bluuebunny/crossref_metadata_2025 huggingface dataset:
Improving plant stress tolerance: potential applications of engineered MAPK cascades
Authors: Moustafa Khaled
Published: July 2018

The need to develop solutions to the problem of worldwide food crop scarcity under exacerbated climate change will be paramount. This motivates an effort to leverage agricultural biotechnology to improve plant adaptation to severe and multiple, simultaneous environmental stresses. Consequently, engineering synthetic signaling pathways, particularly mitogen activated protein kinase (MAPK) cascades utilizing components already involved in plant stress tolerance, is a worthy focus for research to breed new plant varieties with enhanced stress-tolerance traits.
Contributorships are not weighable to be equal
Authors: Moustafa Khaled
Published: July 2018

A new trend to assign some authors as 'first co-authors' is noticeable in scientific publications as a statement highlighting that two or more authors 'contributed equally' to a reported work. However, the requirements of scientific rigor, honesty, and accuracy in academic standards make such statements invalid and, thus, should be avoided. A potential solution is to specify the role of each co-author, from study conception to communication of results, and let readers judge the importance of each contribution by themselves. Alternatively, authors should demonstrate how they contributed 'equally' when they are defined as 'equal contributors'.
مستوى النرجسية لدى المراهق الجزائري المتمدرس دراسة ميدانية على عينة من تلاميذ السنة الثانية ثانوي بمدينة بسكرة
Authors: مجلة العلوم النفسية والتربوية مجلة العلوم النفسية والتربوية مجلة العلوم النفسية والتربوية , جديدي سعاد بن
Published: July 2018

هدفت هذه الدراسة إلى قياس مستوى النرجسية لدى المراهق الجزائري المتمدرس، والكشف عن أية فروق ذات دلالة إحصائية في ذلك تبعا لمتغير (الجنس). ولتحقيق أهداف الدراسة استخدم المنهج الوصفي الاستكشافي، من خلال تطبيق مقياس مستوى النرجسية من إعداد الباحثين على عينة من تلاميذ السنة الثانية ثانوي قدرت بـــ251 تلميذا تم اختيارهم بطريقة العينة العشوائية العنقودية .حيث أسفرت النتائج عما يلي:- مستوى النرجسية لدى أفراد العينة تمثل في: نسبة النرجسية المنخفضة قدرت بـ 26.7%، ونسبة النرجسية التوافقية السوية" تمثلت في 59.4%، أما مستوى النرجسية المرتفعة فقدرت بـ 13.9 %- عدم وجود فروق ذات دلالة إحصائية في مستوى النرجسية بأبعادها (الاستعراضية، التفوق، الغرور، السلطة الاستغلالية) بين تلاميذ السنة الثانية ثانوي بمدينة بسكرة تعزى لمتغير الجنس (ذكور، إناث).
الخط المعياري: أداة لتسهيل كتابة اللغة العربية وتعلمها
Authors: Bouhadjera Abdelmalek
Published: July 2018

سيتم في هذا المقال عرض الأسس التي بني عليها مقترح الخط المعياري لكتابة اللغة العربية بخط منفصل، و هو خطٌ يحافظ على تقاليد الكتابة العربية العريقة، لأنه مبني على نموذج الخط الكوفي الذي استعمل في البداية لتدوين القرآن الكريم، قبل استبداله بالخط النسخي. وهذا الأخير أكثر ملاءمة للكتابة اليدوية. و فيما بعد، تم الرجوع إلى الخط الكوفي، و استعمل خصيصاً للزخرفة على جدران المبـاني و المساجد، و النقش على الآلات، لسهولته وجماليته النابعة من الخطوط المتوازية و المستقيمة في تمثيل الحروف. و إذا كان الخط النسخي يتلاءم مع الكتابة باليد، فالخط الكوفي له قابلية تجاوب أكثر مع الآلةIn this article we present a standardized alphabet for writing Arabic with a detached script. It preserves the traditions of ancient calligraphic writing, because it is based primarily on the Kufic script, which was first used to codify the Qur'an, before being replaced with Naskhi style. The latter is more appropriate for handwriting. Later on, the Kufi style of writing was used exclusively for decoration on walls of buildings and mosques, and engraving, due to its simplicity that stems from the large number of parallel and straight lines in the representation of letters. The Arabic script contains two different styles of writing that lived side by side to perform two different tasks. While the Naskhi style has been used extensively over time and proved to be suitable for hand writing, the Kufic style is more adaptable for writing using hand tools. Therefore it is time to give it the same importance that has been given to Naskhi style by restarting a typographic tradition that could be more consistent with modern machines and computers.
How Often Should We Believe Positive Results? Assessing the Credibility of Research Findings in Development Economics
Authors: Coville Aidan , Vivalt Eva
Published: July 2018

Under-powered studies combined with low prior beliefs about intervention effects increase the chances that a positive result is overstated. We collect prior beliefs about intervention impacts from 125 experts to estimate the false positive and false negative report probabilities (FPRP and FNRP) as well as Type S (sign) and Type M (magnitude) errors for studies in development economics. We find that the large majority of studies in our sample are generally credible. We discuss how more systematic collection and use of prior expectations could help improve the literature.
The evolving preprint landscape: Introductory report for the Knowledge Exchange working group on preprints.
Authors: Tennant Jonathan , Bauin Serge , James Sarah , Kant Juliane
Published: July 2018

