bluuebunny/crossref_metadata_2025_split huggingface dataset:
Close Observation of Hydraulic Fracturing at EGS Collab Experiment 1: Fracture Trajectory, Microseismic Interpretations, and the Role of Natural Fractures
Authors: Fu Pengcheng , Schoenball Martin , Ajo‐Franklin Jonathan B. , Chai Chengping , Maceira Monica , Morris Joseph P. , Wu Hui , Knox Hunter , Schwering Paul C. , White Mark D. , Burghardt Jeffrey A. , Strickland Christopher E. , Johnson Timothy C. , Vermeul Vince R. , Sprinkle Parker , Roberts Benjamin , Ulrich Craig , Guglielmi Yves , Cook Paul J. , Dobson Patrick F. , Wood Todd , Frash Luke P. , Huang Lianjie , Ingraham Mathew D. , Pope Joseph S. , Smith Megan M. , Neupane Ghanashyam , Doe Thomas W. , Roggenthen William M. , Horne Roland , Singh Ankush , Zoback Mark D. , Wang Herb , Condon Kate , Ghassemi Ahmad , Chen Hao , McClure Mark W. , Vandine George , Blankenship Douglas , Kneafsey Timothy J. ,   EGS Collab Team
Published: July 2021

AbstractDespite the wide application of hydraulic fracturing in enhanced geothermal system (EGS) development and unconventional hydrocarbon production, our understanding of the many factors affecting the propagation of hydraulic fractures has relied on circumstantial evidence. This is partly due to the scarcity of direct observations in the subsurface. The EGS Collab project attempts to address these issues in the context of EGS research by performing intermediate‐scale (∼10 m) hydraulic stimulation experiments in a thoroughly characterized and heavily instrumented underground testbed. This paper analyzes the data collected from the first suite of hydraulic fracturing tests in this testbed, consisting of seven stimulation episodes. High‐quality microseismic data delineate five planar features very clearly. Combining fracture‐wellbore intersection observations from distributed temperature sensing (DTS) and visual observations from an open‐hole well, as well as prior in‐situ stress measurements, we conclude with high certainty that the four larger planes were hydraulic fractures. The growth of the hydraulic fractures was temporarily halted by a prominent, open natural fracture in the testbed but they eventually crossed and slightly reoriented under continued stimulation. Mineral‐filled (i.e., healed) natural fractures, though prevalent in the testbed, did not have perceivable effects on hydraulic fracture propagation. The high‐quality, mutually corroborating data sets allowed conclusions to be drawn with high confidence and attests to the advantage of intermediate‐scale experiments in subsurface research.
Earthquake Source Mechanisms and Stress Field Variations Associated With Wastewater‐Induced Seismicity in Southern Kansas, USA
Authors: Amemoutou Amandine , Martínez‐Garzón Patricia , Kwiatek Grzegorz , Rubinstein Justin L. , Bohnhoff Marco 
Published: July 2021

AbstractThe strong increase of seismicity rates in the contiguous USA over the last 10 years is linked to the injection of huge amounts of wastewater from oil and gas production in unconventional hydrocarbon reservoirs. We calculated 549 moment tensors of induced earthquakes (MW ≤ 4.9) in southern Kansas to study their source mechanisms and their relation to injection activity. Seventeen percent of the events analyzed contained significant volumetric (ISO%) components, and these events mostly occurred near the two largest local earthquakes during the 4 months of largest active wastewater disposal. Mapping the local stress field, we determined that most of the region lies within a transtensional stress regime, with a maximum horizontal stress σHmax trending N75°E. In the epicentral area of the MW 4.9 Milan earthquake, the σHmax trend is rotated to about S80°E. Locally, two areas display a change in the stress field orientation with depth, from transtensional above 5.5 km depth to strike slip deeper in the basement. Relating the resolved fault geometries to the obtained local stress field orientation, we find that most of the activated fault planes were optimally oriented to the current stress field and thus small stress perturbations caused by the water injection could lead to failure.
Long‐Term 15N Balance After Single‐Dose Input of 15N‐Labeled NH4+ and NO3− in a Subtropical Forest Under Reducing N Deposition
Authors: Xie Danni , Duan Lei , Si Gaoyue , Liu Wenjing , Zhang Ting , Mulder Jan 
Published: July 2021

