bluuebunny/crossref_metadata_2025 huggingface dataset:
Drivers of deep heat uptake in the North Atlantic Subpolar Gyre
Authors: Desbruyeres Damien , Sinha Bablu , McDonagh Elaine , Josey Simon , Megann Alexis , Smeed David , Holliday Penny , New Adrian , Moat Ben
Published: March 2020

The decadal to multi-decadal temperature variability of the intermediate (700 – 2000 m) North Atlantic Subpolar Gyre (SPG) significantly imprints the global pattern of ocean heat uptake. Here, the origins and dominant pathways of this variability are investigating with an ocean analysis product (EN4), an ocean state estimate (ECCOv4), and idealized modeling approaches. Sustained increases and decreases of intermediate temperature in the SPG correlate with long-lasting warm and cold states of the upper ocean – the Atlantic Multidecadal Variability – with the largest anomalous vertical heat exchanges found in the vicinity of continental boundaries and strong ocean currents. In particular, vertical diffusion along the boundaries of the Labrador and Irminger Seas and advection in the region surrounding Flemish Cap stand as important drivers of the recent warming trend observed during 1996-2014. The impact of those processes is well captured by a 1-dimensional diffusive model with appropriate boundary-like parametrization and illustrated through the continuous downward propagation of a passive tracer in an eddy-permitting numerical simulation. Our results imply that the slow and quasi-periodic variability of intermediate thermohaline properties in the SPG are not strictly driven by the well-known convection-restratification events in the open seas but also receives a key contribution from boundary sinking and mixing. Increased skill for modelling and predicting intermediate-depth ocean properties in the North Atlantic will hence require the appropriate representation of surface-deep dynamical connections within the boundary currents encircling Greenland and Newfoundland.
Automating the pre-processing of time-domain induced polarization data using machine learning
Authors: Barfod* Adrian S. , Larsen Jakob Juul
Published: March 2020

Exploring and studying the earth system is becoming increasingly important as the slow depletion of natural resources ensues. An important data source is geophysical data, collected worldwide. After gathering data, it goes through vigorous quality control, pre-processing, and inverse modelling procedures. Such procedures often have manual components, and require a trained geophysicist who understands the data, in order to translate it into useful information regarding the earth system. The sheer amounts of geophysical data collected today makes manual approaches impractical. Therefore, automating as much of the workflow related to geophysical data as possible, would allow novel opportunities such as fully automated geophysical monitoring systems, real-time modeling during data collection, larger geophysical data sets, etc.

Machine learning has been proposed as a tool for automating workflows related to geophysical data. The field of machine learning encompasses multiple tools, which can be applied in a wide range of geophysical workflows, such as pre-processing, inverse modeling, data exploration etc.

We present a study where machine learning is applied to automate the time domain induced polarization geophysical workflow. Such induced polarization data requires pre-processing, which is manual in nature. One of the pre-processing steps is that a trained geophysicist inspects the data, and removes so-called non-geologic signals, i.e. noise, which does not represent geological variance. Specifically, a real-world case from Grindsted Denmark is presented. Here, a time domain induced polarization survey was conducted containing seven profiles. Two lines were manually processed and used for supervised training of an artificial neural network. The neural net then automatically processed the remaining profiles of the survey, with satisfactory results. Afterwards, the processed data was inverted, yielding the induced polarization parameters respective to the Cole-Cole model. We discuss the limitations and optimization steps related to training such a classification network.
Variability of sediment source attribution with CSSI over temporal and spatial scales – from soil texture to land-use unit and from event to seasonality.
Authors: Birkholz Axel , Glendel Miriam , Brazier Richard E. , Alewell Christine
Published: March 2020

Soil erosion and its accompanying on- and off-site effects represent a serious threat to the environment. Over the last years many studies have been successfully carried out using compound-specific stable carbon isotopes of fatty acids (FA) and n-alkanes to characterize source soils and attribute suspended sediments or sedimentary archives to the characterized sources. One worthy next aim would be the extrapolation to large catchments. Important for this is a deepened knowledge about the variability of the signals over different temporal and spatial scales, which has so far been largely neglected, with the exception of a handful of studies. With this knowledge it should be possible to understand processes better in the catchment and deliver improved interpretation and representation of empirical data, ultimately supporting suitable mitigation actions to minimize sediment transport to aquatic environments.

In our study we present compound-specific stable isotope data of long-chain FAs from two neighbouring yet distinct (in terms of soils and land use) catchments, Aller and Horner Water (17.6km2 and 22km2 respectively), Exmoor, South-west England. To capture the spatial heterogeneity, we analysed possible source soils from different land-uses, including moorland, heather, forest, permanent grassland, arable and ley grassland on different soil textures (clay, loam, and peat) for their FA stable isotope signature. A very interesting outcome is the apparent influence that soil texture has on the stable isotope signal of the FAs of the same land-use units. To consider temporal variability, we present isotope data for FAs of high flow events from the main outlet and 4 sub-catchments of Aller and Horner waters over the course of one year. Three of these events have been sampled at a high temporal resolution of up to 24 sediment samples per event.

