bluuebunny/crossref_metadata_2025 huggingface dataset:
Multiscale 3D stress field modelling for the URL 'Reiche Zeche' using a discontinuum model approach
Authors: Rehde Sebastian , Konietzky Prof. Dr.-Ing. habil. Heinz
Published: March 2020

Underneath the small town of Freiberg, Saxony, stretches the ore mine complex 'Reiche Zeche'. The underground laboratory (URL) inside the mine was inaugurated in 1919 and is an internationally acknowledged institution for experimental work of variable scales and subjects. Our work is part of the Stimtec project, which aims on improving planning and conducting hydraulic stimulation in anisotropic, crystalline rocks. The project comprises numerical modelling and field work inside the URL. Prior to the numerical analysis, we implemented a tool to perform a slip tendency analysis of faults that were mapped along the tunnel walls at the project site. It allows to assess the slip tendency of arbitrarily oriented faults and stress fields. The tool is used for preselection of stimulation intervals, enabling identification of faults which are likely to be reactivated by hydraulic stimulation.
We perform the stress field modelling using a multiscale numerical model approach. Therefore, we set up three different sized models deriving from a large scale 3D geomodel. The geomodel contains the topography, drifts and 47 fault structures taken from mine maps. The project site and measurement points are positioned in the center of the model. From the large scale geomodel, we developed a simplified numerical model geometry with 12 major faults, disregarding the galleries. We use the distinct element code 3DEC for discontinuous numerical modelling of the stress field. This allows to take into account discrete displacements along the faults. Far field stress is taken from previous investigations and literature as boundary and initial conditions. The resulting stress  field provides the stress tensors for calculating the corresponding forces for each gridpoint at the model boundaries of the small scale model. The small scale numerical model is smaller by a factor of 10, including two major fault segments, the galleries and mapped local faults. Hydraulic fracturing stress measurements taken during the field tests indicate that the stress field is strongly distorted in the vicinity of the tunnels and excavations along the ore veins. Hence, we developed a third model approach, a 2.5D slice model, to investigate the influence of the assumed excavation damage zones.
With this work, we provide an approach to predict the stress field inside the complex, anisotropic rock volume. Within the framework of the Stimtec project, we developed a workflow for planning hydraulic stimulation tests and 3D geological models for a diverse set of further appliations in the URL 'Reiche Zeche'.
Global patterns of vertical distribution of soil microbial biomass carbon
Authors: Feng Wenting , Sun Tingting , Wang Yugang , Jing Xin
Published: March 2020

Small changes in soil organic carbon (SOC) may have great influences on the climate-carbon cycling feedback. However, there are large uncertainties in predicting the dynamics of SOC in soil profile at the global scale, especially the role of soil microbial biomass in regulating the vertical distribution of SOC. Here, we developed a global database of soil microbial biomass carbon (SMBC), soil microbial quotient (SMQ, the ratio of SMBC to SOC), and SOC from 312 soil profiles, as well as climate, ecosystem type, and edaphic factors associated with these soil profiles. We assessed the global pattern of vertical distributions of SMBC and SMQ and the contributions of climate, ecosystem type, and edaphic factors to their vertical patterns. Our results showed that SMBC and SMQ decreased exponentially with depth, especially in the top 0-40 cm soil. SOC also decreased exponentially with depth but in different magnitudes compared to SMBC and SMQ. Edaphic factors (e.g., soil clay content and C/N ratio) were the most important controls for the vertical distributions of SMBC and SMQ, probably by mediating the preservation of substrates and nutrient supply for microbial growth in soils. Mean annual temperature and ecosystem types (i.e. forests, grasslands, and croplands) exerted weak influences on SMBC and SMQ. Overall, our data synthesis provides quantitative information of how SMBC, SMQ, and SOC changed along soil profiles globally and identifies important factors that influence their vertical distributions. The findings can help improve the prediction of C cycling in the terrestrial ecosystem by integrating the contributions of soil microbial roles in Earth system carbon models.
Spatial and temporal variability of snow avalanche impact pressure and its importance for structural design
Authors: Sovilla Betty , Kyburz Michael , Ligneau Camille , Fischer Jan-Thomas , Schaer Mark
Published: March 2020

Measurements of snow avalanche impact pressures are performed at the Vallée de la Sionne test site since winter 1999. In these years of operation, we recorded the impact pressure of around 60 avalanches characterized by different flow regimes and dimensions.

Pressure measurements were performed, simultaneously, on three different structures which are spatially distributed with a maximum distance of 30 m, in the run-out zone of the Vallée de la Sionne test site. The structure widths range from 0.25 to 1 m. On these structures pressure sensors ranging from small cells with 0.10 to 0.25 m in diameter to large pressure plates with area of 1m2 are mounted at different heights.

A systematic analysis of all 60 avalanche data sets shows that the pressure measured at the different obstacles varies considerably, even within the same avalanche, both in space and time. Part of these differences can be attributed to different drag coefficients and dependence on obstacle size, but a large part of these differences can only be explained by the spatial variability of the flow properties and the temporal variability of the physical processes governing the interaction of the avalanche and the structures.

