bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance Evaluation of Fire Risk Map from LSA-SAF over Mediterranean region in 2020
Authors: Alonso Catarina , Gouveia Célia
Published: March 2021

Forest fires have always been present in Mediterranean ecosystems; as such, they constitute a major ecological and socioeconomical issue. Despite being mostly of anthropogenic origin, the influence of the recent increase in temperature and evapotranspiration is associated with an increase in the frequency and severity of wildfires in the region. Large fires are promoted by the occurrence of high temperatures and episodes of drought that may lead to total burnt areas being several times larger than the average, such as the burnt areas in Portugal in 2003 and 2005, and Greece in 2007. The fire season of 2017 in Portugal has been catastrophic by most accounts. The authorities reported more than 100 human fatalities, with about 500.000ha of estimated burnt area, which corresponds to the maximum record since 1980. 

The Land Surface Analysis Satellite Applications Facility (LSA SAF) from EUMETSAT operationally disseminates a set of fire related products for the Mediterranean region. The Fire Radiative Power product (FRP-PIXEL) is delivered in near real-time since 2004 with a 15-min temporal resolution. In this work, daily Fire Radiative Energy (FRE) is computed for the Mediterranean region. The Fire Risk Map (FRM) product combines information from the operational forecasts from ECMWF and vegetation state from SEVIRI to derive forecasts of the risk of fire for the Mediterranean region. The FRM algorithm computes the daily values of the set of components of the Canadian Forest Fire Weather Index System (CFFWIS) for Mediterranean Europe, together with levels of fire danger associated with probabilities of occurrence of fires exceeding specified magnitudes. The FRM can be an important tool to support the management of forest fires and the decision making of prescribed burning within the framework of agricultural and forest management practices.

This work aims to assess the performance of the FRM product during 2020 over the Mediterranean region using FRE estimates. In particular, we aim to evaluate if the more severe and intense fires occurred in areas of high fire risk and high probability of occurrence of extreme fires, as obtained using FRM products. This analysis is made for different countries in the Mediterranean Basin, namely Portugal, Spain, Italy, and Greece. Results reveal a good performance of FRM over the Mediterranean region during 2020; however, better results were observed for the fire season in the Iberian Peninsula than for Italy.

Acknowledgements: This study was performed within the framework of the LSA-SAF, co-funded by EUMETSAT This work was partially supported by national funds through FCT (Fundação para a Ciência e a Tecnologia, Portugal) under projects FIRECAST (PCIF/GRF/0204/2017) and IMPECAF (PTDC/CTA-CLI/28902/2017).
The impact of facies heterogeneity on the seismic properties of carbonates: forward modeling and reservoirs potential
Authors: Tomassi Andrea , Trippetta Fabio , De Franco Roberto , Ruggieri Roberta
Published: March 2021

Forward modeling is a fundamental prospecting method to understand reservoirs structure and architecture in the subsurface. Moreover, it also helps maximizing the hydrocarbons extraction of petroleum systems. Carbonate reservoirs result in non-univocal seismic response caused by the facies heterogeneity and due to the possible presence of infilling fluids. The carbonate ramp outcropping in the Majella Massif (Central Italy) is an excellent surface analogue of buried structures. It offers the opportunity to directly analyze a carbonate reservoir which clearly shows facies variations and natural hydrocarbon-impregnations allowing to quantify the induced petrophysical changes. In this study field and laboratory measurements are used to carry out 1D and 2D forward seismic models of the reservoir. Density and porosity of samples were measured through a helium pycnometer on both hydrocarbon-saturated and not-saturated natural samples. Data show density from 2,35 g/cm3 to 2,64 g/cm3 and porosity from 5,9% to 21%. Seismic velocity data from previous works and ongoing measurements show values from 3,24 km/s to 5,93 km/s and they are clearly related to porosity. After building a seismic velocity, density and acoustic impedance model, a low-frequency (40Hz) synthetic 1D seismogram was carried out simulating facies (porosity) and hydrocarbon-saturation variations. The presence of hydrocarbon causes an increase in acoustics impedance by 16,2% and it increases the amplitudes by 13,6% at the reservoir boundaries. A 12 km long synthetic profile from the platform top to the basin, oriented SSE-NNW, was then carried out simulating the outcropping architecture and spatial distribution of the facies. The synthetic 2D model demonstrates how Vp variations related to facies association and distribution slightly influence seismic facies. Sensitivity tests show that Ricker wavelet with 25 Hz of central frequency is the frequency that produces best seismic images. Ongoing laboratory measurements and simulations are expected to help in validating facies interpretations of real seismic profiles and detect the presence of hydrocarbons in carbonate-ramp petroleum systems.
New Space Observation of the Global Cryosphere
Authors: Yu Zhitong , Hu Luojia , Huang Yan , Ma Rong , Xiao Peng , Yao Wei
Published: March 2021

Quantifying changes in Earth’s ice sheets and identifying the climate drivers are central to improving sea level projections. But it is a pity that the future sea level is difficult to predicted. Space observation can provide global multiscale long-term continuous monitoring data. And it is very important for understanding intrinsic mechanisms, improve models and projections and analyze the impacts on human civilization.

