bluuebunny/crossref_metadata_2025 huggingface dataset:
Frictional behaviour of carbonate bearing faults at brittle-ductile transition
Authors: Figura Francesco , Giorgetti Carolina , Lebihain Mathias , Violay Marie
Published: March 2021

One of the most alarming recent findings in geo-science is the dramatic rise in the rate of human-induced earthquakes in the past decade. This is due to the fluid injection or extraction in deep reservoirs for hydrocarbon production, wastewater and CO2 storage and exploitation of geothermal resources which result in the reactivation of nearby faults. These reservoirs are often located 2-3 km depth (i.e. 30 MPa), and are hosted in or covered by sedimentary carbonate layers. As carbonate undergoes a brittle-ductile transition with increasing confining pressure from values of around 20 MPa, ductile deformation can play an important role on the nucleation and propagation of earthquakes on carbonate faults. Here, we investigate the role of increasing ductile behaviour on fault frictional parameters. The research is performed through the new biaxial apparatus installed at EPFL, the HighSTEPS (High Strain TEmperature Pressure Speed) apparatus, able to measure frictional parameters in a wide range of shearing velocities (10-6 m/s – 0.2 m/s) and under unique boundary conditions representative of the Earth’s crust, i.e., normal stress up to 100 MPa, confining pressure up to 100 MPa, pore fluid pressure up to 100 MPa and temperature up to 120°. The induced stress state in bare surface samples was previously studied by a comparison between results of FEM numerical analyses and experimental ones. Under shear loading conditions, the principal stress σ1 is oriented at about 25° to the vertical axis, and the confining pressure corresponds to the principal stress σ2. Tests are performed under different values of applied confining pressure (1 - 60 MPa) and normal stress (1.5 – 90 MPa) on the faults, keeping constant the ratio between σn/σ3 around ~ 3, to mimic faults at different depth. We present experimental results mapping carbonate fault mechanical behaviour from low shearing velocity 10-6 m/s to high shearing velocity 10-1 m/s. Moreover, experimental results are modelled with rate-and-state friction laws (RSFLs) to define rate and state parameters related to the critical conditions for fault stability and its dependence on the presence of ductile deformation. These results shed new light on the nucleation and propagation of earthquake within the brittle-ductile transition in carbonate bearing rocks.
Simulation of wind damages associated with the PRIMAVERA European windstorm event set
Authors: Perotin Tristan
Published: March 2021

Winter windstorms are one of the major natural hazards affecting Europe, potentially causing large damages. The study of windstorm risks is therefore particularly important for the insurance industry. Physical natural catastrophe models for the insurance industry appeared in the 1980s and enable a fine analysis of the risk by taking into account all of its components (hazard, vulnerability and exposure). One main aspect of this catastrophe modeling is the production and validation of extreme hazard scenarios. As observational weather data is very sparse before the 1980s, estimates of extreme windstorm risks are usually based on climate models, despite the limited resolution of these models. Even though this limitation can be partially corrected by statistical or dynamical downscaling and calibration techniques, new generations of climate models can bring new understanding of windstorm risks.

In that context, PRIMAVERA, a European Union Horizon2020 project, made available a windstorm event set based on 21 tier 1 (1950-2014) highresSST-present simulations of the High Resolution Model Intercomparison Project (HighResMIP) component of the sixth phase of the Coupled Model Intercomparison Project (CMIP6). The events were identified with a storm tracking algorithm, footprints were defined for each event as maximum gusts over a 72 hour period, and the footprints were re-gridded to the ERA5 grid and calibrated with a quantile mapping correction method. The native resolution of these simulations ranges from 150km (typical resolution of the CMIP5 models) to 25km.

We have studied the applicability of the PRIMAVERA European windstorm event set for the modeling of European windstorm risks for the insurance sector. Preliminary results show that losses simulated from the event set appear to be consistent with historical data for all of the included simulations. The event set enables a better representation of attritional events and storm clustering than other existing event sets. An alternative calibration technique for extreme gusts and potential future developments of the event set will be proposed.
Gridded Harmonized Dataset for the Spatial Location of the Global Critical Infrastructure Network
Authors: Nirandjan Sadhana , Koks Elco , Ward Philip , Aerts Jeroen
Published: March 2021

Critical infrastructure (CI) is fundamental for the functioning of a society and forms the backbone for socio-economic development. Natural hazards, however, pose a major threat to CI. The destruction of CI, and the disruption of essential services they provide may hamper societies and economies. Moreover, the overall risk for CI is expected to rise. This is due climate change (i.e. intensification and more frequent hazards), and socio-economic development (i.e. increase in the amount and value of CI).

Building sustainable and resilient infrastructure is a key to reducing the impacts of natural hazards and climate change on society. However, an in-depth knowledge of the global CI that is directly at risk for natural hazards is still lacking. The development of a harmonized dataset integrating the geospatial locations of the main CI systems at a global scale will aid to our knowledge on the CI that is exposed and at risk for natural hazards.

