ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Articles  (22,721,462)
Collection
Years
  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Physics Letters B 294 (1992), S. 466-478 
    ISSN: 0370-2693
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Physics Letters B 317 (1993), S. 474-484 
    ISSN: 0370-2693
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Publication Date: 2022-05-19
    Description: Spherical Slepian functions (or ‘Slepian functions’) are mathematical functions which can be used to decompose potential fields, as represented by spherical harmonics, into smaller regions covering part of a spherical surface. This allows a spatio-spectral trade-off between aliasing of the signal at the boundary edges while constraining it within a region of interest. While Slepian functions have previously been applied to crustal magnetic data, this work further applies Slepian functions to flows on the core-mantle boundary. There are two main reasons for restricting flow models to certain parts of the core surface. Firstly, we have reason to believe that different dynamics operate in different parts of the core while, secondly, the modelled flow is ambiguous over certain parts of the surface. Spherical Slepian functions retain many of the advantages of our usual flow description, concerning for example the boundary conditions it must satisfy, and allowing easy calculation of the power
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Publication Date: 2021-12-23
    Description: Major advancements in the monitoring of both the occurrence and impacts of space weather can be made by evaluating the occurrence and distribution of ionospheric disturbances. Previous studies have shown that the fluctuations in total electron content (TEC) values estimated from Global Navigation Satellite System (GNSS) observations clearly exhibit the intensity levels of ionospheric irregularities, which vary continuously in both time and space. The duration and intensity of perturbations depend on the geographic location. They are also dependent on the physical activities of the Sun, the Earth’s magnetic activities, as well as the process of transferring energy from the Sun to the Earth. The aim of this study is to establish ionospheric irregularity maps using ROTI (rate of TEC index) values derived from conventional dual-frequency GNSS measurements (30-s interval). The research areas are located in Southeast Asia (15°S–25°N latitude and 95°E–115°E longitude), which is heavily affected by ionospheric scintillations, as well as in other regions around the globe. The regional ROTI map of Southeast Asia clearly indicates that ionospheric disturbances in this region are dominantly concentrated around the two equatorial ionization anomaly (EIA) crests, occurring mainly during the evening hours. Meanwhile, the global ROTI maps reveal the spatial and temporal distributions of ionospheric scintillations. Within the equatorial region, South America is the most vulnerable area (22.6% of total irregularities), followed by West Africa (8.2%), Southeast Asia (4.7%), East Africa (4.1%), the Pacific (3.8%), and South Asia (2.3%). The generated maps show that the scintillation occurrence is low in the mid-latitude areas during the last solar cycle. In the polar regions, ionospheric irregularities occur at any time of the day. To compare ionospheric disturbances between regions, the Earth is divided into ten sectors and their irregularity coefficients are calculated accordingly. The quantification of the degrees of disturbance reveals that about 58 times more ionospheric irregularities are observed in South America than in the southern mid-latitudes (least affected region). The irregularity coefficients in order from largest to smallest are as follows: South America, 3.49; the Arctic, 1.94; West Africa, 1.77; Southeast Asia, 1.27; South Asia, 1.24; the Antarctic, 1.10; East Africa, 0.89; the Pacific, 0.32; northern mid-latitudes, 0.15; southern mid-latitudes, 0.06.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Publication Date: 2021-12-20
    Description: The study of serpentinites and ophicarbonates from ophiolitic terrains provides a three-dimensional perspective on the hydration and carbonation processes affecting modern oceanic lithosphere. The Chenaillet ophiolite (western Alps) is interpreted as a fragment of an oceanic core complex that resembles a modern slow spreading center, and it was weakly affected by Alpine metamorphism. Ophicarbonates from the Chenaillet ophiolite were targeted in this study for in situ analysis by Secondary Ion Mass Spectrometry (SIMS) of oxygen and carbon isotopes in serpentine, calcite, dolomite and magnetite. The high spatial resolution of SIMS allowed us to target different serpentine, carbonate and magnetite generations intergrown at scales ≤ 50 μm, and reveal systematic zoning in δ18O with a range of 5.8‰ in serpentine (from 3.0 to 8.8‰, V-SMOW), 21.2‰ in carbonate (9.4 to 30.6‰), and 5.6‰ in magnetite (–5.0 to –10.6‰). Coupled analysis of oxygen isotopes in seven different touching-pairs of co-crystallized serpentine+carbonate and serpentine+magnetite provides independent constraints on both the temperatures and δ18O(water) values during serpentinization and carbonation responsible for the formation of the Chenaillet ophicarbonates. The new stable isotope data and thermometric estimates can be directly linked to textural and petrographic observations. These new results identify at least four different stages of hydrothermal alteration in the Chenaillet ophicarbonates: (1) peridotite hydration during seafloor exhumation at temperatures down to 200-130 °C and water δ18O values varying from 5 to 2‰, as documented by serpentine+magnetite in mesh textures; (2) carbonation during exhumation near the seafloor at temperatures as low as 10 °C assuming water δ18O values of –1‰, as documented by the highest oxygen isotope ratios in