Several satellites are applied for Global Cryosphere Watch, including sea ice extent and concentration, ice sheet elevation, glacier area and velocity. Although there are many variable can be measured by satellite sensors. But several variables need to improve the observing capability and developing new methods. Such as snow depth on ice, ice sheets thickness, and permafrost parameters. China has established high-resolution earth observation system to realize stereopsis and dynamic monitoring of the lands, the oceans and the atmosphere.

Currently, Qian Xuesen Laboratory working together with Sun Yat-sen University, is trying to design a new space observation system to support Three Poles Environment and Climate Changes project. We are conceptualizing two series satellites including FluxSats and BingSats for carbon/water cycle and cryosphere observations, respectively. To clarify the mechanism of the cryosphere carbon release and carbon sink effects of the oceans and ecosystems. We are developing a new lidar system for detecting the concentration and wind speed, and then atmospheric boundary layer flux exchange can be estimated. To understand the rapid change of the sea ice, such as drift, fragmentation and freeze. We need a short revisit and wide swath system capabilities. InSAR technology gives the digitial elevation of the ice surface. And temporal difference InSAR (DInSAR) shows the changes of elevation. BingSAT-Tomographic Observation of Polar Ice Sheets (TOPIS) achieves the tomographic observation of polar ice sheets with a wide swath and short revisit time. Over the polar regions, the CubeSats form a large cross-track baseline with the master satellite to realize the high two-dimensional spatial resolution with the along-track synthetic aperture. The MirrorSAR technology is utilized in BingSat-TOPIS to achieve time and phase synchronization more economically than the traditional bistatic radar. Sparse array and digital beamforming are also considered to significantly reduce the number of microsatellites, and achieve tomographic images of polar ice sheets.
Centrifuge modelling of a non-symmetrically heated concrete energy pile group with raft
Authors: Ouzzine Badr , de Sauvage Jean , Ghandri Iheb , Viggiani Giulia , Madabhushi Gopal
Published: March 2021

The growing energy needs of urban areas and the current environmental context have led to the development of new energy technologies. Since the 1980s, energy geo-structures have been developed and applied, in which heat exchanger pipes are attached to the reinforcement cages of geotechnical structures such as pile foundations or diaphragm walls. By circulating a heat transfer fluid in these pipes, and using a heat pump, these low-enthalpy solutions make it possible to produce heating and cooling with significantly reduced CO2 emissions. However, the cyclic thermal loading generates stresses and strains in the geo-structure and in the surrounding soil, due to thermal expansion. Research on the behaviour of energy pile groups is rather limited, particularly for piled foundations in which only a few piles within a group are thermally activated. Indeed, the implementation of this type of energy technology is slow because of the many concerns about the impact of thermal cycles on the mechanical behaviour of the piles. The complexity of this problem is increased if a natural groundwater flow is present, as this has the potential to affect significantly heat transfer between piles in the group.

To tackle these questions, the stresses induced in pile groups by thermal activation were studied by geotechnical centrifuge modelling.  Two reduced scale models of 2*2 pile groups were examined, one in dry and one in saturated Hostun sand. In the tests, only one pile was subjected to cyclic thermal loading, but all the pile heads were connected to the same raft. The model piles were cast in cement and copper pipes were used to model simultaneously the reinforcement cages and the heat exchanger pipes. This modelling highlighted that, when heated, the energy pile goes into additional compression along with the diagonally opposite pile, due to the raft rotation. The other two thermally inactive piles showed a decrease of axial load. The saturation of the sand layer displayed a strong role not only on the transient response, but also on the thermal equilibrium due to additional thermal inertia.

In order to make relevant comparisons between the observations made on the reduced scale models and those made at prototype scale, scaling laws must be respected, so that the model and the full-scale structure undergo the same physical phenomena. Therefore, preliminary theoretical work was carried out to examine the various thermal phenomena involved. For each phenomenon of interest, the quantities that allow keeping dimensionless numbers identical or at least of the same order of magnitude are studied. Some phenomena were verified also numerically or experimentally. This work is presented in the form of a catalog of scaling laws derived for both mechanical and thermal behaviour of pile foundations.
Chromium, Nickel and Iron as clues to the formation histories of exoplanetary bodies
Authors: Buchan Andrew , Bonsor Amy , Shorttle Oliver , Wade Jon , Harrison John
Published: March 2021

We are now entering an era of rocky exoplanet detection. To determine whether an exoplanet is ‘Earth-like’, we must estimate not only its mass, radius and insolation, but also its geological composition. These geological constraints have wide ranging implications, not least for a planet’s subsequent evolution and habitability.

