bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rapid rupture directivity determination of moderate dip‐slip earthquakes with teleseismic body waves assuming reduced finite source approximation
Authors: He X. , Ni S. 
Published: June 2017

AbstractFor an earthquake with along‐dip rupture, there is opposite directivity effects on downgoing direct P wave and upgoing depth phases (pP and sP), and this can be exploited for resolving fault plane and rupture direction. We propose a method to calculate the reduced finite source synthetics for teleseismic P wave and determine the rupture directivity via waveform fitting. We verified the effectiveness of this method with forward tests and investigated its robustness against station selection, uncertainties in point source parameters, and uncertainties in source finiteness parameters. We applied this method to the 2011 Mw5.8 Virginia earthquake, the 2008 Mw6.0 Nevada earthquake, and six other dip‐slip earthquakes. For most cases, we obtained rupture directivity results consistent with previous studies, but the method could fail for along‐strike ruptures and very shallow earthquakes. Our method may help mitigate earthquake hazard by improving shake map with rapid rupture directivity analysis.
Airborne measurements of western U.S. wildfire emissions: Comparison with prescribed burning and air quality implications
Authors: Liu Xiaoxi , Huey L. Gregory , Yokelson Robert J. , Selimovic Vanessa , Simpson Isobel J. , Müller Markus , Jimenez Jose L. , Campuzano‐Jost Pedro , Beyersdorf Andreas J. , Blake Donald R. , Butterfield Zachary , Choi Yonghoon , Crounse John D. , Day Douglas A. , Diskin Glenn S. , Dubey Manvendra K. , Fortner Edward , Hanisco Thomas F. , Hu Weiwei , King Laura E. , Kleinman Lawrence , Meinardi Simone , Mikoviny Tomas , Onasch Timothy B. , Palm Brett B. , Peischl Jeff , Pollack Ilana B. , Ryerson Thomas B. , Sachse Glen W. , Sedlacek Arthur J. , Shilling John E. , Springston Stephen , St. Clair Jason M. , Tanner David J. , Teng Alexander P. , Wennberg Paul O. , Wisthaler Armin , Wolfe Glenn M. 
Published: June 2017

AbstractWildfires emit significant amounts of pollutants that degrade air quality. Plumes from three wildfires in the western U.S. were measured from aircraft during the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) and the Biomass Burning Observation Project (BBOP), both in summer 2013. This study reports an extensive set of emission factors (EFs) for over 80 gases and 5 components of submicron particulate matter (PM1) from these temperate wildfires. These include rarely, or never before, measured oxygenated volatile organic compounds and multifunctional organic nitrates. The observed EFs are compared with previous measurements of temperate wildfires, boreal forest fires, and temperate prescribed fires. The wildfires emitted high amounts of PM1(with organic aerosol (OA) dominating the mass) with an average EF that is more than 2 times the EFs for prescribed fires. The measured EFs were used to estimate the annual wildfire emissions of carbon monoxide, nitrogen oxides, total nonmethane organic compounds, and PM1from 11 western U.S. states. The estimated gas emissions are generally comparable with the 2011 National Emissions Inventory (NEI). However, our PM1emission estimate (1530 ± 570 Gg yr−1) is over 3 times that of the NEI PM2.5estimate and is also higher than the PM2.5emitted from all other sources in these states in the NEI. This study indicates that the source of OA from biomass burning in the western states is significantly underestimated. In addition, our results indicate that prescribed burning may be an effective method to reduce fine particle emissions.
Water and growth: An econometric analysis of climate and policy impacts
Authors: Khan Hassaan Furqan , Morzuch Bernard J. , Brown Casey M. 
Published: June 2017