texturally older calcite; (3) serpentinization and carbonation at temperatures up to 240 °C and water δ18O values of 2-3‰, as documented by serpentine+magnetite in veins crosscutting mesh textures (T = 192±66 °C, δ18O(water) = 2±1‰, 2 standard deviation), serpentine+magnetite (T = 182±32 °C, δ18O(water) = 2±1‰) and serpentine+dolomite (T = 243±79 °C, δ18O(water) = 3±2‰) in recrystallized hourglass domains within serpentinite clasts, serpentine+dolomite (T = 229±50 °C, δ18O(water) = 3±1‰) and serpentine+calcite (T = 208±40 °C, δ18O(water) = 2±1‰) within the fine-grained calcite matrix surrounding serpentinite clasts; (4) late stage carbonation at temperatures down to 70-40 °C assuming water δ18O values of 3 to –1‰, as documented by the highest oxygen isotope ratios in a large calcite vein crosscutting both serpentinite clasts and fine-grained carbonate matrix. We suggest that the textural and isotopic observations are consistent with a protracted serpentinization and carbonation of the lithospheric mantle that started during progressive exhumation to the seafloor and continued due to interaction with hot and isotopically shifted seawater, which circulated at depth in the oceanic crust and was then discharged near the seafloor, similar to modern mid-ocean ridge venting systems.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Publication Date: 2021-11-25
    Description: We introduce the effects of self-attraction and loading (SAL) to the momentum equations of a barotropic global ocean tide model as well as a baroclinic general circulation model. We show for the tidal dynamics, that an explicit treatment of SAL is favourable compared to a scalar approximation or even disregarding the effects all together. For the general circulation the influence on the ocean bottom pressure is shown to be about 1 hPa for short time periods along the coasts and about 0.5 hPa for longer periods in resonant basins in the southern ocean. In contrast to previous studies, we additionally examine the effects of surface pressure anomalies over the continents in the computation of SAL which is shown to have an influence of about 0.5 hPa along the coasts. With those results, we demonstrate that the explicit treatment of SAL is important for satellite applications.
    Language: English
    Type: info:eu-repo/semantics/article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Publication Date: 2021-12-10
    Description: For the first time, rain effects on the polarimetric observations of the global navigation satellite system reflectometry (GNSS-R) are investigated. The physical feasibility of tracking the modifications in the surface roughness by rain splash and the surface salinity by the accumulation of freshwater is theoretically discussed. An empirical analysis is carried out using measurements of a coastal GNSS-R station with two side-looking antennas in right- and left-handed circular polarizations (RHCP and LHCP). Discernible drops in RHCP and LHCP powers are observed during rain over a calm sea. The power drop becomes larger at higher elevation angles. The average LHCP power drops by ≈ 5 dB at an elevation angle of 45°. The amplitude of the correlation sum shows a dampening, responding to rain rate systematically. The LHCP observations show higher sensitivity to rainfall compared to RHCP observations. The retrieved standard deviation of surface heights shows a steady increase with the rain rate. The derived surface salinity shows a decrease at rains higher than 10 mm/h. This study confirms the potential under environmental conditions of the GNSS-R ground-based station, e.g., with salinity mostly lower than 30 psu, over a calm sea, being a starting point for future investigations.
    Language: English
    Type: info:eu-repo/semantics/article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    facet.materialart.
    Unknown
    In:  Precipitation Science : Measurement, Remote Sensing, Microphysics and Modeling
    Publication Date: 2021-11-23
    Description: This chapter assesses the current and emerging satellite-based precipitation estimates (SPEs) from space, and their advantages and limitations from hydrometeorological and agricultural perspectives. Precipitation is one of the main climate variables that greatly benefits from satellite observations. Therefore, having knowledge about the characteristics of precipitation events in space, time, duration, and frequency is essential for a better understanding of the water cycle and climate. The current satellite-based precipitation missions offer opportunities to be used in various hydrometeorological and water management applications. While there are immense opportunities, there are major challenges in terms of accuracy and uncertainty, spatial resolution, data length and continuity, and community acceptability. Therefore the methodologies on how to improve these products in terms of accuracy, spatial resolution, and to generate long-term climate data records, are needed before being used as inputs to the hydrometeorological and water management applications. Lastly, we argue and identify the current major gaps of SPE and the opportunities to be used in flood, weather, and drought applications.
    Type: info:eu-repo/semantics/bookPart
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    facet.materialart.
    Unknown
    In:  Acoustic Emission Testing: Basics for Research – Applications in Engineering | Springer Tracts in Civil Engineering
    Publication Date: 2021-08-11
    Description: This chapter provides a general review of ongoing activities related to the geotechnical applications of the acoustic emission (AE) technique on various rock specimens. Recent and current worldwide AE studies are reviewed. This study highlights some key issues concerning the applications of many methods ranging from simple event counting with few AE sensors to complex focal mechanism investigations using multiple AE sensors.
