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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 Mw 7.1 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. Plain Language Summary: 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). Key Points: 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 [ABSTRACT FROM AUTHOR]

Strong and sustained winds on Mars have been considered rare, on the basis of surface meteorology measurements and global circulation models (1,2), raising the question of whether the abundant dunes and evidence for wind erosion seen on the planet are a current process. Recent studies (3-6) showed sand activity, but could not determine whether entire dunes were moving--implying large sand fluxes--or whether more localized and surficial changes had occurred. Here we present measurements of the migration rate of sand ripples and dune lee fronts at the Nili Patera dune field. We show that the dunes are near steady state, with their entire volumes composed of mobile sand. The dunes have unexpectedly high sand fluxes, similar, for example, to those in Victoria Valley, Antarctica, implying that rates of landscape modification on Mars and Earth are similar., The Martian surface displays abundant bedforms (ripples and dunes) (7), and evidence for wind erosion ranging from centimetre-scale ventifact rock textures (8) to kilometre-scale yardangs and exhumed mantles (7). But [...]

We model evolution of a continent-continent collision and draw some parallels with the tectonic evolution of the Himalaya. We use a large-scale visco-plasto-elastic thermomechanical model that has a free upper surface, accounts for erosion and deposition and allows for all modes of lithospheric deformation. For quartz/olivine rheology and 60 mm/yr convergence rate, the continental subduction is stable, and the model predicts three distinct phases. During the phase 1 (120 km or 6% of shortening), deformation is characterized by back thrusting around the suture zone. Some amount of delaminated lower crust accumulates at depth. During phase 2 (120 km-420 km or 6%-22% of shortening), this crustal root is exhumed (medium- to high-grade rocks) along a newly formed major thrust fault. This stage bears similarities with the period of coeval activity of the Main Central thrust and of the South Tibetan Detachment between 20-16 Myr ago. During phase 3 (>420 km or 22% of shortening), the crust is scraped off from the mantle lithosphere and is incorporated into large crustal wedge. Deformation is localized around frontal thrust faults. This kinematics should produce only low- to medium-grade exhumation. This stage might be compared with the tectonics that has prevailed in the Himalaya over the last 15 Myr allowing for the formation of the Lesser Himalaya. The experiment is conducted at constant convergence rate, which implies increasing compressive force. Considering that this force is constant in nature, this result may be equivalent to a slowing down of the convergence rate as was observed during the India-Asia collision. INDEX TERMS: 8120 Tectonophysics: Dynamics of lithosphere and mantle--general: 8102 Tectonophysics: Continental contractional orogenic belts: 8159 Tectonophysics: Rheology--crust and lithosphere; 8110 Tectonophysics: Continental tectonics general (0905): 3210 Mathematical Geophysics: Modeling; KEYWORDS: continental subduction, numerical modeling, Himalaya, rheology, mountain building.

The increasing density of geodetic measurements makes it possible to map surface strain rate in many zones of active tectonics with unprecedented spatial resolution. Here we show that the strain tensor rate calculated from GPS in the India–Asia collision zone represents well the strain released in earthquakes. This means that geodetic data in the India–Asia collision zone region can be extrapolated back in time to estimate strain buildup on active faults, or the kinematics of continental deformation. We infer that the geodetic strain rates can be assumed stationary through time on the timescale needed to build up the elastic strain released by larger earthquakes, and that they can be used to estimate the probability of triggering earthquakes. We show that the background seismicity rate correlates with the geodetic strain rate. A good fit is obtained assuming a linear relationship (⁠|$\dot{N} = \lambda \ \cdot \dot{\epsilon }$|⁠ , where |$\dot{N}$| is the density of the rate of M w ≥ 4 earthquakes, |$\dot{\epsilon }$| is strain rate and λ = 2.5 ± 0.1 × 10−3 m−2), as would be expected from a standard Coulomb failure model. However, the fit is significantly better for a non-linear relationship (⁠|$\dot{N} = \gamma _1 \cdot \dot{\epsilon }^{\gamma _2}$| with γ1 = 2.5 ± 0.6 m−2 and γ 2 = 1.42 ± 0.15). The b -value of the Gutenberg–Richter law, which characterize the magnitude–frequency distribution, is found to be insensitive to the strain rate. In the case of a linear correlation between seismicity and strain rate, the maximum magnitude earthquake, derived from the moment conservation principle, is expected to be independent of the strain rate. By contrast, the non-linear case implies that the maximum magnitude earthquake would be larger in zones of low strain rate. We show that within areas of constant strain rate, earthquakes above M w 4 follow a Poisson distribution in time and and are uniformly distributed in space. These findings provide a framework to estimate the probability of occurrence and magnitude of earthquakes as a function of the geodetic strain rate. We describe how the seismicity models derived from this approach can be used as an input for probabilistic seismic hazard analysis. This method is easy to automatically update, and can be applied in a consistent manner to any continental zone of active tectonics with sufficient geodetic coverage. [ABSTRACT FROM AUTHOR]