In this contribution we show how spatial and temporal impact pressure variabilities correlate to avalanche dimension and flow regimes and we discuss the implication of such variations for structural design and hazard mapping.
Influence of Pacific Decadal Oscillation on global precipitation extremes on decadal time scales
Authors: Wei Wenguang , Yan Zhongwei , Li Zhen
Published: March 2020

On the decadal time scales, while the influence of Pacific Decadal Oscillation (PDO) on total or average precipitation had been extensively studied, works about its influence on precipitation extremes were limited, especially lack of a global picture.  Using two independent methods, nonstationary generalized extreme value (GEV) model which directly incorporates PDO index into its location parameter and moving GEV model which fits the annual extremes with a sliding window of 30 years and regresses the resulted changing location parameter onto the PDO index, we show that precipitation extremes over a large portion of stations are significantly affected by the PDO with stations in the Pacific Rim demonstrating distinct regional patterns. Over eastern China, the famous ‘southern flood and norther drought’ pattern corresponding to a positive PDO phase extends to extreme rainfalls; over Australia, a tri-polar pattern was revealed, in which the extremes over central Australia positively correlate with the PDO index and those over eastern and western Australia show a negative correlation; and the North America also demonstrates a dipole pattern, by which the northwest (southeast) experiences less (more) intense extreme rainfall in a PDO positive phase. Moreover, the western Europe and the large area between the Ural mountain and eastern Europe were discovered to hold a positive correlation with the PDO in their precipitation extremes. A comparative analysis to the local circulation controlling the precipitation extremes under different PDO phases further confirms the discovered relationships above. These findings have important implication for the future projection of extreme precipitation over related regions because the internal climate variability should be appropriately accounted for beyond the effects induced by global warming.
The soil factor of geodiversity â€“ perspectives on erodibility classification in the Soutpansberg, South Africa
Authors: Kori Edmore
Published: March 2020

Soil diversity is one of the factors considered in geodiversity assessment. Its classification is usually based on expert knowledge of soils. One way of expert classification is through soil erodibility. High erodibility is allocated a high diversity class. Notwithstanding the debate on erodibility computation, soil classification for geodiversity based on erodibility is not a straightforward matter. Empirical evidence from the Soutpansberg range in South Africa reveals that high erodibility does not directly translate to a higher geodiversity. Though other factors may also play a role, river networks and slope angles are directly influenced by soil erodibility. Rivers follow easily erodible terrain while highly erodible soils create plains. Soils with high clay content tend to promote surface runoff. The cementing effect of clay promote strong substrates that can support a bigger angle of repose. Slopes and river channels in the Soutpansberg do not readily conform with this general anticipation. Rivers do not always coincide with high soil erodibility. Steep slopes do not always coincide with low soil erodibility. Neither do they always coincide with low soil erodibility. This leads to the conclusion that the contribution of erodibility to landform development and diversity is contextual rather than generic. Other factors such as aggradation and degradation may have to be considered in soil factor classification.

 

Key words: soil erosion; geodiversity; erodibility; hydrology; slope.
Impact of Atlantic water variability on sea ice changes in the Fram Strait and north of Svalbard
Authors: Grynczel Agata , Beszczynska-Moeller Agnieszka , Walczowski Waldemar
Published: March 2020

Recent satellite passive microwave observations indicate significant negative Arctic sea ice extent trends in all months and substantial reduction of winter sea ice in the Atlantic sector. Warm and salty oceanic water masses from the North Atlantic flow towards the Arctic Ocean along the eastern Fram Strait, carried by the West Spitsbergen Current (WSC). Fram Strait, as well as the region north of Svalbard, play a key role in controlling the amount of oceanic heat supplied to the Arctic Ocean and are the place of dynamic interaction between the ocean and sea ice. The north of Svalbard area is one of the regions where the substantial changes in sea ice concentrations are observed both in summer and in winter. One of the possible reasons can be sought in the observed warming of Atlantic water, carried through Fram Strait into the Arctic Ocean. The main goal of this work is to analyse and explain the sea ice variability along main pathways of the Atlantic origin water (AW) in the context of observed warming of Atlantic water layer. Shrinking sea ice cover in the southern part of Nansen Basin (north of Svalbard) and shifting the ice edge in Fram Strait are driven by the interplay between increased advection of oceanic heat in the Atlantic origin water and changes in the local atmospheric conditions that result in the increased ocean-air-sea ice exchange in winter seasons. The basis for this hypothesis is warming of winter mean surface air temperature observed north of Svalbard and withdrawal of the sea ice cover towards the northeast, along with the pathways of water inflow in the Atlantic sector of the Arctic Ocean. Hydrographic data from vertical CTD profiles were collected during annual summer expeditions of the research vessel "Oceania", conducted in Fram Strait and the southern part of the Nansen Basin over the past two decades. The measurement strategy of the original research program AREX, which consists of the performance of cross-sections perpendicular to the presumed direction of the West Spitsbergen Current, allowed to observe changes in the properties and transport of the Atlantic Water carried to the Arctic Ocean. The analysis of past and present changes in the sea ice cover in relation to Atlantic water variability and atmospheric forcing employs hydrographic data from the repeated CTD sections, systematically collected since 1996 during annual summer Arctic long-term monitoring program AREX, satellite products of sea ice concentration and drift, and selected reanalysis data sets.
Failure and dynamic process of Luhu landslide inferred from the geologic investigation, numerical modeling and seismic signals
Authors: Yang Che-Ming , Chao Wei-An , Liao Jyh-Jong , Pan Yii-Wen
Published: March 2020

