Coseismic and post-seismic signatures of the Sumatra 2004 December and 2005 March earthquakes in GRACE satellite gravity

International audienceS U M M A R Y The GRACE satellite mission has been measuring the Earth's gravity field and its temporal variations since 2002 April. Although these variations are mainly due to mass transfer within the geofluid envelops, they also result from mass displacements associated with phenomena including glacial isostatic adjustment and earthquakes. However, these last contributions are difficult to isolate because of the presence of noise and of geofluid signals, and because of GRACE's coarse spatial resolution (>400 km half-wavelength). In this paper, we show that a wavelet analysis on the sphere helps to retrieve earthquake signatures from GRACE geoid products. Using a wavelet analysis of GRACE geoids products, we show that the geoid variations caused by the 2004 December (M w = 9.2) and 2005 March (M w = 8.7) Sumatra earthquakes can be detected. At GRACE resolution, the 2004 December earthquake produced a strong coseismic decrease of the gravity field in the Andaman Sea, followed by relaxation in the area affected by both the Andaman 2004 and the Nias 2005 earthquakes. We find two characteristic timescales for the relaxation, with a fast variation occurring in the vicinity of the Central Andaman ridge. We discuss our coseismic observations in terms of density changes of crustal and upper-mantle rocks, and of the vertical displacements in the Andaman Sea. We interpret the post-seismic signal in terms of the viscoelastic response of the Earth's mantle. The transient component of the relaxation may indicate the presence of hot, viscous material beneath the active Central Andaman Basin

COST-G: towards a new GRACE and GRACE-FO combination

The combination service for time-variable gravity fields (COST-G) provides the full time-series of monthly GRACE gravity fields: COST-G GRACE RL01, combined in reprocessing mode, and a steadily growing time-series of monthly GRACE-FO gravity fields: COST-G GRACE-FO RL01 OP, combined on an operational basis. Both time-series are currently considered for re-combination. In case of GRACE, new high-quality time-series from Chinese analysis centers are available for combination. In case of GRACE-FO, a revision of the weighting scheme, developed in the frame of the Horizon2020 project Global Gravity-based Groundwater Product (G3P), and the availability of reprocessed GRACE-FO time-series from AIUB, CSR, GFZ, and JPL, lead to a significant improvement of the combined gravity fields. We present the preliminary re-combined GRACE and GRACE-FO time-series and quantify the differences with respect to the COST-G RL01 series in terms of signal and noise content

Lithium-Beryllium-Boron : Origin and Evolution

The origin and evolution of Lithium-Beryllium-Boron is a crossing point between different astrophysical fields : optical and gamma spectroscopy, non thermal nucleosynthesis, Big Bang and stellar nucleosynthesis and finally galactic evolution. We describe the production and the evolution of Lithium-Beryllium-Boron from Big Bang up to now through the interaction of the Standard Galactic Cosmic Rays with the interstellar medium, supernova neutrino spallation and a low energy component related to supernova explosions in galactic superbubbles.Comment: 28 pages, 7 figures, to be published in a special memorial volume of Physics Reports in honor of David Schram

Observing the prompt emission of gamma-ray bursts

Gamma-ray bursts (GRBs) were first detected thanks to their prompt emission, which was the only information available for decades. In 2010, while the high-energy prompt emission remains the main tool for the detection and the first localization of GRB sources, our understanding of this crucial phase of GRBs has made great progress. We discuss some recent advances in this field, like the occasional detection of the prompt emission at all wavelengths, from optical to GeV; the existence of sub-luminous GRBs; the attempts to standardize GRBs; and the possible detection of polarization in two very bright GRBs. Despite these advances, tantalizing observational and theoretical challenges still exist, concerning the detection of the faintest GRBs, the panchromatic observation of GRBs from their very beginning, the origin of the prompt emission, or the understanding of the physics at work during this phase. Significant progress on this last topic is expected with SVOM thanks to the observation of dozens of GRBs from optical to MeV during the burst itself, and the measure of the redshift for the majority of them. SVOM will also change our view of the prompt GRB phase in another way. Within a few years, the sensitivity of sky surveys at optical and radio frequencies, and outside the electromagnetic domain in gravitational waves or neutrinos, will allow them to detect several new types of transient signals, and SVOM will be uniquely suited to identify which of these transients are associated with GRBs. This radically novel look at GRBs may elucidate the complex physics producing these bright flashes.Comment: To appear in a special issue of Comptes Rendus Physique "GRB studies in the SVOM era", Eds. F. Daigne, G. Dubus. 15 pages 9 figure