Introductory report for the Knowledge Exchange working group on preprints.
Mapping the Universe of Registered Reports
Authors: Hardwicke Tom Elis , Ioannidis john
Published: July 2018

Registered reports present a substantial departure from traditional publishing models with the goal of enhancing the transparency and credibility of the scientific literature. We map the evolving universe of registered reports to assess their growth, implementation, and shortcomings at journals across scientific disciplines.
Examining the Reproducibility of Meta-Analyses in Psychology: A Preliminary Report
Authors: Lakens Daniel , Page-Gould Elizabeth , van Assen Marcel A. L. M. , Spellman Bobbie , Schönbrodt Felix D. , Hasselman Fred , Corker Katherine S. , Grange James A. , Sharples Amanda , Cavender Corinne , Augusteijn Hilde Elisabeth Maria , Augusteijn Hilde , Gerger Heike , Locher Cosima , Miller Ian Dennis , Anvari Farid , Scheel Anne M.
Published: July 2018

Meta-analyses are an important tool to evaluate the literature. It is essential that meta-analyses can easily be reproduced to allow researchers to evaluate the impact of subjective choices on meta-analytic effect sizes, but also to update meta-analyses as new data comes in, or as novel statistical techniques (for example to correct for publication bias) are developed. Research in medicine has revealed meta-analyses often cannot be reproduced. In this project, we examined the reproducibility of meta-analyses in psychology by reproducing twenty published meta-analyses. Reproducing published meta-analyses was surprisingly difficult. 96% of meta-analyses published in 2013-2014 did not adhere to reporting guidelines. A third of these meta-analyses did not contain a table specifying all individual effect sizes. Five of the 20 randomly selected meta-analyses we attempted to reproduce could not be reproduced at all due to lack of access to raw data, no details about the effect sizes extracted from each study, or a lack of information about how effect sizes were coded. In the remaining meta-analyses, differences between the reported and reproduced effect size or sample size were common. We discuss a range of possible improvements, such as more clearly indicating which data were used to calculate an effect size, specifying all individual effect sizes, adding detailed information about equations that are used, and how multiple effect size estimates from the same study are combined, but also sharing raw data retrieved from original authors, or unpublished research reports. This project clearly illustrates there is a lot of room for improvement when it comes to the transparency and reproducibility of published meta-analyses.
Groundwater controls on post-fire permafrost thaw: Water and energy balance effects
Authors: Zipper Samuel , Lamontagne-Halle Pierrick , McKenzie Jeffrey , Rocha Adrian
Published: July 2018

Fire frequency and severity are increasing in high latitude regions, but the degree to which groundwater flow impacts the response of permafrost to fire remains poorly understood. Here, we use the Anaktuvuk River Fire (Alaska, USA) as an example for simulating groundwater-permafrost interactions following fire. We identify key thermal and hydrologic parameters controlling permafrost response to fire both with and without groundwater flow, and separate the relative influence of changes to the water and energy balances on active layer thickness. Our results show that mineral soil porosity, which influences the bulk subsurface thermal conductivity, is a key parameter controlling active layer response to fire in both the absence and presence of groundwater flow. However, neglecting groundwater flow increases the perceived importance of subsurface thermal properties, such as the thermal conductivity of soil solids, and decreases the perceived importance of hydrologic properties, such as the soil permeability. Furthermore, we demonstrate that changes to the energy balance (increased soil temperature) drive increased active layer thickness following fire, while changes to the water balance (decreased groundwater recharge) lead to reduced landscape-scale variability in active layer thickness and groundwater discharge to surface water features such as streams. These results indicate that explicit consideration of groundwater flow is critical to understanding how permafrost environments respond to fire.
The crisis of a paradigm. A methodological interpretation of Tohoku and Fukushima catastrophe
Authors: Lacassin Robin , Lavelle Sylvain
Published: July 2018

The 2011 Japanese disaster often presented as a ‘new Chernobyl’ accumulated the effects of earthquake, tsunami and of the subsequent nuclear accident at Fukushima. In the light of this disaster, we review methodological rea- sons both from geophysical and philosophical perspectives that lead the scientific and technological communities to flawed conclusions, prime cause of the disaster. The origin of the scientific mistake lies in several factors that challenge a dominant paradigm of seismology: the shallower part of the subduction was considered as weak, un- able to produce large earthquakes; a complete breakage of the fault up to the sea-floor was excluded. Actually, it appears that such complete rupture of the subduction interface did characterize megathrust ruptures, but also that hazard evaluations and technical implementation were in line with the flawed consensual paradigm. We give a philosophical interpretation to this mistake by weighing the opposition between a prescriptive account and a descriptive account of the dynamics of research. We finally emphasize that imagination, boldness, and openness (especially to alternatives to consensual paradigms) appear as core values for research. Those values may function as both epistemic and ethical standards and are so essential as rigor and precision. Ability to doubt and to consider all uncertainties indeed appears essential when dealing with rare extreme natural hazards that may potentially be catastrophic.Postprint (accepted version) of paper published in Earth Science Reviews (2016)
Comparing submarine and fluvial channel kinematics: Implications for stratigraphic architecture
Authors: Jobe Zane , Howes Nick , Auchter Neal
Published: July 2018

