Abstract: Using an inversion strategy based on adjoint methods, we developed a three-dimensional seismological model of the southern California crust. The resulting model involved 16 tomographic iterations, which required 6800 wavefield simulations and a total of 0.8 million central processing unit hours. The new crustal model reveals strong heterogeneity, including local changes of ±30% with respect to the initial three-dimensional model provided by the Southern California Earthquake Center. The model illuminates shallow features such as sedimentary basins and compositional contrasts across faults. It also reveals crustal features at depth that aid in the tectonic reconstruction of southern California, such as subduction-captured oceanic crustal fragments. The new model enables more realistic and accurate assessments of seismic hazard.

Abstract: Summary Optimal diving models have been developed to investigate how air?breathing predators should adjust their diving behaviour to optimize their foraging efficiency. Using time?depth recorders and 3D accelerometers, we addressed this question on six free?ranging Southern Elephant Seal (SES) females equipped on Kerguelen Island. We hypothesize that seals would initially increase their foraging time with distance to the foraging patches before reducing it for physiological reasons, regardless of the prey encountered. We expect that SES spends more time at depths where more Prey Catch Attempts (PCA) occur, that is at the bottom. We also hypothesize that bottom time should be related to both the seal body density and the swimming effort dedicated to catching prey, as we expect seals to be more active when catching prey. Finally, because oxygen is acquired at the surface only, we expect that recovery times increase with the duration of the previous dives. A total of 72·6% of PCA detected by accelerometer occurred at the bottom of the dive. At shallow depths (<300 m), seals spent more time at the bottom in dives where PCA occurred compared to non?PCA dives. At deeper depths, SES had shorter bottom times in PCA dives due to higher swimming effort. When only dives associated with PCA were considered, the time spent at the bottom increased with the number of PCA. In addition, the closer the seal was to neutral buoyancy, the longer was the bottom duration. Body density, that is buoyancy, was found to be a critical factor in controlling variations in the dive duration through the swimming effort to access the prey at the bottom of the dive. Finally, post?dive surface intervals were related to the duration and swimming effort of the previous dive. This study reveals how a marine top predator adjusts the time spent at the bottom depending on its body density, prey encounter rate and prey accessibility. It also highlights that using the duration of the foraging phase as a proxy of foraging success can be seriously misleading in SES. Finally, the need to use an energetic approach with bio?logging technology to study behavioural ecology is emphasized.

Abstract: The adsorption isotherms of acetone on ice were measured at 193, 203 and 213 K using a volumetric method with mass spectrometric detection. Henry's law applies for values of the acetone partial pressure, Pacetone, lower than 10?3 Pa. Where Henry's law applies, the number of acetone molecules adsorbed per cm2 of ice, is: nads = 90.53 × Pacetone × exp (6610.2/T), with Pacetone in Pa and T in K. The measured enthalpy of adsorption of acetone on ice is ?Hads = ?55±7 kJ/mol. Acetone values previously measured in Arctic snow are too high to be due to adsorbed acetone. Acetone was then probably dissolved in ice or in organic aerosols contained in snow. Adsorption of acetone in the snowpack or on ice crystals in cirrus clouds is insufficient to affect Pacetone above the snow or in the clouds.