    Language: English
    Type: info:eu-repo/semantics/bookPart
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Publication Date: 2022-01-05
    Description: The wind shear theory is widely accepted as an explanation for the formation of a sporadic E (Es) layer, but the direct comparison of Es with the local wind shear has been limited due to the lack of neutral wind measurements. This study examines the role of the vertical wind shear for Es, using signal-to-noise ratio profiles from COSMIC-2 radio occultation measurements and concurrent measurements of neutral wind profiles from the Ionospheric Connection Explorer. It is observed that the Es occurrence rate and average S4 index are correlated with the negative vertical shear of the eastward wind, providing observational support for the wind shear theory. Es can be observed even when the vertical wind shear is positive, which is interpreted as metallic ion layers generated at an earlier time.
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 11
    Publication Date: 2022-01-05
    Description: Ocean tide (OT) background models (BMs) used for a priori de-aliasing of GRACE/GRACE-FO observations feature distinct spatial uncertainties (primarily in coastal proximity and in latitudes above ±60°), and therefore pose one of the largest contributors to the overall retrieval error. The retrieval performance can be expected to increase if this underlying spatial error distribution is stochastically modelled and incorporated into the data processing chain. In this contribution, we derive realistic error variance-covariance matrices (VCM) based on a set of five state-of-the-art OT models. The additional value of using such VCMs is assessed through numerical closed-loop simulations, where they are rigorously propagated from model to observation level. Further, different approximations of the resulting VCM of observations are assumed, that is full, block-diagonal and diagonal, in order to evaluate the trade-off between computational efficiency and accuracy. It is asserted that correctly weighting the OT BM error can improve the gravity retrieval performance by up to three orders of magnitude, provided no further error contributors are considered. In comparison, the overall gain in retrieval performance is reduced to 75 per cent once instrument noise is taken into account. Here, it is shown that simultaneously modelling the OT BM and the instrument errors is critical, as each effect induces different types of correlations between observations, and exclusively considering covariance information based on the sensor noise may degrade the solution. We further demonstrate that the additional benefit of incorporating OT error VCMs is primarily limited by the de-aliasing performance for non-tidal mass variations of atmosphere (A) and oceans (O). This emphasizes the necessity of best-possible AO-de-aliasing (e.g. through optimized processing techniques and/or improved BMs) in order to optimally exploit the OT BM weighting.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 12
    Publication Date: 2022-01-03
    Description: Degassing of CO2 and precipitation of calcite to the surface of stalagmites can strongly impact isotope signals imprinted into the calcite of these speleothems. Here, we show that in all the variety of conditions occurring in nature only two distinct types of degassing exist. First, when a thin film of calcareous solution comes in contact to cave air lower pCO2 value than that of the aqueous CO2 in the water, molecular CO2 escapes by physical diffusion in several seconds. In a next step lasting several ten seconds, pH and DIC in the solution achieve chemical equilibrium with respect to the CO2 in the cave atmosphere. This solution becomes supersaturated with respect to calcite. During precipitation for each unit CaCO3 deposited one molecule of CO2 is generated and escapes from the solution. This precipitation driven degassing is active during precipitation onlyWe show that all variations of out gassing proposed in the literature are either diffusive outgassing or precipitation driven degassing and that diffusive outgassing has no influence on the isotope composition of the HCO3− pool and consequently on that of calcite. Its isotope imprint is determined solely by precipitation driven degassing in contrast to most explanations in the literature. We present a theoretical model of δ13C and δ18O that explains the contributions of various parameters such as changes in temperature, changes of pCO2 in the cave atmosphere, and changes in the drip intervals to the isotope composition of calcite precipitated to the apex of the stalagmite. We use this model to calculate quantitatively changes of δ13C and δ18O observed in field experiments (Carlson et al., 2020) in agreement to their experimental data. We also apply our model to prior calcite precipitation (PCP) in the field as reported by Mickler et al. (2019). We discuss how PCP influences isotope composition signals. In summary, we present a transparent method based on few commonly accepted equations that allows calculation of the isotope composition δ13C and δ18O of CaCO3 under various temperatures, pCO2 in the cave air, degrees of PCP, and concentrations of the water entering the cave.
    Type: info:eu-repo/semantics/article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 13
    Publication Date: 2022-01-24
    Description: Stress maps show the orientation of the current maximum horizontal stress (SHmax) in the earth's crust. Assuming that the vertical stress (SV) is a principal stress, SHmax defines the orientation of the 3D stress tensor; the minimum horizontal stress Shmin is than perpendicular to SHmax. In stress maps SHmax orientations are represented as lines of different lengths. The length of the line is a measure of the quality of data and the symbol shows the stress indicator and the color the stress regime. The stress data are freely available and part of the World Stress Map (WSM) project. For more information about the data and criteria of data analysis and quality mapping are plotted along the WSM website at http://www.world-stress-map.org. The stress map of Taiwan 2022 is based on the WSM database release 2016. However, all data records have been checked and we added a large number of new data from earthquake focal mechanisms from the national earthquake catalog and from publications. The total number of data records has increased from n=401 in the WSM 2016 to n=6,498 (4,234 with A-C quality) in the stress map of Taiwan 2022 The update with earthquake focal mechanims is even larger since another 1313 earthquake focal mechanism data records beyond the scale of this map have been added to the WSM database. The digital version of the stress map is a layered pdf file generated with GMT (Wessel et al., 2019). It also provide estimates of the mean SHmax orientation on a regular 0.1° grid using the tool stress2grid (Ziegler and Heidbach, 2019). Two mean SHmax orientations are estimated with search radii of r=25 and 50 km, respectively, and with weights according to distance and data quality. The stress map and data are available on the landing page at https://doi.org/10.5880/WSM.Taiwan2022 where further information is provided. The earthquake focal mechanism that are used for this stress map are provided by the Taiwan Earthquake Research Center (TEC) available at the TEC Data Center (https://tec.earth.sinica.edu.tw).