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)σ to 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 ~3·1016–3·1017 Pa·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. Key Points: 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 [ABSTRACT FROM AUTHOR]

The article offers information about the slow earthquakes result from unstable frictional slip. It characterizes the system dynamics using embedding theory and extreme value theory, along with information on the analysis reveals a low-dimensional nonlinear chaotic system rather than a stochastic system.

Abstract Objective Rituximab (RTX) is an anti-CD20 monoclonal antibody that selectively depletes B-cell population. Thus, it presents a potential risk for the development of hypogammaglobulinemia and related infectious events. Our aim was to identify predictors of hypogammaglobulinemia in RA patients long-term treated with RTX. Methods Multicenter observational usual care study of patients with RA on RTX maintenance therapy (minimal exposition of 30 months). Serum protein electrophoresis was performed before each RTX infusion. Hypogammaglobulinemia and severe hypogammaglobulinemia were defined as total gammaglobulin <6 g/L and <4 g/L, respectively. The primary outcome was the occurrence within the follow-up period of hypogammaglobulinemia. Results 134 patients met inclusion criteria and were followed-up for 79.5 ± 24.6 months. Hypogammaglobulinemia occurred during the follow-up period in 23 patients (2.7 events per 100 pt-yrs). The mean time to development of hypogammaglobulinemia was 64 ± 23 months. Patients who developed hypogammaglobulinemia were more likely to experience severe infections (26.1% vs. 6.3%, P = 0.033). Multivariate Cox analysis identified gammaglobulin levels <8 g/L at baseline as an independent predictor of hypogammaglobulinemia (HR 7.34 [95% CI: 2.00–26.90], P = 0.003). Concomitant methotrexate (MTX) intake was also predictive of a reduced risk of hypogammaglobulinemia occurrence (HR 0.26 [95% CI: 0.08–0.87], P = 0.03). Conclusion Our results show that gammaglobulin levels of less than 8 g/L at baseline is a strong independent risk factor for developing subsequent hypogammaglobulinemia, whereas concomitant MTX therapy seems to be a protective factor in RA patients treated long-term with RTX. [ABSTRACT FROM AUTHOR]

We describe a simple method to determine the probability distribution function of the magnitude Mmax and return period TR of the maximum plausible earthquake on crustal faults. The method requires the background seismicity rate (estimated from instrumental data) and the rate of interseismic moment buildup. The method assumes that the moment released by the seismic slip is in balance with the moment deficit accumulated in between earthquakes. It also assumes that the seismicity obeys the Gutenberg-Richter (GR) law up to Mmax. We took into account the aftershocks of large infrequent events that were not represented in the instrumental record, so that we could estimate the average seismicity rate over the entire fault history. We extrapolated the instrumental record, using the GR law to model the frequency of larger events and their aftershocks. This increased the frequencies of smaller events on average; when these smaller events were newly extrapolated, they predicted a higher frequency of larger events. We iterated this process until stability was reached, and then we assumed moment balance when we found the maximum magnitude; we have found this method to be appropriate in applications involving examples of fault with good historical catalogs. We then showed examples of applications to faults with no historical catalogs. We present results from nine cases. For the San Andreas fault system, we find Mmax=8.1±0.3, with TR380950120 yrs; for the North Anatolian fault, Mmax=8.0±0.3, with TR275650135 yrs; for the Main Himalayan thrust, Mmax=9.0±0.2, with TR12002700550 yrs; for the Japan trench, Mmax=9.3±0.3, with TR5201200220 yrs; for the Sumatra-Andaman trench, Mmax=9.0±0.3, with TR20045080 yrs; for the Boconó fault, Mmax=7.3±0.3, with TR16036070 yrs; for the Altyn Tagh fault, Mmax=8.0±0.3, with TR9002000400 yrs; for the Dead Sea Transform, Mmax=7.8±0.3, with TR10002400450 yrs; and for the Kunlun fault, Mmax=8.0±0.3, with TR10002000450 yrs. [ABSTRACT FROM AUTHOR]

