Local amplification of Rayleigh waves in the continental United States observed on the USArray

We develop a method based on ratios of amplitudes measured at adjacent stations to determine local amplification of surface waves across an array of seismic stations. We isolate the effects of local structure from those of the earthquake and propagation by systematic averaging of ratios corresponding to many sources. We apply the method to data recorded on the USArray for the years 2006–2011 and determine amplification factors at each station of the array for Rayleigh waves at periods between 35 s and 125 s. Local amplification factors are spatially coherent and display variations of ±10% at a period of 125 s and greater variations at shorter periods. Maps of local amplification exhibit spatial correlation with topography and geologic structures in the western and central United States. At long periods, the observed amplification factors correlate well with predictions from a regional crust and mantle model of North America. At short periods, correlations are weaker, suggesting that the local amplification factors can be useful for constraining shallow structure better

Ice-front variation and tidewater behavior on Helheim and Kangerdlugssuaq Glaciers, Greenland

We used satellite images to examine the calving behavior of Helheim and Kangerdlugssuaq Glaciers, Greenland, from 2001 to 2006, a period in which they retreated and sped up. These data show that many large iceberg-calving episodes coincided with teleseismically detected glacial earthquakes, suggesting that calving-related processes are the source of the seismicity. For each of several events for which we have observations, the ice front calved back to a large, pre-existing rift. These rifts form where the ice has thinned to near flotation as the ice front retreats down the back side of a bathymetric high, which agrees well with earlier theoretical predictions. In addition to the recent retreat in a period of higher temperatures, analysis of several images shows that Helheim retreated in the 20th Century during a warmer period and then re-advanced during a subsequent cooler period. This apparent sensitivity to warming suggests that higher temperatures may promote an initial retreat off a bathymetric high that is then sustained by tidewater dynamics as the ice front retreats into deeper water. The cycle of frontal advance and retreat in less than a century indicates that tidewater glaciers in Greenland can advance rapidly. Greenland's larger reservoir of inland ice and conditions that favor the formation of ice shelves likely contribute to the rapid rates of advance

The 28 November 2020 landslide, tsunami, and outburst flood – a hazard cascade associated with rapid deglaciation at Elliot Creek, British Columbia, Canada

We describe and model the evolution of a recent landslide, tsunami, outburst flood, and sediment plume in the southern Coast Mountains, British Columbia, Canada. On November 28, 2020, about 18 million m3 of rock descended 1,000 m from a steep valley wall and traveled across the toe of a glacier before entering a 0.6 km2 glacier lake and producing >100-m high run-up. Water overtopped the lake outlet and scoured a 10-km long channel before depositing debris on a 2-km2 fan below the lake outlet. Floodwater, organic debris, and fine sediment entered a fjord where it produced a 60+km long sediment plume and altered turbidity, water temperature, and water chemistry for weeks. The outburst flood destroyed forest and salmon spawning habitat. Physically based models of the landslide, tsunami, and flood provide real-time simulations of the event and can improve understanding of similar hazard cascades and the risk they pose

The Shear-Wave Velocity Structure in the Upper Mantle beneath Eurasia

We develop an approach that allows us to invert for the mantle velocity structure within a finely parametrized region as a perturbation with respect to a low-resolution, global tomographic model. We implement this technique to investigate the upper-mantle structure beneath Eurasia and present a new model of shear wave velocity, parametrized laterally using spherical splines with similar to 2.9 degrees spacing in Eurasia and similar to 11.5 degrees spacing elsewhere. The model is obtained from a combined data set of surface wave phase velocities, long-period waveforms and body-wave traveltimes. We identify many features as narrow as few hundred kilometres in diameter, such as subducting slabs in eastern Eurasia and slow-velocity anomalies beneath tectonically active regions. In contrast to regional studies in which these features have been identified, our model encompasses the structure of the entire Eurasian continent. Furthermore, including mantle- and body-wave waveforms helped us constrain structures at depths larger than 250 km, which are poorly resolved in earlier models. We find that up to +9 per cent faster-than-average anomalies within the uppermost similar to 200 km of the mantle beneath cratons and some orogenic regions are separated by a sharp gradient zone from deeper, +1 to +2 per cent anomalies. We speculate that this gradient zone may represent a boundary separating the lithosphere from the continental root, which might be compositionally distinct from the overlying lithosphere and remain stable either due to its compositional buoyancy or due to higher viscosity compared with the suboceanic mantle. Our regional model of anisotropy is not significantly different from the global one.Earth and Planetary Science

Sex effects on short-term complications after hip fracture : a prospective cohort study