    Language: English
    Type: info:eu-repo/semantics/workingPaper
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 14
    Publication Date: 2022-01-24
    Description: The dataset presented here is an earthquake catalog for the central Sea of Marmara (Turkey) obtained by applying a traditional STA/LTA technique to the continuous waveforms. The magnitude of completeness of this catalog is MW = 1.4. The full description of the data processing and creation of the catalog is provided in the paper “Near - fault monitoring reveals combined seismic and slow activation of a fault branch within the Istanbul-Marmara seismic gap in NW Turkey” published by Martínez-Garzón et al., in Seismological Research Letters. The data are provided as the following two ASCII tables: The file 2021-004_Martinez-Garcon-et-al_Initial_seismicity_catalog contains the seismic events for which we could successfully calculate an earthquake location. The ASCII table has the following columns: columns: id, year, month, day, hour, minute, second, serial time, latitude, longitude, depth [km], magnitude, horizontal error [km], vertical error [km], RMS, maximum azimuthal gap [degree]. The table 2021-004_Martinez-Garcon-et-al_Relocated_seismicity_catalog contains the seismic events for which we could refine the initial location and obtain a double-difference refined location. The ASCII table has the following columns: id, latitude, longitude, depth [km], horizontal error [km], vertical error [km].
    Language: English
    Type: info:eu-repo/semantics/workingPaper
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 15
    Publication Date: 2022-01-24
    Description: The TTZ-South seismic profile follows the Teisseyre-Tornquist zone (TTZ) at the SW margin of the East European craton (EEC). Investigation results reveal the upper lithospheric structure as representing the NW-vergent, NE-SW striking overthrust-type, Paleoproterozoic (~1.84–1.8 Ga) Fennoscandia-Sarmatia suture. The Sarmatian segment of the EEC comprises two crustal-scale tectonic thrust slices: the Moldavo-Podolian and Lublino-Volhynian basement units, overriding the northerly located Lysogoro-Radomian unit of Fennoscandian affinity. The combined results of the TTZ-South and other nearby deep seismic profiles are consistent with a continuation of the EEC cratonic basement across the TTZ to the SW and its plunging into the deep substratum of the adjacent Paleozoic platform. Extensional deformation responsible for the formation of the mid to late Proterozoic (~1.4–0.6 Ga), SW-NE trending Orsha-Volhynia rift basin is probably also recorded. The thick Ediacaran succession deposited in the rift was later tectonically thickened due to Variscan deformation. The Moho depth varies between 37 and 49 km, resulting in the thinnest crust in the SE, sharp depth changes across the TTZ, and slow shallowing from 49 to 43 km to the NW. The abrupt Moho depth increase from 43 to 49 km is considered to reflect the overlying lower crust tectonic duplication within the suture zone.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 16
    Publication Date: 2022-01-24
    Description: Very large tsunamis are associated with low probabilities of occurrence. In many parts of the world, these events have usually occurred in a distant time in the past. As a result, there is low risk perception and a lack of collective memories, making tsunami risk communication both challenging and complex. Furthermore, immense challenges lie ahead as population and risk exposure continue to increase in coastal areas. Through the last decades, tsunamis have caught coastal populations off-guard, providing evidence of lack of preparedness. Recent tsunamis, such as the Indian Ocean Tsunami in 2004, 2011 Tohoku and 2018 Palu, have shaped the way tsunami risk is perceived and acted upon. Based on lessons learned from a selection of past tsunami events, this paper aims to review the existing body of knowledge and the current challenges in tsunami risk communication, and to identify the gaps in the tsunami risk management methodologies. The important lessons provided by the past events call for strengthening community resilience and improvement in risk-informed actions and policy measures. This paper shows that research efforts related to tsunami risk communication remain fragmented. The analysis of tsunami risk together with a thorough understanding of risk communication gaps and challenges is indispensable towards developing and deploying comprehensive disaster risk reduction measures. Moving from a broad and interdisciplinary perspective, the paper suggests that probabilistic hazard and risk assessments could potentially contribute towards better science communication and improved planning and implementation of risk mitigation measures.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 17
    Publication Date: 2022-01-21
    Description: Drainage-divide migration, controlled by rock-uplift and rainfall patterns, may play a major role in the geomorphic evolution of mountain ranges. However, divide-migration rates over geologic timescales have only been estimated by theoretical studies and remain empirically poorly constrained. Geomorphological evidence suggests that the Sierra de Aconquija, on the eastern side of the southern Central Andes, northwest Argentina, is undergoing active westward drainage-divide migration. The mountain range has been subjected to steep rock trajectories and pronounced orographic rainfall for the last several million years, presenting an ideal setting for using low-temperature thermochronometric data to explore its topographic evolution. We perform three-dimensional thermal-kinematic modeling of previously published thermochronometric data spanning the windward and leeward sides of the range to explore the most likely structural and topographic evolution of the range. We find that the data can be explained by scenarios involving drainage-divide migration alone, or by scenarios that also involve changes in the structures that have accommodated deformation through time. By combining new 10Be-derived catchment-average denudation rates with geomorphic constraints on probable fault activity, we conclude that the evolution of the range was likely dominated by west-vergent faulting on a high-angle reverse fault underlying the range, together with westward drainage-divide migration at a rate of several km per million years. Our findings place new constraints on the magnitudes and rates of drainage-divide migration in real landscapes, quantify the effects of orographic rainfall and erosion on the topographic evolution of a mountain range, and highlight the importance of considering drainage-divide migration when interpreting thermochronometer age patterns.