AbstractNitrogen (N) deposition in Europe and North America decreased in the 1990s, whereas N deposition in China began to decline in the early 2010s. The response of temperate forests to decreasing N deposition implied a delay recovery, but it remains unknown whether recovery in subtropical forests follows a similar trend. Therefore, the effects of decreased N deposition on N leaching were simulated in an N‐saturated forest in southwest China following ten years of N application 4.00 g N m−2 yr−1. The addition of N (NH4+ or NO3−) was stopped in 2014. In 2017, a single in‐situ 15N addition as NH4+ or NO3− was performed to trace the fate of N under reducing N deposition. Combining the monitoring results of the N fluxes and 15N fates, both the actual N leaching and contribution of a “new” N input to N leaching were significantly reduced in response to decreasing the N input. The termination of N addition resulted in immediate decreases in the N mineralization and immobilization rates, which were even lower than those in the control plots with moderate (naturally occurring) deposition reduction. The ratio of N leaching from mineralization was also reduced, implying the critical role of N mineralization in the recovery from N saturation. Because the forest was still N‐saturated, decreasing N deposition slightly reduced the N leaching to the gross N input ratio (including both N deposition and N mineralization). The significant decrease in the ratio and thus leaching recovery may occur due to a significant N deposition reduction.
Chinese Regulations Are Working—Why Is Surface Ozone Over Industrialized Areas Still High? Applying Lessons From Northeast US Air Quality Evolution
Authors: Chen Xiaokang , Jiang Zhe , Shen Yanan , Li Rui , Fu Yunfei , Liu Jane , Han Han , Liao Hong , Cheng Xugeng , Jones Dylan B. A. , Worden Helen , Abad Gonzalo González 
Published: July 2021

AbstractObservational data indicate increasing trends of surface ozone (O3) in China, despite emission controls that have resulted in reductions of precursor emissions. Here, we explore the cause of this contradiction, through analysis of surface observations (2014–2019) in China and historical observation record in the United States (US, 1990–2019). Our observation‐based analysis indicates that the reductions of nitrogen oxides (NOx) emissions led to increase of surface O3 in North China Plain (NCP) and Yangtze River Delta (YRD) of around 8 ppb. However, NOx controls resulted in shift of O3 chemical regimes over NCP and YRD, with turning points between NOx‐ and volatile organic compound (VOC)‐limited regimes around 2019, while model simulations suggest transitional or NOx‐limited regimes over the rest of China. The impacts of high fine particles (PM2.5) on O3 formation has declined because of the reduction of PM2.5 concentrations. Stricter NOx controls can mitigate O3 pollutions over industrialized areas in China.
Anthropogenic Impacts on Tropospheric Reactive Chlorine Since the Preindustrial
Authors: Zhai Shuting , Wang Xuan , McConnell Joseph R. , Geng Lei , Cole‐Dai Jihong , Sigl Michael , Chellman Nathan , Sherwen Tomás , Pound Ryan , Fujita Koji , Hattori Shohei , Moch Jonathan M. , Zhu Lei , Evans Mat , Legrand Michel , Liu Pengfei , Pasteris Daniel , Chan Yuk‐Chun , Murray Lee T. , Alexander Becky 
Published: July 2021

AbstractTropospheric reactive gaseous chlorine (Cly) impacts the atmosphere's oxidation capacity with implications for chemically reduced gases such as methane. Here we use Greenland ice‐core records of chlorine, sodium, and acidity, and global model simulations to show how tropospheric Cly has been impacted by anthropogenic emissions since the 1940s. We show that anthropogenic contribution of nonsea‐salt chlorine significantly influenced total chlorine and its trends after the 1940s. The modeled regional 170% Cly increase from preindustrial to the 1970s was driven by acid displacement from sea‐salt‐aerosol, direct emission of hydrochloric acid (HCl) from combustion, and chemical reactions driven by anthropogenic nitrogen oxide (NOx) emissions. Since the 1970s, the modeled 6% Cly decrease was caused mainly by reduced anthropogenic HCl emissions from air pollution mitigation policies. Our findings suggest that anthropogenic emissions of acidic gases and their emission control strategies have substantial impacts on Cly with implications for tropospheric oxidants, methane, and mercury.
On Contributions of Multiscale Dynamic Processes to the Steric Height in the Northeastern South China Sea as Revealed by Moored Observations
Authors: Miao Mingfang , Zhang Zhiwei , Qiu Bo , Liu Zhiyu , Zhang Xincheng , Zhou Chun , Guan Shoude , Huang Xiaodong , Zhao Wei , Tian Jiwei 
Published: July 2021