Polluted white dwarfs which have accreted fragments of planetary material provide a unique opportunity to probe exoplanetary interiors. We can also learn about their formation histories, including the geological process of core-mantle differentiation.

Cr, Ni and Fe behave differently during differentiation, depending on the conditions under which it occurs. This alters the Cr/Fe and Ni/Fe ratios in the core and mantle of differentiated bodies. The pressure inside the body is a key parameter, and depends on the body’s size.

In our work, we present a novel approach for modelling this behaviour and use it to gain crucial insight into the sizes of exoplanetary bodies which pollute white dwarfs.
Toward an improved characterisation of climate and environmental changes during warm periods of the past: First results from the MOPGA HOTCLIM project 
Authors: Legrain Etienne , Capron Emilie , Parrenin Frederic
Published: March 2021

The current and future anthropogenic-induced high-latitude warming will have global climatic implications due to polar ice mass loss, sea level rise and ocean circulation changes. However, uncertainty remains on future climate projections mainly due to an incomplete understanding of climate, cryosphere and carbon cycle feedback processes occurring at centennial to millennial- timescales. Progress can be achieved by exploring climate and environmental changes that occurred in the past. In the HOTCLIM project, we are studying past warm periods, also referred to as interglacials, which exhibit a polar warming comparable to that projected by 2100 due to specific combinations of orbital and CO2 forcing. Especially, we are investigating the link between the carbon cycle dynamics and climate changes. To do so, we are combining (i) new analyses on the air trapped in Antarctic deep ice cores to inform on past changes in Antarctic climate and atmospheric CO2 concentrations (ii) climate and environmental data synthesis looking into the lower latitudes using terrestrial and oceanic archives (sea surface temperature, hydrological cycles, ocean circulation) (iii) an evaluation of outputs from climate models using the new comparison of the paleoclimatic datasynthesis and models output. The HOTCLIM project will improve our understanding of the natural climate variability and the processes involved during past periods associated with temperature changes comparable to projected future warming, hence helping improve climate projections

Here, we present the first results from the HOTCLIM project which is a multi-archive synthesis focused on the warm interval occurring between 190 and 243 ka BP, also refered to as Marine Isotopic Stage 7 (MIS 7). This warm period is of special interest because it follows the fastest transition between a cold (glacial) and a hot (interglacial) period of the last 800 000 ka, with a polar warming of 10 degrees in less than 5ka. We have compiled more than 30 oceanic cores, 9 speleothems and 3 ice cores covering the MIS 7 period. To compare them, we are now building a common chronology to these records. The use of combined continental (ice cores, speleothems) and oceanic (sediment cores) archives located on the whole surface of the Earth will allows to characterize (i) the amplitude and the temporal structure of the surface warming across the globe (ii) the contrast between oceanic and continental warming.
High-Frequency Sea-Level Variations driven by Self-Attraction and Loading from Atmospheric Surface Pressure at the Continents
Authors: Dobslaw Henryk , Shihora Linus , Sulzbach Roman
Published: March 2021

Surface mass anomalies on Earth modify the external gravity field via both Newtonian attraction and elastic deformation of the underlying crust. Time-variable mass transport divergence leading to quickly changing surface mass distributions induces additional horizontal pressure gradients that feed back into the dynamics of the transport process. In view of the present-day accuracy of geodetic observations, this feedback is well known to be important for global ocean tide modelling (Ray, 1998). The same feedback, however, is also affecting the barotropic response of the global oceans to surface wind stress and atmospheric pressure loading. It is typically termed as "Self Attraction and Loading" and can be seen as one contribution to sea-level variability induced by "Gravity, Rotation, and Deformation (GRD)" as defined by Gregory et al. (2019).

In this presentation, we will specifically discuss the contribution to sea-level variability induced by surface pressure variations over the continents, which are by now often ignored in numerical ocean modelling. Induced ocean bottom pressure signals are specifically prominent at the shortest periods between hours and days, and frequently exceed 1 hPa in coastal regions. The signals are found to be relevant for the satellite gravimetry missions GRACE and GRACE-FO, and the process will be therefore included in the next release of the AOD1B non-tidal de-aliasing product.  
Geoinformation in support of sustainable soils’ management to strengthen resilience under the pressure of climate change
Authors: Lekka Christina , Petropoulos George P. , Triantakonstantis Dimitrios , Detsikas Spyros , Chalkias Christos
Published: March 2021

Abstract

The National Map of Saline – Alkaline Soils of Greece was recently developed within the initiative of the European Soil Partnership (ESP) of FAO. The technique combines between other MODIS satellite imagery, spatial interpolation methods and ground surveying to derive at 1 km spatial resolution maps of soil’s salinity (SS) and soil organic carbon (SOC).

The present study investigates for the first time the development of higher resolution maps of these soil properties adopting the aforementioned methodology. Furthermore, this study attempted to estimate the Carbon sequestration (SOC) using Remote Sensing and geostatistic methods of spatial analysis, a concern that is eminent today due to its effect on climate change mitigation.