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 18
    Publication Date: 2022-01-21
    Description: Comparing the performance of different satellite sensors in global land cover change (LCC) monitoring is necessary to assess their potential and limitations for more accurate and operational LCC estimations. This paper aims to examine and compare the performance in LCC monitoring using three satellite sensors: PROBA-V, Landsat 8 OLI, and Sentinel-2 MSI. We utilized a unique set of global reference data containing four years of records (2015–2018) at 29,263 land cover change/no-change 100 × 100-m sites. The LCC monitoring was conducted using the BFAST(s)-Random Forest (BRF) change detection framework involving 15 global timeseries vegetation indices and three BFAST models. Due to the different spectral characteristics and data availability of the sensors, we designed 30 comparison scenarios to extensively evaluate their performance. The overall results were: 1) for global general LCC monitoring, Landsat 8 OLI slightly outperformed Sentinel-2, and PROBA-V performed the worst. The performance among the three sensors differed consistently despite different data availability and spectral observation regions. Sentinel-2 was more competitive with Landsat 8 when the red-edge 1 band was included; 2) Landsat 8 was more accurate in forest, herbaceous vegetation, and water monitoring. Sentinel-2 performed particularly well in wetland monitoring. In addition, we further observed: 3) missing data in time series decreased the accuracy in all sensors, but had little influence on the relative performance across sensors; 4) combining sensors would not necessarily improve the accuracy because the complementary effects enhanced the accuracy only when there was a large amount of data missing for all sensors; 5) the BRF framework maintained the performance gap among sensors, but obtained a higher and more balanced accuracy overall when compared with using BFAST methods alone, by involving ensemble learning with an embedded sample-balancing strategy; 6) among the random forest variables, the ‘magnitude’ proved to be the most important contributor, and the NDVI had the most consistently good performance across sensors when compared against other vegetation indices. All sensors using BRF still had some errors in change detection, with a tendency to underestimate the global LCC. A potential reason for this is the complexity of the diverse change/no-change characteristics at the global extent and the fact that smaller, more subtle LCCs might not be well detected. These limitations could be addressed by taking advantage of ensemble learning approaches with a combination of multiple independent region/thematic-adapted LCC monitoring models and using the original Sentinel-2 (10 m) and Landsat 8 (30 m) in the future.
    Language: English
    Type: info:eu-repo/semantics/article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 19
    Publication Date: 2022-01-21
    Description: Here we report on the oxygen isotope compositions of four proposed apatite reference materials (chlorapatite MGMH#133648 and fluorapatite specimens MGMH#128441A, MZ-TH, and ES-MM). The samples were initially screened for 18O/16O homogeneity using secondary ion mass spectrometry (SIMS) followed by δ18O determinations in six gas source isotope ratio mass spectrometry laboratories (GS-IRMS) employing a variety of analytical protocols for determining either phosphate-bonded or “bulk” oxygen compositions. We also report preliminary δ17O and Δ’17O data, major and trace element compositions collected using EPMA as well as CO32- and OH- contents in the apatite structure assessed using thermogravimetric analysis and infrared spectroscopy. The repeatability of our SIMS measurements was better than ± 0.25 ‰ (1s) for all four materials that cover a wide range of 103δ18O values between +5.8 and +21.7. The GS-IRMS results show, however, a significant offset of 103δ18O values between the “phosphate” and “bulk” analyses that could not be correlated with chemical characteristics of the studied samples. Therefore, we provide two sets of working values specific to these two classes of analytical methodologies as well as current working values for SIMS data calibration.