AbstractBased on 2‐year moored measurements in the northeastern South China Sea, contributions of multiscale dynamic processes to steric height (SH) at 60 m are quantified. It shows that on average, root‐mean‐squared (RMS) SHs of mesoscales, submesoscales, diurnal and semidiurnal internal tides (ITs), and supertidal internal gravity waves (IGWs) are 7.56, 1.01, 1.19, 2.84, and 1.46 cm, respectively, with their respective relative contributions of 53.8%, 7.2%, 8.5%, 20.2%, and 10.4%. The SHs of ITs and supertidal IGWs are dominated by stationary and nonstationary components, respectively. Seasonally, mesoscales and submesoscales show larger RMS SHs in winter than summer but the opposite occurs for ITs and supertidal IGWs. Although the RMS SH of submesoscales exceeds nonstationary ITs in winter, it is much smaller than the sum of nonstationary ITs and supertidal IGWs. Therefore, to detect submesoscales using SWOT data, approaches to remove the SHs of nonstationary ITs and supertidal IGWs are called for.
X‐Discontinuity Beneath the Indian Shield—Evidence for Remnant Tethyan Oceanic Lithosphere in the Mantle
Authors: Srinu Uppala , Kumar Prakash , Haldar C. , Kumar M. Ravi , Srinagesh D. , Illa Bhaskar 
Published: July 2021

AbstractBeneath the continents and island arcs, a seismic discontinuity is often detected around 300 km depth, referred to as the X‐discontinuity. Various mineralogical and petrological mechanisms have been put forth to explain its occurrence. Because of the large depth variability, it is challenging to explain its origin invoking a single mineralogical phase transition. In order to investigate this discontinuity beneath India, we analyzed 10,216 P wave receiver functions at seismological stations deployed on the Indian shield and the Himalayas. We detect the X‐discontinuity as a sporadic and thin feature, in the depth range of 246–335 km, with a sharp shear velocity jump of 2.5%–3.6%. It neither bears a clear tectonic affinity nor has any correlation with the transition zone discontinuities. Interpreting its origin due to a single mineralogical change warrants a large spatial variation in the mantle temperature. Therefore, we suggest that the observed widespread X‐discontinuity beneath the Indian shield owes its origin to two mechanisms, that is, Orthoenstatite to high pressure Clinoenstatite transformation which shifts to lower pressures (∼2 GPa) due to the presence of water (0.13 wt% H2O) in MgSiO3 and coesite‐stishovite transition occurring at 8–11 GPa due to excess silica in an eclogitic component derived from the Tethys oceanic lithosphere subducted during lower Eocene. The identification of such a discontinuity could allow tracking of subducted material within the upper mantle providing a measure of mantle geochemical heterogeneity.
Assessing Margin‐Wide Rupture Behaviors Along the Cascadia Megathrust With 3‐D Dynamic Rupture Simulations
Authors: Ramos Marlon D. , Huang Yihe , Ulrich Thomas , Li Duo , Gabriel Alice‐Agnes , Thomas Amanda M. 
Published: July 2021

AbstractFrom California to British Columbia, the Pacific Northwest coast bears an omnipresent earthquake and tsunami hazard from the Cascadia subduction zone. Multiple lines of evidence suggests that magnitude eight and greater megathrust earthquakes have occurred ‐ the most recent being 321 years ago (i.e., 1700 A.D.). Outstanding questions for the next great megathrust event include where it will initiate, what conditions are favorable for rupture to span the convergent margin, and how much slip may be expected. We develop the first 3‐D fully dynamic rupture simulations for the Cascadia subduction zone that are driven by fault stress, strength and friction to address these questions. The initial dynamic stress drop distribution in our simulations is constrained by geodetic coupling models, with segment locations taken from geologic analyses. We document the sensitivity of nucleation location and stress drop to the final seismic moment and coseismic subsidence amplitudes. We find that the final earthquake size strongly depends on the amount of slip deficit in the central Cascadia region, which is inferred to be creeping interseismically, for a given initiation location in southern or northern Cascadia. Several simulations are also presented here that can closely approximate recorded coastal subsidence from the 1700 A.D. event without invoking localized high‐stress asperities along the down‐dip locked region of the megathrust. These results can be used to inform earthquake and tsunami hazards for not only Cascadia, but other subduction zones that have limited seismic observations but a wealth of geodetic inference.
Uplift and Seismicity Driven by Magmatic Inflation at Sierra Negra Volcano, Galápagos Islands
Authors: Bell Andrew Forbes , Hernandez Stephen , La Femina Peter Christopher , Ruiz Mario Calixto 
Published: July 2021