Analyzing the displacement time series from continuous GPS (cGPS) with an Independent Component Analysis, we detect a transient deformation signal that correlates both in space and time with a seismic swarm activity (maximum M w=3.69 ± 0.09) occurred in the hanging wall of the Altotiberina normal fault (Northern Apennines, Italy) in 2013-2014. The geodetic transient lasted ∼6 months and produced a NW-SE trending extension of ∼5.3 mm, consistent with the regional tectonic regime. The seismicity and the geodetic signal are consistent with slip on two splay faults in the Altotiberina fault (ATF) hanging wall. Comparing the seismic moment associated with the geodetic transient and the seismic events, we observe that seismicity accounts for only a fraction of the measured geodetic deformation. The combined seismic and aseismic slip decreased the Coulomb stress on the locked shallow portion of the ATF, while the transition region to the creeping section has been loaded. [ABSTRACT FROM AUTHOR]

Measurement of interseismic strain along subduction zones reveals the location of both locked asperities, which might rupture during megathrust earthquakes, and creeping zones, which tend to arrest such seismic ruptures. The heterogeneous pattern of interseismic coupling presumably relates to spatial variations of frictional properties along the subduction interface and may also show up in the fore-arc morphology. To investigate this hypothesis, we compiled information on the extent of earthquake ruptures for the last 500 years and uplift rates derived from dated marine terraces along the South American coastline from central Peru to southern Chile. We additionally calculated a new interseismic coupling model for that same area based on a compilation of GPS data. We show that the coastline geometry, characterized by the distance between the coast and the trench; the latitudinal variations of long-term uplift rates; and the spatial pattern of interseismic coupling are correlated. Zones of faster and long-term permanent coastal uplift, evidenced by uplifted marine terraces, coincide with peninsulas and also with areas of creep on the megathrust where slip is mostly aseismic and tend to arrest seismic ruptures. We conclude that spatial variations of frictional properties along the megathrust dictate the tectono-geomorphological evolution of the coastal zone and the extent of seismic ruptures along strike. [ABSTRACT FROM AUTHOR]

Introduction: Non-steroidal anti-inflammatory drugs' (NSAIDs) symptomatic efficacy in osteoarthritis (OA) is often assessed in trials with a "flare design", i.e., including only patients with an increase in their pain after stopping their usual treatment (NSAIDs or analgesic).Objective: To evaluate the influence of the "flare design" on NSAIDs apparent symptomatic efficacy in OA.Design: Search Strategy: a systematic literature research was performed in Medline, EMBASE and The Cochrane Register up to March 2009. All randomized controlled trials comparing NSAIDs vs placebo symptomatic efficacy in hip, knee, or digital OA were included.Data Collection and Analysis: efficacy was evaluated on pain (visual analog scale), and on function (Western Ontario and McMaster Universities OA index or Lequesne index). The magnitude of the treatment effect was evaluated by calculating Cohen's effect size (ES). Meta-analysis of ES according to flare design yes/no was performed.Results: Among the 343 identified studies, 33 (20,915 patients) were included: 27 (18,667 patients) vs 6 (2248 patients) respectively in the group with vs without "flare design". Populations were comparable in each group. ESs were, for pain, -0.66 (95% confidence interval, -0.71 to -0.61), vs -0.45 (-0.54 to -0.36) in the flare design vs "no flare design" group, and for function, -0.50 (-0.55 to -0.44) vs -0.25 (-0.36 to -0.14) respectively.Conclusion: Our study suggests that the flare design used in clinical trials evaluating NSAIDs results in a treatment effect of higher magnitude. These results should be considered when designing a trial and/or interpreting the results of a trial. [ABSTRACT FROM AUTHOR]