Submarine and fluvial channels exhibit qualitatively similar geomorphic patterns, yet produce very different stratigraphic records. We reconcile these seemingly contradictory observations by focusing on the channel-belt scale and quantifying the time-integrated stratigraphic record of the belt as a function of (1) the geometric scale and (2) the trajectory of the geomorphic channel, applying the concept of stratigraphic mobility. By comparing 297 submarine and fluvial channel belts from a range of tectonic settings and time intervals, we identify channel kinematics (trajectory) rather than channel morphology (scale) as the first order control on stratigraphic architecture and show that seemingly similar channel forms (in terms of scaling) have the potential to produce markedly different stratigraphy. Submarine channel-belt architecture is dominated by vertical accretion (aggradational channel fill deposits), in contrast to fluvial systems that are dominated by lateral accretion (point bar deposits). This difference is best described with the channel-belt aspect ratio, which is 9 for submarine systems and 72 for fluvial systems. Differences in channel kinematics and thus stratigraphic architecture between the two environments appear to result from markedly different coupling between channel aggradation and overbank deposition. The methodology and results presented here are also applicable to interpreting channelized stratigraphy on other planets and moons.
Climate-driven unsteady denudation and sediment flux in a high-relief unglaciated catchment-fan using 26Al and 10Be: Panamint Valley, California
Authors: Mason Cody , Romans Brian
Published: July 2018

Environmental changes within erosional catchments of sediment routing systems are predicted to modulate sediment transfer dynamics. However, empirical and numerical models that predict such phenomena are difficult to test in natural systems over multi-millennial timescales. Tectonic boundary conditions and climate history in the Panamint Range, California, are relatively well-constrained by existing low-temperature thermochronology and regional multi-proxy paleoclimate studies, respectively. Catchment-fan systems present there minimize sediment storage and recycling, offering an excellent natural laboratory to test models of climate-sedimentary dynamics. We used stratigraphic characterization and cosmogenic radionuclides (CRNs; 26Al & 10Be) in the Pleasant Canyon complex (PCC), a linked catchment-fan system, to examine the effects of Pleistocene high-magnitude, high-frequency climate change on CRN-derived denudation rates and sediment flux in a high-relief, unglaciated catchment-fan system. Calculated 26Al/10Be burial ages from 13 samples collected in an ~180 m thick outcropping stratigraphic succession range from ca. 1.55 ± 0.22 Ma in basal strata, to ca. 0.36 ± 0.18 - 0.52 ± 0.20 Ma within stratigraphically highest portions of the fan. The mean long-term CRN-derived paleodenudation rate, 36 ± 8 mm/kyr (1σ), is higher than the modern rate of 24 ± 0.6 mm/kyr from Pleasant Canyon, and paleodenudation rates during the middle Pleistocene display some high-frequency variability in the high end (up to 54 ± 10 mm/kyr). The highest CRN-derived denudation rates are associated with stratigraphic evidence for increased precipitation during glacial-pluvial events after the middle Pleistocene transition (post ca. 0.75 Ma), suggesting 100 kyr Milankovitch periodicity could drive the observed variability. We investigated the potential for non-equilibrium sedimentary processes, i.e. increased landslides or sediment storage/recycling, to influence apparent paleodenudation rates; end-member mixing models suggest that a mixture of >50% low-CRN-concentration sediment from landslides is required to produce the largest observed increase in paleodenudation rate. The overall pattern of CRN-derived burial ages, paleodenudation rates, and stratigraphic facies suggests Milankovitch timescale climate transitions drive variability in catchment denudation rates and sediment flux, or alternatively that climate transitions affect sedimentary process regimes that result in measurable variability of CRN concentrations in unglaciated catchment-fan systems.
Morphometric analysis in Geographic Information Systems: applications of free software GRASS and R
Authors: Grohmann Carlos
Published: July 2018

Development and interpretation of morphometric maps are important tools in studies related to neotectonics and geomorphology; Geographic Information Systems (GIS) allows speed and precision to this process, but applied methodology will vary according to available tools and degree of knowledge of each researcher about involved software.A methodology to integrate GIS and statistics in morphometric analysis is presented for the most usual morphometric parameters - hypsometry, slope, aspect, swath profiles, lineaments and drainage density, surface roughness, isobase and hydraulic gradient.The GIS used was the Geographic Resources Analysis Support System (GRASS-GIS), an open- source project that offers an integrated environment for raster and vector analysis, image processing and maps/graphics creation. Statistical analysis of parameters can be carried out on R, a system for statistical computation and graphics, through an interface with GRASS that allows raster maps and points files to be treated as variables for analysis.The basic element for deriving morphometric maps is the digital elevation model (DEM). It can be interpolated from scattered points or contours, either in raster or vector format; it is also possible to use DEMs from NASAs Shuttle Radar Topographic Mission, with 30m of ground resolution for the USA and 90m for other countries.Proposed methodology can be adapted according to necessities and available tools. The use of free and open-source tools guarantees access to everyone, and its increasing popularization opens new development perspectives in this research field.
The Mesozoic and Palaeozoic granitoids of north-western New Guinea
Authors: Jost Benjamin , Webb Max , White Lloyd
Published: July 2018