We present a first-of-its-kind globally consistent spatial dataset for the representation of CI. In this study, an index to express the spatial intensity of CI at the global scale is developed: the Critical Infrastructure System Index (CISI). The CISI is expressed in a dimensionless value ranging between 0 (being no CI intensity) and 1 (being highest CI intensity). The CISI aggregates high resolution spatial information of CI based on OpenStreetMap (OSM) data. For the development of this index, a total of 34 CI types (e.g. primary roads, waste-water plants and hospitals) are defined and categorized under seven overarching CI systems: transportation, energy, tele-communication, waste, water, health and education. Spatial data on these CI types are extracted by using a selection of 78 OSM tags. The detailed spatial data is rasterized into a harmonized and consistent dataset with a resolution of 0.1x0.1 degrees.

This novel global dataset will be a valuable starting point for policy makers, planners, and researchers in several fields. The dataset can be deployed as a tool to gain insights in the current landscape of the CI network, to identify hotspots of CI, and to gain exposure information for risk assessments. We use open data hosted by OSM, and provide code for further use and development. In this study, we demonstrate the database and CISI at a global scale, but the publicly accessible code can also be used to further develop the dataset with latest releases of data on CI provided by OSM as well as other (open) sources for any location and any resolution.
The post-Caledonian thermo-tectonic evolution of Fennoscandia
Authors: Japsen Peter , Green Paul F. , Bonow Johan M. , Chalmers James A. , Duddy Ian , Kokkunen Ilmo
Published: March 2021

Here we present apatite fission-track analysis (AFTA) data and thermal history interpretations in 332 samples from outcrops and boreholes at elevations between +2 and -6 km relative to sea level across Fennoscandia. The data define episodes of burial and exhumation which involved deposition and removal of kilometre-scale thicknesses of sediment as well as denudation of the underlying basement rocks that resulted in the formation of peneplains of different age and characteristics.  Many of these episodes correlate with similar episodes over a much wider region, and this argues for regional tectonic control, related to plate-tectonic processes.

Post-Caledonian development of Fennoscandia involved five dominant episodes of exhumation, beginning in late Carboniferous, Middle Triassic, Middle Jurassic, mid-Cretaceous and early Miocene times.  These episodes affected not only the present-day Atlantic margin but also the continental interior which is considered by many to represent a stable cratonic region because of the low relief and limited remnants of sedimentary cover. Pronounced offsets in the magnitude of the pre-Cenozoic episodes over short distances occur close to the Atlantic margin, and around the Oslo Rift, attesting to the tectonic origin of these episodes.  In contrast, the Middle Triassic and mid-Cretaceous episodes display little variation over vast regions in the interior. Yet even here, our results show that the vertical movements involved deposition and removal of substantial sedimentary covers. 

The late Carboniferous, Middle Triassic and Middle Jurassic episodes can be linked with the break-up of Pangaea.  The mid-Cretaceous episode correlates with a global plate reorganization.  The early Miocene episode appears to be earlier than analogous episodes in Greenland, and it is not yet clear how these episodes fit into the pattern of plate-tectonic forces.  The youngest tectono-thermal episode to affect Fennoscandia began in the early Pliocene and is only revealed by AFTA data from a few deep boreholes. But this episode had a major impact in shaping the present-day topography on both sides of the Atlantic and may have been driven by dynamic support from the Iceland Plume.

A key aspect of the paleo-thermal episodes identified in this study is that they involve both deposition and removal of kilometre-scale thicknesses of sediment (i.e. subsidence and uplift), rather than progressive emergence and monotonic cooling of the continents as assumed in many studies.  Dynamic topography and far-field transmission of stress thus appear to be likely candidates for driving the ups and downs of both marginal and interior regions. 
The recovery of the biological pump across the K/Pg boundary in the GSSP of El Kef, Tunisia
Authors: van Dijk Joep , Sepúlveda Julio , Alegret Laia , Birch Heather , Bralower Timothy , Jones Heather , Henehan Michael , Hull Pincelli , Hedi Negra Mohamed , Ridgwell Andy , Röhl Ursula , Vellekoop Johan , Westerhold Thomas , Whiteside Jessica , Zeebe Richard
Published: March 2021