    Type: info:eu-repo/semantics/article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 20
    Publication Date: 2022-01-21
    Description: Several forest change detection algorithms are available for tracking and quantifying deforestation based on dense Landsat and Sentinel time series satellite data. Only few also capture regrowth after clearing in an accurate and continuous way across a diversity of forest types (including dry and seasonal forests) and are thus suitable to address the need for better information on secondary forest succession and for assessing forest restoration activities. We present a new change detection algorithm that makes use of the flexibility of kernel density estimations to create a forest reference phenology, taking into account all historical phenological variations of the forest rather than smoothing these out by curve fitting. The AVOCADO (Anomaly Vegetation Change Detection) algorithm allows detection of anomalies with a spatially explicit likelihood measure. We demonstrate the flexibility of the algorithm for three contrasting sites using all available Landsat time series data; ranging from tropical rainforest to dry miombo forest ecosystems, with different time series data densities, and characterized by different forest change types (e.g. selective logging, shifting cultivation). We found that the approach produced in general high overall accuracies (〉 90%) across these varying conditions, but had lower accuracies in the dry forest site with a slight overestimation of disturbances and regrowth. The latter was due to the similarity of crops in the time series NDMI signal, causing false regrowth detections. In the moist forest site the low producer accuracies in the intact forest and regrowth class was due to its very small area class (most forest disappeared by the nineties). We showed that the algorithm is capable of capturing small-scale (gradual) changes (e.g. selective logging, forest edge logging) and the multiple changes associated to shifting cultivation. The performance of the algorithm has been shown at regional scale, but if larger scale studies are required a representative selection of reference forest types need to be selected carefully. The outputs of the change maps allow the estimation of the spatio-temporal trends in the proportions of intact forest, secondary forest and non-forest - information that is useful for assessing the areas and potential of secondary forests to accumulate carbon and forest restoration targets. The algorithm can be used for disturbance and regrowth monitoring in different ecozones, is user friendly, and open source.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 21
    Publication Date: 2022-01-21
    Description: For monitoring and reporting forest carbon stocks and fluxes, many countries in the tropics and subtropics rely on default values of forest aboveground biomass (AGB) from the Intergovernmental Panel on Climate Change (IPCC) guidelines for National Greenhouse Gas (GHG) Inventories. Default IPCC forest AGB values originated from 2006, and are relatively crude estimates of average values per continent and ecological zone. The 2006 default values were based on limited plot data available at the time, methods for their derivation were not fully clear, and no distinction between successional stages was made. As part of the 2019 Refinement to the 2006 IPCC Guidelines for GHG Inventories, we updated the default AGB values for tropical and subtropical forests based on AGB data from 〉25 000 plots in natural forests and a global AGB map where no plot data were available. We calculated refined AGB default values per continent, ecological zone, and successional stage, and provided a measure of uncertainty. AGB in tropical and subtropical forests varies by an order of magnitude across continents, ecological zones, and successional stage. Our refined default values generally reflect the climatic gradients in the tropics, with more AGB in wetter areas. AGB is generally higher in old-growth than in secondary forests, and higher in older secondary (regrowth 〉20 years old and degraded/logged forests) than in young secondary forests (⩽20 years old). While refined default values for tropical old-growth forest are largely similar to the previous 2006 default values, the new default values are 4.0–7.7-fold lower for young secondary forests. Thus, the refined values will strongly alter estimated carbon stocks and fluxes, and emphasize the critical importance of old-growth forest conservation. We provide a reproducible approach to facilitate future refinements and encourage targeted efforts to establish permanent plots in areas with data gaps.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 22
    Publication Date: 2022-01-28
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 23
    Publication Date: 2022-01-28
    Description: The Jebel El Akhouat Zn-Pb-(Ba-Sr) ore deposit, located in the Tunisian Dome zone, is hosted mainly in the organic matter-rich Albian and Cenomanian–Turonian rocks. The orebodies occur mainly as open-space fillings and are structurally-controlled. The paragenetic sequence consists of three stages, which reflect three ore events. Three discrete stages of Zn-Pb sulfide and/or Zn-Pb-Ba-Sr sulfide-sulfate ores are identified. Fluid inclusion study carried out on selected minerals of different stages reveals that sphalerite, galena, marcasite, celestine, barite, and fluorite precipitated as a result of mixing between a hydrothermal, saline, metal-rich basinal fluid and a low-temperature, less saline, metal-depleted, sulfur- or sulfate-rich fluid with the intermittent involvement of hydrocarbons. Based on sulfur isotope data, sulfur of sulfides was derived from the reduction of the dissolved Triassic sulfates primary through thermochemical sulfate reduction with a contribution of bacterial sulfate reduction. The Pb isotopic composition of galena samples and trace elements data of the host carbonate rocks suggest that metals were derived primarily from the Paleozoic siliciclastic rocks with a contribution of the organic matter-rich Albian and Cenomanian–Turonian rocks. The Alpine orogeny triggered the migration of the metalliferous fluids from the deep parts of the basin towards the peridiapiric paleohigh of Ech Chehid diapir through major faults towards the loci of deposition.