Previous research by our group found a significant importance of the seasonal variability in the suspended sediment origin in the Baldegg Lake catchment, Switzerland.  In addition to such seasonal understanding, this study will allow us to understand the short-term variability in the origin of the transported sediments during storm events and to link it with high spatial resolution of the characterized source soils.
NDE1.0 – A new database of earthquake data recordings from buildings for performance based earthquake engineering, vulnerability assessment and seismic structural health monitoring
Authors: Guéguen Philippe , Astorga Ariana , Ghimire Subash
Published: March 2020

Over the last two decades, seismic ground motion prediction has been significantly improved thanks to the development of shared, open, worldwide databases (waveform and parametric values). Unlike seismic ground motion, earthquake data recorded in buildings are rarely shared. However, their contribution could be essential for evaluating the performance of structures. Increasing interest in deploying instrumentation in buildings gives hope for new observations, leading to better understanding of behavior. This manuscript presents a flat-file containing information on earthquake responses of instrumented buildings. Herein, we present the structure of the NDE1.0 flat-file containing site and earthquake characteristics (vs30, Magnitude, Distance...), structural response parameters (i.e. drift ratio, peak top values of acceleration, velocity and displacement, pre- and co-seismic fundamental frequencies) computed for several intensity measures characterizing ground motion (peak and spectral values, duration...). The data are from real earthquake recordings collected in buildings over the years. This 1.0 version contains 8,520 strong motion recordings that correspond to 118 buildings and 2,737 events, providing useful information for analyses related to seismic hazard, variability of building responses, structural health monitoring, nonlinear studies, damage prediction, etc. Some specific analysis will be presented concerning seismic structural health monitoring and damage prediction, with a special focus on the engineering demand parameter versus intensity measures variability.
Effect of sewage sludge biochar on tomato plant (Solanum lycopersicum L.) cultivation
Authors: Diamadopoulos Evan , Velli Paraskevi , Manolikaki Ioanna
Published: March 2020

The present study refers to biochar production, its application to soil with or without combining it with compost, as well as its effect on tomato (Solanum Lycopersicum L.) cultivation. The feedstock selected for biochar production was a mixture of primary and secondary sewage sludge, which had previously been anaerobically digested and thermally dehydrated. Sewage sludge pyrolysis was conducted at 300 °C. The produced biochar was initially characterized and subsequently applied to soil, in order to study its effect on Solanum Lycopersicum L. cultivation. Pot trials which included four treatments, each comprising of three replicates, were carried out during a period of three months, using pots with a 10 kg capacity. More specifically, the following treatments were studied: i) Control (soil without biochar addition), ii) soil with biochar at a rate of 2% w/w (BC-SS), iii) soil with compost at a rate of 2% w/w (Compost), and iv) soil with a mixture of biochar and compost at a total rate of 2% w/w (BC-SS+Compost). The aim of the study was to examine whether sewage sludge biochar with or without compost affects: a) the dry weight and morphological characteristics of the plant, b) the concentrations of macronutrients, micronutrients and heavy metals in aboveground and belowground plant tissues, c) soil properties, including nutrients and heavy metals.

With biochar application a number of soil properties exhibited substantial improvement. Specifically, significant increases were noticed for TOC (67% - 85% increase), NO3–N (55% increase) and ΝΗ4–Ν (145% increase). Moreover, biochar with or without compost, substantially improved plant growth (25% – 34% increase in the first 40 days), and led to a significant increase of the dry weight of aboveground and belowground plant tissues. Heavy metal concentrations in plant tissues were quite low. Specifically, traces of Cr, Ni and Co were found only in plant roots, while Si was present in plant roots and stems. As, Mo and Pb were present in all plant tissues, albeit without exceeding the permissible levels established for vegetables. Finally, no traces of Hg, Se and Cd were found in any of the tissues.

Generally, sewage sludge biochar addition to soil, with or without compost, improved soil characteristics and increased plant yield. Moreover, heavy metal concentrations within permissible levels do not raise any concerns regarding safe consumption of tomato fruits.

 
Assessing the relationship between the TGF durations and the onset times of the TGFs and the main optical pulses as detected by ASIM
Authors: Skeie Chris Alexander , Østgaard Nikolai , Bjørge-Engeland Ingrid , Mezentsev Andrey , Neubert Torsten , Reglero Victor , Marisaldi Martino , Kochkin Pavlo , Lehtinen Nikolai , Sarria David , Maiorana Carolina , Lindanger Anders , Ullaland Kjetil , Genov Georgi , Heumesser Matthias , Christiansen Freddy , Chanrion Olivier
Published: March 2020