The study of Earth’s Big Five mass extinctions provides insight into the resilience of ecosystems to environmental perturbations. Earth’s most recent mass extinction at the Cretaceous/Paleogene boundary (K/Pg) was caused by the impact of an asteroid in the Yucatan peninsula rather than by intense volcanism. Mass extinctions among marine calcareous nannoplankton heavily disrupted the marine food web resulting in a severe weakening of the ocean’s biological pump. The timing and heterogeneous nature of the recovery of the biological pump remain poorly resolved in the neritic zone in the aftermath of the impact. Here, we address the evolution of the biological pump across the K/Pg at the Global Boundary Stratotype Section (GSSP) at El Kef, Tunisia using high-resolution compound-specific carbon isotope records (δ13Cbiomarker) of non-calcareous marine phototrophs from an outer shelf to upper bathyal setting of the southwestern Tethys Ocean. We use δ13Cbiomarker to reconstruct εp, which is a function of the community structure of marine phototrophs, their rate of carbon fixation, and the concentration and isotopic composition of aqueous CO2. We then use our εp record to constrain the recovery of the biological pump in this region while considering the composition of marine phytoplankton, the assemblage and isotopic composition of benthic foraminifera, state-of-the-art physiological models for εp, and carbon cycle simulations using cGENIE. Our results indicate that the recovery of the biological pump in the outer shelf-upper bathyal zone likely outpaced the recovery in the open ocean. This is in agreement with the selective extinctions among phytoplankton at the K/Pg, with most survivors that would later repopulate open-ocean sites being adapted to neritic environments.
Modern atmospheric monitoring using pollen analysis of ice cores: a case study from the Elbrus Western Plateau, Caucasus, Russia
Authors: Batalova Vlada , Mikhalenko Vladimir , Kutuzov Stanislav , Shumilovskikh Lyudmila , Shukurov Karim
Published: March 2021

The report highlights the results of first ice-core palynology studies from the Elbrus Western Plateau. The title of the highest point in Europe and the geographical location of Elbrus determine the diversity of natural conditions and, as a result, palynological spectra, which act as markers of seasonal vegetation, climate dynamics, fires and anthropogenic activities in the Mediterranean, southern European Russia, the Middle East, and North Africa.

The 24-m ice core from the Elbrus Western Plateau collected in 2017 (5115 m a.s.l., 43о20′53,9′′ N, 42о25′36′′ E) covers the period 2012-2017. Pollen analysis revealed a significant number of biological markers contained in the ice core, including pollen and spores, fungi, algae, testate amoebae, feather barbules, microcharcoal, and black carbon.

The obtained results show that taxonomic diversity and concentration of biomarkers in the ice core were determined by the seasons of the year and their inherent convective flows. Pollen assemblages are characterized by predominance of native Caucasian plant species. Among them pollen values of Picea forming the high-altitude forest belt in the Western Caucasus significantly exceed pollen frequency of Pinus growing near the upper timber line on Elbrus Mt in the Central Caucasus that suggests a westerlies of air masses and transfer of microparticles. A high abundance of non-pollen palynomorphs in pollen assemblages demonstrates a high potential for studying of human impact on mountain ecosystems. The first pollen data from the ice core evidences a promising resource of the high-altitude temperate glaciers as a flexible tool for atmospheric monitoring of microparticle transfer and fixing its seasonality and biotic relationships.

This work was supported by the Russian Science Foundation, project № 17-17-01270.
Satellite-based remote sensing of carbon dioxide over snow-covered surfaces
Authors: Mikkonen Antti , Lindqvist Hannakaisa , Peltoniemi Jouni , Tamminen Johanna
Published: March 2021

Global coverage of carbon dioxide (CO2) satellite observations is necessary for accurate seasonal carbon flux estimates. Sufficient seasonal coverage is particularly important for quantifying the carbon cycle at high Northern latitudes which are sensitive to the rapidly changing climate. However, high latitudes pose significant challenges to reliable space-based observations of greenhouse gases. One reason for the shortage of good quality CO2 observations in the high latitudes is the low reflectivity of snow-covered surfaces in the CO2 absorption bands, in addition to large solar zenith angles and frequent cloud coverage over the Arctic and boreal regions. Snow surfaces are highly forward-scattering and therefore the traditional nadir-viewing geometries over land might not be optimal. In addition, the contributions from the 1.6 um and 2.0 um CO2 absorption bands need to be evaluated over snow. In this work, we present a realistic, non-Lambertian surface reflection model of snow based on snow reflectance measurements and examine results of atmospheric radiative transfer simulations in various satellite observation geometries and the contributions from different absorption bands. This research lays important ground work for a dedicated feasibility study of CO2 retrievals over snow, which would ultimately help increase the quantity and reliability of satellite observations at high latitudes from late winter to spring – an important period for the carbon cycle in the rapidly changing Arctic climate.
Towards the use of hydrometeorological thresholds for the regional-scale LEWS of Catalonia (NE Spain).
Authors: Palau Rosa M , Hürlimann Marcel , Berenguer Marc , Sempere-Torres Daniel
Published: March 2021

Risk mitigation for shallow slides and debris flows at a regional scale is a challenge. Landslide early warning systems (LEWS) are a helpful tool to anticipate the time and location of possible landslide events so that the authorities in charge of managing the landslide risk can plan their actions.

Traditionally, regional LEWS rely on rainfall information to asses if the landslide triggering conditions are met. However, in many cases, soil moisture is a predisposing factor that plays a major role in landslide initiation. Therefore, accounting for soil moisture conditions could improve the performance of LEWS.