As a case study the island of Mytilene in Greece is used, for which detailed information on soil properties as well as climatic, geomorphological, geological and soil data was available from previous studies. An MCDA (Multiple Criteria Decision Analysis) method was applied in a GIS environment using Landsat satellite imagery for the composition of a Saline - Alkaline map. Between the key soil parameters estimated spatially included the Electrical Conductivity (EC), Exchangeable Sodium Percentage (ESP) and pH. Geospatial data analysis methods were implemented to visualize all the derived parameters related for the study area and to analyze the final products in the spatial domain.

Finding suggests that climate change and soil directly affect one another. The impact of environmental and climate change in addition to unsustainable agricultural practices seems to be linked to salinity increase, soil erosion and loss of organic matter.  In addition, when land degradation as well as erosion and loss of vegetation occur, SOC emissions increase. Under these conditions, soil cannot absorb enough amounts of CO2, especially when soil salinization and sodicity exists; inputs are further limited due to declines in vegetation health. The role of geoinformation technologies in support of sustainable agricultural production under the pressure of both climate change and anthropogenic activities is also discussed within the present study framework.  

KEYWORDS: geoinformation, soil, pH, salinity, soil organic carbon, geostatistics, earth observation, GIS, Greece
Using Graph Neural Networks for 3-D Structural Geological Modelling
Authors: Hillier Michael , Wellmann Florian , Brodaric Boyan , de Kemp Eric , Schetselaar Ernst
Published: March 2021

A new approach for constrained 3-D structural geological modelling using Graph Neural Networks (GNN) has been developed that is driven by a learning through training paradigm. Graph neural networks are an emerging deep learning model for graph structured data which can produce vector embeddings of graph elements including nodes, edges, and graphs themselves, useful for various learning objectives. In this work our graphs represent unstructured volumetric meshes. Our developed GNN architecture can generate spatially interpolated implicit scalar fields and discrete geological unit predictions on graph nodes (e.g. mesh vertices) to construct 3-D structural models. Interpolations are constrained by scattered point data sampling geological units, interfaces, as well as linear and planar orientation measurements. Interpolation constraints are incorporated into the neural architecture using loss functions associated with each constraint type that measure the error between the network’s predictions and data observations. This presentation will describe key concepts involved within this approach including vector embeddings, spatial-based convolutions on graphs, and loss functions for structural geological features. In addition, several modelling results will be given that demonstrate the capabilities and potential of GNNs for representing geological structures.
Vertical crustal deformations and climate variability through PCA and SVD
Authors: Elia Letizia , Zerbini Susanna , Raicich Fabio
Published: March 2021

We investigated a large network of permanent GPS stations to identify and analyse common patterns in the series of the GPS height, environmental parameters, and climate indexes.

The study is confined to Europe, the Mediterranean, and the North-eastern Atlantic area, where 114 GPS stations were selected from the Nevada Geodetic Laboratory (NGL) archive. The GPS time series were selected on the basis of the completeness and the length of the series.

In addition to the GPS height, the parameters analysed in this study are the atmospheric surface pressure (SP), the terrestrial water storage (TWS), and a few climate indexes, such as MEI (Multivariate ENSO Index). The Principal Component Analysis (PCA) is the methodology adopted to extract the main patterns of space/time variability of the parameters.

Moreover, the coupled modes of space/time interannual variability between pairs of variables was investigated. The methodology adopted is the Singular Value Decomposition (SVD).

Over the study area, main modes of variability in the time series of the GPS height, SP and TWS were identified. For each parameter, the main modes of variability are the first four. In particular, the first mode explains about 30% of the variance for GPS height and TWS and about 46% for SP. The relevant spatial patterns are coherent over the entire study area in all three cases.

The SVD analysis of coupled parameters, namely H-AP and H-TWS, shows that most of the common variability is explained by the first 3 modes, which account for almost 80% and 45% of the covariance, respectively.

Finally, we investigated the relation between the GPS height and a few climate indexes. Significant correlations, up to 50%, were found between the MEI (Multivariate Enso Index) and about half of the stations in the network.
Extreme weather associated with atmospheric rivers over Morocco
Authors: Khouakhi Abdou , Driouech Fatima , Slater Louise , Waine Toby , Chafki Omar , Raji Otmane
Published: March 2021

