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

Structure of the uppermost mantle beneath North America : Regional surface wave tomography and thermo-chemical interpretation

Seismology is the primary tool to probe the interior of the Earth. The main requirement to obtain a high quality image of the Earth's structure is the achievement of an extensive dataset of seismograms. The North American and Caribbean regions offer a good opportunity in that matter. The large deployment of broad-band seismological stations over the region, provides a dense regional dataset. Phase velocity measurements and waveforms derived from this data are used to image the seismic velocity structure of the uppermantle, before investigating its thermal and compositional structure. The phase velocity maps are first obtained by waveform inversion for periods between 40 and 150 s, using fundamental mode Rayleigh waves. The ray path coverage yields a high resolution over most of Canada, the United States and Central America. Comparison with a recent global scale tomographic model shows that regional phase velocity maps present higher resolution and better prediction of independent data. This last statement is an important issue for future moment tensor calculations. The resolution of small scale heterogeneities may, however, be limited, as the inversion method used relies on the great circle path approximation (ray theory), which states that a wave is sensitive to velocity heterogeneities only along the geometrical ray path that links source and receiver. Neglecting off-great circle path effects may affect regional tomographic results significantly. Therefore, in a second step, the effect of finite frequency of surface waves is incorporated into the inversion of phase velocities measurements (scattering theory). Comparison is made between phase velocity maps obtained with ray and scattering theories. The results show that small scale anomalies (less than $800 km) are not imaged with sufficient resolution. Due to the large uncertainties in the data, a regularization operator is required, leading to the creation of a significant model null space, and a poor constrain of small scale anomalies. The structure of the upper mantle, from 50 to 250 km, is afterwards imaged by ray theory inversion of the phase velocity dispersion curves obtained. The results show high velocities beneath Canada and the eastern United States from the Rocky Mountains to the Atlantic coast, associated with a thick archean lithosphere (up to 220 km). Low velocities are observed beneath the western Cordillera, along the Pacific ocean from Canada to Mexico, induced by the intense tectonic activity of the region. Mexico is defined as a low velocity zone associated with the subduction of the Cocos plate. Positive anomalies are imaged in the Gulf of Mexico. The Caribbean region displays two low velocity zones: one beneath eastern Caribbean, as a result of back arc magmatism, and the other beneath western Caribbean, separated by a positive velocity arm. Finally, the seismological velocity model obtained is interpreted in terms of temperature and compositional variations in the depth range 60 to 260 km. Seismic velocities are primarily sensitive to thermal perturbations. In order to simultaneously infer temperature and composition, independent data are needed. In this thesis, we use density anomalies as additional constrain on the compositional variations in the upper mantle. Estimates of these anomalies are obtained through the scaling factor between density and velocity, which is derived from gravity anomalies data. Our results show that tectonically active regions consist of a mantle close to the Earth's average in terms of temperature and composition. On the contrary, cratonic areas are underlain by a mantle cooler than average and depleted in iron, which supports the idea that negative buoyancy induced by thermal anomalies are balanced by positive buoyancy due to compositional anomalies. This may explain the stability of cratons over geological times

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

RESORCE (Reference database for seismic ground motion in Europe)

With the aim of improving seismic ground-motion models in Europe and reducing associated uncertainties, the compilation of a high-quality database of seismic-motion recordings and associated metadata is of primary importance. SIGMA research and development project, devoted to the improvement of seismic hazard estimates, methods and data for France and nearby regions, has been funding the implementation of RESORCE (Reference databaSe fOR seismiC ground-motion in Europe, Akkar et al., 2014)

Social and cognitive development of deaf children after cochlear implantation

International audienc

Speech Performance and Sound Localization in a Complex Noisy Environment in Bilaterally Implanted Adult Patients.

International audienceObjective: To evaluate speech performance, in quiet and noise, and localization ability in adult patients who had undergone bilateral and simultaneous implantation. Study Design: Prospective multi-center study. Methods: Twenty-seven adult patients with profound or total hearing loss were bilaterally implanted in a single-stage procedure, and simultaneously activated (Med-El, Combi 40/40+). Subjects were assessed before implantation and at 3, 6 and 12 months after switch-on. Speech perception tests in monaural and binaural conditions were performed in quiet and in noise using disyllabic words, with speech coming from the front and a cocktail party background noise coming from 5 loudspeakers. Sound localization measurements were also performed in background noise coming from 5 loudspeakers positioned from -90 degrees to +90 degrees azimuth in the horizontal plane, and using a speech stimulus. Results: There was a bilateral advantage at 12 months in quiet (77 +/- 5.0% in bilateral condition, 67 +/- 5.3% for the better ear, p /=60% for the better ear, n = 19) and 'poor performers' (n = 8). Subjects were also categorized as 'asymmetrical' (difference between their 2 unilateral speech scores >/=20%, n = 11) or 'symmetrical' (n = 16). The largest advantage (bilateral compared to the better ear) was obtained in poor performers: +19% compared to +7% in good performers (p < 0.05). In the group of good performers, there was a bilateral advantage only in cases of symmetrical results between the 2 ears (n = 10). In the group of poor performers, the bilateral advantage was shown in both patients with symmetrical (n = 6) and asymmetrical results (n = 2). In bilateral conditions, the sound localization ability in noise was improved compared to monaural conditions in patients with symmetrical and asymmetrical performance between the 2 ears. No preoperative factor (age, duration of deafness, use of hearing aids, etiology, etc.) could predict the asymmetrical performance, nor which ear would be the best. Conclusion: This study demonstrates a bilateral advantage (at 12 months after the implantation) in speech intelligibility and sound localization in a complex noisy environment. In quiet, this bilateral advantage is shown in cases of poor performance of both ears, and in cases of good performance with symmetrical results between the 2 ears. No preoperative factor can predict the best candidates for a simultaneous bilateral implantation

SI-Hex: a new catalogue of instrumental seismicity for metropolitan France

Abstract. – The aim of the SI-Hex project (acronym for « Sismicité Instrumentale de l’Hexagone ») is to provide a cata-logue of seismicity for metropolitan France and the French marine economic zone for the period 1962-2009 by taking into account the contributions of the various seismological networks and observatories from France and its neighbouring coun-tries. The project has been launched jointly by the Bureau Central Sismologique Français (CNRS-University/BCSF) and the Laboratoire de Détection et de Géophysique (CEA-DAM/LDG). One of the main motivations of the project is to pro-vide the end user with the best possible information on location and magnitude of each earthquake. So far, due to the vari-ous procedures in use in the observatories, the different locations and magnitudes of earthquakes located in the SI-Hex zone were presenting large discrepancies. In the 2014 version of the catalogue, 1D localizations of hypocentres performed with a unique computational scheme and covering the whole 1962-2009 period constitute the backbone of the catalogue (SI-Hex solutions). When available, they are replaced by more precise localizations made at LDG or, for recent times, by the regional observatories within: 1) the French Alps, 2) the southernmost Alps and the Mediterranean domain including Corsica, 3) the Pyrenees, and 4) the Armorican massif. Moment magnitudes Mw are systematically reported in the SI-Hex catalogue. They are computed from coda-wave analysis of the LDG records for most Mw&gt;3.4 events, and are converte