Here we present the preliminary results defining hydrometeorological thresholds for the region of Catalonia (NE Spain). Such thresholds have been derived combining rainfall information from ground-based radar observations and the volumetric water content simulated by the LISFLOOD hydrological model. The information of recent and historical landslide events contained in a landslide inventory has been used to adjust the hydrometeorological thresholds.

The new hydrometeorological thresholds have been implemented into the regional-scale LEWS for the region of Catalonia.  Finally, the performance of the two versions of the LEWS (i.e. solely based on rainfall observations and adding soil moisture conditions) has been analysed for a recent rainfall event that triggered multiple landslides.
Southern Ocean water mass properties and circulation under CMIP6 climate forcing
Authors: Meijers Andrew , Munday David , Roy Tilla , Sallée Jean-Baptiste
Published: March 2021

We examine the representation of Southern Ocean water mass properties, circulation and transformation in an ensemble of CMIP6 models, under historical climate forcing conditions and under a range of future climate scenarios. By using a dynamically defined water mass classification scheme based on physical characteristics (salinity minimum, potential vorticity minimum etc) rather than fixed water mass properties, we are able to compare water masses across a range of models, often with significant water mass property differences, as well as within single models where water mass properties change under climate forcing. We find that under strong climate forcing scenarios (ssp585) the heat content of SubAntarctic Mode Water (SAMW), Antarctic Intermediate Water (AAIW) and Circumpolar Deep Water (CDW) all increase consistently across models, while Antarctic Bottom Water (AABW) does not change significantly. Importantly this change is strongly modulated by using dynamic definitions. Both SAMW and AAIW lighten significantly in density, and using time varying definitions their volumes remain relatively constant, whereas using a time invariant definition both experience extremely significant increases in volume and heat content. We show that dynamically it is the ocean interior, CDW and AAIW, that dominate heat uptake under strong forcing. Similarly, dissolved inorganic carbon uptake occurs predominantly in the CDW. In contrast AABW volumes decrease significantly.

There is a consistent ‘fingerprint’ of temperature change in density space across all models under strong forcing scenarios, with CDW experiencing surface intensified warming as it shoals to the south, and SAMW/AAIW demonstrating cooling and freshening in their subducted layers and a uniform warming in the surface layers. We show that the upper cell of the residual overturning circulation (calculated with the new availability of eddy parametrisation terms in CMIP6) consistently increases across all models evaluated, by 10-50% (up to 10 Sv in some models), while the lower cell is dramatically decreased in strength, declining by up to 70% in some models. We provide evidence that surface warming may be modulated by increased eddy driven upwelling, as well as surface freshening driving the shutdown of AABW formation. Finally we compute a Walin water mass budget, balancing surface forcing, interior storage and meridional export and inferring interior mixing between water masses, and contrast all findings with similar analyses in CMIP5.

 
Meso-scale weather systems and their interaction in the Tibetan Plateau region
Authors: Kukulies Julia , Curio Julia , Chen Deliang
Published: March 2021

Meso-scale weather systems have been identified as major precipitation bearing systems in the Tibetan Plateau (TP) region. They can pose a risk for people's life and livelihoods, by causing flooding, extreme winds and heavy rainfall in the populous downstream regions. As local hydroclimatic conditions and large-scale atmospheric circulation patterns change with global warming, it is important to understand the role of such weather systems and the associated precipitation-producing mechanisms for the regional water cycle. Two important systems which are often named in this context are meso-scale convective systems (MCSs) and Tibetan Plateau vortices (TPVs). MCSs are recognized as cloud clusters that produce large areas of heavy rainfall, while TPVs refer to frequently occurring meso-scale cyclonic vortices around 500 hPa that are initiated over the TP. Only few studies have looked at the relationship between the dynamical disturbances like TPVs and observations of MCSs. We present here the key characteristics of MCSs as observed by satellite observations from the past two decades and compare it to the key characteristics of TPVs identified by minima in relative vorticity in reanalysis data. Further, we explore in what way TPVs and MCSs are linked to each other by focusing on the most extreme cases of both systems. Finally, we discuss the role of large-scale circulation for both TPVs and MCSs and suggest that future research about extreme precipitation around the TP region should focus more on the mechanisms that link together both systems.
Surface processes control on orogenic evolution: inferences from 3D coupled numerical models and observations from the India-Eurasia collision zone
Authors: van Agtmaal Luuk , Balazs Attila , May Dave , Gerya Taras
Published: March 2021

The inherent links between tectonics, surface processes and climatic variations have long since been recognised as the main drivers for the evolution of orogens. Oceanic and continental subduction and collision processes lead to distinct topographic signals. Simultaneously, different climatic forcing factors and denudation rates substantially modify the style of deformation leading to different stress and thermal fields, strain localisation and even deep mantle evolution. An ideal area where the above-mentioned processes and their connections can be studied is the India-Eurasia collision zone.

