Abstract: We pursue the study of S Arae, an RRab Lyrae Blazho star, using unique, uninterrupted and accurate optical photometric data acquired from Antarctica at Dome C by PAIX – Photometer AntarctIca eXtraction – during 150 d. The PAIX data were analysed using both Period04 and PDM13. Besides a main pulsation period of 0.452 d and a modulation period of 47.264 d, three other significant frequencies were found. Multiplet patterns, up to the ninth order, were also extracted, showing a clear asymmetric structure. Following these results, a new approximation of the main-frequency harmonics amplitude decrease is suggested, replacing the usual exponential fit by a hyperbolic one. The physical properties of the Blazhko star, namely metallicity, temperature, mass, were obtained using a new approach based on the study of these parameters for each Blazhko phase. Finally, the PAIX data reveal a residual scatter that occurs during a small phase interval, 10 per cent of the pulsation period, corresponding to the phase of the main shock passage across the atmosphere. The position of the so-called main bump, corresponding to the shock resulting from the infalling atmosphere and the expanding photosphere, varies from one cycle to another and, moreover, around this main bump, two other bumps appear and vanish at different phases during a Blazhko cycle. Following these observations, we discuss the relation between the bump topology and the Blazhko period and give new insights for future Blazhko theoretical investigations.

Abstract: We proposed a simple algorithm to retrieve the total ozone column and snow properties (spectral albedo and effective light absorption path) using the high spatial resolution single–view MSI/S-2 measurements over Antarctica. In addition, the algorithm allows the retrieval of the snow grain size on a scale of 10–20 m. This algorithm should be useful for the understanding of intra-pixel total ozone and snow albedo variability in complement to satellite observations performed on a much coarser spatial resolution scale (0.3–1 km and even larger spatial scales).

Abstract: We propose a new rapid procedure for determining the energy magnitude Me for shallow events from broadband teleseismic P-wave signals within the distance range 20–98. To accomplish this task, we compute spectral amplitude decay functions for different periods using numerical simulations based on the reference Earth model AK135Q. By means of these functions, we correct the spectra of the teleseismic recordings for the propagation path effects, and calculate the radiated seismic energy E S , and hence Me. We use cumulative P-wave windows for simulating a real- or near real-time procedure and test it for 61 shallow earthquakes. The results show that our approach is able to provide a rapid and reliable Me determination within 7–15 minutes after the earthquake origin time, and is therefore suitable for implementation in rapid response systems.

Abstract: We present the results of synthetic tests that aim at evaluating the relative performance of three different definitions of misfit functionals in the context of 3-D imaging of shear wave attenuation in the earth’s upper mantle at the global scale, using long-period full-waveform data. The synthetic tests are conducted with simple hypothetical upper-mantle models that contain Qμ anomalies centred at different depths and locations, with or without additional seismic velocity anomalies. To build synthetic waveform data sets, we performed simulations of 50 events in the hypothetical (target) models, using the spectral element method, filtered in the period range 60–400 s. The selected events are chosen among 273 events used in the development of radially anisotropic model SEMUCB-WM1 and recorded at 495 stations worldwide. The synthetic Z-component waveforms correspond to paths and time intervals (fundamental mode and overtone Rayleigh waves) that exist in the real waveform data set. The inversions for shear attenuation structure are carried out using a Gauss–Newton optimization scheme in which the gradient and Hessian are computed using normal mode perturbation theory. The three different misfit functionals considered are based on time domain waveform (WF) and waveform envelope (E-WF) differences, as well as spectral amplitude ratios (SA), between observed and predicted waveforms. We evaluate the performance of the three misfit functional definitions in the presence of seismic noise and unresolved S-wave velocity heterogeneity and discuss the relative importance of physical dispersion effects due to 3-D Qμ structure. We observed that the performance of WF is poorer than the other two misfit functionals in recovering attenuation structure, unless anelastic dispersion effects are taken into account in the calculation of partial derivatives. WF also turns out to be more sensitive to seismic noise than E-WF and SA. Overall, SA performs best for attenuation imaging. Our tests show that it is important to account for 3-D elastic effects (focusing) before inverting for Qμ. Additionally, we show that including high signal-to-noise ratio overtone wave packets is necessary to resolve Qμ structure at depths greater than 250 km.

Abstract: We present the results of a study of the morphometric properties of a talus slope in subarctic Quebec (Nunavik) using field-based methods, including geomorphological, granulometric and plant distribution surveys, and statistical analyses. Slope processes are currently active, despite the limited altitudinal difference between the apical-to-distal parts of the slope and the imminent depletion of the debris supply. The near-rectilinear long profiles of the talus highlight the distribution of debris across the slope and demonstrate that free-fall of rock fragments is not the only process operating (redistribution is higher in the westernmost profile, which exhibits a clear concave shape). The spatial distribution of vegetation covering the screes highlights the recent age of parts of the talus, showing that present-day processes are still active, although limited. The short remaining apical rockwall highlights the shortage of debris following deglaciation, as debris are mostly supplied by freeze-thaw processes to the talus, and are then reworked by other processes which need to be better defined in subsequent research.