AbstractAlthough episodes of surface uplift and elevated seismicity precede many volcanic eruptions, their temporal evolution is often complex, and apparently in contradiction to simple trends predicted by mechanical deformation models. Here, we use continuous global positioning system and seismic data recorded at Sierra Negra volcano, Galápagos Islands, to show how the edifice responded to stress changes driven by magma accumulation in a shallow sill. The rate of uplift varied during the 13 years and 6.5 m of inflation before the 2018 eruption. The number of earthquakes per unit of uplift increased exponentially with total uplift as the differential stress increased. Accordingly, the temporal seismicity rate varied in time as a function of both the total uplift and the uplift rate. The Gutenberg‐Richter b‐value decreased as a function of total uplift. In the final six months before the eruption, a sequence of large (M > 4) earthquakes regulated the state of stress on the fault, each being followed by 2–3 days of postseismic quiescence, and retarding the increase in seismicity rate. These earthquakes did not affect the overall uplift rate. Subsidence of 8.5 m accompanied the 2‐month eruption. On resumption of uplift, the number of earthquakes per unit of uplift was very low, and the b‐value high, reflecting the relaxed stress state of the fault system. These observations show that crustal deformation becomes increasingly brittle at higher stress states, and supports theoretical models based on elastic‐brittle mechanics. They suggest that joint interpretation of deformation and seismicity is key for forecasting future eruptions in similar volcanic settings.
GPS Imaging of Global Vertical Land Motion for Studies of Sea Level Rise
Authors: Hammond William C. , Blewitt Geoffrey , Kreemer Corné , Nerem R. Steven 
Published: July 2021

AbstractWe estimate the rates and patterns of vertical land motion (VLM) on all locations on Earth's land surface using GPS Imaging. The solution is based on a large database of uniformly processed GPS data from solutions that are aligned to the International Terrestrial Reference Frame. We provide global maps and estimates of VLM at all tide gauges of the Permanent Service for Mean Sea Level to better constrain the difference between geocentric and relative sea level rise. To enable critical assessment of the VLM estimate, the temporal and spatial contributions to rate uncertainty and variability are generated and included for every gauge. Seasonality and trends of uplift are assessed and found to be strongly correlated with observations from gravity data suggesting that loading from the terrestrial hydrosphere is a dominant driver of non‐glacial isostatic adjustment (non‐GIA) VLM. Although stations are dominantly concentrated at subsiding parts of continents, GPS Imaging geographically balances VLM signals, correcting for bias associated with network distribution. This allows us to make a global assessment of the budget of uplift and subsidence attributable to GIA and non‐GIA sources. We show that the surface motion of the continents is on average upward, implying that the unobserved areas (composed of the ocean basins and ice‐covered areas) move on average downward with respect to Earth center. However, after correcting for the GIA the reverse is true, and observed areas subside on average implying that the unobserved areas undergo net non‐GIA‐related uplift.
Position, Magnitude, and Size of Warm‐Pool El Niño: Variability, Seasonal Predictability, and Climate Impacts
Authors: Cheung Paxson K. Y. , Leung Marco Y. T. , Zhou Wen 
Published: July 2021

AbstractThis study surveys the variability and predictability of the position, magnitude, and size of warm‐pool El Niño (WP El Niño), as well as its impacts on the climate. A new detection method for WP El Niño that is flexible regarding its position, magnitude, and size is developed. Thirteen WP El Niño events are found from 1950 to 2018 using this detector. These events have a mean (standard deviation) center position of 31.7 (12.4)° longitude, a mean peak sea surface temperature anomaly (SSTA) of 1.87 (0.62) K, and a zonal size parameter of 19.99 (5.13)° longitude. Also, stronger WP El Niño events tend to be larger and take place farther east. Based on these distributions, a set of model experiments is conducted to evaluate climate sensitivity to these three features. The wintertime North American temperature dipole due to WP El Niño is chosen as an example. Its bearing is linearly controlled by the position of the SSTA field of WP El Niño, and this control is stronger when the SSTA field is stronger or smaller. Predictability of position, magnitude, and size of WP El Niño on seasonal scale by the North American Multi‐Model Ensemble is examined. With a 2‐month lead‐time, the position and magnitude of WP El Niño are predicted accurately, but size tends to be large‐biased. Increasing the lead‐time generally leads to more eastward bias, cold bias, and large bias. Precision of the predictions is also reduced with lead‐time.
3D Simulations of the Early Martian Hydrological Cycle Mediated by a H2‐CO2Greenhouse
Authors: Guzewich Scott D. , Way Michael J. , Aleinov Igor , Wolf Eric T. , Del Genio Anthony , Wordsworth Robin , Tsigaridis Kostas 
Published: July 2021