AbstractWater‐related hazards such as floods, droughts, and disease cause damage to an economy through the destruction of physical capital including property and infrastructure, the loss of human capital, and the interruption of economic activities, like trade and education. The question for policy makers is whether the impacts of water‐related risk accrue to manifest as a drag on economic growth at a scale suggesting policy intervention. In this study, the average drag on economic growth from water‐related hazards faced by society at a global level is estimated. We use panel regressions with various specifications to investigate the relationship between economic growth and hydroclimatic variables at the country‐river basin level. In doing so, we make use of surface water runoff variables never used before. The analysis of the climate variables shows that water availability and water hazards have significant effects on economic growth, providing further evidence beyond earlier studies finding that precipitation extremes were at least as important or likely more important than temperature effects. We then incorporate a broad set of variables representing the areas of infrastructure, institutions, and information to identify the characteristics of a region that determine its vulnerability to water‐related risks. The results identify water scarcity, governance, and agricultural intensity as the most relevant measures affecting vulnerabilities to climate variability effects.
Earthworms and tree roots: A model study of the effect of preferential flow paths on runoff generation and groundwater recharge in steep, saprolitic, tropical lowland catchments
Authors: Cheng Yanyan , Ogden Fred L. , Zhu Jianting 
Published: June 2017

AbstractPreferential flow paths (PFPs) affect the hydrological response of humid tropical catchments but have not received sufficient attention. We consider PFPs created by tree roots and earthworms in a near‐surface soil layer in steep, humid, tropical lowland catchments and hypothesize that observed hydrological behaviors can be better captured by reasonably considering PFPs in this layer. We test this hypothesis by evaluating the performance of four different physically based distributed model structures without and with PFPs in different configurations. Model structures are tested both quantitatively and qualitatively using hydrological, geophysical, and geochemical data both from the Smithsonian Tropical Research Institute Agua Salud Project experimental catchment(s) in Central Panama and other sources in the literature. The performance of different model structures is evaluated using runoff Volume Error and three Nash‐Sutcliffe efficiency measures against observed total runoff, stormflows, and base flows along with visual comparison of simulated and observed hydrographs. Two of the four proposed model structures which include both lateral and vertical PFPs are plausible, but the one with explicit simulation of PFPs performs the best. A small number of vertical PFPs that fully extend below the root zone allow the model to reasonably simulate deep groundwater recharge, which plays a crucial role in base flow generation. Results also show that the shallow lateral PFPs are the main contributor to the observed high flow characteristics. Their number and size distribution are found to be more important than the depth distribution. Our model results are corroborated by geochemical and geophysical observations.
How Jordan and Saudi Arabia are avoiding a tragedy of the commons over shared groundwater
Authors: Müller Marc F. , Müller‐Itten Michèle C. , Gorelick Steven M. 
Published: June 2017

AbstractTransboundary aquifers are ubiquitous and strategically important to global food and water security. Yet these shared resources are being depleted at an alarming rate. Focusing on the Disi aquifer, a key nonrenewable source of groundwater shared by Jordan and Saudi Arabia, this study develops a two‐stage game that evaluates optimal transboundary strategies of common‐pool resource exploitation under various assumptions. The analysis relies on estimates of agricultural water use from satellite imagery, which were obtained using three independent remote sensing approaches. Drawdown response to pumping is simulated using a 2‐D regional aquifer model. Jordan and Saudi Arabia developed a buffer‐zone strategy with a prescribed minimum distance between each country's pumping centers. We show that by limiting the marginal impact of pumping decisions on the other country's pumping costs, this strategy will likely avoid an impeding tragedy of the commons for at least 60 years. Our analysis underscores the role played by distance between wells and disparities in groundwater exploitation costs on common‐pool overdraft. In effect, if pumping centers are distant enough, a shared aquifer no longer behaves as a common‐pool resource and a tragedy of the commons can be avoided. The 2015 Disi aquifer pumping agreement between Jordan and Saudi Arabia, which in practice relies on a joint technical commission to enforce exclusion zones, is the first agreement of this type between sovereign countries and has a promising potential to avoid conflicts or resolve potential transboundary groundwater disputes over comparable aquifer systems elsewhere.
How uncertainty analysis of streamflow data can reduce costs and promote robust decisions in water management applications
Authors: McMillan Hilary , Seibert Jan , Petersen‐Overleir Asgeir , Lang Michel , White Paul , Snelder Ton , Rutherford Kit , Krueger Tobias , Mason Robert , Kiang Julie 
Published: June 2017