Understanding the complex interplay between tectonics, erosion, sediment transportation and deposition requires the coupled application of thermo-mechanical and surface processes modelling techniques. To this aim, we used a 3D coupled numerical modelling approach. The influence of different plate convergence, erosion and sedimentation rates has been tested by the thermo-mechanical code I3ELVIS (Gerya and Yuen, 2007) coupled to the diffusion-advection based (FDSPM) surface processes model.

We show preliminary results to demonstrate  that the diffusion-advection erosion implementation has significant effects on local and regional mass redistribution and topographic evolution within narrow, curved, high orogens such as the Himalayas and their syntaxes, where erosion is a dominant forcing factor. We also discuss possible implications from different erosion/sedimentation implementations such as DAC (Ueda et al., 2015; Goren et al., 2014) in combination with the reference thermo-mechanical model to analyse changes in orogenic development as a consequence of different erosional processes in more detail.

References:

Gerya, T. V., & Yuen, D. A. (2007). Robust characteristics method for modelling multiphase visco-elasto-plastic thermo-mechanical problems. Physics of the Earth and Planetary Interiors, 163(1-4), 83-105.
Ueda, K., Willett, S. D., Gerya, T., & Ruh, J. (2015). Geomorphological–thermo-mechanical modeling: Application to orogenic wedge dynamics. Tectonophysics, 659, 12-30.
Goren, L., Willett, S. D., Herman, F., & Braun, J. (2014). Coupled numerical–analytical approach to landscape evolution modeling. Earth Surface Processes and Landforms, 39(4), 522-545.
The circulation near the Reykjanes Ridge in summers 2015, 2016 and 2017
Authors: Salaün Ivane , Thierry Virginie , Mercier Herlé
Published: March 2021

Located south of Iceland, the Reykjanes Ridge is a major topographic structure of the North Atlantic Ocean that strongly influences the spatial distribution and circulation of the North Atlantic Subpolar Gyre water masses. Around the ridge, the circulation is composed of two main along-ridge currents, the southwestward East Reykjanes Ridge Current (ERRC) in the Iceland Basin and the northeastward Irminger Current (IC) in the Irminger Sea. To study the along Reykjanes Ridge flow variability and the inter-basin connection through the ridge and connections with the interior of each basin, volume and water mass transports over the Reykjanes Ridge during summer 2015, 2016 and 2017 are analyzed. Data used are velocity and hydrographic measurements carried out along and perpendicular to the crest of the Reykjanes Ridge during the RREX (Reykjanes Ridge Experiment Project) cruises in June–July 2015 and June–July 2017 and BOCATS cruise in July 2016. The new circulation scheme in the area described in 2015  by Petit et al. (J. Geophys. Res., 2018) with flows connecting the ERRC and IC branches at specific locations set by the bathymetry of the ridge is again observed  in 2016 and  2017, with variations concerning the connections with the interiors of the basins. The data set reveals remarkable changes in the hydrological properties and transports of the ERRC, IC and cross ridge flows. The westward transport across the ridge, which represents the subpolar gyre intensity, was estimated at -19.6±3.4 Sv in 2015 and -35.2±3 Sv in 2017. A freshening and a decline in density mainly affecting the Subpolar Mode Water was observed in 2017. It was associated with a lower mode water  transport partly compensated by a higher transport of intermediate and Arctic waters. We further document each water mass contribution to the westward flow of the gyre and the structure of the ERRC and IC.
Formation of box canyons by mass failure in limestone: A modelling study of the role of groundwater seepage
Authors: Saadatkhah Nader , Micallef Aaron
Published: March 2021

Groundwater seepage has been shown to unambiguously lead to channel formation inunconsolidated sand to gravel sized sediments. However, its role in the evolution of bedrocklandscapes remains controversial. In this study, we use the coastline of the Maltese Islands as a case study to establish if and how groundwater seepage can form box canyons in limestones. The study area comprises up to 40 m high coralline limestone cliffs, with a mean fracturedensity of 1 in 5 m, overlying a ductile marl layer. The permeability contrast promotes the development of a perched aquifer and groundwater seepage at the cliff face. We  ran numerical simulations using a 3D distinct element model based on geological, geotechnical and hydrological baseline information from the study state, and explored three potential mechanisms: (i) fracture widening by fluid pressure and dissolution associated to groundwater flow and seepage, (ii) fracture widening by loss of support at the base due tomarl displacement resulting from increased water content, and (iii) a combination of (i) and (ii). We also took into consideration two scenarios: (a) uniform groundwater seepage, and (b)focused groundwater seepage. Our results suggest that the combination of mechanisms (iii) and the scenario with focused groundwater seepage (b) give rise to the box canyonmorphology observed at the site. Box canyons thus initiate and grow via detachment of limestone blocks and their toppling, which is more concentrated at the head where groundwater seepage occurs.
Seismic activity in stable continental regions
Authors: Labidi Manel , Whitney Beau , Drouet Stéphane
Published: March 2021