A large portion of the Birds Head Peninsula of NW New Guinea is an inlier that reveals the pre-Cenozoic geological history of the northern margin of eastern Gondwana. The peninsula is dominated by a regional basement high exposing Gondwanan (Australian) Palaeozoic metasediments intruded by Palaeozoic and Mesozoic granitoids. Here, we present the first comprehensive study of these granitoids, including field and petrographic descriptions, bulk rock geochemistry, and U-Pb zircon age data. We further revise and update previous subdivisions ofgranitoids in the area. Most granitoids were emplaced as small to medium scale intrusions during two episodes in the Devonian-Carboniferous and the Late Permian-Triassic, separated by a period of apparent magmatic quiescence. The oldest rocks went unrecognised until this study, likelydue to the younger intrusive events resetting the K¬-Ar isotopic system used in previous studies. Most of the Palaeozoic and Mesozoic granitoids are peraluminous and in large parts derived from partial melts of the country rock. This is corroborated by local migmatites and country rockxenoliths. Although rare, the metaluminous and mafic rocks show that partial melts of mantle-derived material played a minor role in granitoid petrogenesis, especially during the Permian-Triassic. The Devonian-Carboniferous granitoids and associated volcanics are locally restricted, whereas the Permian-Triassic intrusions are found across NW New Guinea and further afield. The latter were likely part of an extensive active continental margin above a subduction system spanning the length of what is now New Guinea and likely extending southward through easternAustralia and Antarctica.
Formation of a cohesive floodplain in a dynamic experimental meandering river
Authors: van Dijk Wout , van de Lageweg Wietse , Kleinhans Maarten
Published: July 2018

Field studies suggest that a cohesive floodplain is a necessary condition for meandering in contrast to braided rivers. However, it is only partly understood how the balance between floodplain construction by overbank deposition and removal by bank erosion and chutes leads to meandering. This is needed because only then does a dynamic equilibrium exist and channels maintain meandering with low width–depth ratios. Our objective is to understand how different styles of floodplain formation such as overbank deposition and lateral accretion cause narrower channels and prevent chute cutoffs that lead to meandering. In this study we present two experiments with a self-forming channel in identical conditions, but to one we added cohesive silt at the upstream boundary. The effect of cohesive silt on bank stability was tested in auxiliary bank erosion experiments and showed that an increase in silt reduced erosion rates by a factor of 2. The experiment without silt developed to a braided river by continuous and extensive shifting of multiple channels. In contrast, in the meandering river silt deposits increased bank stability of the cohesive floodplain and resulted in a reduction of chute cutoffs and increased sinuosity by continuous lateral migration of a single channel. Overbank flow led to deposition of the silt and two styles of cohesive floodplain were observed: first, overbank vertical-accretion of silt, e.g. levee, overbank sedimentation or splays; and second, lateral point bar accretion with silt on the scrolls and in the swales. The first style led to a reduction in bank erosion, while the second style reduced excavation of chutes. We conclude that sedimentation of fine cohesive material on the floodplain by discharge exceeding bankfull is a necessary condition for meandering.
Sequential growth of deformation bands in carbonate grainstones in the hangingwall of an active growth fault: Implications for deformation mechanisms in different tectonic regimes
Authors: Rotevatn Atle , Thorsheim Elin , Bastesen Eivind , Fossmark Heidi , Torabi Anita , Sælen Gunnar
Published: July 2018

Deformation bands in porous sandstones have been extensively studied for four decades, whereas comparatively less is known about deformation bands in porous carbonate rocks, particularly in extensional settings. Here, we investigate porous grainstones of the Globigerina Limestone Formation in Malta, which contain several types of deformation bands in the hangingwall of the Maghlaq Fault: (i) bed-parallel pure compaction bands (PCB); (ii) pressure solution-dominated compactive shear bands (SCSB) and iii) cataclasis-dominated compactive shear bands (CCSB). Geometric and kinematic analyses show that the bands formed sequentially in the hangingwall of the evolving Maghlaq growth fault. PCBs formed first due to fault-controlled subsidence and vertical loading; a (semi-)tectonic control on PCB formation is thus documented for the first time in an extensional setting. Pressure solution (dominatingSCSBs) and cataclasis (dominating CCSBs) appear to have operated separately, and not in concert. Our findings therefore suggest that, in some carbonate rocks, cataclasis within deformation bands may develop irrespective of whether pressure solution processes are involved.We suggest this may be related to stress state, and that whereas pressure solution is a significant facilitator of grain size reduction in contractional settings, grain size reduction within deformation bands in extensional settings is less dependent on pressure solution processes.
A systematic study of earthquake detectability using Sentinel-1 Interferometric Wide-Swath data
Authors: Funning Gareth , Garcia Astrid
Published: July 2018