Atmospheric rivers (ARs) are long, narrow, and transient corridors of enhanced water vapour content in the lower troposphere, often connected to the warm sector of extratropical cyclones and associated with strong low-level winds. These features play a major role in the global water cycle and drive weather extremes in many parts of the world. Here, we investigated the characteristics of landfilling ARs, including their frequency and magnitude over Morocco for the period 1979–2020. We used ECMWF ERA5 reanalysis data to detect and track landfilling ARs, and compared different gridded precipitation products (i.e. Integrated Multi-satellite Retrievals for GPM (IMERG), ERA5 Land, and CHIRPS) with a set of gauging stations datasets distributed across Morocco. We assessed AR association with rainfall at the annual and seasonal scales, as well as for extreme rainfall events, in different datasets. Preliminary results indicate that around 20 ARs/year make landfall or have their centroids within 200 km from Morocco. AR occurrence varies spatially and seasonally with highest occurrences in winter (DJF) across northern regions and spring (MAM) in the southern part of country. Rainfall events of up to 250 mm/year are driven by ARs; with the southernmost and driest regions receiving most of their rainfall from ARs. This paper will provide an overview of extreme rainfall and wind associated with ARs across Morocco.
Process-based flood risk assessment for Germany
Authors: Sairam Nivedita , Brill Fabio , Sieg Tobias , Kellermann Patric , Schröter Kai , Nguyen Viet Dung , Merz Bruno , Lüdtke Stefan , Farrag Mostafa , Vorogushyn Sergiy , Kreibich Heidi
Published: March 2021

Floods affect people worldwide and account for more than USD 100 billion losses on average every year. Hazard, Exposure and Vulnerability are the three components that influence flood risk. Flood Risk Management (FRM) decisions especially, with respect to new flood defense schemes and resilience initiatives are generally taken based on the assessment of impacts for hazard scenarios. Current large-scale studies are comprehensive in terms of sectors covered in impact assessment. However, these studies often deploy generalized data and methods on the model components resulting in coarse risk estimates with low spatial resolution.

In this study, we use process-based models with 100m resolution on the national scale within a systems approach to develop and simulate a 5000 year flood event catalogue for Germany. The events are then analyzed per economic sector, including residential, commercial and agriculture sectors. The risk chain includes continuous simulation of high-resolution hazard maps, obtained from coupled hydrology and hydraulic models; NUTS3-level exposure asset values further disaggregated to ATKIS land-use data and calibrated object-level vulnerability models that provide high-resolution quantification of economic damage. Spatial dependence of flood events is addressed by the continuous simulation approach. For each model component in the risk assessment (hazard, exposure and vulnerability), uncertainty in data and methods are integrated into the risk predictions. Based on these simulations, we present a sector-wise flood risk assessment for Germany along with the reliability of the risk estimates. This process-based, systemic flood risk assessment is valuable for policy making, adaptation planning and estimating insurance premiums.
Surface reflectivity in polar regions retrieved from TDS-1 mission data
Authors: Kreß Frederik , Semmling Maximilian , Cardellach Estel , Li Weiqiang , Hoque Mainul , Wickert Jens
Published: March 2021

In current times of a changing global climate, a special interest is focused on the
large-scale recording of sea ice. Among the existing remote sensing methods, bi-
statically reflected signals of Global Navigation Satellite Systems (GNSS) could
play an important role in fulfilling the task. Within this project, sensitivity of
GNSS signal reflections to sea ice properties like its occurrence, sea ice thick-
ness (SIT) and sea concentration (SIC) is evaluated. When getting older, sea
ice tends go get thicker. Because of decreasing salinity, i.e. less permittivity,
as well as relatively higher surface roughness of older ice, it can be assumed
that reflected signal strength decreases with increasing SIT. The reflection data
used were recorded in the years 2015 and 2016 by the TechDemoSat-1 (TDS-1)
satellite over the Arctic and Antarctic. It includes a down-looking antenna for
the reflected as well as an up-looking antenna dedicated to receive the direct sig-
nal. The raw data, provided by the manufacturer SSTL, were pre-processed by
IEEC/ICE-CSIC to derive georeferenced signal power values. The reflectivity
was estimated by comparing the power of the up- and down-looking links. The
project focuses on the signal link budget to apply necessary corrections. For this
reason, the receiver antenna gain as well as the Free-Space Path Loss (FSPL)
were calculated and applied for reflectivity correction. Differences of nadir and
zenith antenna FSPL and gain show influence of up to 6 dB and −9 dB to 9 dB
respectively on the recorded signal strength. All retrieved reflectivity values are
compared to model predictions based on Fresnel coefficients but also to avail-
able ancillary truth data of other remote sensing missions to identify possible
patterns: SIT relations are investigated using Level-2 data of the Soil Moisture
and Ocean Salinity (SMOS) satellite. The SIC comparison was done with an
AMSR-2 product. The results show sensitivity of the reflectivity value to both
SIT and SIC simultaneously, whereby the surface roughness is also likely to
have an influence. This on-going study aims at the consolidation of retrieval
algorithms for sea-ice observation. The resolution of different ice types and the
retrieval of SIT and SIC based on satellite data is a challenge for future work
in this respect.
Induced micro seismicity due to raising mine water level in former coal mines in the eastern Ruhr area (Germany)
Authors: Rische Martina , Fischer Kasper D. , Allgaier Felix , Friederich Wolfgang
Published: March 2021