Stable continental regions (SCRs) have low seismicity and large magnitude earthquakes are infrequent and diffuse compared to plate boundary settings. Because of this, seismicity parameters required for seismic hazard analysis (SHA) are difficult to constrain. A method to overcome this challenge involves using an analogue approach to generate seismic hazard inputs in SCRs. Seismic hazard analysis of these regions develops recurrence parameters by drawing upon data from a larger global database than what is typically done for plate boundary regions. This is completed by choosing regions that are considered seismotectonically analogous and then amalgamating data from the regions to generate larger and perceivably more robust seismicity data sets. Historically, this is done by considering all SCRs as analogous and including all of their data into the analysis.

This study refines and updates this approach by assessing whether there is internal variability of seismogenic potential within SCR crust that can be distinguished by comparing properties of the crust to seismicity. We completed this analysis by: (1) compiling a global homogeneous earthquake catalog for earthquakes >= Mw 2 up to July 2020 which includes historical and instrumental events; (2) subdividing global SCR crust into five geological domains that distinguish crustal criteria within SCRs; (3) calculating and comparing the seismic parameters between the different SCRs and sub-domains to better understand the range in values across different SCRs and determine if there is statistically observable variation between sub-domains. Our results provide an initial step towards redefining what crustal characteristics define analog regions for use in seismic hazard studies.
Potential field constraints on the basement structure of the Taiwan thrust-and-fold belt: preliminary results
Authors: Lozano Olivia , Ayarza Puy , Alvarez-Marrón Joaquina , Brown Dennis
Published: March 2021

The Taiwan orogen forms an active mountain range that has been evolving since the Late Miocene as a result of the oblique collision between the Luzon Arc, located in the Philippine Sea Plate, and the continental margin of the Eurasian Plate. Due to this configuration, some inherited structures from the continental margin are at high angle to the structural trend of the Taiwan thrust-and-fold belt and are thought to play an important role in present day tectonics. The inherited structures resulted from processes undergone by the Eurasian margin, such as rifting in the Early Eocene, and further local extension in the Middle Miocene. They comprise sub-vertical faults that are presently being reactivated and are actively involved in the evolution of the structure, seismicity and topography of Taiwan, causing transverse zones in its thrust-and-fold belt and foreland.

The key objective of this research is to help define the deep structure in southern Taiwan, as well as the location and kinematics of these inherited east-northeast striking faults. To achieve this goal, we undergo a multidisciplinary approach based on the analysis and modelling of gravity (free-air and Bouguer anomaly) and magnetic data. The application of analytical techniques, such as horizontal directional derivatives allows us to identify gradients that can be related to the geometry and minimum horizontal extent of these basement structures in the margin and in Taiwan. Forward modelling of gravity and magnetic data contributes further to provide a better-constrained quantitative approach to their depth as they appear to affect the top of the basement. Finally, these results have been integrated with structural studies and earthquake information in order to improve our understanding of the southern Taiwan and Eurasian continental margin structure.

The preliminary results allow us to discuss the limitations of vertical derivatives and residual potential field data when dealing with deep inherited basement structures. The present dataset has proven to be useful to discern the existence of a deformed reactivated basement in the foreland and frontal part of the Taiwan thrust-and-fold belt, and improve our comprehension of its crustal structure. Due to the limitations of potential field data as the depth of the source increases, the resolution diminishes towards the E of the thrust-and-fold belt.

This research is part of project PGC2018-094227-B-I00 funded by the Spanish Research Agency of the Ministry of Science and Innovation of Spain. Olivia Lozano acknowledges funding from the same agency through contract PRE2019-091431.
Decision support system for evaluation of available surface water resources for use in Slovenia – development of the basis 
Authors: Šantl Sašo , Rojnik Anže , Javornik Luka , Rozman Davor , Zabret Katarina
Published: March 2021

According to the Water Law of the Republic of Slovenia anyone who wants to use water resources in addition to the general use (e.g. drinking, swimming and other recreational uses) needs to acquire a water right. Approving the water rights is in principal based on two conditions: (i) the discharge downstream from the withdrawal should be at least equal to ecologically acceptable flow and (ii) the withdrawal of the water should not influence the natural conditions or other already present uses and needs of water resources. Through the development of the system’s basis we have focused on the first condition, the hydrologically available water resources.