Luhu landslide occurred at April 13 2018 and locates in Luhu village, Miaoli county, Taiwan during intermittent rainfall. A sequence of rockfall events has been documented also by the local government in early April. Frequent rockfalls and gully erosion possibly resulted failure of a deep-seated landslide (DSL). The estimated maximum thickness, collapsed area and volume of the landslide are about 60 m, 65,000 m2 and 2 million m3, respectively. The purpose of this study is to clarify the failure mechanism and dynamic process of Luhu landslide, which is practically critical case to understanding the susceptibility of deep-seated landslide without direct triggered factors (thereafter uses the term ‘non-triggered DSL’), including earthquake and intense rainfall. Study site is a steep anaclinal slope consisting of thick sandstone, interbedded of sandstone and shale. Multi-temporal ortho-images and digital elevation (surface) models from 1980 to 2019 are collected for geological investigation and geomorphological interpretation. The study area contains three sub-regions: the north, the northwest and the west slopes. The slope failure occurred repeatedly inside the north and the northwest slopes in the early stage. Gully erosion in the west slope progressed to a landslide in early April first and expanded to cover the DSL failure in the northwest slope eventually, blocking the Luchang River and forming a natural dam. In order to further investigating landslide dynamics, seismic records generated by landslide are collected from the broadband seismic network. A series of time-frequency analysis shows that the spectral power distributed in a wide frequency range. Low-frequency seismic signals, which are generated by the unloading/reloading cycle of landslide mass, would be helpful for force history inversion. We propose that the relative high-frequency (HF) signals contains the information about the small block particles interacting with the topographic barriers. The automatic scheme of HF signal detection was adopted to find out the activity of collision/impact of rock block, which can be an indicator of increasing instability. Aforementioned results combined with numerical simulations provide not only the better understanding of failure mechanism of Luhu landslide but also crucial for the identification of non-triggered DSLs and their hazard assessment.
Cost-Benefit Analysis of continuous cover forestry and buffer zones as Nature Based Solutions to preserve water quality level in Lake Puruvesi and in its sub-catchment area.
Authors: Juvonen Jaakko
Published: March 2020

Mitigation of the perceived risks of climate change is urgent issue in many fields. This research focuses on providing information to support decision making in mitigation of hydro-meteorological risks that climate change causes to the water quality in Lake Puruvesi and in its sub-catchment area. This study reviews continuous cover forestry (CCF) and buffer zones as possible nature-based solutions (NBS) that could achieve the goal of keeping the water quality level in study site on current level or improve it. The main research question of this research is: Is it economically cost-efficient to implement continuous cover forestry and buffer zones as nature-based solutions to mitigate nutrient loading in research area so that the water quality will stay at least at the current level in the future?

Previous research has shown that CCF can be economically feasible way to manage forests. In addition to this, continuous cover forestry and buffer zones can reduce nutrient loading from forests to nearby waters. These solutions are evaluated in the framework of cost-benefit analysis which is the main method in this study. The aim is to monetize costs and benefits that NBS implementation will cause. If the net social benefits after analysis are positive, the project should be recommended. In this study recreation values from the study site were obtained by utilizing pre-existing valuation studies made by Finnish Natural Resource Center. Costs on the other hand were derived by using size-structured forest optimization model. The economic loss for forest owners is the difference between their optimal forest management choice, and the optimized solution, where clearcutting is restricted. In the buffer zone case optimization was similar but the costs from buffer zones are directly the maximized profits from forest as the buffer zone is completely left out from any forestry.

In both cases CCF was the optimal forest management regime for the sample forests. When these costs were compared to the benefits this study produced positive net social benefits and hence CCF and buffer zones should be recommended as NBS in the study site. However, there are quite large assumptions made in this study, and further modeling of nutrient flow in study site is required as the quantified impacts of nutrient run-off are still unclear. For this reason, further research is required for more precise analysis regarding quantified impacts.
Operational hydrology in highly steep areas: evaluation of tin-based toolchain
Authors: Silantyeva Olga , Burkhart John F. , Bhattarai Bikas C. , Skavhaug Ola , Helset Sigbjørn
Published: March 2020

Triangular Irregular Network (TIN) is known to be an efficient way to represent surface topography (Marsh et al. 2018). However, little attention has been given to assess direct benefits of the TIN-based terrain representation in operational hydrology. We connect Shyft-hydrology, a part of Shyft open-source project dedicated to distributed hydrologic modelling in operational environments, with Rasputin software intended for conversion of digital elevation models into simplified triangular meshes. Shyft is known for its high flexibility: the framework lets researcher test different functioning hypothesis with very little programming effort. We implemented new routine in Shyft-hydrology, which allows translation of solar radiation onto inclined surfaces based on (Allen et al. 2006). Thus, Shyft and Rasputin is a unique toolchain to study impact of hillslope variations in solar radiation onto snowmelt, evapotranspiration and discharge simulation.