AbstractStreamflow data are used for important environmental and economic decisions, such as specifying and regulating minimum flows, managing water supplies, and planning for flood hazards. Despite significant uncertainty in most flow data, the flow series for these applications are often communicated and used without uncertainty information. In this commentary, we argue that proper analysis of uncertainty in river flow data can reduce costs and promote robust conclusions in water management applications. We substantiate our argument by providing case studies from Norway and New Zealand where streamflow uncertainty analysis has uncovered economic costs in the hydropower industry, improved public acceptance of a controversial water management policy, and tested the accuracy of water quality trends. We discuss the need for practical uncertainty assessment tools that generate multiple flow series realizations rather than simple error bounds. Although examples of such tools are in development, considerable barriers for uncertainty analysis and communication still exist for practitioners, and future research must aim to provide easier access and usability of uncertainty estimates. We conclude that flow uncertainty analysis is critical for good water management decisions.
Joint inversion of satellite‐detected tidal and magnetospheric signals constrains electrical conductivity and water content of the upper mantle and transition zone
Authors: Grayver A. V. , Munch F. D. , Kuvshinov A. V. , Khan A. , Sabaka T. J. , Tøffner‐Clausen L. 
Published: June 2017

AbstractWe present a new global electrical conductivity model of Earth's mantle. The model was derived by using a novel methodology, which is based on inverting satellite magnetic field measurements from different sources simultaneously. Specifically, we estimated responses of magnetospheric origin and ocean tidal magnetic signals from the most recent Swarm and CHAMP data. The challenging task of properly accounting for the ocean effect in the data was addressed through full three‐dimensional solution of Maxwell's equations. We show that simultaneous inversion of magnetospheric and tidal magnetic signals results in a model with much improved resolution. Comparison with laboratory‐based conductivity profiles shows that obtained models are compatible with a pyrolytic composition and a water content of 0.01 wt % and 0.1 wt % in the upper mantle and transition zone, respectively.
Enhanced permeability due to apparent oil/brine slippage in limestone and its dependence on wettability
Authors: Christensen M. , Tanino Y. 
Published: June 2017

AbstractEnd point relative permeabilities were measured in three limestones with permeabilities ranging from 0.6 to 220 mD under five wettability states established by adding different organic acids, of similar molecular structure but different alkyl chain length, to the oil phase. The altered wettability corresponding to each oil/brine pair is characterized by their dynamic contact angle on a polished calcite substrate, θw, which varied between 50° and 150°. Saturation‐normalized relative permeability to oil exceeds one at θw<140° in all rock considered. The equivalent slip length, defined by modeling the porous medium as a capillary tube with the defending phase distributed as an annular film on the tube wall, was below 200 nm in all experiments. The results indicate that commonly used models of relative permeability, which assume that the maximum permeability is the single‐phase permeability, underestimate oil displacement for a much wider range of contact angles than previously documented.
Subduction of thick oceanic plateau and high‐angle normal‐fault earthquakes intersecting the slab
Authors: Arai Ryuta , Kodaira Shuichi , Yamada Tomoaki , Takahashi Tsutomu , Miura Seiichi , Kaneda Yoshiyuki , Nishizawa Azusa , Oikawa Mitsuhiro 
Published: June 2017

AbstractThe role of seamounts on interplate earthquakes has been debated. However, its impact on intraslab deformation is poorly understood. Here we present unexpected evidence for large normal‐fault earthquakes intersecting the slab just ahead of a subducting seamount. In 1995, a series of earthquakes with maximum magnitude of 7.1 occurred in northern Ryukyu where oceanic plateaus are subducting. The aftershock distribution shows that conjugate faults with an unusually high dip angle of 70–80° ruptured the entire subducting crust. Seismic reflection images reveal that the plate interface is displaced over 1 km along one of the fault planes of the 1995 events. These results suggest that a lateral variation in slab buoyancy can produce sufficient differential stress leading to near‐vertical normal‐fault earthquakes within the slab. On the contrary, the upper surface of the seamount (plate interface) may correspond to a weakly coupled region, reflecting the dual effects of seamounts/plateaus on subduction earthquakes.
Reduced convergence within the Tibetan Plateau by 26 Ma?
Authors: Meng Jun , Coe Robert S. , Wang Chengshan , Gilder Stuart A. , Zhao Xixi , Liu Hao , Li Yalin , Ma Pengfei , Shi Kai , Li Shuai 
Published: June 2017