European Gravity Service for Improved Emergency Management - Status and project highlights

European Gravity Service for Improved Emergency Management - Status and project highlight

European Gravity Service for Improved Emergency Management - Status and project highlights

European Gravity Service for Improved Emergency Management - Status and project highlight

Ville et campagne de Fréjus romaine

En 2006, une fouille d’archéologie préventive, désignée sous le nom de « Villa Romana », a été réalisée dans le quartier de Villeneuve à Fréjus. Durant l’Antiquité il s’agit d’une zone périurbaine située entre la ville de Forum Iulii et le débouché de l’Argens. Connu depuis longtemps en raison de la présence d’un édifice thermal toujours en élévation, le quartier a été fouillé à plusieurs occasions et est interprété comme étant l’emplacement du camp de la flotte, établi après la bataille d’Actium. Celui-ci se transforme progressivement durant le Ier siècle apr. J.-C. en quartier suburbain au fur et à mesure que se développe Forum Iulii. Le secteur fouillé se situe dans la partie sud du camp, bordée par la mer durant les premiers temps de l’Antiquité. La fouille a permis de révéler la présence d’une plage aménagée. Les terrains ont ensuite été rapidement gagnés sur la mer, en raison d’une avancée rapide du littoral, que des études récentes ont permis de bien connaitre à Fréjus. Des jardins y sont alors aménagés. A partir du IIe siècle, cet espace est transformé en zone agricole, et constitue l’illustration de l’exploitation de la campagne aux portes de Fréjus, et cela, jusqu’à la fin de l’Antiquité. S’ensuit une longue période d’abandon de plusieurs siècles, avant que l’espace ne soit à nouveau voué à l’agriculture et ce jusqu’à l’orée des années soixante. Depuis, le développement de la ville actuelle de Fréjus a de nouveau transformé ce quartier en zone urbaine. Cet ouvrage, publié quelques années seulement après la fouille, présente l’ensemble des études archéologiques et paléoenvironnementales, réalisées à l’occasion de cette opération, largement pluridisciplinaire. Elles fournissent un contexte environnemental nouveau pour ce quartier antique et permettent de redéfinir un paysage à partir d’analyses bioarchéologiques et paléoécologiques récentes. L’étude de l’ensemble des mobiliers archéologiques est également présentée, en suivant la chronologie et l’évolution de ce quartier à travers l’Antiquité et l’époque moderne

Bone Marrow Transplant

Mucopolysaccharidosis type I-H (MPS I-H) is a rare lysosomal storage disorder caused by α-L-Iduronidase deficiency. Early haematopoietic stem cell transplantation (HSCT) is the sole available therapeutic option to preserve neurocognitive functions. We report long-term follow-up (median 9 years, interquartile range 8-16.5) for 51 MPS I-H patients who underwent HSCT between 1986 and 2018 in France. 4 patients died from complications of HSCT and one from disease progression. Complete chimerism and normal α-L-Iduronidase activity were obtained in 84% and 71% of patients respectively. No difference of outcomes was observed between bone marrow and cord blood stem cell sources. All patients acquired independent walking and 91% and 78% acquired intelligible language or reading and writing. Intelligence Quotient evaluation (n = 23) showed that 69% had IQ ≥ 70 at last follow-up. 58% of patients had normal or remedial schooling and 62% of the 13 adults had good socio-professional insertion. Skeletal dysplasia as well as vision and hearing impairments progressed despite HSCT, with significant disability. These results provide a long-term assessment of HSCT efficacy in MPS I-H and could be useful in the evaluation of novel promising treatments such as gene therapy