requiĂšre des infrastructures telles quâun pilier sismologique deÌdieÌ, une salle de tests et des expertises speÌcifiques. Le service Pise (Plateforme Instrumentale Sismologique de lâEost) est nĂ© en 2016 Ă Strasbourg pour rĂ©pondre Ă ce besoin. Dans un premier temps, Pise a deÌveloppeÌ une seÌrie de proceÌdures normaliseÌes dâeÌtalonnages absolus et relatifs pour les systeÌmes caÌbleÌs (capteur et numeÌriseur dissocieÌs). Par exemple, l'usage d'une table vibrante et l'analyse de la rĂ©ponse par injection d'un signal dans la bobine de calibration du capteur permettent le calcul complet de la fonction de transfert. Par la suite, lâachat des nodes en nombre bien plus important, et ne disposant pas de bobine de calibration, a nĂ©cessitĂ© la mise au point dâĂ©talonnages strictement relatifs. Ainsi, Pise est capable de caractĂ©riser leurs rĂ©ponses lorsquâils sont disposĂ©s simultanĂ©ment autour du capteur de rĂ©fĂ©rence, mais aussi dâestimer leur seuil de dĂ©tection (self-noise). La photo montre lâopĂ©ration de calibration dâune sĂ©rie de nodes du parc Eost. Pise est un outil de l'action RLBP (RĂ©seau large bande permanent) de l'infrastructure de recherche RĂ©sif dĂ©diĂ©e Ă lâobservation et la comprĂ©hension de la structure et de la dynamique Terre interne. RĂ©sif se base sur des rĂ©seaux dâobservation de haut niveau technologique, composĂ©s dâinstruments sismologiques, gĂ©odĂ©siques et gravimĂ©triques dĂ©ployĂ©s de maniĂšre dense sur tout le territoire français. Les donnĂ©es recueillies permettent dâĂ©tudier avec une haute rĂ©solution spatio-temporelle la dĂ©formation du sol, les structures superficielles et profondes, la sismicitĂ© Ă lâĂ©chelle locale et globale et les alĂ©as naturels, et plus particuliĂšrement sismiques, sur le territoire français. RĂ©sif sâintĂšgre aux dispositifs europĂ©ens (EPOS - European Plate Observing System) et mondiaux dâinstruments permettant dâimager lâintĂ©rieur de la Terre dans sa globalitĂ© et dâĂ©tudier de nombreux phĂ©nomĂšnes naturels
SismomÚtre, situé dans une cave à 12 m de profondeur, sous le shelter, Concordia
Le sismomÚtre, situé dans une cave à 12 m de profondeur, sous le shelter, Dome
Le shelter abritant la station sismologique de Concordia (code CCD)., Dome C
Le shelter abritant la station sismologique de Concordia (code CCD), Dome