The Sentinel-1 mission comprises two synthetic aperture radar satellites, each with a 12 day orbital repeat, orbiting 6 days apart within a narrow tube. The mission design promises the ability to respond quickly to earthquakes with InSAR, and to facilitate production of interferograms with good interferometric correlation globally. We report on our efforts to study global seismicity using Sentinel-1 Interferometric Wide-Swath data between April 2015 and December 2016. We select 35 potentially detectable terrestrial earthquakes in the range 5.5 ≤ Mw ≤ 7.8 on the basis of their locations, depths and magnitudes, and process the first post-event interferogram with the shortest possible time-span for each using the ISCE software. We evaluate each interferogram for earthquake deformation signals by visual inspection. We can identify deformation signals attributable to earthquakes in 18 of these interferograms (51%); a further six interferograms (17%) have ambiguous interferometric phase affected by tropospheric noise. 11 events (31%) could not be identified from their interferograms. The majority of these failed detections were due to interferogram decorrelation, particularly apparent for earthquakes that occurred between 15°N and 15°S, where climate conditions promote dense vegetation. The majority of the ambiguous interferograms are affected by tropospheric noise, suggesting that techniques to mitigate such noise could improve detection performance. The largest event we do not detect with Sentinel-1 data is a Mw7.0 earthquake that occurred in Vanuatu in April 2016; we also fail to detect the 2016 Mw6.2 Kurayoshi earthquake in one out of two possible 24-day interferograms. We propose these as upper and lower estimates on the magnitude of completeness for earthquakes studied with Sentinel-1 data; to lower the magnitude of completeness we suggest that more frequent (e.g. six day) recurrence may be necessary in low latitude areas.
Ice shelf rift propagation and the mechanics of wave-induced fracture
Authors: Lipovsky Bradley
Published: July 2018

Distant storms, tsunamis, and earthquakes generate waves on floating ice shelves. Previous studies, however, have disagreed about whether the resulting wave-induced stresses may cause ice shelf rift propagation. Most ice shelf rifts show long periods of dormancy suggesting that they have low background stress concentrations and may therefore be susceptible to wave-induced stresses. Here, I quantify wave-induced stresses on the Ross Ice Shelf Nascent Rift and the Amery Ice Shelf Loose Tooth T2 Rift using passive seismology. I then relate these stresses to a fracture mechanical model of rift propagation that accounts for rift cohesive strength due to refrozen melange, ice inertia, and spatial heterogeneity in fracture toughness due to the presence of high toughness suture zones. I infer wave-induced stresses using the wave impedance tensor, a rank three tensor that relates seismically observable particle velocities to components of the stress tensor. I find that wave-induced stresses are an order of magnitude larger on the Ross Ice Shelf as compared to the Amery Ice Shelf. In the absence of additional rift strength, my model predicts that the Nascent Rift should have experienced extensive rift propagation. The observation that no such propagation occurred during this time therefore suggests that the Nascent Rift experiences cohesive strengthening from either refrozen melange or rift tip processes zone dynamics. This study illustrates one way in which passive seismology may illuminate glacier calving physics.
Criteria and Tools for Determining Drainage Divide Stability
Authors: Forte Adam , Whipple Kelin
Published: July 2018

Watersheds are the fundamental organizing units in landscapes and thus the controls on drainage divide location and mobility are an essential facet of landscape evolution. Additionally, many common topographic analyses fundamentally assume that river network topology and divide locations are largely static, allowing channel profile form to be interpreted in terms of spatio-temporal patterns of rock uplift rate relative to base level, climate, or rock properties. Recently however, it has been suggested that drainage divides are more mobile than previously thought and that divide mobility, and resulting changes in drainage area, could potentially confound interpretations of river profiles. Ultimately, reliable metrics are needed to diagnose the mobility of divides as part of routine landscape analyses. One such recently proposed metric is cross-divide contrasts in chi, a proxy for steady-state channel elevation, but cross-divide contrasts in a number of topographic metrics show promise. Here we use a series of landscape evolution simulations in which we induce divide mobility under different conditions to test the utility of a suite of topographic metrics of divide mobility and for comparison with natural examples in the eastern Greater Caucasus Mountains, the Kars Volcanic Plateau, and the western San Bernadino Mountains. Specifically, we test cross-divide contrasts in mean gradient, mean local relief, channel bed elevation, and chi all measured at, or averaged upstream of, a reference drainage area. Our results highlight that cross-divide contrasts in chi only faithfully reflect current divide mobility when uplift, rock erodibility, climate, and catchment outlet elevation are uniform across both river networks on either side of the divide, otherwise a chi-anomaly only indicates a possible future divide instability. The other metrics appear to be more reliable representations of current divide motion, but in natural landscapes, only cross-divide contrasts in mean gradient and local relief appear to consistently provide useful information. Multiple divide metrics should be considered simultaneously and across-divide values of all metrics examined quantitatively as visual assessment is not sufficiently reliable in many cases. We provide a series of Matlab tools built using TopoToolbox to facilitate routine analysis.
Continuous separation of land use and climate effects on the past and future water balance
Authors: Zipper Samuel , Motew Melissa , Booth Eric , Chen Xi , Qiu Jiangxiao , Kucharik Christopher , Carpenter Stephen , Loheide Steven
Published: July 2018