We conducted several experiments on subcatchments of Narayani river located in Central Nepal. This area is known to be very steep, with meteorological stations, located mainly in the low-land. The re-analysis data for the area is coarse and prone to different kind of issues (Bhattarai et al 2020). The outcomes are promising: tin-based solution outperfoms regular grid, when running with Shyft-hydrology model most used in the operations. The new model with translated radiation also works well, giving us no decrease in performance of discharge simulations, but some more insights in snow modelling. We clearly see, what we expect from observations: sunny slopes melt earlier while shady ones keep snow for longer periods.

Acknowledgments. This project contributes to LATICE (Land Atmosphere Interaction in Cold Environments) initiative at the University of Oslo.

References

Marsh, C. B., Spiteri, R. J., Pomeroy, J. W., and Wheater, H. S.: Multi-objective unstructured triangular mesh generation for use in hydro- logical and land surface models, Computers and Geo- sciences, 119, 4967, 2018.

Richard G. Allen, Ricardo Trezza, and Masahiro Tasumi. Analytical integrated functions for daily solar radiation on slopes. Agricultural and Forest Meteorology, 139:5573, 2006.

Bhattarai, B. C., Burkhart, J. F., Tallaksen, L. M., Xu, C.-Y., and Matt, F. N.: Evaluation of forcing datasets for hydropower inflow simulation in Nepal, Accepted for publication. Hydrology research, 2020
Impact of Arctic amplification on declining spring dust events in East Asia
Authors: Wang Xin , Liu Jun
Published: March 2020

Dust aerosols play key roles in affecting the regional and global climate through their direct, indirect, and semi-direct effects. Dust events have decreased rapidly since the 1980s in East Asia, particularly over northern China, primarily because of changes in meteorological parameters (e.g. surface wind speed and precipitation). In this study, we found that winter (December– January–February) Arctic amplification associated with weakened temperature gradients along with decreased zonal winds is primarily responsible for the large decline in following spring (March–April–May) dust event occurrences over northern China since the mid-1980s. A dust index was developed for northern China by combining the daily frequency of three types of dust events (dust storm, blowing dust, and floating dust). Using the empirical orthogonal function (EOF) analysis, the first pattern of dust events was obtained for spring dust index anomalies, which accounts for 56.2% of the variability from 1961–2014. Moreover, the enhanced Arctic amplification and stronger Northern Hemisphere annular mode (NAM) in winter can result in the anticyclonic anomalies over Siberia and Mongolia, while cyclonic anomalies over East Europe in spring. These results are significantly correlated with the weakened temperature gradients, increased precipitation, and soil moisture, and decreased snow cover extent in the mid-latitude over Northern Hemisphere. Based on the future predictions obtained from the Fifth Climate Models Intercomparison Project (CMIP5), we found that the dust event occurrences may continually decrease over northern China due to the enhanced Arctic amplification in future climate.
Short-term SSEs in the Kanto region, central Japan using GNSS data for a quarter century
Authors: Nishimura Takuya
Published: March 2020

The Kanto region, central Japan situated in the complex tectonic region where two oceanic plates subducts from the Japan trench and Sagami trough. Although many previous studies clarified repeated Mw~6.6 Slow Slip Events (SSEs) with a duration of a week in an offshore region of the Boso Peninsula along the Sagami trough, the number of the detected SSEs are limited and overall activity of SSEs have not been fully understood in these regions. We, here, applied our SSE detection in these regions to the whole available GNSS dataset for a quarter century spanning from 1994 to 2019 and clarify the relation between SSE and tremor distribution.

We use daily coordinates at 291 GNSS stations using a precise point positioning strategy of the GIPSY 6.4 software. We apply the method of Nishimura et al. (2013) and Nishimura (2014) to detect a jump associated with short-term SSEs in GNSS time-series and estimate their fault models from observed displacements. A rectangular fault on the Philippine Sea or the Pacific plates is assumed for each SSE. The stacking of GNSS time-series based on the displacement predicted by the fault model [Miyaoka and Yokota, 2012] enable us to estimate duration of SSEs.