AbstractUnderstanding the dynamics of double‐thickening and uplifting of the Tibetan crust requires constraints on the magnitude and timing of crustal shortening. New elongation/inclination (E/I)‐corrected paleomagnetic data from ~26–22 Ma sediments indicate that the latitude of southern Tibet in the early Miocene was 31.1/−6.8/+5.2°N, not significantly different from today. This implies that the southern margin of Asia, which was at 21–24°N latitude from the Late Cretaceous to the early Eocene, advanced 8–10° northward between the early Eocene and the latest Oligocene. Our results therefore suggest that at least 900–1100 km of continental shortening and significant regional uplift of the plateau occurred between the early Eocene and late Oligocene. Our results suggest that N‐S intra‐Asian convergence was considerably reduced around 26 Ma, corresponding to a transition from compression to extension within the Tibetan Plateau.
Low‐frequency oscillatory flow signatures and high‐speed flows in the Earth's magnetotail
Authors: De Spiegeleer A. , Hamrin M. , Pitkänen T. , Volwerk M. , Mann I. , Nilsson H. , Norqvist P. , Andersson L. , Vaverka J. 
Published: June 2017

AbstractUsing plasma sheet data from Cluster 1 spacecraft from 2001 till 2011, we statistically investigate oscillatory signatures in the plasma bulk flow. These periodic oscillations are compared to high‐speed and quiet flows. Periodic oscillations are observed approximately 8% of the time, while high‐speed flows and quiet flows are observed around 0.5% and 12% of the time, respectively. We remark that periodic oscillations can roughly occur everywhere for xgsm<−10RE and |ygsm|<10RE, while quiet flows mainly occur toward the flanks of this region and toward x =− 10RE. The relation between the geomagnetic and solar activity and the occurrence of periodic oscillations is investigated and reveal that periodic oscillations occur for most Kp values and solar activity, while quiet flows are more common during low magnetospheric and solar activity. We find that the median oscillation frequency of periodic oscillations is 1.7 mHz and the median duration of the oscillation events is 41 min. We also observe that their associated Poynting vectors show a tendency to be earthward (Sx≥0). Finally, the distribution of high‐speed flows and periodic oscillations as a function of the velocity is investigated and reveals that thresholds lower than 200 km/s should not be used to identify high‐speed flows as it could result in misinterpreting a periodic oscillations for a high‐speed flow.
Testing the expanding‐contracting polar cap paradigm
Authors: Sotirelis Thomas , Keller Mary Ruth , Liou Kan , Smith Daniel , Barnes Robin J. , Talaat Elsayed , Baker Joseph B. H. 
Published: June 2017

AbstractThe expanding‐contracting polar cap (ECPC) paradigm is tested. Under the ECPC paradigm ionospheric convection in the polar cap is driven by the combined effects of magnetic field dayside merging and nightside reconnection, as opposed to being mapped down from higher altitudes. The ECPC paradigm is tested by separately examining the cross polar cap potential when the polar cap is expanding versus contracting. The open magnetic flux is estimated from Super Dual Auroral Radar Network (SuperDARN) observations of the convection reversal boundary (CRB) made simultaneously at different local times. Sotirelis et al. (2005) established the CRB as a proxy for the open‐closed boundary. The correlation of the ionospheric convection potential, determined from SuperDARN, with solar wind/interplanetary magnetic field (IMF) driving is indeed found to depend on whether the polar cap is expanding or contracting. Specifically, when the polar cap is expanding, ionospheric convection potential correlates best (0.86) with the most recent 10 min of solar wind/IMF driving (versus 0.57 for contracting). When contracting, convection potential correlates best (0.87) with 90 min averages of solar wind/IMF driving (versus 0.51 for expanding). This result is consistent with the expectations of the ECPC paradigm.
Global modeling of thermospheric airglow in the far ultraviolet
Authors: Solomon Stanley C. 
Published: June 2017

