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The variation of stress on faults is important for our understanding of fault friction and the dynamics of earthquake ruptures. However, we still have little observational constraints on their absolute magnitude, or their variations in space and in time over the seismic cycle. Here we use a new geodetic imaging technique to measure the 3D coseismic slip vectors along the 2019 Ridgecrest surface ruptures and invert them for the coseismic stress state. We find that the coseismic stresses show an eastward rotation that becomes increasingly transtensional from south‐to‐north along the rupture, that matches the known background stress state. We find that the main fault near the Mw7.1 mainshock hypocenter was critically stressed. Coseismic slip was maximum there and decreased gradually along strike as the fault became less optimally oriented due its curved geometry. The variations of slip and stress along the curved faults are used to infer the static and dynamic fault friction assuming Mohr‐Coulomb failure. We find shear stresses of 4–9 MPa in the shallow crust (∼1.3 km depth) and that fault friction drops from a static, Byerlee‐type, value of 0.61 ±$\pm $0.14 to a dynamic value of 0.29 ±$\pm $0.04 during seismic slip. These values explain quantitatively the slip variations along a transpressional fault bend. Understanding the orientation and magnitude of stresses within the crust are important because they can affect the location, size and spatial extent of earthquake rupture. However, measuring the absolute magnitude and orientation of stresses as well as the frictional properties of the fault surface (i.e., how strongly the fault resists the applied driving forces) is very difficult. Here we use optical images acquired by satellites to measure how the surface deformed in 3D during the 2019 Ridgecrest event. These 3D measurements allow us to extract the direction of fault slip movement along the entire rupture length which we use to estimate the direction of stresses by assuming the shear stress is parallel to the direction of the observed fault slip motion. We find that the main fault near the mainshock epicenter was the most optimally aligned for failure, which could be one contributing reason for the location of rupture initiation. By deriving a relation between how much a fault slips with how well aligned it is to the stress field we can estimate the absolute magnitude of stresses, the frictional resistance at initial fault sliding (finding a static friction = 0.61) and during sliding (a dynamic friction = 0.29). Inverting surface coseismic slip vectors show a variable stress state that matches the background stresses constrained by seismicityFaults at the mainshock epicenter were the most critically stressed; we find slip increases linearly as faults become more optimally alignedWe find absolute stress magnitudes of 8–26 MPa in the upper crust, a static frictional coefficient of 0.61 and a dynamic value of 0.29 Inverting surface coseismic slip vectors show a variable stress state that matches the background stresses constrained by seismicity Faults at the mainshock epicenter were the most critically stressed; we find slip increases linearly as faults become more optimally aligned We find absolute stress magnitudes of 8–26 MPa in the upper crust, a static frictional coefficient of 0.61 and a dynamic value of 0.29

The Himalayan arc produced the largest known continental earthquake, the Mw≈ 8.7 Assam earthquake of 1950, but how frequently and where else in the Himalaya such large‐magnitude earthquakes occur is not known. Paleoseismic evidence for coseismic ruptures at the front of the Himalaya with 15 to 30 m of slip suggests even larger events in medieval times, but this inference is debated. Here we estimate the frequency and magnitude of the largest earthquake in the Himalaya needed so that the moment released by seismicity balances the deficit of moment derived from measurements of geodetic strain. Assuming one third of the moment buildup is released aseismically and the earthquakes roughly follow a Gutenberg‐Richter distribution, we find that Mw> 9.0 events are needed with a confidence level of at least 60% and must return approximately once per 800 years on average. Geodetic and seismic observations require millenary Mw> 9.0 earthquakes along the Himalaya

We report Global Positioning System (GPS) measurements of postseismic deformation following the 2015 Mw7.8 Gorkha (Nepal) earthquake, including previously unpublished data from 13 continuous GPS stations installed in southern Tibet shortly after the earthquake. We use variational Bayesian Independent Component Analysis (vbICA) to extract the signal of postseismic deformation from the GPS time series, revealing a broad displacement field extending >150 km northward from the rupture. Kinematic inversions and dynamic forward models show that these displacements could have been produced solely by afterslip on the Main Himalayan Thrust (MHT) but would require a broad distribution of afterslip extending similarly far north. This would require the constitutive parameter (a− b)σto decrease northward on the MHT to ≤0.05 MPa (an extreme sensitivity of creep rate to stress change) and seems unlikely in light of the low interseismic coupling and high midcrustal temperatures beneath southern Tibet. We conclude that the northward reach of postseismic deformation more likely results from distributed viscoelastic relaxation, possibly in a midcrustal shear zone extending northward from the seismogenic MHT. Assuming a shear zone 5–20 km thick, we estimate an effective shear‐zone viscosity of ~3·1016–3·1017Pa·s over the first 1.12 postseismic years. Near‐field deformation can be more plausibly explained by afterslip itself and implies (a− b)σ~ 0.5–1 MPa, consistent with other afterslip studies. This near‐field afterslip by itself would have re‐increased the Coulomb stress by ≥0.05 MPa over >30% of the Gorkha rupture zone in the first postseismic year, and deformation further north would have compounded this reloading. New GPS data show that postseismic deformation of the 2015 Mw7.8 Gorkha (Nepal) earthquake extended far northward into southern TibetKinematic and dynamic models suggest that the northward reach of deformation likely reflects the influence of viscoelastic relaxationAfterslip likely dominated postseismic deformation in the near field, transferring stress back to the (relocked) Gorkha rupture zone

La sarcoïdose est une affection granulomateuse systémique dont la physiopathologie est mal élucidée. La symptomatologie est variable : si 90 % des cas ont une atteinte médiastino-pulmonaire, les atteintes osseuses et unguéales restent rares. Nous rapportons un cas de sarcoïdose osseuse, révélée par une lésion pseudo-tumorale sous-unguéale avec modifications unguéales.

Les télangiectasies cutanées (TC) sont fréquentes chez les patients atteints de sclérodermie systémique (ScS) mais leur valeur pronostique est peu décrite. L’objectif de notre étude était de déterminer si nombre et taille des TC étaient associés à des anomalies morphologiques des capillaires digitaux à la capillaroscopie péri-unguéale ou à des marqueurs reflétant la sévérité de la vasculopathie associée à la ScS (vasculopathie-ScS).