    Type: info:eu-repo/semantics/article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 24
    Publication Date: 2022-01-28
    Description: Transmission electron microscopy and 3D focused ion beam/scanning electron microscope nanotomography are applied to grain and phase boundaries between quartz, plagioclase, K-feldspar, clinopyroxene, amphibole, and calcite. The samples come from metamorphic, plutonic and volcanic rocks, and hydrothermal quartz, and experienced cooling and decompression after highly variable P–T peak conditions. Most of the boundaries are partially open in the range of up to several hundred nanometres and partly to totally filled with secondary minerals, such as actinolite, biotite, chlorite, sheet silicates, and quartz, as well as with amorphous matter. Cracking and opening of boundaries are suggested to be related to anisotropic thermoelastic response of crystals to cooling. It starts below the brittle–ductile transition of the involved minerals. The partially open grain and phase boundaries, together with dissolution-generated cavities, can form porosity of more than 2 vol.% and permeability under conditions of at least lowermost greenschist facies. Such networks of partially open or partially refilled boundaries potentially affect properties of crystalline rocks and processes in the upper crust, such as metasomatism, weathering, migration of radionuclides through bedrock of geological repositories of nuclear waste, and deformation in nature and in experiment.
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 25
    Publication Date: 2022-01-28
    Description: Marine terraces are a cornerstone for the study of paleo sea level and crustal deformation. Commonly, individual erosive marine terraces are attributed to unique sea-level high stands based on the reasoning that marine platforms could only be significantly widened at the beginning of an interglacial. However, this logic implies that wave erosion is insignificant at other times. We postulate that the erosion potential at a given bedrock elevation datum is proportional to the total duration of sea-level occupation at that datum. The total duration of sea-level occupation depends strongly on rock uplift rate. Certain rock uplift rates may promote the generation and preservation of particular terraces while others prevent them. For example, at rock uplift of ~1.2 mm/yr, the Marine Isotope Stage (MIS) 5e (ca. 120 ka) high stand reoccupies the elevation of the MIS 6d–e mid-stand, favoring creation of a wider terrace than at higher or lower rock uplift rates. Thus, misidentification of terraces can occur if each terrace in a sequence is assumed to form uniquely at successive interglacial high stands and to reflect their relative elevations. Developing a graphical proxy for the entire erosion potential of sea-level history allows us to address creation and preservation biases at different rock uplift rates.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 26
    Publication Date: 2022-01-28
    Description: The mid-Proterozoic (1.64 Ga) stratigraphy of the McArthur Basin (Australia) contains some of the most well-preserved sedimentary rocks of Precambrian age, which are also host to giant, clastic dominant (CD-type) massive sulfide Zn deposits. The most recently discovered CD-type deposit (the Teena deposit) is located in the Teena subbasin and hosted by the 1.64 Ga Barney Creek Formation. The Teena subbasin, therefore, provides the perfect natural laboratory for evaluating authigenic and hydrothermal controls on TE (TE) variability, both of which contribute to paleoenvironmental reconstructions and ore deposit models. As the Teena deposit formed beneath the paleoseafloor, this also provides the opportunity to evaluate TE zonation around a fossilized subseafloor replacement hydrothermal system. In situ laser ablation inductively coupled mass spectrometry (LA-ICP-MS) has been used to define compositional end members in diagenetic and hydrothermal pyrite. The overgrowth of hydrothermal sulfides on diagenetic pyrite is associated with TE anomalism (Tl, Pb, As, Zn) that extends 〉 100 meters above the main high grade sulfide mineralization the Teena subbasin. The vertical zonation in TEs is consistent with the diffusion of hydrothermal fluids into overlying hangingwall sediments that were undergoing diagenesis. Bulk rock lithogeochemical data record covariation between total organic carbon (TOC) and a suite of TEs (Mo, Co, Ni, V). We suggest this was caused by local hydrographic factors during deposition of the Barney Creek Formation. High TOC/P molar ratios, resulting from regeneration of P in a euxinic water column, are associated with an interval overlying the main maximum flooding surface in the subbasin. The relationships between TOC, P and TEs resemble the redox architecture of a silled basin rather than an open marine margin. Sulfidic conditions developed during periods of high productivity, which were linked to nutrient supply that was enhanced by connectivity with surrounding water masses. The evidence of redox bistability, involving a delicate balance between ferruginous (anoxic, non-sulfidic) and euxinic (sulfidic) conditions, is consistent with recent models for other mid-Proterozoic sedimentary units. Nevertheless, there was a strong localised (101 km2) control on the authigenic and hydrothermal TE chemistry of the Barney Creek Formation in the Teena subbasin, which highlights a key challenge when extrapolating from data collected in partially restricted intracontinental marine settings.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 27
    Publication Date: 2022-01-28
    Description: End-member modelling analysis is a statistic approach to unmixing multimodal grain size distributions to identify and quantify processes of sediment generation, transport and deposition. While the different computational implementations have been extensively benchmarked and show similarly high reliability characteristics, there is a series of unknowns regarding the applicability, quality and limitations of the method from a practical point of view. This study explores these important unknowns using both empirical and synthetic samples along with Monte Carlo tests. Under ideal conditions (all avail able samples, randomly mixed components, 116 grain-size classes), EMMA is able to model the grain-size distributions of input end-members (loadings) with R2 between 0.63 and 0.98 and their relative contributions to each sample (scores) with R2 between 0.71 and 0.81, thus setting the baseline for model quality. Inappropriate model parameter settings cause severe drops in R2. EMMA is able to detect an end-member even if it is present in only one sample or when it contributes less than 10 vol.-%. With 20 to 40 samples or more, stable, high quality model results are possible. With 15 or more grain-size classes, model results also reach such stable high reproducibility levels. EMMA can depict originally multimodal end-members (R2 between 0.78 and 0.99). End-members with identical relative grain-size distribution shape can overlap significantly without causing quality drops; R2 of identical distributions are invariantly high until mode positions are less than three grain-size classes apart from each other. Gradually widening end-member distributions do not affect the results significantly. However, shifting mode positions have a severe impact. Post-depositional mixing causes drastic deviations of the modelled scores, whereas the loadings are virtually unaffected. In light of these tests, EMMA is a reliable, mostly unbiased tool to identify and quantify sediment generation/transport/deposition regimes from mixed sediment deposits, given it is used in a geoscientifically meaningful context.