AbstractThe Global Airglow (GLOW) model has been updated and extended to calculate thermospheric emissions in the far ultraviolet, including sources from daytime photoelectron‐driven processes, nighttime recombination radiation, and auroral excitation. It can be run using inputs from empirical models of the neutral atmosphere and ionosphere or from numerical general circulation models of the coupled ionosphere‐thermosphere system. It uses a solar flux module, photoelectron generation routine, and the Nagy‐Banks two‐stream electron transport algorithm to simultaneously handle energetic electron distributions from photon and auroral electron sources. It contains an ion‐neutral chemistry module that calculates excited and ionized species densities and the resulting airglow volume emission rates. This paper describes the inputs, algorithms, and code structure of the model and demonstrates example outputs for daytime and auroral cases. Simulations of far ultraviolet emissions by the atomic oxygen doublet at 135.6 nm and the molecular nitrogen Lyman‐Birge‐Hopfield bands, as viewed from geostationary orbit, are shown, and model calculations are compared to limb‐scan observations by the Global Ultraviolet Imager on the TIMED satellite. The GLOW model code is provided to the community through an open‐source academic research license.
Aftershocks, groundwater changes and postseismic ground displacements related to pore pressure gradients: Insights from the 2012 Emilia‐Romagna earthquake
Authors: Albano Matteo , Barba Salvatore , Solaro Giuseppe , Pepe Antonio , Bignami Christian , Moro Marco , Saroli Michele , Stramondo Salvatore 
Published: June 2017

AbstractDuring the 2012 Emilia‐Romagna (Italy) seismic sequence, several time‐dependent phenomena occurred, such as changes in the groundwater regime and chemistry, liquefaction, and postseismic ground displacements. Because time‐dependent phenomena require time‐dependent physical mechanisms, we interpreted such events as the result of the poroelastic response of the crust after the main shock. In our study, we performed a two‐dimensional poroelastic numerical analysis calibrated with Cosmo‐SkyMed interferometric data and measured piezometric levels in water wells. The simulation results are consistent with the observed postseismic ground displacement and water level changes. The simulations show that crustal volumetric changes induced by poroelastic relaxation and the afterslip along the main shock fault are both required to reproduce the amplitude (approximately 4 cm) and temporal evolution of the observed postseismic uplift. Poroelastic relaxation also affects the aftershock distribution. In fact, the aftershocks are correlated with the postseismic Coulomb stress evolution. In particular, a considerably higher fraction of aftershocks occurs when the evolving poroelastic Coulomb stress is positive. These findings highlight the need to perform calculations that adequately consider the time‐dependent poroelastic effect when modeling postseismic scenarios, especially for forecasting the temporal and spatial evolution of stresses after a large earthquake. Failing to do so results in an overestimation of the afterslip and an inaccurate definition of stress and strain in the postseismic phase.
Correlated error reduction in GRACE data over Greenland using extended empirical orthogonal functions
Authors: Eom Jooyoung , Seo Ki‐Weon , Lee Choon‐Ki , Wilson C. R. 
Published: June 2017

AbstractSurface mass change estimates from Gravity Recovery and Climate Experiment (GRACE) spherical harmonic solutions are contaminated by north‐south stripe noise due largely to aliasing of high‐frequency variations into monthly samples. These meridional stripes are especially troubling for ice mass balance studies of the Greenland Ice Sheet (GrIS) where large ice mass variations are known to occur along north‐south trending coastlines. By assuming that mass variations and noise have different patterns in both space and time over Greenland, we use extended empirical orthogonal functions (EEOFs) to filter out this noise. The method is compared with a conventional approach, by examining both continent‐wide estimates and regional changes. GRACE results are compared with independent regional estimates derived from a climate model. The EEOF filter is effective at separating ice mass change signals from meridional stripe noise, with better rejection of high temporal frequency noise and less signal attenuation and spatial smoothing compared to a conventional method. We use EEOF‐filtered GRACE data to examine regional seasonal variations. Consistent with surface and other data, results show ice mass loss along the west, southwest, and east coasts during summer and gain in these regions during winter. In addition, there is summer ice mass gain in the central region of the GrIS.