  We detected ≥ 150 possible SSEs along both the Japan trench and Sagami trough but we here focus on SSEs along the southernmost part of the Japan trench. Total slip distribution of the detected possible SSEs shows that large slip (≥ 0.3 m) is limited near the trench. A comparison with low-frequency tremors (LFTs) along the Japan trench (Nishikawa et al., 2019) suggests SSEs occur in the same depth range (10-20 km) of LFTs but their distribution is rather complimentary whereas a minor tremor activity exists at the edge of the SSE total slip. This complimentary distribution is contrast to overlapping distribution of SSEs and LFTs observed in a deep episodic and tremor region in the other subduction zones including southwest Japan. Another distinctive feature is that SSEs continuously occur from the trench to a depth of ~60 km only at ~ 35.5ºN. Because the subducted seamounts locate at this latitude, geometry of plate interface may control a genesis of SSEs in these regions.
An early Paleozoic silicic large igneous province in NE Gondwana: a preliminary synthesis
Authors: Dan Wei , Murphy J. Brendan , Tang Gong-Jian , Zhang Xiu-Zheng , Wang Qiang
Published: March 2020

Five major oceans (Iapetus, Rheic, Proto-Tethys, Paleo-Tethys and Paleo-Asian) formed during or after assembly of the Gondwana continent. However, the relationship between them is poorly understood, largely due to the complex and disputed evolution of NE Gondwana in the early Paleozoic. Here we present a summary of early Paleozoic tectono-thermal events in the NE Gondwana and discuss their tectonic settings. Early Paleozoic magmatic rocks are widely distributed in the Himalaya, Lhasa, Southern Qiangtang, Baoshan, Sibumasu and Tengchong terranes, and their ages were loosely constrained to be ca. 530-430 Ma. However, after a critical review of these dating results, we propose the magmatic rocks were mostly formed between ca. 500-460 Ma. Although bimodal, they are dominated by granitoid rocks distributed over an area of >2500 km × 900 km. Thus, they constitute a typical silicic large igneous province. Almost all granitoid rocks were derived from partial melting of sedimentary rocks, but a few show A-type characteristics. Coeval amphibolite-facies metamorphic rocks yield ages of 490-465 Ma. A sedimentary hiatus marked by either a disconformity or angular unconformity coeval with the major magmatic flare-up period is evident in all terranes. Thus, present evidence doesn’t favor either the conventional Andean-type subduction model, in which these magmatic rocks reflect subduction of Proto-Tethys oceanic lithosphere beneath the northern Gondwanan margin, or a post-collision setting, in which extension is associated with the collapse of the Pan-African orogeny in NE Gondwana. The tectonic setting for this magmatic province is tentatively related to a plume in a far-field subduction zone.
From risk assessment to adaptation pathways: improvement of Climate Risk Informed Decision Analysis for the Limari basin in Chile
Authors: Luger Christianne , Jeuken Ad , Verbist Koen , Pande Saket , Warren Andrew , Vivanco Christopher , Maureira Hector , Alvarez Pablo
Published: March 2020

The Climate Risk Informed Decision Analysis (CRIDA) framework incorporates the uncertainties of climate change that impact project planning, socioeconomic justification, and engineering design into a step-wise and collaborative planning process to guide a technical analyst to low-regret risk- and cost-effective solutions;
Research has been carried out to demonstrate and improve, through additional guidelines, the usability of CRIDA, in a pilot for the Limari basin in Chile. The added guidelines (1) offer the analyst numerically based justifications for analytical decisions to ensure a more structured application of CRIDA and (2) improves on co-design aspects by incorporating stakeholder risk perceptions and opinions explicitly in the process.
The Limari Basin has experienced an increase in drought frequency and severity over the last decades. A strategic approach for adaptation is recommended through CRIDA based on an evaluation of the future risk to climate change and the confidence in this analysis and a subsequent systematic assessments of adaptation options. The resulting strategy requires the increase of water supply robustness by adding new water sources that can be implemented in combination with flexible measures for managing demand (i.e. implementing agricultural meshes and improving irrigation efficiency) in parallel or in series to create adaptation pathways.
The study demonstrated the functionality of CRIDA. While the added guidelines required more processing time, subjectivity in the method is reduced thus also reducing possible bias introduced by the analyst. In addition, overall acceptability of the proposed strategies is improved by incorporating stakeholder risk perceptions and opinions explicitly in the process.
Multi-scale coastal surface temperature in the Bay of Biscay and the English Channel
Authors: Charria Guillaume , Theetten Sébastien , Ayouche Adam , Poppeschi Coline , Sudre Joël , Yahia Hussein , Garçon Véronique , Schmitt François
Published: March 2020

The Bay of Biscay and the English Channel, in the North-eastern Atlantic, are considered as a natural laboratory to explore the coastal dynamics at different spatial and temporal scales. In those regions, the coastal circulation is constrained by a complex topography (e.g. varying width of the continental shelf, canyons), river runoffs, strong tides and a seasonally contrasted wind-driven circulation.

 

Based on different numerical model experiments (from 400m to 4km spatial resolution, from 40 to 100 sigma vertical layers using 3D primitive equation ocean models), different features of the Bay of Biscay and English Channel circulation are assessed and explored. Both spatial (submesoscale and mesoscale) and temporal (from hourly to monthly) scales are considered. Modelled spatial scales, with a specific focus on the variability of fine scale features (e.g. fronts, filaments, eddies), are compared with remotely sensed observations (i.e. Sea Surface Temperature). Different methodologies as singularity and Lyapunov exponents allow describing fine scales features and are applied on both modelled and observed datasets. For temporal scales, in situ high frequency surface temperature measurements from coastal moorings (from COAST-HF observing network) provide a reference for the temporal variability to be modelled. Exploring differences in the temporal scales (from an Empirical Mode Decomposition) advises on the efficiency of our coastal modelling approach.