The accuracy, reliability and best practises of Tiin- quartz thermobarometry (TitaniQ) in greenschist facies rocks have not been established. To address these issues, we measured Ti concentrations in rutile-bearing samples of moderately deformed, partially recrystallized quartzite and vein quartz from the Hsüehshan range, Taiwan. The spread of Ti concentrations of recrystallized grains in quartzite correlates with recrystallized grain size. Recrystallized quartz (grain size ~100-200 μm) that formed during early deformation within the biotite stability field shows a marked increase in intermediate Ti-concentration grains (~1-10 ppm) relative to detrital porphyroclasts (Ti ~0.1-200 ppm). Fine recrystallized quartz (~5% of the samples by area, grain size ~10-20 μm) has a further restricted Ti concentration peaking at 0.8-2 ppm. This trend suggests equilibration of Ti in recrystallized quartz with a matrix phase during deformation and cooling. Unlike previously documented examples, Ti concentration in the quartzite is inversely correlated with blue cathodoluminescence. Deformation was associated with a minimum grain boundary diffusivity of Ti on the order of 10-22 m2 s-1. Vein emplacement and quartzite recrystallization are independently shown to have occurred at 250-350 °C and 300-410 °C, respectively, with lithostatic pressure of 3- 4 kbar (assuming a geothermal gradient of 25° km-1), and with hydrostatic fluid pressure. Estimates of the accuracy of TitaniQ at these conditions depend on whether lithostatic or fluid pressure is used in the TitaniQ calibration. Using lithostatic pressure and these temperatures, the Thomas et al. (2010) calibration yields Ti concentrations within error of concentrations measured by SIMS. If fluid pressure is instead used, predicted temperatures are ~30-40 °C too low. TitaniQ has potential to yield accurate PT information for vein emplacement and dynamic recrystallization of quartz at temperatures as low as ~250 °C, however clarification of the relevant pressure term and further tests in rutile-present rocks are warranted. [ABSTRACT FROM AUTHOR]

The article presents a study on the accuracy, reliability and best practices of titanium-in-quartz thermobarometry (TitaniQ) in greenschist facies rocks in the Hsüehshan range, Taiwan. The study measured the Ti concentrations in rutile-bearing samples of recrystallized quartzite and vein quartz from Hsüehshan range. The results showed that TitaniQ has the potential to give accurate predicted temperature (PT) information for dynamic recrystallization of quartz and vein emlplacement.

Summary: Objectives: To determine the analgesic effectiveness, the effect on physical function and the safety of opioids in patients with osteoarthritis (OA). Search strategy: A systematic literature search was performed in electronic databases up to October 2006. A hand search of references was also performed. Selection criteria: All randomized controlled trials evaluating the efficacy and/or the safety of opioids vs placebo or non-opioid analgesics in patients with OA were selected. Data collection and analysis: Data were collected using a predetermined form. Statistical analysis determined in each trial the effect size to assess the magnitude of treatment effect and the number needed to harm (NNH) to evaluate opioids safety. Main results: Eighteen randomized placebo-controlled trials were analyzed, i.e., a total of 3244 participants who received opioids and 1612 who received placebo. The mean trial duration was 13±18 weeks. The pooled effect sizes of all opioids vs placebo for pain intensity and physical function were −0.79 (95% confidence interval, CI, −0.98 to −0.59) and −0.31 (95% CI −0.39 to −0.24), respectively. The NNH was calculated to be 5 vs placebo. The number of studies (n =4) that compared opioids with non-opioid analgesics (paracetamol and non-steroidal anti-inflammatory drugs) was too limited to provide robust data. Conclusions: Opioids significantly decrease pain intensity and have small benefits on function compared with placebo in patients with OA. Adverse events, although reversible and not life threatening, often cause participants to stop taking the medication and could limit opioid usefulness. Moreover, the long-term efficacy and safety of these drugs for OA is yet to be determined due to the short mean trial duration. [Copyright &y& Elsevier]