Using the Modular X- and Gamma-ray Sensor (MXGS) and the Modular Multi-spectral Imaging Array (MMIA) of the Atmosphere-Space Interactions Monitor (ASIM), we investigate the time sequence of the Terrestrial gamma-ray flashes and the optical emissions from the associated lighting. A common observation in the ASIM data is that the TGFs are observed before or during a weak increase in the optical signals in 337 nm and 777.4 nm, and prior to- or at the onset of the main optical pulse. Using data from the MXGS and MMIA instruments for the period from April 2019, we assess the time sequence and the relationship between the observed TGF duration and the time between the onset of the TGF and the onset of the main optical pulse, with a relative timeing uncertainty of +/- 5 µs. The data prior to April 2019 is presented in Bjørge-Engeland et al.
Towards Water Security in Central Asia: Evaluation of Experts’ Views through Delphi Approach
Authors: Assubayeva Aliya
Published: March 2020

Water security in Central Asia has been studied by researchers and international organizations using hydrological, engineering, and modeling approaches. Attention has been paid on assessments about water security and insecurity perceptions in Central Asia. Various assessments have perceived water securitization concept through technical, socio-economic, and environmental dimensions. This paper attempts to identify the current trends of water security and insecurity perceptions in Central Asian as evaluated through different experts from the region. The experts originate from a diverse professional background like ministries, NGOs, research, and academic institutes.  The analysis is conducted through the Delphi approach, which has been widely used for the identification of experts' views by also attempting to reach a consensus on various subjects. In this study, the Delphi method will help in the elicitation of experts’ opinions about different dimensions and attributes of water security that have been suggested from the relevant literature.  An online questionnaire will be designed where the participating experts will be initially asked to express their views towards different security components (1st questionnaire round). The questionnaire results will be circulated among the experts in two more sequential rounds to query about their consent with the outcomes while the anonymity of respondents will be ensured.
Evidence of active magmatic rifting in Ma’alalta marginal volcano (Afar, Ethiopia)
Authors: Tortelli Gianmaria , Gioncada Anna , Pagli Carolina , Rosi Mauro , Keir Derek , De Dosso Laura
Published: March 2020

Growth of rift segments and development of crustal magmatic systems in continental rifts remain debated issues. We integrate volcanological, geochemical, petrological and seismic data from the Ma’alalta stratovolcano near the western rift margin of Afar to show that active magmatic rifting occurs there. Growth of Ma’alalta started around 0.55 ± 0.05 Ma (Barberi et al. 1972) with the age of the youngest flows unknown. Ma’alalta produced lava flows but also large-volume, caldera-forming ignimbrites, as well as silicic intracaldera domes. The products are mainly trachytic and some are slightly peralkaline. The most recent magmatic activity of Ma’alalta consists of mafic lava fields, scoria cones and peralkaline obsidianaceous silicic domes produced along the ~40 km long magmatic segment and erupted from several vents aligned NNW-SSE rather than from central volcanic activity. Local seismicity (2005-2009 and 2011-2013) also shows a NNW-SSE-trending alignment of earthquakes with good correlation to where the recent magmatic products were erupted. The geochemical features of the mafic rocks (e.g., Ba/La, Rb/Ta and Zr/Ta) as well as the petrogenesis of the recent NNW-SSE-trending silicic domes are similar to the nearby on-rift Dabbahu and Durrie volcanoes. Inferred magma storage depth from mineral geobarometry show that a shallow, silicic chamber existed at ~4-5 km depth below the stratovolcano, while a stacked plumbing system with at least two magma storage levels at ~14 and ~24 km of depth fed the recent basalts. We interpret the wide set of observations from Ma’alalta as evidences that the area is an active rift segment, showing that localised axial extension can be heavily offset towards the rift margin.

 

 
Seismic sources at intermediate depth in the Alboran Sea
Authors: Buforn Elisa , Lozano Lucía , Cesca Simone , Cantavella Juan Vicente , Mattesini Maurizio , Udias Agustín
Published: March 2020

The occurrence of moderate magnitude earthquakes in intermediate depth (40<h<150 km) is a characteristic of the seismicity of the Ibero-Magrebian region. The most important concentration of this activity is in the western part of the Alboran Sea, with the epicenters following an N-S direction. In order to improve the knowledge of the geometry of these seismogenic structures, we have carried out a study of the hypocenters distribution and focal mechanisms for earthquakes that occurred in the period 2000-2020 (M>4.0). For the hypocentral location, we have used a non-linear probabilistic approach (NonLinLoc algorithm) jointly with 3-D lithospheric velocity tomography models recently developed for the Alboran-Betic-Rif zone. Focal mechanisms have been obtained from moment tensor inversion of stations at regional distances (Kiwi tools). Maximum likelihood hypocentres confirm a near vertical N-S distribution in a depth range between 50 and 100 km. Focal mechanisms show a different stress pattern, changing from a vertical tension axis for earthquakes located off-shore and western of 4.5ºW to vertical pressure axis for earthquakes inland and at eastern of 4.5ºW.
Rapid assessment of floating macroplastic transport in the Rhine
Authors: Vriend Paul , van Emmerik Tim , van Calcar Caroline , Kooi Merel , Landman Harm , Pikaar Remco
Published: March 2020