Understanding the combined and separate effects of climate and land use change on the water cycle is necessary to mitigate negative impacts. However, existing methodologies typically divide data into discrete (before and after) periods, implicitly representing climate and land use as step changes when in reality these changes are often gradual. Here, we introduce a new regression-based methodological framework designed to separate climate and land use effects on any hydrological flux of interest continuously through time, and estimate uncertainty in the contribution of these two drivers. We present two applications in the Yahara River watershed (Wisconsin, USA) demonstrating how our approach can be used to understand synergistic or antagonistic relationships between land use and climate in either the past or the future: (1) historical streamflow, baseflow, and quickflow in an urbanizing subwatershed; and (2) simulated future evapotranspiration, drainage, and direct runoff from a suite of contrasting climate and land use scenarios for the entire watershed. In the historical analysis, we show that ~60% of recent streamflow changes can be attributed to climate, with approximately equal contributions from quickflow and baseflow. However, our continuous method reveals that baseflow is significantly increasing through time, primarily due to land use change and potentially influenced by long-term increases in groundwater storage. In the simulation of future changes, we show that all components of the future water balance will respond more strongly to changes in climate than land use, with the largest potential land use effects on drainage. These results indicate that diverse land use change trajectories may counteract each other while the effects of climate are more homogeneous at watershed scales. Therefore, management opportunities to counteract climate change effects will likely be more effective at smaller spatial scales, where land use trajectories are unidirectional.
Pseudotachylyte as field evidence for lower crustal earthquakes during the intracontinental Petermann Orogeny (Musgrave Block, Central Australia)
Authors: Hawemann Friedrich , Mancktelow Neil , Wex Sebastian , Camacho Alfredo , Pennacchioni Giorgio
Published: July 2018

Geophysical evidence for lower continental crustal earthquakes in almost all collisional orogens is in conflict with the widely accepted notion that rocks, under high grade conditions, should flow rather than fracture. Pseudotachylytes are remnants of frictional melts generated during seismic slip and can therefore be used as an indicator of former seismogenic fault zones. The Fregon Domain in Central Australia, was deformed under dry sub-eclogitic conditions during the intracontinental Petermann Orogeny (ca. 550 Ma) and contains abundant pseudotachylyte. These pseudotachylytes are commonly foliated, recrystallized, and crosscut by other pseudotachylytes, reflecting repeated generation during ongoing ductile deformation under generally dry conditions. This interplay is interpreted as a cycle of seismic brittle failure and post- to inter seismic creep under dry lower crustal conditions. Thermodynamic modelling of the pseudotachylyte bulk composition gives conditions of shearing of 600-700 °C and 1.0-1.2 GPa, the same as in surrounding mylonites. We conclude that pseudotachylytes in the Fregon Domain are a direct analogue of current seismicity in dry lower continental crust.
Linked Geoscience Data in practice: Where W3C standards meet domain knowledge, data visualization and OGC standards
Authors: Ma Xiaogang
Published: July 2018

The geoscience community is now facing both the challenge and the opportunity caused by the vast amount of datasets that can be made available on the Web. An efficient “data environment” on the Web has the potential to enable geoscientists to conduct their research in ways that never existed before. Standards developed by the Open Geospatial Consortium have already been used widely to build data services among different subjects in geosciences. In recent years, the Linked Open Data approach initiated by the World Wide Web Consortium has received increasing attention. In this paper, the author presents a pilot study that uses a domain specific knowledge base and data visualization techniques to leverage the functionality of geoscience data services in the Web of Data. The study focuses on the topic of the geologic time scale. Detailed works such as semantic modeling and encoding, multilingual vocabularies, exploratory data visualization, web map service and processing, and the query of linked data are introduced through real-world datasets. This study faces a broad perspective of the Linked Geoscience Data and leverages the functionalities of existing standards into a new level for geoscience applications.
Post-critical SsPmp and Its Applications to Virtual Deep Seismic Sounding (VDSS): 1. Sensitivity to Lithospheric 1D and 2D structure
Authors: Liu Tianze , Klemperer Simon , Yu Chunquan , Ning Jieyuan
Published: July 2018

Virtual Deep Seismic Sounding (VDSS) has recently emerged as a novel method to image the Moho and potentially other lithospheric boundaries. The behavior of SsPmp, the post-critical reflection phase at the Moho that is utilized in VDSS, is rich with complexities not yet widely utilized. Here, motivated by observations from the Ordos Plateau in North China, we use synthetic seismograms computed with a broad range of 1D models to evaluate how different parts of the lithosphere along the ray path of SsPmp affect its phase, amplitude, and arrival time. Our findings include: (1) When the crust-mantle boundary is a sharp discontinuity, the SsPmp phase shift relative to the direct S wave is controlled by lower-crustal Vp, upper-mantle Vp and ray parameter. This property indicates the possibility of using SsPmp to constrain Vp in the lower crust and uppermost mantle. (2) When the crust-mantle boundary is a velocity-gradient zone, SsPmp arrival times vary as different functions of ray parameter from cases with a sharp crust-mantle boundary, because different rays turn at different depths. This feature allows measurement of the vertical velocity gradient in the crust-mantle transition zone with SsPmp. (3) When the virtual source (location of S-to-P conversion at the free surface) is in a sedimentary basin, SsPmp amplitude can be significantly reduced due to low S-to-P reflected energy at the virtual source. This may cause the absence of SsPmp despite appropriate source-receiver geometry. In addition to 1D models, we further conduct 2D waveform modeling and find that the SsPmp arrival time relative to direct S is not only controlled by crustal thickness at the reflection point, but also by lateral variation of Vs beneath the virtual source and receiver. Therefore, in areas with significant lateral heterogeneity in the lithosphere the accuracy of crustal-thickness measurements from SsPmp arrival times depends on our knowledge of the variability of lithospheric structure across a broad region.
Prediction of wave ripple characteristics using genetic programming
Authors: Goldstein Evan , Coco Giovanni , Murray A.
Published: July 2018