 

This result overview in the Bay of Biscay and the English Channel aims illustrating the input of coastal modelling activities in understanding multi-scale interactions (spatial and temporal).
Imaging of active faults from the temporal and spatial distributions of relocated seismicity induced beneath an EGS site in the Pohang region of southeastern Korea
Authors: Chiu Jer-Ming , Kim Kwanghee , Chiu Shu-Chioung , Kang Suyoung , Seo Wooseok , Han Jongwon
Published: March 2020

The 2017 Pohang earthquake (ML 5.4) is the second largest earthquake occurred in an intraplate in modern Korea and is considered the largest induced earthquake from an EGS system around the world.  The mainshock was proceeded by a few foreshocks and followed by a few thousands of aftershocks.  Numerous densely distributed seismic stations in local and regional distances were deployed to monitor this earthquake sequence.  Original hypocenters in the Pohang region were located using HYPODD that is independent on crustal structures.  A comprehensive crustal Vp and Vs model was recently available from an invited committee of foreign experts based on well logs and regional seismic data.  This model is then revised, especially the uppermost few hundred meters, based on results from a study of S to P converted waves from shallow interfaces beneath various stations, from the traditional Wadati plots analysis, and from the interpretation of two short seismic reflection/refraction profiles.  From continuous data, 5 to 10 folds of additional earthquakes than the original manually picked events can be identified and located. P and S arrival times from all earthquakes are re-picked from continuous data and are relocated using the revised model and Hypoellipse program.  Temporal and spatial distribution of relocated seismicity at depths range from 3 to 7 km are more clustered and confined than that from the original catalog.  A few thin vertical cross-sectional views of hypocenters parallel and perpendicular to the seismicity reveal that seismicity propagates along multiple NE-SW trending faults beneath the Pohang basin and extending NE offshore into East Sea.  These fault system is sandwiched between the Yongshan fault and a few other secondary faults to the south.  The main shock (5.4) and the two largest aftershocks (4.3 and 4.6) as well as their associated aftershocks show predominantly NE-SW strike-slip with reverse faulting propagating along three different adjacent faults.  Geometry of active faults and their tectonic implications will be presented and discussed in the meeting.
Soil organic carbon mapping from remote sensing: The effect of crop residues
Authors: Dvorakova Klara , Shi Pu , Quentin Limbourg , van Wesemael Bas
Published: March 2020

Since the onset of agriculture, soils have lost their organic carbon to such an extent that the soil functions of many croplands are threatened and there is therefore a strong demand for mapping and monitoring critical soil properties and in particular soil organic carbon (SOC). Pilot studies have demonstrated the potential for remote sensing techniques for SOC mapping in croplands, given their large spatial coverage and high temporal resolution. It has however been shown that the assessment of SOC may be hampered by crop residues. In this study we tested the effect of the threshold for the cellulose absorption index (CAI), on the performance of SOC prediction models for bare cropland soils. Airborne Prism Experiment (APEX) hyperspectral images covering an area of 230 km2 in the Belgian Loam Belt were used together with a local soil dataset. We used the partial least square regression (PLSR) model to estimate the SOC content based on 104 georeferenced calibration samples, firstly without setting a CAI threshold, and obtained a satisfactory result (R²=0.49, RPD=1.4 and RMSE=2.14 g kgC-1 for cross-validation). However, a cross comparison of the estimated SOC values to grid-based measurements of SOC content within three fields revealed a systematic overestimation for fields with high residue cover. We then tested different thresholds of CAI in order to mask pixels with high residue cover, by eliminating calibration samples used in the PLSR model based on this threshold. The best model was obtained for CAI threshold of 0.8 (R²=0.59, RPD=1.5 and RMSE=1.76 g kgC-1 for cross-validation). These results reveal that the purity of the pixels needs to be assessed aforehand in order to produce reliable SOC maps. Preliminary results indicate that an index based on the SWIR bands of the MSI Sentinel 2 sensor is also capable of detecting crop residues. However, the application under moist conditions and for different types of residues needs to be confirmed.
Consolidating Sea Level Acceleration Estimates from Altimetry for the 1991-2019 Period
Authors: Andersen Ole Baltazar , Veng Tadea
Published: March 2020

More than 28 years of high precision satellite altimetry enables analysis of recent global sea level changes. Several studies have determined the trend and acceleration of global mean sea level (GMSL). This is however done almost exclusively with data from the TOPEX/Poseidon, Jason-1, Jason-2 and Jason-3 satellites (TPJ data). In this study we extend the altimetry record in both time and space by including independent data from the ERS-1, ERS-2, Envisat and CryoSat-2 satellites (ESA data). This increases the time-series to span more than 28 years (1991.7-2020.0) and the spatial coverage is extended from ± 66⁰ to ± 82⁰ latitude. Another advantage of the ESA data is that it is independent of the Cal-1 mode issues which introduces a significant uncertainty to the first 6 years of data from the TOPEX altimeter. Resulting GMSL accelerations of 0.080 ± 0.008 mm/yr2 (TPJ) and 0.095 ± 0.009 mm/yr2 (ESA).The distribution of sea level acceleration across the global ocean are highly similar between the ESA and TPJ dataset. 