Most marine litter pollution is assumed to originate from land-based sources, entering the marine environment through rivers. To better understand and quantify the risk that plastic pollution poses on aquatic ecosystems, and to develop effective prevention and mitigation methods, a better understanding of riverine plastic transport is needed. To achieve this, quantification of riverine plastic transport is crucial. Here, we demonstrate how established methods can be combined to provide a rapid and cost-effective characterization and quantification of floating macroplastic transport in the River Rhine We combine visual observations with passive sampling to arrive at a first-order estimate of macroplastic transport, both in number (10 - 75 items per hour) and mass per unit of time (1.3 – 9.7 kg per day). Additionally, our assessment gives insight in the most abundant macroplastic polymer types the downstream reach of the River Rhine. Furthermore, we explore the spatial and temporal variation of plastic transport within the river, and discuss the benefits and drawbacks of current sampling methods. Finally, we present an outlook for future monitoring of major rivers, including several suggestions on how to expand the rapid assessment presented in this paper.
Modular AWI-CM: An Earth System Model (ESM) prototype using the esm-interface library for a modular ESM coupling approach
Authors: Wieters Nadine , Barbi Dirk , Cristini Luisa
Published: March 2020

Earth System Models (ESMs) are composed of different components, including submodels as well as whole domain models. Within such an ESM, these model components need to exchange information to account for the interactions between the different compartments. This exchange of data is the purpose of a “model coupler”.

Within the Advanced Earth System Modelling Capacity (ESM) project, a goal is to develop a modular framework that allows for a flexible ESM configuration. One approach is to implement purpose build model couplers in a more modular way.

For this purpose, we developed the esm-interface library, in consideration of the following objectives: (i) To obtain a more modular ESM, that allows model components and model couplers to be exchangeable; and (ii) to account for a more flexible coupling configuration of an ESM setup.

As a first application of the esm-interface library, we implemented it into the AWI Climate Model (AWI-CM) [Sidorenko et al., 2015] as an interface between the model components and the model coupler (OASIS3-MCT; Valcke [2013]). In a second step, we extended the esm-interface library for a second coupler (YAC; Hanke et al. [2016]).

In this presentation, we will discuss the general idea of the esm-interface library, it’s implementation in an ESM setup and show first results from the first modular prototype of AWI-CM.
Thermal convection of air in a two-layers snow cover of immobile sea ice
Authors: Bogorodskii Petr , Kustov Vasilii , Laurila Tuomas
Published: March 2020

Sea ice, as a rule, is covered with a heat-insulating snow cover, consisting of an ice skeleton and air-saturated pores. However, the temperature difference between the sea and the atmosphere during the cold season provides favorable conditions for macroscopic air movement, which significantly reduces the thermal resistance of snow and, thereby, affects the thermal and dynamic interaction of the atmosphere with the upper layers of the sea.

Actual snow cover accumulating on the surface of sea ice has significant heterogeneity and anisotropy of geometric and thermophysical characteristics conditioned by snow density stratification. Our work is aimed to studying the occurrence of convective instability in a system of two porous layers with permeable common boundary for boundary conditions taking into account the oceanographic aspect of the problem. The analytical solution of the problem in the Darcy-Boussinesq approximation is obtained by the Galerkin method, by selecting approximations of the vertical amplitudes of dimensionless temperature and velocity perturbations that satisfy the boundary conditions of the problem. A qualitative originality of the problem is revealed in comparison with a similar problem for a homogeneous porous layer. It is shown that the stability criteria (critical filtering Rayleigh numbers) due to the difference in the thermophysical and structural properties (coefficients of thermal conductivity, porosity and air permeability) of the layers can significantly differ from each other. According to detailed measurements of the thermal structure and metric characteristics of the fixed snow-ice cover in Amba Bay (Shokalsky Strait, Severnaya Zemlya Archipelago) during Winter 2015-2016, as well as calculations of its thermodynamic evolution, the values and temporal variability of the Rayleigh numbers are estimated. By comparing the observational and modeling data, the reality of the existence of a convective heat transfer regime in the snow cover is revealed. It is concluded that it is necessary to take into account its contribution to the thermal and mass balance of sea ice during winter period.
A continuum between structurally controlled Cu-Au and Au-only systems in northern Sweden
Authors: Bauer Tobias
Published: March 2020