The Lesser Himalaya (LH) consists of metasedimentary rocks that have been scrapped off from the underthrusting Indian crust and accreted to the mountain range over the last ∼20 Myr. It now forms a significant fraction of the Himalayan collisional orogen. We document the kinematics and thermal metamorphism associated with the deformation and exhumation of the LH, combining thermometric and thermochronological methods with structural geology. Peak metamorphic temperatures estimated from Raman spectroscopy of carbonaceous material decrease gradually from 520°-550°C below the Main Central Thrust zone down to less than 330°C. These temperatures describe structurally a 20°-50°C/km inverted apparent gradient. The Ar muscovite ages from LH samples and from the overlying crystalline thrust sheets all indicate the same regular trend; i.e., an increase from about 3-4 Ma near the front of the high range to about 20 Ma near the leading edge of the thrust sheets, about 80 km to the south. This suggests that the LH has been exhumed jointly with the overlying nappes as a result of overthrusting by about 5 mm/yr. For a convergence rate of about 20 mm/yr, this implies underthrusting of the Indian basement below the Himalaya by about 15 mm/yr. The structure, metamorphic grade and exhumation history of the LH supports the view that, since the mid-Miocene, the Himalayan orogen has essentially grown by underplating, rather than by frontal accretion. This process has resulted from duplexing at a depth close to the brittle-ductile transition zone, by southward migration of a midcrustal ramp along the Main Himalayan Thrust fault, and is estimated to have resulted in a net flux of up to 150 m2/yr of LH rocks into the Himalayan orogenic wedge. The steep inverse thermal gradient across the LH is interpreted to have resulted from a combination of underplating and post metamorphic shearing of the underplated units. [ABSTRACT FROM AUTHOR]

Underthrusting of the Indian lithosphere beneath the Himalayas occurs during the Quaternary period along a gently north-dipping main basal detachment (main Himalayan thrust: MHT), from which the southernmost emergent ramp (main frontal thrust: MFT) branches. Historical seismicity shows that slip on the MHT is frequently accommodated through shallow earthquakes, but shows a seismic gap in western Nepal. This absence of major historical earthquakes in western Nepal can be explained either by an aseismic slip on the MHT or a long-lived elastic strain accumulation. To test these hypotheses, the present-day displacement field has been measured for a GPS network formed of 35 sites. The updated solution presented in this paper combines data from 1995, 1997, 1998 and 2000 measurements. The lack of deformation (less than ) through the outer belt does not fit with a regional aseismic slip along the southern part of MHT. A less than 3 mm yr−1 aseismic slip could nonetheless affect restricted areas of the outer belt. In contrast, a strain accumulation of more than is measured south of the Higher Himalayas, in a zone where an intense microseismicity reflects a stress build-up. It is presumably generated by locking of the aseismic creep that occurs along the MHT beneath the Higher Himalayas and Tibet. The displacement field is simulated by a dual-dislocation model that takes into account the pattern of microseismicity, and particularly a segmentation between central and western Nepal. The best fit between the measured and simulated displacement fields is obtained with 19 mm yr−1 thrust and 0–1 mm yr−1 dextral strike-slip components along a 117°NE dislocation locked to a depth of 20–21 km beneath western Nepal, and 19–20 mm yr−1 thrust and 0–2 mm yr−1 dextral strike-slip components along a 108°NE dislocation locked to a depth of 17–21 km beneath central Nepal. The width of the locked zone between the main frontal thrust and the creeping zone is of the same order, but rather greater, in western Nepal than in central Nepal. Therefore it is expected that earthquakes could occur in western Nepal. [ABSTRACT FROM AUTHOR]