The information about the amount of the water in a river or a stream is provided by the discharge measurements, performed at locations of the water gauging stations by the Slovenian Environmental agency (ARSO). However, when granting a water permit, the location of certain water withdrawal can be anywhere along the watercourse. Therefore, we have tested seven advanced statistical models to connect characteristic discharges (mean and mean minimal discharge for a selected 30-year period) at measured points with attribute data describing the properties of the corresponding catchment. The 49 attribute values were gathered through analysis of spatial data in GIS environment and provided information about precipitation, temperature, geological structure, land use and water use in the area. According to the comparison of models performance we have selected the neural networks. They were used to estimate characteristic discharges in 340 selected points on the water courses all over the country. These values provide the basis for calculation of the ecologically acceptable flow and the amount of discharge available for use under certain terms. In addition, for the selected points (340 points) also the natural (reference) discharge was estimated as a discharge which would be observed without any water use present upstream. Simulations of natural discharge situation were performed for various scenarios and multiple selected test cases. The estimated differences between natural and measured discharge for selected points was than generalized for all the other points using the hierarchical clustering approach. So far the basic information about the amount of water available for use on watercourses with basins larger than 10 km2 was estimated. However, the project is ongoing with the focus on improving the models, including the complex interactions between surface waters and groundwaters, and taking into account the vulnerability of the natural environment and ecosystem services they provide as well as sectoral needs.
A numerical approach for modeling thermo-poro-elastic deformation sources in volcanic and hydrothermal regions.
Authors: Nespoli Massimo , Belardinelli Maria Elina , Bonafede Maurizio
Published: March 2021

The Thermo-Poro-Elastic (TPE) inclusions contribute to deformation and stress in volcanic and hydrothermal areas. Differently from other deformation source models (e.g. magma chambers), the TPE sources effects are due to pore-pressure and temperature changes of the fluid within the inclusion. So that the TPE inclusions can allow large deformations even in those volcanic environments in which there is no evidence of a shallow magmatic body. This kind of sources also provides large deviatoric stresses, promoting different types of focal mechanisms both inside and around them. With respect to a previous work, we propose a numerical model that allows for a more realistic representation of TPE sources: we can represent inclusions with an arbitrary geometry and we take into account the elastic stratification of the crust, thanks to a modified version of the EDGRN/EDCMP code. We can also represent the case of a depth dependent distribution of pore pressure and temperature changes within inclusions, as expected during the transient stage of fluid propagation and temperature diffusion. We found that elastic layering and transient changes of the TPE source can promote both normal and thrust earthquakes in its interior. For the 1982-84 unrest episode at Campi Flegrei the inversion of geodetic data leads to a lower misfit between modeled and measured deformation data, with respect to a homogeneous medium and the retrieved geometry and location of the thermo-poro-elastic are in good agreement with the observed distribution of seismicity.
The role of aerosol process representation in uncertainty in the North Atlantic region in CMIP6 
Authors: Wilcox Laura , Griffiths Paul , Grosvenor Daniel , Keeble James , Robson Jon
Published: March 2021

Previous studies have shown that anthropogenic aerosol emissions drive a strengthening of the Atlantic Meridional Overturning Circulation (AMOC) in CMIP6 historical simulations that was not simulated in the CMIP5 multi-model mean. The strength of the CMIP6 AMOC trend has been linked to the strength of the aerosol forcing, with the inclusion of aerosol-cloud interactions accounting for a large proportion of the difference between CMIP5 and CMIP6. However, there is large uncertainty in the magnitude and distribution of aerosol effective radiative forcing in CMIP6. Understanding this uncertainty is important for the interpretation of simulated AMOC variability.

 

We present an evaluation of the atmospheric variables with the potential to influence AMOC changes in CMIP6 historical and AMIP simulations, including downwelling shortwave radiation, surface heat fluxes, surface air temperature, and precipitation. We examine the links between aerosol effective radiative forcing, the magnitude and pattern of biases in the mean and trends in modelled quantities, and the complexity of the representation of aerosol chemistry and aerosol-cloud interactions. Using these results, we highlight areas where model diversity in the representation of aerosol process may be particularly important for uncertainty in simulations of North Atlantic climate.
Adjoint tomography with full envelope for scattering and intrinsic attenuation - resolution and trade-off
Authors: Zhang Tuo , Sens-Schönfelder Christoph
Published: March 2021

A rigorous framework exists for deterministic imaging the subsurface seismic velocity structure. Full-waveform inversion (FWI) that combines the forward simulation of waveforms with an adjoint (backward) simulation of the data misfit provides the gradient of the model misfit with respect to the changes in the model parameters. This gradient is used for iterative improvements of the model to minimize the data misfit. To investigate the small scale heterogeneity of the medium below the resolution limits the waveform tomography the envelopes of high-frequency seismic waves have been used to derive a statistical description of the small scale structure. Such studies employed a variety of misfit measures or empirical parameters and various assumptions about the spatial sensitivity of the measurements to derive some information about the spatial distribution of the high-frequency attenuation and scattering properties. A rigorous framework for the inversion of seismogram envelopes for the spatial imaging of heterogeneity and attenuation has been missing so far. Here we present a mathematical framework for the full envelope inversion that is based on a forward simulation of seismogram envelopes and an adjoint (backward) simulation of the envelope misfit, in full analogy to FWI. 