The Pinatubo eruption in 1991 and El-Nino Southern Ocean Oscillation will both affect GMSL. Particularly so as Pinatubo erupted right before the launch of the first ERS-1 satellite. The decrease in GMSL during the first years is seen in the ERS-1 data. We conclude that the effect of the Pinatubo as well as the ENSO effect on GMSL acceleration estimates are below the noise level with the extended time series.

 
Phytoremediation: Nature based solution for contaminated urban soils
Authors: Hrkic Ilic Zorana , Kapovic Solomun Marijana , Sumatic Nada
Published: March 2020

Abstract: Rapid growth of urban population and consequential increasing traffic, construction of buildings, roads, industrial areas, affects urban soils as well as urban environment in general. Urban soils differ from the natural soils by their disturbed structure resulting from waste disposal, construction sites, pollution from atmospheric deposition, traffic and industrial activities. Mismanagement of urban environment can cause severe contamination of green areas in cities, with serious health risk for urban population. To prevail those issues and improve the sustainability of urban green areas, innovative and nature based solutions (NBS) should gain more attention, particularly those easily applied such as tree-based phytoremediation. Unlike traditional remediation techniques that are expensive, very demanding and can cause secondary pollution, tree-based phytoremediation is NBS with wide spectrum of application. It is low-cost technique, based on urban green infrastructure (parks, alleys, community gardens) and has numerous benefits reflected throught sustainable management of urban soils and improvement of general environmental, health, social and economic conditions for urban population. Primarly, urban green infrastructure consist of different tree species capable to mitigate soil contamination, especially contamination with toxic heavy metals (HMs). Regeneration of urban ecosystems based on the role of tree species is connected to ability of trees to retain, uptake and decompose pollutants (including HMs) from contaminated urban soils, enabling their re-use process and turning them into green and environmental friendly areas. Taking into account advantages of phytoremediation technique, the aim of this paper is to present concentration of some HMs (cadmium, lead and zinc) in urban soils of cities accross Bosnia and Herzegovina and look into phytoremediation potential of common urban tree species: horse chestnut (Aesculus hippocastanum L.) and planetree (Platanus × acerifolia (Aiton) Willd.). Results showed high phytoremediation potential of above mentioned tree species, which opens space for further research and introduction of this NBS for remediation of many severely polluted urban soils, drawing attention to better-understood urban sustainability and importance of application of phytoremediation as NBS on local level.

Key words: nature-based solutions, phytoremediation, urban soil, trees, heavy metals
Solar Particle Radiation Storms Forecasting and Analysis - The HESPERIA tools
Authors: Malandraki Olga , Heber Bernd , Kuehl Patrick , Núñez Marlon , Posner Arik , Karavolos Michalis , Milas Nikos
Published: March 2020

Solar Energetic Particles (SEPs), ranging in energy from tens of keV to a few GeV, constitute an important con-tributor to the characterization of the space environment. SEP radiation storms may have durations from a period of hours to days or even weeks and have a large range of energy spectrum profiles. They pose a threat to mod-ern technology strongly relying on spacecraft and are a serious radiation hazard to humans in space, and are additionally of concern for avionics and commercial aviation in extreme cases. The High Energy Solar Particle Events forecasting and Analysis (HESPERIA) project, supported by the HORIZON 2020 programme of the Eu-ropean Union, has furthered our prediction capability of high-energy SEP events by developing new European capabilities for SEP forecasting and warning, while exploiting novel as well as already existing datasets. The HESPERIA UMASEP-500 tool makes real-time predictions of the occurrence of >500 MeV and Ground Level Enhancement (GLE) events from the analysis of soft X-ray flux and high-energy differential proton flux measured by the GOES satellite network. Regarding the prediction of GLE events for the period 2000-2016, this tool had a Probability of Detection (POD) of 53.8% and a False Alarm Ratio (FAR) of 30.0%. For this period, the tool obtained an Advanced Warning Time (AWT) of 8 min taking as reference the alert time from the first NMstation; using the time of the warning issued by the GLE Alert Plus tool for the aforementioned period as reference, the tool obtained an AWT of 15 min (Núñez et al. 2017). Based on the Relativistic Electron Alert System for Exploration (REleASE) forecasting scheme (Posner, 2007), the HESPERIA REleASE tools generate real-time predictions of the proton flux (30-50 MeV) at the Lagrangian point L1, making use of relativistic electrons (v>0.9c) and near-relativistic (v<0.8c) electron measurements provided by the SOHO/EPHIN and ACE/EPAM experiments, respectively. Analysis of historic data from 2009 to 2016 has shown the HESPERIA REleASE tools have a low FAR (∼30%) and a high POD (63%). Both HESPERIA tools are operational through the project’s website (http://www.hesperia.astro.noa.gr) at the National Observatory of Athens and presented in the recently published book on 'Solar Particle Radiation Storms Forecasting and Analysis, The HESPERIA HORIZON 2020 Project and Beyond', edited by Malandraki and Crosby, Springer, Astrophysics and Space Sciences Library, 2018, freely available at https://www.springer.com/de/book/9783319600505. The HESPERIA tools have been selected as a top priority internationally by NASA/CCMC to be included in the simulations of the manned-mission to Mars by Johnson Space Center (ISEP project). The National Observatory of Athens participates in the ISEP project with a relevant contract.
Fire history and the relationship with late Holocene mining activities in the NW Romanian Carpathians reconstructed from two peat core sequences
Authors: Petras Ancuta , Florescu Gabriela , Hutchinson Simon M. , Brun Cécile , Bal Marie-Claude , Saragaglia Vanessa Py , Mindrescu Marcel
Published: March 2020