Northern Sweden is dominated by supracrustal and related intrusive rocks formed and deformed during the Svecofennian orogeny (1.90-1.78 Ga). The orogeny comprises several phases of crustal extension and shortening, resulting from subduction and repeated arc-accretion events. An early-Svecofennian extensional phase (c. 1.90-1.88) Ga results in the formation of iron oxide-apatite deposits (IOA, e.g. Kiruna and Malmberget) in the back-arc region and volcanogenic massive sulfide deposits (VMS, e.g. Kristineberg) in the arc. These deposits have been subjected to deformation and regional metamorphism resulting in transposition and re-mobilisation of ore bodies. The latest phase of the Svecofennian orogeny (1.80-1.78 Ga) is characterized by a distinct E-W-directed crustal shortening at high crustal levels representing the last continental assembly resulting from late arc-accretion and followed by a post-orogenic collapse. This leads to folding of early metamorphic fabrics and mainly brittle to brittle-ductile shear zone re-activation. A general N-S gradient from deeper-crustal conditions in Northern Norrbotten (north) to higher-crustal conditions in Västerbotten (south) is observable. The emplacement of syn-tectonic, felsic and mafic intrusive bodies causes high temperature conditions while pressures remain low. Such conditions are favorable for driving fluids and leading to the formation of structurally controlled, Au-bearing deposits in 3rd and 4th order structures of large, crustal-scale, re-activated shear zone complexes. Deposits in Northern Norrbotten that are related to this late-Svecofennian phase show both ductile and brittle features and host Cu and Au, hence often assigned to the IOCG group of deposits. Deposits that formed during the same phase in Västerbotten are typically characterized by Au-bearing quartz veins that formed as lower-order structures, hence often classified as orogenic Au-deposits. Weather these deposits are entirely newly formed or just represent various grades of re-mobilization of older mineralization remains an open question. Looking at these deposits on a crustal-scale, they represent structurally-controlled deposits, hosted by lower-order structures in re-activated shear zone complexes whereas differences in mineralogy and hydrothermal alteration assemblages are an effect of different crustal levels during formation and differences in host rock compositions.
Lateral crustal flow along discrete flat-lying lower crustal shear zones during Archean continent construction
Authors: Hill Graham , Roots Eric , Frieman Ben , Craven Jim , Smith Richard , Haugaard Ras , Cheraghi Saeid , Adetunji Ademola
Published: March 2020

The nature of lithospheric evolution and style of the driving ‘tectonic’ processes occurring during Archean continent construction remain enigmatic. A significantly hotter thermal regime characterised the early Earth and was pervasive for much of the Archean. This resulted in construction of continents that were significantly weaker and unable to support the thick crustal sequences and topographies common to modern orogens. Gravitational collapse of these early continents may have occurred when deeper material became less dense by heating or partial melting and created a density contrast beyond the crustal competence and/or due to post-orogenic relaxation. Such a collapse could result in large scale horizontal spreading within the middle to lower crust and the development of lateral crustal flow along flat-lying shear zones producing fluid-deposited graphitic and metallic sulphide films at these depths, which, if preserved would produce broad scale quasi-horizontal mid-lower crustal low resistivity anomalies. Here we show 3D magnetotelluric resistivity models of the Archean Superior Province of Canada that reveal these types of anomalies that could represent lateral crustal flow in the middle to lower crust. Further, the magnetotelluric model shows narrow sub-vertical zones of low resistivity extending from the mid crust to the near surface, interpreted to represent remnant fluid pathways that potentially formed prior to gravitational collapse. These sub-vertical low resistivity features correlate spatially with crustal-scale deformation zones that potentially are host to hydrothermal ore deposits and abundant metasomatic mineral assemblages. The well preserved record of primary crustal amalgamation within the Superior Province of Canada with both features expected of autochthonous vertical ‘drip’ tectonics (sub-vertical fluid pathways) and allochthonous horizontal plate tectonics (flat-lying lower crustal shear zones) regimes, suggests a potential transitional period of tectonic evolution might have characterised the region during the late Archean.
The relevance of preferential flow in catchment scale simulations
Authors: Hopp Luisa , Glaser Barbara , Klaus Julian , Schramm Thilo
Published: March 2020

Despite experimental evidence preferential flow is rarely included in hydrologic catchment scale models. This is, at least partly, due to the challenge of deriving preferential flow parameters. Here, we successfully used the optimization algorithm DREAM to calibrate a 3D physics-based dual-permeability model directly at the catchment scale. We limited the number of parameters to be calibrated to the ones being most influential for the simulation of discharge, and we also calibrated parameters of the matrix domain and the macropore domain with a fixed parameter ratio between soil layers. During calibration, saturated hydraulic conductivities of the macropore domain and of the matrix domain converged to very similar values. The dual-permeability parameter sets also did not outperform a calibrated single-domain reference model scenario. We conclude that the incorporation of vertical preferential flow as represented by the dual-permeability approach was not advantageous for reproducing the hydrometric response reasonably well in the studied catchment.
Evidences of high diffusivity near a waste water injection well in the Val d’Agri oil field (Italy) from noise-based monitoring
Authors: Berbellini Andrea , Zaccarelli Lucia , Morelli Andrea , Faenza Licia , Garcia-Aristizabal Alexander , Improta Luigi , De Gori Pasquale
Published: March 2020