We integrate published data sets of field and laboratory experiments of wave ripples and use genetic programming, a machine learning paradigm, in an attempt to develop a universal equilibrium predictor for ripple wavelength, height, and steepness. We train our genetic programming algorithm with data selected using a maximum dissimilarity selection routine. Thanks to this selection algorithm we use less data to train the genetic programming software, allowing more data to be used as testing (i.e. to compare our predictor vs. common prediction schemes). Our resulting predictor is smooth and physically meaningful, different from other machine learning derived results. Furthermore our predictor incorporates wave orbital ripples that were previously excluded from empirical prediction schemes, notably ripples in coarse sediment and long wavelength, low height ripples (‘hummocks’). This new predictor shows ripple length to be a weakly nonlinear function of both bottom orbital excursion and grain size. Ripple height and steepness are both nonlinear functions of grain size and predicted ripple length (i.e. bottom orbital excursion and grain size). We test this new prediction scheme against common (and recent) predictors and the new predictors yield a lower normalized root mean squared error using the testing data. This study further demonstrates the applicability of machine learning techniques to successfully develop well performing predictors if data sets are large in size, extensive in scope, multidimensional, and nonlinear. © 2017. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
238U/235U Systematics in Terrestrial Uranium-Bearing Minerals
Authors: Hiess Joe , Condon Daniel , McLean Noah , Noble Stephen
Published: July 2018

The present-day 238U/235U ratio has fundamental implications for uranium-lead geochronology and cosmochronology. A value of 137.88 has previously been considered invariant and has been used without uncertainty to calculate terrestrial mineral ages. We report high-precision 238U/235U measurements for a suite of uranium-bearing minerals from 58 samples representing a diverse range of lithologies. This data set exhibits a range in 238U/235U values of >5 per mil, with no clear relation to any petrogenetic, secular, or regional trends. Variation between comagmatic minerals suggests that 238U/235U fractionation processes operate at magmatic temperatures. A mean 238U/235U value of 137.818 ± 0.045 (2σ) in zircon samples reflects the average uranium isotopic composition and variability of terrestrial zircon. This distribution is broadly representative of the average crustal and “bulk Earth” 238U/235U composition.
J2: an evaluation of new estimates from GPS, GRACE and load models compared to SLR
Authors: Lavallee David , Moore Philip , Clarke Peter , Petrie Elizabeth , van Dam Tonie , King Matt
Published: July 2018

Changes in J2, resulting from past and present changes in Earth’s climate, are traditionally observed by Satellite Laser ranging (SLR). Assuming an elastic Earth, it is possible to infer changes in J2 from changes in Earth’s shape observed by GPS. We compare estimates of non-secular J2 changes from GPS, SLR, GRACE and a load model. The GPS and SLR annual signals agree but are different (16%) to the load model. Subtraction of the load model removes the annual variation from GPS, SLR and GRACE, and the semi-annual variation in GPS. The GPS and SLR long-term signals are highly correlated, but GPS is better correlated with the loading model. Subtraction of the load model removes the 1998 anomaly from the GPS J2 series but not completely from the SLR J2 series, suggesting that the SLR anomaly may not be entirely due to mass redistribution as has been presumed.
Could the IMS Infrasound Stations Support a Global Network of Small Aperture Seismic Arrays?
Authors: Gibbons Steven , Kværna Tormod , Mykkeltveit Svein
Published: July 2018

The IMS infrasound arrays have up to 15 sites with apertures up to 3 km. They are distributed remarkably uniformly over the globe, providing excellent coverage of South America, Africa, and Antarctica. Therefore, many infrasound arrays are in regions thousands of kilometers from the closest seismic array. Existing 3-component seismic stations, co-located with infrasound arrays, show how typical seismic signals look at these locations. We estimate a theoretical array response assuming a seismometer at each infrasound sensor, although the true performance would depend upon both SNR and coherence. These properties can however only be determined experimentally and borehole deployments may be needed to record seismic data of sufficient quality. We demonstrate, from a purely geometrical perspective, that essentially all IMS infrasound array configurations would provide seismic arrays with acceptable slowness resolution. Such arrays in many regions would likely enhance significantly the seismic monitoring capability in parts of the world where only 3-component stations are currently available. Co-locating seismic and infrasound sensors would mitigate the development and operational costs due to shared infrastructure, and hosting countries might find such added capabilities valuable from a national perspective. The seismic data may allow far more information to be gleaned from the infrasound data.(Note that SRL papers at the time did not have abstracts. The above abstract was for a presentation with the same name held at the CTBTO Science and Technology Conference 2015.)
Detecting lightning infrasound using a high-altitude balloon
Authors: Lamb Oliver , Lees Jonathan , Bowman Daniel
Published: July 2018