Little is known about how areas of high ecological value and biodiversity hotpots will be impacted in the long-term by increasing anthropogenic pressure, added to future climate warming. One such example is the Romanian Carpathians, among the richest biogeographical regions in Europe in terms of biodiversity indicators and home to the largest unmanaged old-growth forests in Europe. This area is currently threatened by forest clearance and other anthropogenic land-use change, poor management practices and increased risk to wildfire. Peat bogs are among the most important palaeo-archives for the reconstruction of past environmental changes and disturbance regimes, with the potential to provide the longer-term perspective at a local to regional scale necessary for a sustainable management and restoration of these areas. Here we reconstruct late Holocene fire history and the relationship with anthropogenic disturbance, particularly mining, in a former mining area located in Lapus Mts, NW Romanian Carpathians, based on two peat sequences.

To reconstruct past fire activity, we used sedimentary macroscopic charcoal and also employed macro-charcoal morphologies to determine the type of material burnt (wood, grass, forbs). Past local soil/bedrock erosion and regional atmospheric pollution from historical mining were reconstructed on the basis of abiotic sediment properties such as elemental geochemistry, magnetic mineral characteristics, organic matter content and particle size. Our results show clear variations in macro-charcoal concentration, which coincide with changes in the geochemical, magnetic and grain-size indicators. Specifically, increases in macro-charcoal concentration, particularly the wood charcoal morphotype, were shortly followed in both cores by marked increases in heavy metal concentration and by enhanced soil and bedrock erosion, as inferred from geochemical, magnetic and grain-size proxies. This suggests increased local disturbance during intervals with mining activities and indicates the likelihood that humans used fire to clear the forests and open the access to the mining sites. Such actions likely resulted in topsoil removal and bedrock left exposed to environmental and climatic factors. Over the last centuries, the recovery of the local environment is evident in the proxies, with low fire activity and low soil/bedrock erosion, which coincides with the cessation of local mining activities. 

By showing both impact and recovery of the landscape, our study offers insight into the past evolution of this area and can be used to predict future possible responses of the local environment to anthropogenic stressors.   
Gully Erosion: A Threat to Livable Cities in Developing Countries
Authors: Olusola Adeyemi , Yakubu Samuel
Published: March 2020

The United Nations Centre for Human Settlement in 2007 estimated that out of about 6 billion people in the world, 3 billion (50%) live in urban cities. A projection of about 61% of the total world population will be living in urban cities by 2030. As these cities grow, certain aspects of the urban space are significantly affected due to this unavoidable growth especially in developing countries. Aspects such as demographic, environmental and economic are severely altered. This study employs a ‘mixed approach’ to explaining how gully erosion, is a threat to liveable settlements/cities in the 21st century. The first part of the study is a meta-research on gully erosion and how it affects human settlements in Nigeria, then a field study on gullies within Osogbo Metropolis, southwestern Nigeria, its morphology and distribution. The morphology (width and depth) of each of the identified gully was determined using standard instruments. Structures around the gullies were also identified spatially using a handheld GPS (Global Positioning System). Gully clusters were analysed using Moran I index. The identified gullies within Osogbo Metropolis at its deepest section are about 10metres, while the widest of the gullies is 2.5metres. On the average the measured gullies are about 0.7meteres wide and 1.7meteres deep. All the measured gullies are still undergoing downcutting and almost all of them are affecting one structure or the other within their catchment area. Given a z-score of -0.40 and -1.15 Moran I index I, the pattern does not appear to be significantly different than random. Hence, the occurrence of these gullies cannot be said to be associated with natural factors like lithology or soil properties. Out of the twelve major gullies identified, nine (9) were as a result of poor engineering, largely due to the on-going urban renewal process. Osogbo and elsewhere in Nigeria suffer from the havocs of gully erosion. Urban sprawl coupled with urban renewal processses in many parts Nigeira (particularly in the Third World) leads to the rapid development of large gully channels (urban gullies) endangering the bearing function of soils and causing damage to infrastructure and private property. The implication of the result is that, as good as the renewal process being carried out mostly in southwestern cities is a good one especially to achieve livable cities in the 21st century, there is the need for such planning to ensure that most engineering works adhere to best practices. The government at all levels in Nigeria and stakeholders in environmental management should ensure proper planning and make it a duty to create cities that are livable and healthy.