We monitor the relative variations of crustal velocity during a stop of water injection at the Val d’Agri oilfield (Italy) in January-February 2015 from the analysis of the ambient seismic noise cross-correlations. This technique allows the continuous estimations of the relative velocity variations occurred in the superficial layers of the Earth crust independently from the earthquake occurrence. Our results show a relative decrease in seismic velocity of about 0.08%, detected seven days after the injection restart of fluids injection and can be compatible with an increase of fluids in the medium. We estimate the medium diffusivity from this delay time obtaining a value of about 2.0 m2/s. Independently, we compute diffusivity from the observed delay time of small-magnitude (ML ≤ 1.8) seismicity induced by the first injection tests in June 2006, finding a similar value. The high diffusivity values found from the two independent analysis are compatible with the hydraulic properties of the hydrocarbon reservoir. Finally, we estimate the spatial distribution of the observed variations finding that the largest changes are located in the North-West direction, where the oilfield is elongated. Our results show that fluids propagate efficiently from the wellbore in the reservoir direction through a strongly fractured medium following efficient hydraulic pathways, and that the noise-based monitoring technique adequately map in time and space this perturbation.
Unified Scaling Law for Earthquakes: space-time dependent assessment in Kamchatka region
Authors: Nekrasova Anastasia , Kossobokov Vladimir
Published: March 2020

The observed variability of seismic dynamics of the Kamchatka Region is characterized in terms of several moving averages, including (i) seismic rate, (ii) the Benioff strain release, (iii) inter-event time, τ, and (iv) the USLE control parameter, η (where USLE stands for Unified Scaling Law for Earthquakes, i.e. a generalization of the Gutenberg-Richter relationship accounting for naturally fractal distribution of earthquake loci, which states that the distribution of inter-event times τ depends only on the value of variable η).

The variability of seismic dynamics have been evaluated and compared at each of four out of ten separate seismic focal zones of the Kamchatka region and the adjacent areas defined by Levina et al. (2013), i.e., (1) seismic focal zone of the Kuril and South Kamchatka, (2) the northern part of the Kamchatka seismic focal zone, (3) commander segment of the Aleutian arc; and (4) the continental region of Kamchatka. In particular, we considered all magnitude 3.5 or larger earthquakes in 1996-2019 available from open data catalog of the Kamchatka Branch of GS RAS, Earthquakes Catalogue for Kamchatka and the Commander Islands (1962–present) http://sdis.emsd.ru/info/earthquakes/catalogue.ph).
Assessing the role of colloidal phosphorus delivery processes in groundwater-fed agricultural catchments
Authors: Fresne Maelle , Jordan Phil , Daly Karen , Fenton Owen , Mellander Per-Erik
Published: March 2020

Soil colloids with high sorbing capacities can enhance transport of phosphorus (P) from soils to groundwater and the delivery of P to surface water via groundwater pathways. However, only particulate and dissolved P fractions are generally monitored at the catchment scale.

To add important insights into the particulate to dissolved P concentration spectrum in the soil-water environment, the role of colloidal P delivery processes to surface water was studied in two agricultural catchments. The catchments were dominated by belowground pathways but had contrasting land use (arable and grassland). Particulate, coarse colloidal (0.20 – 0.45 μm) and finer colloidal (< 0.20 μm) P fractions were monitored along hillslopes in the free soil solution, shallow groundwater and stream water on a weekly basis for background characterisation and at higher frequency during rainfall events. An automated sampler was deployed in the stream and an automated, low-flow and low-disturbance sampler was developed to sample groundwater. Multi-parameter probes were also deployed to monitor stream water and shallow groundwater physico-chemical parameters. Stream discharge was measured at high frequency using a flow velocimeter in order to quantify P loads, apportion hydrological pathways and study concentration-discharge hysteresis.

Preliminary findings showed higher background P and unreactive P concentrations in the stream and groundwater in the grassland catchment. In the arable catchment (rainfall event in June 2019) P was mainly lost through deeper baseflow (92% of the total event flow) as reactive P in the finer colloidal fraction (0.070 mg P/ha) and only a small fraction lost as particulate unreactive P (0.008 mg P/ha). In the grassland catchment (rainfall event in October 2019), P was mainly lost through quickflow (37% of the total flow) even tough deeper baseflow was also important (33%). Losses were mainly reactive P in the finer colloidal fraction (13.6 mg P/ha) but also as unreactive P (4.5 mg P/ha). Concentration-discharge hysteresis suggested a smaller and easily mobilised P source in the arable catchment and a larger P source, followed by the mobilisation of a second but smaller source via a second hydrological surface pathway in the grassland catchment.

Further monitoring campaigns during more rainfall events in the grassland catchment are required to better understand colloidal P delivery and the spatial/temporal dynamics between rainfall events in relation to soil conditions and rainfall patterns. This will help to better target mitigations measures according to P species and fractions, hydrological flowpaths, and rainfall patterns – important in the context of a changing climate.
Impacts of land cover changes and global warming on climate in Colombia using the regional climate model WRF
Authors: Manciu Astrid , Krause Andreas , Rammig Anja , Quesada Benjamin
Published: March 2020

Deforestation in Colombia has drastically increased in recent years. At the same time, droughts and floods are affecting the country more frequently due to climate change. Analyzing the impacts and interactions of deforestation and global warming is challenging due to the terrain’s complexity and the high climate variability along with the severe lack of regional climate modelling.