Acoustic waves with a wide range of frequencies are generated by lightning strokes during thunderstorms, including infrasonic waves (0.1 to 20 Hz). The source mechanism for these low frequency acoustic waves is still debated and studies have so far been limited to ground-based instruments. Here we report the first confirmed detection of lightning generated infrasound with acoustic instruments suspended at stratospheric altitudes using a free-flying balloon. We observe high-amplitude signals generated by lightning strokes located within 100 km of the balloon as it flew over the Tasman Sea on 17 May 2016. The signals share many characteristics with waveforms recorded previously by ground-based instruments near thunderstorms. The ability to measure lightning activity with high-altitude infrasound instruments has demonstrated the potential for using these platforms to image the full acoustic wavefield in the atmosphere. Furthermore, it validates the use of these platforms for recording and characterizing infrasonic sources located beyond the detection range of ground-based instruments.
Shallow water benthic imaging and substrate characterization using recreational-grade sidescan-sonar
Authors: Buscombe Daniel
Published: July 2018

In recent years, lightweight, inexpensive, vessel-mounted ‘recreational grade’ sonar systems have rapidly grown in popularity among aquatic scientists, for swath imaging of benthic substrates. To promote an ongoing ‘democratization’ of acoustical imaging of shallow water environments, methods to carry out geometric and radiometric correction and georectification of sonar echograms are presented, based on simplified models for sonar-target geometry and acoustic backscattering and attenuation in shallow water. Procedures are described for automated removal of the acoustic shadows, identification of bed-water interface for situations when the water is too turbid or turbulent for reliable depth echosounding, and for automated bed substrate classification based on singlebeam full-waveform analysis. These methods are encoded in an open-source and freely-available software package, which should further facilitate use of recreational-grade sidescan sonar, in a fully automated and objective manner. The sequential correction, mapping, and analysis steps are demonstrated using a data set from a shallow freshwater environment.
Surface wave array tomography in SE Tibet from ambient seismic noise and two-station analysis - II. Crustal and upper-mantle structure
Authors: Yao Huajian , Beghein Caroline , van der Hilst Robert
Published: July 2018

We determine the 3-D shear wave speed variations in the crust and upper mantle in the southeastern borderland of the Tibetan Plateau, SW China, with data from 25 temporary broad-band stations and one permanent station. Interstation Rayleigh wave (phase velocity) dispersion curves were obtained at periods from 10 to 50 s from empirical Greens function (EGF) derived from (ambient noise) interferometry and from 20 to 150 s from traditional two-station (TS) analysis. Here, we use these measurements to construct phase velocity maps (from 10 to 150 s, using the average interstation dispersion from the EGF and TS methods between 20 and 50 s) and estimate from them (with the Neighbourhood Algorithm) the 3-D wave speed variations and their uncertainty. The crust structure, parametrized in three layers, can be well resolved with a horizontal resolution about of 100 km or less. Because of the possible effect of mechanically weak layers on regional deformation, of particular interest is the existence and geometry of low (shear) velocity layers (LVLs). In some regions prominent LVLs occur in the middle crust, in others they may appear in the lower crust. In some cases the lateral transition of shear wave speed coincides with major fault zones. The spatial variation in strength and depth of crustal LVLs suggests that the 3-D geometry of weak layers is complex and that unhindered crustal flow over large regions may not occur. Consideration of such complexity may be the key to a better understanding of relative block motion and patterns of seismicity.
Microstructural controls on the pressure-dependent permeability of Whitby Mudstone
Authors: Mecklenburgh Julian , Taylor Kevin , Rutter Ernie , Mckernan Rosanne
Published: July 2018

A combination of permeability and ultrasonic velocity measurements allied with image analysis is used to distinguish the primary microstructural controls on effective-pressure dependent permeability. Permeabilities of cylindrical samples of Whitby Mudstone were measured using the oscillating pore pressure method at confining pressures ranging between 30-95 MPa and pore pressures ranging between 1-80 MPa. The permeability-effective pressure relationship is empirically described using a modified effective pressure law in terms of confining pressure, pore pressure and a Klinkenberg effect. Measured permeability ranges between 3×10-21 m2 and 2 ×10-19 m2 (3 and 200 nd), and decreases by ~1 order of magnitude across the applied effective pressure range. Permeability is shown to be less sensitive to changes in pore pressure than changes in confining pressure, yielding permeability effective pressure coefficients (χ) between 0.42 and 0.97. Based on a pore-conductivity model which considers the measured changes in acoustic wave velocity and pore volume with pressure, the observed loss of permeability with increasing effective pressure is attributed dominantly to the progressive closure of bedding-parallel, crack-like pores associated with grain boundaries. Despite only constituting a fraction of the total porosity, these pores form an interconnected network that significantly enhances permeability at low effective pressures.