Distributed archive and single access system for accelerometric event data : a NERIES initiative

We developed a common access facility to homogeneously formatted accelerometric event data and to the corresponding sheet of ground motion parameters. This paper is focused on the description of the technical development of the accelerometric data server and the link with the accelerometric data explorer. The server is the third node of the 3-tier architecture of the distributed archive system for accelerometric data. The server is the link between the data users and the accelero- metric data portal. The server follows three main steps: (1) Reading and analysis of the end-user request; (2) Processing and converting data; and (3) Archiving and updating the accelerometric data explorer. This paper presents the description of the data server and the data explorer for accessing data

Seismic imaging of the lithospheric structure of the Zagros mountain belt (Iran)

International audienceWe present a synthesis and a comparison of the results of two temporary passive seismic experiments installed for a few months across Central and Northern Zagros. The receiver function analysis of teleseismic earthquake records gives a high-resolution image of the Moho beneath the seismic transects. On both cross-sections, the crust has an average thickness of 43±2 km beneath the Zagros fold-and-thrust belt and the Central domain. The crust is thicker beneath the hanging wall of the Main Zagros Reverse Fault (MZRF), with a larger maximum Moho depth in Central (69±2 km) than in Northern Zagros (56±2 km). The thickening affects a narrower region (170 km) beneath the Sanandaj-Sirjan zone of Central Zagros and a wider region (320 km) in Northern Zagros. We propose that this thickening is related to overthrusting of the crust of the Arabian margin by the crust of Central Iran along the MZRF considered as a major thrust fault cross-cutting the whole crust. The fault is imaged as a lowvelocity layer in the receiver function data of the Northern Zagros profile. Moreover, the crustal-scale thrust model reconciles the imaged seismic Moho with the Bouguer anomaly data measured on the Central Zagros transect. At upper mantle depth, P-wave tomography confirms the previously observed strong contrast between the faster velocities of the Arabian margin and the lower velocities of the Iranian micro-blocks. Our higher-resolution tomography combined with surface-wave analysis locates the suture in the shallow mantle of the Sanandaj-Sirjan zone beneath Central Zagros. The Arabian upper-mantle has shield-like shear-wave velocities, while the lower velocities of the Iranian upper mantle are likely due to higher temperature. But these velocities are not low enough and the low-velocity layer not thick enough to conclude on a delamination of the lithospheric mantle lid beneath Iran. The lack of a high-velocity anomaly in the mantle beneath Central Iran suggests that the Neotethyan oceanic lithosphere is probably detached from the Arabian margin

The European-Mediterranean Distributed Accelerometric Data-Base

International audienceWe created an archive for European acceleration data, based on distributed database of accelerogram waveforms, accessed through the new European Earthquake Data Portal (http://www.seismicportal.eu). Data are open to the scientific and engineering community. Currently the 6 core partners contribute data from 1,379 earthquakes with magnitudes ranging from M1.0 to M7.4. Strong Motion Data are available with epicentral distances up to 1,000 km. Additionally, agencies are encouraged to contribute data. Waveforms included in the database are uniformly processed to create a set of engineering parameters that are used to search the database. In addition to the database, we compiled a survey of the existing accelerometric stations in the Euro-Mediterranean region. We expect this platform to be the basis for growing sharing of European Strong Motion Data in an open environment, in as near to real-time as is possible from network operators

Crustal Thinning From Orogen to Back-Arc Basin: The Structure of the Pannonian Basin Region Revealed by P-to-S Converted Seismic Waves

We present the results of P-to-S receiver function analysis to improve the 3D image of the sedimentary layer, the upper crust, and lower crust in the Pannonian Basin area. The Pannonian Basin hosts deep sedimentary depocentres superimposed on a complex basement structure and it is surrounded by mountain belts. We processed waveforms from 221 three-component broadband seismological stations. As a result of the dense station coverage, we were able to achieve so far unprecedented spatial resolution in determining the velocity structure of the crust. We applied a three-fold quality control process; the first two being applied to the observed waveforms and the third to the calculated radial receiver functions. This work is the first comprehensive receiver function study of the entire region. To prepare the inversions, we performed station-wise H-Vp/Vs grid search, as well as Common Conversion Point migration. Our main focus was then the S-wave velocity structure of the area, which we determined by the Neighborhood Algorithm inversion method at each station, where data were sub-divided into back-azimuthal bundles based on similar Ps delay times. The 1D, nonlinear inversions provided the depth of the discontinuities, shear-wave velocities and Vp/Vs ratios of each layer per bundle, and we calculated uncertainty values for each of these parameters. We then developed a 3D interpolation method based on natural neighbor interpolation to obtain the 3D crustal structure from the local inversion results. We present the sedimentary thickness map, the first Conrad depth map and an improved, detailed Moho map, as well as the first upper and lower crustal thickness maps obtained from receiver function analysis. The velocity jump across the Conrad discontinuity is estimated at less than 0.2 km/s over most of the investigated area. We also compare the new Moho map from our approach to simple grid search results and prior knowledge from other techniques. Our Moho depth map presents local variations in the investigated area: the crust-mantle boundary is at 20–26 km beneath the sedimentary basins, while it is situated deeper below the Apuseni Mountains, Transdanubian and North Hungarian Ranges (28–33 km), and it is the deepest beneath the Eastern Alps and the Southern Carpathians (40–45 km). These values reflect well the Neogene evolution of the region, such as crustal thinning of the Pannonian Basin and orogenic thickening in the neighboring mountain belts