Here, we quantify the impact of historical anthropogenic global warming (CC) and land cover changes (LCC) on precipitation, temperature and the surface energy balance in Colombia by running the Weather Research and Forecasting model WRF v3.9.1.1. across different land cover and climate scenarios during the study period 2009-2011 for Colombia.

We find that precipitation is increased by CC with a stronger effect over forests. LCC implies a small reduction of precipitation which is strongly enhanced above deforested areas. LCC is found to be a strong driver of regional precipitation changes representing up to 25% and 60% of the CC effects magnitude in Coastal Caribbean and Andean regions, respectively. CC causes a temperature increase across the whole domain, in particular with increasing altitude. Surprisingly however, WRF simulates a slight cooling after deforestation which is not in line with almost all observations and modelling studies regarding biophysical effects of tropical deforestation. This apparent bias is further investigated across different WRF schemes and parameters because of its great importance for climate studies using WRF with default parametrization in tropical contexts.

 
Primary deformation phases during "magma-poor" rifting with special focus on the tectono-thermal evolution during the necking process
Authors: Chenin Pauline , Manatschal Gianreto , Schmalholz Stefan M. , Duretz Thibault
Published: March 2020

Although so-called "magma-poor" rifted margins display a large variability on a local scale, they are characterized by a number of common primary features worldwide such as their first-order architecture (proximal, necking, hyperextended, exhumation and oceanic domains), their lithological evolution along dip and the deformation processes associated with their different rifting stages. In this contribution, we first emphasize the primary morphological and lithological architecture of magma-poor rifted margins and how they relate to specific deformation modes (pure shear thinning, mechanical necking, frictional extensional wedge, detachment faulting and seafloor spreading). Second, we focus on the necking stage of rifting, which corresponds to the first major thinning event (when the crust is thinned from its initial thickness to ~ 10 km). We display the range of possible topographic and thermal evolutions of "magma-poor" and "sedimentary starved" rift systems depending on their lithosphere rheology. Our two-dimensional thermo-mechanical numerical models suggest that extension of lithospheres where the crust and the mantle are mechanically decoupled by a weak lower crust results in a complex morphotectonic evolution of rift systems, with formation of temporary restricted sub-basins framed by uplifted parts of the future distal margin. Mechanical decoupling between the crust and the mantle controls also largely the thermal evolution of rift systems during the necking phase since for equivalent extension rates and initial geotherms: (i) weak/decoupled lithospheres have a higher geothermal gradient at the end of the necking phase than strong/coupled lithospheres; and (ii) weak/decoupled lithospheres show intense heating of the lower crust at the rift center and intense cooling of the crust on either side of the rift center, unlike strong/coupled lithospheres. These behaviors contrast with the continuous subsidence and cooling predicted by the commonly used depth-uniform thinning model.
The role of a laterally varying density contrast for gravity inversion of the Moho depth
Authors: Haas Peter , Ebbing Joerg , Szwillus Wolfgang , Tabelow Philipp
Published: March 2020

We present a new inverse approach to invert satellite gravity gradients for the Moho depth under consideration of a laterally varying density contrast between crust and mantle. The inverse problem is linearized and solved with the classical Gauss-Newton algorithm in a spherical geometry. To ensure stable solutions, the Jacobian is smoothed with second-order Tikhonov regularization. During the inversion, the Moho depth is discretized into tesseroids by reference Moho depth and density contrast, from which the gravitational effect can be calculated. As a computational benefit, the Jacobian is calculated only once and afterwards weighted with the laterally varying density contrast. We look for a Moho depth model that simultaneously explains the gravity gradient field and a least misfit to existing seismic Moho depth determinations. We perform the inversion both on regional and global scale.

The laterally varying density contrast is based on different tectonic units, which are defined by independent global geological and geophysical data, such as regionalization of dispersion curves. This is beneficial in remote areas, where seismic investigations are very sparse and the crustal structure is to a large extent unknown. Applying the inversion to the Amazonian Craton and its surroundings shows a lower density contrast at the Moho depth for the continental interior compared to oceanic domains. This is in accordance with the tectono-thermal architecture of the lithosphere. The inverted values of the density vary between 300-450 kg/m3. The inverted Moho depth shows a clear separation between the Sao Francisco Craton and shallower Amazonian Craton.