Different from FWI that works with the wave equation, our approach is based on the Radiative Transfer Equation. In this study, the forward problem is solved by modelling the 2-D multiple nonisotropic scattering in a random elastic medium with spatially variable heterogeneity and attenuation using the Monte-Carlo method. The fluctuation strength ε and intrinsic quality factors QP-1 and QS-1 in the random medium are used to describe the spatial variability of attenuation and scattering. The misfit function is defined as the differences between the full observed and modelled envelopes.

We derived the sensitivity kernels corresponding to this misfit function that is minimized during the iterative adjoint inversion with the L-BFGS method. We have applied this algorithm in some numerical tests in the acoustic approximation. We show that it is possible in a rigorous way to image the spatial distribution of small scale heterogeneity and attenuation separately using seismogram envelopes. The resolution and the trade-off between scattering and intrinsic attenuation are discussed. Our analysis shows that relative importance of scattering and attenuation anomalies need to be considered when the model resolution is assessed. The inversions confirm, that the early coda is important for imaging the distribution of heterogeneity while later coda waves are more sensitive to intrinsic attenuation.
Applying a storyline approach to explore the impact of future Atmospheric River induced floods in western Norway 
Authors: Hegdahl Trine Jahr , Engeland Kolbjørn , Müller Malte , Sillman Jana
Published: March 2021

Atmospheric rivers (AR) are responsible for the most extreme precipitation events causing devastating landslides and floods in western Norway. In this study an event-based storyline approach is used to compare the flood impact of extreme AR events in a warmer climate to those of the current climate.  The four most extreme precipitation events were selected from 30 years of present and future climate simulations from the high-resolution global climate model, the EC-Earth model. For each of the four events, EC-Earth was rerun creating 10 perturbed realizations. A regional convective permitting weather prediction model, AROME-MetCoOp, was used to further downscale the events, and thereafter the operational Norwegian flood-forecasting model was used to estimate the flood levels for 37 catchments in western Norway. The magnitude and the spatial impact were analyzed, and different hydrological initial conditions, which affect the total flooding, were analyzed.

The results show that more catchments were affected with larger floods in the future climate events compared to the current climate events. In addition, the combination of multiple realizations of meteorological forcing and different hydrological initial conditions, for example soil saturation and snow storage, were important for the estimation of the maximum flood level. The meteorological forcing had the highest overall effect on flood magnitude; however, varying and depending on event and catchment. Finally, operational flood warning levels were used to visualize the difference between future and current climate flood events. Applying a setup similar to the one used operationally and relating the future events to known current events associated with ARs, enables a common reference and ease communication with end-users and decision makers.
Identifying changes in hydrological behaviour of Russian Plain rivers over the last 70 years by using clustering analysis
Authors: Ivanov Alexander , Kireeva Maria
Published: March 2021

In the past two decades we see many signs of changing behaviour in hydrological regimes of Russian Plain rivers. River regimes classification was done in the early 1990s and it's possible that some rivers (especially in Don and Oka river basins) have already changed their behaviour. We believe that's the first time this was done by objective analysis and without reliance on experts opinion.

In this work we make an attempt at automatic and objective classification of water regime types for 220 rivers of Russian Plain and propose a method for automatic assesment of changes in hydrological behaviour of local rivers. We use monthly data and k-means clustering algorithm to classify each river water regime for every year with available data. Unlike most of other approaches we do not divide data by year but create clusters from all datapoints simultaniously. This allows us to use more datapoints and establish a more robust result. Next, when we have annual clusters for every datapoint we can assess the stability of water regime for each catchment over several decades and identify catchments with unstable and changing behaviour. 

By using this method we're able to automatically identify 5 distinct water regimes for the rivers of Russian Plain: three with dominant peaks caused by spring freshets in March, April and Februaty with most discharge happening over the course of a single month and two types of water regimes with maximal discharges in April and June, but lacking a pronounced peak in these months. Unlike previous calssifications we can identify the closest water regime for every year and therefore make an attempt at quantifying stability of these regimes and changes over time. By using a very naive approach and calculating a standard deviation over a moving window of 10 years it's possible to detect unstable regions and therefore select periods of stability and shifts for each subregion of Russian Plain.

We're able to identify Don and Oka basins as regions with the most changes in water regimes and it corresponds with research data. In addition rivers in Kola peninsula and Ural regions peninsula demonstrate a slight shift in stability. In terms of hydrological behaviour we see siginificant changes in Don and Oka river basins that shifted from spring freshet peak in April into water regime type with a peak in March or a more southern water regime with less pronounced April peak having precedenig winter thaws.

We believe that this simple approach at identifying water regimes and changes in them can be successfuly used for other regions than Russian Plane.

The study was supported by the Russian Science Foundation (grant No.19-77-10032) in methods and Russian Foundation for Basic Research (grant No.18-05-60021) for analyses in Arctic region 