FloodRisk is an interdisciplinary project focusing on the effects of mine water level rise in abandoned coal mine regions in Germany. Such effects are heterogeneous ground uplift, stress changes due to the change in pore pressure and the reactivation of potential faults. One of the most directly measurable effects is certainly the induced micro seismicity. It is known from previous studies that the flooding of old mines can lead to a renewed increase level in induced micro seismicity in these regions.
In this study  the relationship between mine water rise, fluid-induced stress changes and induced seismicity in the Haus Aden dewatering area in the eastern Ruhr area (Germany) will be investigated in more detail. 
For this purpose, we operate a network of currently 21 short period seismic stations in the region of the former "Bergwerk Ost" colliery, which had the highest seismicity rate in the Ruhr area during active underground coal mining. This network is still to be expanded to cover the entire water drainage area, about 30 Raspberry Shake sensors are waiting for the possibility of installation. 
Nevertheless, the existing network registered almost 1000 induced micro seismic events in a magnitude range from -0.7 up to 2.6 MLv. Many of these events are  spatially clustered and some show quite high waveform similarity. This allows relative localisation  and can increase the accuracy of the location. The depth location of the earthquakes, within the limits of localisation accuracy, agrees very well with the distribution of seismicity at the time of active mining. The spatial distribution so far seems to be limited by a large inactive transverse fault in the west. It needs to be clarified what influence this fault has on the propagation of mine water in the  underground.
The measured temporal trend of the mine water level, after pumps were shut down in mid-2019, shows a strong correlation with the temporal evolution of the observed micro seismicity. In the first  months after the pumps are switched off, the water levels at the observation points rise only slowly and isolated microseismic events occur again. In November 2019, the rise in water levels doubled and at the same time, the strongest induced event in the measurement period was recorded with a magnitude of 2.6 MLv. In the following months, the seismicity rate ranged from 8 to 34 events above 0.5 MLv per month, some of which were felt. A structural geological 3D subsurface model is developed to help to understand the distribution of induced seismicity and the role of the raising mine water level.
The Samos Mw6.9 event: Damage investigation in the town of Vathy incorporating a stochastic finite-fault source with site and structural information
Authors: Giannaraki Georgia , Roumelioti Zafeiria , Melis Nikolaos S.
Published: March 2021

The stochastic method is applied for the finite-fault modelling of strong ground motion from the October 30, 2020, shallow earthquake of Mw=6.9 which occurred offshore the northern part of Samos island in the Aegean Sea, Greece. The earthquake resulted to several human casualties and many injuries, to considerable infrastructure damage in Samos island and Western Turkey, especially in the city of Izmir, and a tsunami affecting both the Greek and Turkish coast. We focus this research on reproducing the ground motion field and damage pattern observed in Vathy, the capital of Samos Island. Different source representations, based on preliminary finite-fault slip distribution models, are tested against their capability to reproduce the two acceleration records available in Vathy. Site effects are incorporated in our modelling in the form of empirical amplification factors assigned according to a Vs30 distribution for the Samos island, which we constructed based on local geology and terrain-based proxies and on the Vs profiles at the sites of the two permanent accelerometric stations. The analysis further focuses on the empirical assessment of structural vulnerability for an estimated exposure model per building block in Vathy, which suffered structural damage due to the mainshock, mainly to a number of old and monumental buildings. The estimated exposure model in Vathy, when combined with the synthetic ground motion derived from the validated stochastic model, provides results in good agreement with available macroseismic intensities and damage reports. Our results contribute to better understanding the observed spatial distribution of damage in Vathy with respect to variations in the quality of buildings, the foundation soil and the frequency content of the excitation motion as radiated from the seismic source. The usefulness of our validated stochastic model is further demonstrated through blind predictions at sites of considerable earthquake effects, at which no record of the Mw=6.9 earthquake is available, such as in the town of Karlovasi in Samos and in the port of Chios Island.
Towards an advanced description and modelling of the atmospheric multiphase chemistry of mercury: CAPRAM HG module 1.0
Authors: Hoffmann Erik Hans , Li Tao , Tilgner Andreas , Wang Yan , Herrmann Hartmut
Published: March 2021

Mercury is a neurotoxic element emitted predominantly in its less-reactive form as gaseous elemental mercury (GEM) into the atmosphere by various natural and anthropogenic processes. Once emitted it undergoes chemical processing in the atmospheric gas and aqueous phase. There, GEM is oxidised into gaseous oxidised mercury (GOM), which partitions into aerosol particles residing there as particulate bounded mercury (PBM) due to its much higher solubility. The faster deposition of GOM and PBM compared to GEM is of special environmental importance, because they can be converted into more toxic organic mercury in aquatic environments and then take serious place in the food web. Thus, it is crucial for models to understand the transformation of GEM into GOM and PBM and vice versa. To date, numerous gas-phase chemistry simulations were performed, but reveal missing oxidation and reduction processes. However, only few models exist that investigate the multiphase mercury chemistry in a detailed manner.