Vers un nouveau portail web Résif

This poster, presented during the Résif 2019 Scientific and Technical Meetings in Biarritz, graphically presents the project for a new web portal for the distribution of Résif data: its objectives, the stages of development, its strengths and weaknesses, as well as suggestions for improving the visibility of data producers, the quality of the data put online, and the presentation of stations and networks. Résif is a national research infrastructure dedicated to the observation and understanding of the Earth's internal structure and dynamics. Résif is based on high technology observation networks, composed of seismological, geodetic and gravimetric instruments deployed in a dense manner throughout the French territory. The data collected allow the study of ground deformation, surface and deep structures, local and global seismicity and natural hazards, particularly seismic, on the French territory with a high spatio-temporal resolution. Résif is integrated into the European (EPOS - European Plate Observing System) and worldwide instruments that allow to image the Earth's interior in its entirety and to study many natural phenomena.Ce poster, présenté lors des Rencontres scientifiques et techniques Résif 2019 à Biarritz, présente à l’aide de graphiques le projet de nouveau portail web de distribution des données Résif : ses objectifs, les étapes de développement, ses points forts et ses points faibles, ainsi que des suggestions pour améliorer la visibilité des producteurs de données, la qualité des données mises en ligne, et la présentation des stations et des réseaux. Résif est une infrastructure de recherche nationale dédiée à l’observation et la compréhension de la structure et de la dynamique Terre interne. Résif se base sur des réseaux d’observation de haut niveau technologique, composés d’instruments sismologiques, géodésiques et gravimétriques déployés de manière dense sur tout le territoire français. Les données recueillies permettent d’étudier avec une haute résolution spatio-temporelle la déformation du sol, les structures superficielles et profondes, la sismicité à l’échelle locale et globale et les aléas naturels, et plus particulièrement sismiques, sur le territoire français. Résif s’intègre aux dispositifs européens (EPOS - European Plate Observing System) et mondiaux d’instruments permettant d’imager l’intérieur de la Terre dans sa globalité et d’étudier de nombreux phénomènes naturels

Sismob

International audienceSismob est le parc national d'instruments sismologiques mobiles terrestres. Il est donc l'antenne sismologique mobile de Résif. Comme pour les autres parcs du même type, par exemple Seis-UK en Grande-Bretagne ou Passcal aux Etats-Unis, l'objectif de Sismob est de permettre la collecte de données sismologiques sur des objectifs ciblés en l'absence d'observatoires permanents, ou, en complément de ces observatoires, en permettant une densification significative de l'échantillonnage spatial. Par essence, les expériences utilisant le matériel Sismob sont temporaires et leur durée varie de quelques jours à deux ans

Sismob

International audienceSismob est le parc national d'instruments sismologiques mobiles terrestres. Il est donc l'antenne sismologique mobile de Résif. Comme pour les autres parcs du même type, par exemple Seis-UK en Grande-Bretagne ou Passcal aux Etats-Unis, l'objectif de Sismob est de permettre la collecte de données sismologiques sur des objectifs ciblés en l'absence d'observatoires permanents, ou, en complément de ces observatoires, en permettant une densification significative de l'échantillonnage spatial. Par essence, les expériences utilisant le matériel Sismob sont temporaires et leur durée varie de quelques jours à deux ans

Sismob

International audienceSismob est le parc national d'instruments sismologiques mobiles terrestres. Il est donc l'antenne sismologique mobile de Résif. Comme pour les autres parcs du même type, par exemple Seis-UK en Grande-Bretagne ou Passcal aux Etats-Unis, l'objectif de Sismob est de permettre la collecte de données sismologiques sur des objectifs ciblés en l'absence d'observatoires permanents, ou, en complément de ces observatoires, en permettant une densification significative de l'échantillonnage spatial. Par essence, les expériences utilisant le matériel Sismob sont temporaires et leur durée varie de quelques jours à deux ans

Sismob

International audienceSismob est le parc national d'instruments sismologiques mobiles terrestres. Il est donc l'antenne sismologique mobile de Résif. Comme pour les autres parcs du même type, par exemple Seis-UK en Grande-Bretagne ou Passcal aux Etats-Unis, l'objectif de Sismob est de permettre la collecte de données sismologiques sur des objectifs ciblés en l'absence d'observatoires permanents, ou, en complément de ces observatoires, en permettant une densification significative de l'échantillonnage spatial. Par essence, les expériences utilisant le matériel Sismob sont temporaires et leur durée varie de quelques jours à deux ans

Discours et raisonnement

International audienc