AbstractFor decades, the scientific community has been trying to reconcile abundant evidence for fluvial activity on Noachian and early Hesperian Mars with the faint young Sun and reasonable constraints on ancient atmospheric pressure and composition. Recently, the investigation of H2‐CO2collision‐induced absorption has opened up a new avenue to warm Noachian Mars. We use the ROCKE‐3D global climate model to simulate plausible states of the ancient Martian climate with this absorptive warming and reasonable constraints on surface paleopressure. We find that 1.5–2 bar CO2‐dominated atmospheres with ≥3% H2can produce global mean surface temperatures above freezing, while also providing sufficient warming to avoid surface atmospheric CO2condensation at 0°–45° obliquity. Simulations conducted with both modern topography and a paleotopography, before Tharsis formed, highlight the importance of Tharsis as a cold trap for water on the planet. Additionally, we find that low obliquity (modern and 0°) is more conducive to rainfall over valley network locations than high (45°) obliquity.
Nontuberculous mycobacterial infection and environmental molybdenum in persons with cystic fibrosis: a case–control study in Colorado
Authors: Lipner Ettie M. , Crooks James L. , French Joshua , Strong Michael , Nick Jerry A. , Prevots D. Rebecca 
Published: July 2021

Abstract
Rationale
Nontuberculous mycobacteria (NTM) are ubiquitous environmental bacteria that may cause chronic lung disease and are one of the most difficult-to-treat infections among persons with cystic fibrosis (pwCF). Environmental factors likely contribute to increased NTM densities, with higher potential for exposure and infection.

Objective
To identify water-quality constituents that influence odds of NTM infection among pwCF in Colorado.

Methods
We conducted a population-based nested case–control study using patient data from the Colorado CF Center NTM database. We associated data from pwCF and water-quality data extracted from the Water Quality Portal to estimate odds of NTM infection. Using Bayesian generalized linear models with binomial-distributed discrete responses, we modeled three separate outcomes; any NTM infection, infections due to Mycobacterium avium complex species, and infections due to M. abscessus group species.

Results
We observed a consistent association with molybdenum in the source water and M. abscessus group species infection among pwCF in all models. For every 1-unit increase in the log concentration of molybdenum in surface water, the odds of infection for those with M. abscessus group species compared to those who were NTM culture-negative increased by 79%. The odds of M. abscessus group infection varied by county; the counties with the highest probability of infection are located along the major rivers.

Conclusions
We have identified molybdenum in the source water as the most predictive factor of M. abscessus group infection among pwCF in Colorado. This finding will help inform patients at risk for NTM of their relative risks in residing within specific regions.
Genetic and phylogenetic analysis of dissimilatory iodate-reducing bacteria identifies potential niches across the world’s oceans
Authors: Reyes-Umana Victor , Henning Zachary , Lee Kristina , Barnum Tyler P , Coates John D 
Published: July 2021

Abstract
Iodine is oxidized and reduced as part of a biogeochemical cycle that is especially pronounced in the oceans, where the element naturally concentrates. The use of oxidized iodine in the form of iodate (IO3−) as an electron acceptor by microorganisms is poorly understood. Here, we outline genetic, physiological, and ecological models for dissimilatory IO3− reduction to iodide (I−) by a novel estuarine bacterium, Denitromonas sp. IR-12. Our results show that dissimilatory iodate reduction (DIR) by strain IR-12 is molybdenum-dependent and requires an IO3− reductase (idrA) and likely other genes in a mobile cluster with a conserved association across known and predicted DIR microorganisms (DIRM). Based on genetic and physiological data, we propose a model where three molecules of IO3− are likely reduced to three molecules of hypoiodous acid (HIO), which rapidly disproportionate into one molecule of IO3− and two molecules of iodide (I−), in a respiratory pathway that provides an energy yield equivalent to that of nitrate or perchlorate respiration. Consistent with the ecological niche expected of such a metabolism, idrA is enriched in the metagenome sequence databases of marine sites with a specific biogeochemical signature (high concentrations of nitrate and phosphate) and diminished oxygen. Taken together, these data suggest that DIRM help explain the disequilibrium of the IO3−:I− concentration ratio above oxygen-minimum zones and support a widespread iodine redox cycle mediated by microbiology.