Therefore, a comprehensive multiphase mercury chemistry mechanism, the CAPRAM HG module 1.0 (CAPRAM-HG1.0), has been developed. The CAPRAM-HG1.0 includes 74 gas-phase reactions, 22 phase transfers and 77 aqueous-phase reactions. It was coupled to the multiphase chemistry mechanism MCMv3.2/CAPRAM4.0 and the extended CAPRAM halogen module 3.0 (CAPRAM-HM3.0) for investigations of multiphase Hg redox under Chinese polluted conditions. Simulations were performed for summer conditions in 2014 using the air parcel model SPACCIM to investigate the performance of the model to simulate typical concentrations and patterns of GEM, GOM and PBM.

Under non-cloud conditions, model results reveal good coincides with concentrations and patterns for GEM, GOM and PBM measured in China. However, the simulations also show that there are still high uncertainties in atmospheric mercury chemistry. Especially, the complexation with HULIS within aerosol particles needs evaluation as the simulations indicate this process as key process driving concentrations and patterns of both GOM and PBM. Further, the present study demonstrates the need of a better understanding of continental concentrations of reactive halogen species and particle bounded halides as well as their link to the multiphase chemistry and atmospheric cycling of mercury.
New functional topographic, lithology and climatic indices to define shallow groundwater systems in (un)gauged basins
Authors: Tootchi Ardalan , Ameli Ali
Published: March 2021

The dynamics of the rainfall-runoff processes are complex and variable both spatially and temporally. There is a rich literature on physical representation of streamflow generation processes, such as saturation excess overland flow, often at small scales. Yet, continental-scale estimations of the streamflow generation processes in zones with shallow groundwater systems are still poor. This has led to inability of earth system models or large-scale hydrologic models to correctly simulate stream flows at (un)gauged basins with high potential for the presence of saturation excess overland flow. Zones with shallow groundwater have a direct impact on the hydrologic response of rainfall events. Depending on the subsurface storage, climate signals and topography, they can enhance the overland flow, or act as a buffer zone to flatten the flood hydrographs.
We have introduced new indices, inspired by the concept of hydrologic function, that include the interactions amongst climatic and geophysical characteristics (soil parameters, topography and lithology) to delineate zones of shallow groundwater over the United States and Canada. We have evaluated and tested the ability of these indices in locating high-resolution zones of shallow groundwater against in-situ observations of water table depth. The knowledge of the spatial pattern of shallow groundwater zones at (un)gauged basins allows an accurate inclusion of hydrologic connectivity in earth system models or large-scale hydrologic models, improving their prediction of stream peak flow. Furthermore, as a significant part of incoming precipitation is transformed to overland flow due to oversaturation, these datasets could be introduced as a useful indicator of areas with flood and erosion susceptibility.
UAV monitoring of urban stream restoration sustainability
Authors: Langhammer Jakub
Published: March 2021

High-resolution imaging using unmanned aerial vehicles (UAV, UAS, drones) opened up in the last decade a new potential for a detailed, reliable, operable, and affordable approach for riverscape monitoring. Based on the experience with the pilot research on UAV detection of fluvial dynamics on natural and modified streams, we have proposed a framework for the assessment of the sustainability of stream restoration projects based on UAV imaging and photogrammetry. The approach focuses on aspects where the high-resolution UAV imagery can bring reliable and quantitative information, applicable for assessing restoration success and incorporation into standard assessment schemes.

We distinguish four critical aspects of stream restorations, where the UAV monitoring can provide reliable quantitative information, applicable for assessment of stream restoration success or failure: (i) Restoration effect, (ii) Dynamics of fluvial processes, (iii) Hydrological connectivity, and (iv) Riparian vegetation. For each aspect, there are derived relevant indicators, allowing quantitative assessment and scoring.

We have tested the framework on the evaluation of restorations on three urban streams in the metropolitan area of Prague, Czech Republic, which were subject of revitalization in the past decade. We have maintained regular recurrent UAV monitoring campaigns of these streams over four years, which enabled tracking the restorations since their completion and identifying the positive aspects and the failures in the sustainability of the realized restoration projects. 

UAV monitoring enabled to identify stream restoration features that would be hard or impossible to assess by other mapping techniques. As for the restoration effect, the UAV assessment revealed that although the basic goals of restoration projects were fulfilled, the newly shaped stream patterns significantly differ from the approved restoration plans. The restored channels are typically less complex and featuring simpler geometry than planned. Multitemporal assessment enabled to track stream instability and to measure the extent of bank erosion. UAV monitoring over a low flow period enabled to identify the stream segments where the inappropriate channel transformation led to disruptions in hydrological connectivity, and to detect and measure the extent of eutrophication in the stream and the newly created shallow ponds. UAV monitoring also enabled tracking the progress of vegetation succession after the restoration and quantitatively assessing the extent of riparian shading as a substantial element of sustainability of stream restoration.