Gravity inversion with a laterally varying density contrast requires a uniform reference Moho depth. On a global scale, we utilize our inversion to estimate a reference Moho depth that is in accordance with crustal buoyancy. The inverted density contrasts show a similar trend like the regional study area. The inverted Moho depth shows expected tectonic features. Our method of computing the Jacobian once and weighting with lateral variable density contrasts is a valuable optimization of standard gravity inversion.
The nature of the Albstadt Shear Zone, Germany
Authors: Mader Sarah , Reicherter Klaus , Ritter Joachim , Working Group the AlpArray
Published: March 2020

The region around the town of Albstadt, SW Germany, is one of the most seismically active regions in Central Europe. In the last century alone three earthquakes with a magnitude greater than five happened and caused major damage. The ruptures occur along the Albstadt Shear Zone (ASZ), an approx. 20-30 km long, N-S striking fault with left-lateral strike slip. As there is no evidence for surface rupture the nature of the Albstadt Shear Zone can only be studied by its seismicity.

To characterize the ASZ we continuously complement the earthquake catalog of the State Earthquake Service of Baden-Württemberg with additional seismic phase onsets. For the latter we use the station network of AlpArray as well as 5 additional, in 2018/2019 installed seismic stations from the KArlsruhe BroadBand Array. We inverted for a new minimum 1D seismic velocity model of the study region. We use this seismic velocity model to relocalize the complemented catalog and to calculate focal mechanisms.

The majority of the seismicity happens between the towns Tübingen and Albstadt at around 9°E in a depth range of about 1.5 to 16 km and aligns north-south. Additionally, we see a clustering of events at the towns Hechingen and Albstadt. The dominating focal mechanism is strike-slip, but we also observe minor components of normal and reverse faulting.
Our results image the ASZ by its mainly micro-seismic activity between 2011 and 2018 confirming the N-S striking character, but also indicating a more complex fault system.

We thank the State Earthquake Service in Freiburg for using their data (Az. 4784//18_3303).

 
Robust Color Maps That Work for Most Audiences (Including the U.S. President)
Authors: Stauffer Reto , Zeileis Achim
Published: March 2020

Color is an integral element in many visualizations in (geo-)sciences, specifically in maps but also bar plots, scatter plots, or time series displays. Well-chosen colors can make graphics more appealing and, more importantly, help to clearly communicate the underlying information. Conversely, poorly-chosen colors can obscure information or confuse the readers. One example for the latter gained prominence in the controversy over Hurricane Dorian: Using an official weather forecast map, U.S. President Donald Trump repeatedly claimed that early forecasts showed a high probability of Alabama being hit. We demonstrate that a potentially confusing rainbow color map may have attributed to an overestimation of the risk (among other factors that stirred the discussion).

To avoid such problems, we introduce general strategies for selecting robust color maps that are intuitive for many audiences, including readers with color vision deficiencies. The construction of sequential, diverging, or qualitative palettes is based on on appropriate light-dark "luminance" contrasts while suitably controlling the "hue" and the colorfulness ("chroma"). The strategies are also easy to put into practice using computations based on the so-called Hue-Chroma-Luminance (HCL) color model, e.g., as provided in our "colorspace" software package (http://hclwizard.org), available for both the R and Python programming languages. In addition to the HCL-based color maps the package provides interactive apps for exploring and modifying palettes along with further tools for manipulation and customization, demonstration plots, and emulation of visual constraints.
Characterization of ERA5 daily precipitation using the extended generalized Pareto distribution
Authors: Rivoire Pauline , Martius Olivia , Naveau Philippe
Published: March 2020

Both mean and extreme precipitation are highly relevant and a probability distribution that models the entire precipitation distribution therefore provides important information. Very low and extremely high precipitation amounts have traditionally been modeled separately. Gamma distributions are often used to model low and moderate precipitation amounts and extreme value theory allows to model the upper tail of the distribution. However, difficulties arise when making a link between upper and lower tail. One solution is to define a threshold that separates the distribution into extreme and non-extreme values, but the assignment of such a threshold for many locations is not trivial. 

Here we apply the Extended Generalized Pareto Distribution (EGPD) used by Tencaliec & al. 2019. This method overcomes the problem of finding a threshold between upper and lower tails thanks to a transition function (G) that describes the transition between the empirical distribution of precipitation and a Pareto distribution. The transition cumulative distribution function G has to be constrained by the upper tail and lower tail behavior. G can be estimated using Bernstein polynomials.

EGPD is used here to characterize ERA-5 precipitation. ERA-5 is a new ECMWF climate re-analysis dataset that provides a numerical description of the recent climate by combining a numerical weather model with observations. The data set is global with a spatial resolution of 0.25° and currently covers the period from 1979 to present.

ERA-5 daily precipitation is compared to EOBS, a gridded dataset spatially interpolated from observations over Europe, and to CMORPH, a satellite-based global precipitation product. Simultaneous occurrence of extreme events is assessed with a hit rate. An intensity comparison is conducted with return levels confidence intervals and a Kullback Leibler divergence test, both derived from the EGPD.

Overall, extreme event occurrences between ERA5 and EOBS over Europe appear to agree. The presence of overlap between 95% confidence intervals on return levels highly depends on the season and the probability of occurrence.