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The western Alpine belt is the focal point of moderate but constant seismic activity. Numerous geodynamic and seismological studies underline the many scientific questions linked to Alpine dynamic processes and the associated rate of deformation resulting from late continental collision phases, and the assessment of seismic hazard and its associated risks. Seismic monitoring in the northern French Alps was launched in 1987 with the installation of the first seismological network, hosted by the Earth Science Observatory at Grenoble Alpes University. Since then, the network has been updated over the years, keeping pace with technical developments in seismic instrumentation, monitoring and data management. The homogenization of information described in this scientific data paper is motivated by the need for a single instrumental seismic catalogue, consisting in arrival times picks and hypocenters using the same velocity model. The final catalogue SISMalp-1987-2023 (CC-BY-4.0) contains 50,822 weak-to-moderate earthquakes with local magnitude between -1.8 and 5.0; it can serve as a basis for all general seismotectonic and risk assessment studies in the region., Competing Interests: Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

Built-up on top of ancient lake deposits, Mexico City experiences some of the largest seismic site effects worldwide. Besides the extreme amplification of seismic waves, duration of intense ground motion from large subduction earthquakes exceeds three minutes in the lake-bed zone of the basin, where hundreds of buildings collapsed or were seriously damaged during the magnitude 8.0 Michoacán earthquake in 1985. Different mechanisms contribute to the long lasting motions, such as the regional dispersion and multiple-scattering of the incoming wavefield from the coast, more than 300 km away the city. By means of high performance computational modeling we show that, despite the highly dissipative basin deposits, seismic energy can propagate long distances in the deep structure of the valley, promoting also a large elongation of motion. Our simulations reveal that the seismic response of the basin is dominated by surface-waves overtones, and that this mechanism increases the duration of ground motion by more than 170% and 290% of the incoming wavefield duration at 0.5 and 0.3 Hz, respectively, which are two frequencies with the largest observed amplification. This conclusion contradicts what has been previously stated from observational and modeling investigations, where the basin itself has been discarded as a preponderant factor promoting long and devastating shaking in Mexico City.

Acoustic tomography in a shallow ultrasonic waveguide is demonstrated at the laboratory scale between two source-receiver arrays. At a 1/1,000 scale, the waveguide represents a 1.1-km-long, 52-m-deep ocean acoustic channel in the kilohertz frequency range. Two coplanar arrays record the transfer matrix in the time domain of the waveguide between each pair of source-receiver transducers. A time-domain, double-beamforming algorithm is simultaneously performed on the source and receiver arrays that projects the multi-reflected acoustic echoes into an equivalent set of eigenrays, which are characterized by their travel times and their launch and arrival angles. Travel-time differences are measured for each eigenray every 0.1 s when a thermal plume is generated at a given location in the waveguide. Travel-time tomography inversion is then performed using two forward models based either on ray theory or on the diffraction-based sensitivity kernel. The spatially resolved range and depth inversion data confirm the feasibility of acoustic tomography in shallow water. Comparisons are made between inversion results at 1 and 3 MHz with the inversion procedure using ray theory or the finite-frequency approach. The influence of surface fluctuations at the air-water interface is shown and discussed in the framework of shallow-water ocean tomography., (© 2011 Acoustical Society of America)

In recent years, the use of sensitivity kernels for tomographic purposes has been frequently discussed in the literature. Sensitivity kernels of different observables (e.g., amplitude, travel-time, and polarization for seismic waves) have been proposed, and relationships between adjoint formulation, time-reversal theory, and sensitivity kernels have been developed. In the present study, travel-time sensitivity kernels (TSKs) are derived for two source-receiver arrays in an acoustic waveguide. More precisely, the TSKs are combined with a double time-delay beam-forming algorithm performed on two source-receiver arrays to isolate and identify each eigenray of the multipath propagation between a source-receiver pair in the acoustic waveguide. A relationship is then obtained between TSKs and diffraction theory. It appears that the spatial shapes of TSKs are equivalent to the gradients of the combined direction patterns of the source and receiver arrays. In the finite-frequency regimes, the combination of TSKs and double beam-forming both simplifies the calculation of TSK and increases the domain of validity for ray theory in shallow-water ocean acoustic tomography.

Mt. Vesuvius is a small volcano associated with an elevated risk. Seismic data were used to better define its magmatic system. We found evidence of an extended (at least 400 square kilometers) low-velocity layer at about 8-kilometer depth. The inferred S-wave (approximately 0.6 to 1.0 kilometer per second) and P-wave velocities (approximately 2.0 kilometer per second) as well as other evidence indicate an extended sill with magma interspersed in a solid matrix.

Since 1994, important modifications have been implemented in the dental curriculum in France, and an additional year has been included in the dental curriculum. The 1st year has remained unchanged; it is common to both medical and dental schools and leads to a selection procedure of 1 in 10 dental students. In the new curriculum, the dental student is engaged in a 5-year programme in dental school (years 2 to 6), as opposed to 4 years in the former programme (years 2 to 5). Basically, this new curriculum emphasises research initiation, links with medical training and offers broader clinical experience. During the academic year 1998-1999, dental schools had 2 different types of students: the 4th year students belonging to the new programme along with the 5th year students in their final year of the old curriculum. Using a specially devised questionnaire, we investigated the students' perception of their respective training, their motivation and professional plans. At the Faculty of Odontology in Lyon, the new curriculum is perceived as an increased strain by the dental students.