Despite the limitations stemming from the nature of optical sensing, UAV monitoring proved to be a highly efficient and reliable technique suitable for evaluating stream restoration projects with versatile applications even in the urban environment’s specific conditions.
Wind Energy Forecast Conditioned on Großwetterlage (large scale weather situation)
Authors: Denisenko Greta , Abel Markus , Siebert Detlef , Seidler Paul , Seidler Thomas
Published: March 2021

Obtaining a quantitative measure for the uncertainty of forecasts for renewable energy has proven to be a challenging problem in the past. We present results on predicting uncertainty of a forecast conditioned on the large weather situation (Großwetterlage). As a first attempt, we use the objective weather classification by the German Meteorological Service (DWD), which sorts the weather into 40 situations based on wind direction, cyclonality and moisture in the atmosphere.

The considered forecasts concern the day-ahead production of solar power for two exemplary solar parks. To quantify the uncertainty, we define five different metrics (based on normalized absolute error and probability distribution), where each one is trained individually using machine learning. As a result, we obtain measures for over- and underprediction conditioned on the said Großwetterlage.

We consider this to be a very promising yet accessible approach to derive a quantitative measure for uncertainties based on the current, day-to-day weather situation. Future work may concern an improvement of the Großwetterlagencharacterization and a general, probabilistic formulation of the problem, e.g. using Bayesian inference.
A stratigraphy-based method for reconstructing ice core orientation
Authors: Westhoff Julien , Stoll Nicolas , Franke Steven , Weikusat Ilka , Bons Paul , Kerch Johanna , Jansen Daniela , Kipfstuhl Sepp , Dahl-Jensen Dorthe
Published: March 2021

Ever since the first deep ice cores were drilled, it has been a challenge to determine their original, in-situ orientation. In general, the orientation of an ice core is lost as the drill is free to rotate during transport to the surface. For shallow ice cores, it is usually possible to match the adjacent core breaks, which preserves the orientation of the ice column. However, this method fails for deep ice cores, such as the EastGRIP ice core in Northeast Greenland. We provide a method to reconstruct ice core orientation using visual stratigraphy and borehole geometry. As the EastGRIP ice core is drilled through the Northeast Greenland Ice Stream, we use information about the directional structures to perform a full geographical re-orientation. We compared the core orientation with logging data from core break matching and the pattern of the stereographic projections of the crystals’c-axis orientations. Both comparisons agree very well with the proposed orientation method. The method works well for 441 out of 451 samples from a depth of 1375–2120 m in the EastGRIP ice core. It can also be applied to other ice cores, providing a better foundation for interpreting physical properties and understanding the flow of ice.
High-frequency ambient noise surface wave tomography at the Marathon PGE-Cu deposit (Ontario, Canada)
Authors: Teodor Daniela , Beard Charles , Pinzon-Rincon Laura Alejandra , Mordret Aurélien , Lavoué François , Beaupretre Sophie , Boué Pierre , Brenguier Florent
Published: March 2021

Ambient noise surface wave tomography (ANSWT) is an environmentally friendly and cost-effective technique for subsurface imaging. In this study, we used natural (low-frequency) and anthropogenic (high-frequency) noise sources to map the velocity structure of the Marathon Cu-PGE deposit (Ontario, Canada) to a depth of 1 km. The Marathon deposit is a circular (ø = 25 km) alkaline intrusion comprising gabbros at the rim and an overlying series of syenites in the centre. Cu-PGE mineralisation is hosted by gabbros close to the inward-dipping footwall of the intrusion. The country rocks are Archaean volcanic breccias that are seismically slower than the gabbros, and similar in velocity to the syenites. We used ANSWT to image the footwall contact that controls the location of the mineralisation.

An array of 1024 vertical-component receivers were deployed for 30 days to record ambient noise required for surface wave analysis. Two overlapping grids were used: a 200 m x 6040 m dense array with node spacing of 50 m, and a 2500 m x 4000 m sparse array with node spacing of 150 m.  The signal was down-sampled to 50 Hz, divided into segments of 30 minutes, cross-correlated and stacked. Surface wave analysis was conducted over the dense array and the sparse array data. We considered the fundamental mode of Rayleigh wave propagation for our frequency-wavenumber (F-K) analysis and focused on the phase velocity variation in the high-frequency ambient noise signal (up to 22 Hz). We reconstructed the shallow structure with progressively increased resolution using surface wave dispersion curves extracted from receiver arrays divided into segments of variable lengths. Several average dispersion curves were computed from individual dispersion curves belonging to different seismic lines. Each average dispersion curve was inverted to obtain S-wave velocity models using an McMC transdimensional Bayesian approach.

The tomographic images reveal a shallow high-velocity anomaly, which we interpret as being related to the gabbro intrusion that hosts the mineralization. The large-wavelength structures in the S-wave velocity models are relatively consistent with the geological structures inferred from surface mapping and drill core data. These results show that the ANSWT, focused on the high-frequency signal provided by anthropogenic noise sources, is an efficient technique for imaging “shallow" (1 km depth) geological structures in a mineral exploration context. 