Objectives: To evaluate potential sex differences and other factors associated with complications within 4 months after a hip fracture. Methods: A total of 1,915 patients. 65 years (480 men) with hip fracture were consecutively included in a prospective multicenter cohort study. A review of medical records and patient interviews according to a study protocol based on the Standardized Audit of Hip Fractures in Europe (SAHFE, RIKSHOFT) was performed. Sex differences in comorbidity according to the American Society of Anesthesiologists score and complications 4 months after a hip fracture were registered. Multivariate logistic regression analysis was performed to identify factors related to complications. Results: Male sex was associated with worse general health according to the American Society of Anesthesiologists classification (P=0.005) and with more comorbidities (P<0.001). Male sex emerged as a risk factor for developing pneumonia (P<0.001), and additionally, 18% of the men suffered from cardiac complications compared with 13% of the females (P=0.018). Female sex was predisposed for urinary tract infections, 30% vs 23% in males (P=0.001). Mortality was higher in the male vs female group, both within 30 days (15% vs 10%, P=0.001) and at 4 months (24% vs 14%, P=0.001). Conditions associated with pneumonia were male sex, pulmonary disease, and cognitive impairment. Cardiac complications were associated with delayed surgery and cardiovascular and pulmonary disease. Conclusion: Before surgery, men with hip fracture already have a poorer health status and higher comorbidity rate than women, thus resulting in a twofold increased risk of pneumonia. Cognitive dysfunction and pulmonary disease contributed to pneumonia in men. Delayed surgery seems to increase the risk for cardiac complications. It is important to consider the sex perspective early on together with cardiopulmonary comorbidity and cognitive dysfunction to be able to counteract serious complications that may lead to death

Effects of smoking, gender and occupational exposure on the risk of severe pulmonary fibrosis : a population-based case-control study

Objectives: To estimate the effects of smoking, gender and occupational exposure on the risk of developing severe pulmonary fibrosis (PF), including dose-response and interaction effects. Methods: National case-control study of 171 patients (cases) who had started a long-term oxygen therapy for PF in Sweden between February 1997 and April 2000, and 719 random control participants from the general population. Of these cases, 137 had probable idiopathic PF (IPF). The ORs for smoking, gender and occupational exposure were estimated using Mantel-Haenszel analysis and conditional logistic regression, controlling for age and year of diagnosis. Results: The adverse effect of smoking was amplified by male gender and occupational exposure, OR 4.6 (95% CI 2.1 to 10.3) for PF, and OR 3.0 (1.3 to 6.5) for IPF, compared with in non-exposed women. Higher cumulative smoking exposure was linearly associated with increased risks. Compared with smoking less than 10 pack-years, smoking >= 20 pack-years was associated with increased risk of PF and IPF, OR 2.6 (1.4 to 4.9) and OR 2.5 (1.3 to 5.0), respectively. Conclusions: Smoking has a dose-related association with increased risk of severe PF. Men with a history of smoking and occupational exposure is a particular risk group for developing severe PF

Rapid Changes in Ground Vegetation of Mature Boreal Forests-An Analysis of Swedish National Forest Inventory Data

The boreal forest floor vegetation is critical for ecosystem functioning and an important part of forest biodiversity. Given the ongoing global change, knowledge on broad-scale changes in the composition and abundance of different plant species and species groups is hence important for both forest conservation and management. Here, we analyse permanent plot data from the National Forest Inventory (NFI) on changes in the vegetation over a 10-year period in four regions of Sweden. To limit the direct and relatively well-known effects of forest management and associated succession, we only included mature forest stands not influenced by forestry during the 10 years between inventories, and focused on vegetation change mainly related to other factors. Results show strong decrease among many species and species groups. This includes dominant species such as Vaccinimum myrtillus and Deschampsia flexuosa as well as several forest herbs. The only species increasing are some mosses in the southern regions. Our data do not allow for a causal interpretation of the observed patterns. However, the changes probably result from latent succession in combination with climate change and nitrogen deposition, and with time lags complicating the interpretation of their relative importance. Regardless of the cause, the observed changes are on a magnitude that suggest impacts on ecosystem functioning and hence highlight the need for more experimental work

The Pacific OBS Research into Convecting Asthenosphere (ORCA) Experiment

Abstract: The Pacific ocean-bottom seismometer (OBS) Research into Convecting Asthenosphere (ORCA) experiment deployed two 30-station seismic arrays between 2018 and 2020—a US contribution to the international PacificArray project. The “Young ORCA” array deployed on ∼40 Ma central Pacific seafloor had a ∼68% data recovery rate, whereas the “Old ORCA” array deployed on ∼120 Ma southwest Pacific seafloor had a ∼80% recovery rate. We detail here the seismic data quality, spectral characteristics, and engineering challenges of this experiment. We provide information to assist users of this dataset, including OBS orientations and tables of daily data quality for all channels. Preliminary analysis illustrates the utility of these data for surface- and body-wave seismic imaging