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 28
    Publication Date: 2022-01-28
    Description: Induced seismicity associated with fluid injection into underground formations jeopardizes the sustainable utilization of the subsurface. Understanding the fault behavior is the key to successful management and mitigation of injection-induced seismic risks. As a fundamental approach, laboratory experiments have been extensively conducted to assist constraining the processes that lead to and sustain various injection-induced fault slip modes. Here, we present a state-of-the-art review on the emerging topic of injection-induced seismicity from the laboratory perspective. The basics of fault behavior, including fault strength and instability, are first briefly summarized, followed by the paradoxical stability analysis arising from the current theoretical framework. After the description of common laboratory methods and auxiliary techniques, we then comprehensively review the effects of fault properties, stress state, temperature, fluid physics, fluid chemistry and injection protocol on fault behavior with particular focus on the implications for injection-induced seismicity. We find that most of the shear tests are conducted under displacement-driven conditions, while the number of injection-driven shear tests is comparatively limited. The review shows that the previous work on displacement-driven rock friction and fault slip modes partially unravel the mystery of injection-induced fault behavior, and recent experimental studies on the injection-driven response of critically stressed faults provide complementary insights. Overall, laboratory experiments have substantially advanced especially our understanding of the roles of fault roughness, fault mineralogy, stress state, fluid viscosity, fluid induced mineral dissolution, and injection rate in injection-induced seismicity, which has been successfully used to interpret many field observations. However, there are still outstanding questions in this area, which could be addressed by future experimental studies, such as the feasibility of seismic-informed adaptive injection strategy for mitigating seismic risks, cold fluid injection into critically stressed faults under hydrothermal conditions, and fault friction evolution during cyclic injection spanning from undrained to drained conditions.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 29
    Publication Date: 2022-01-28
    Description: High-elevation, low-relief surfaces are widespread in many mountain belts. However, the origin of these surfaces has long been debated. In particular, the southeast Tibetan Plateau has extensive low-relief surfaces perched above deep valleys and in the headwaters of three of the world’s largest rivers (Salween, Mekong, and Yangtze Rivers). Various geologic data and geodynamic models show that many mountain belts grow first to a certain height and then laterally in an outward propagation sequence. By translating this information into a kinematic propagating uplift function in a landscape evolution model, we propose that the high-elevation, low-relief surfaces in the southeast Tibetan Plateau are simply a consequence of mountain growth and do not require a special process to form. The propagating uplift forms an elongated river network geometry with broad high-elevation, low-relief headwaters and interfluves that persist for tens of millions of years, consistent with the observed geochronology. We suggest that the low-relief interfluves can be long-lived because they lack the drainage networks necessary to keep pace with the rapid incision of the large main-stem rivers. The propagating uplift also produces spatial and temporal exhumation patterns and river profile morphologies that match observations. Our modeling therefore reconciles geomorphic observations with geodynamic models of uplift of the southeast Tibetan Plateau, and it provides a simple mechanism to explain the low-relief surfaces observed in several mountain belts on Earth.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 30
    facet.materialart.
    Unknown
    In:  Journal of Geophysical Research: Solid Earth
    Publication Date: 2022-01-28
    Description: We propose a global geomagnetic field model for the last fourteen thousand years, based on thermoremanent records. We call the model ArchKalmag14k. ArchKalmag14k is constructed by modifying recently proposed algorithms, based on space-time correlations. Due to the amount of data and complexity of the model, the full Bayesian posterior is numerically intractable. To tackle this, we sequentialize the inversion by implementing a Kalman-filter with a fixed time step. Every step consists of a prediction, based on a degree dependent temporal covariance, and a correction via Gaussian process regression. Dating errors are treated via a noisy input formulation. Cross-correlations are re-introduced by a smoothing algorithm and model parameters are inferred from the data. Due to the specific statistical nature of the proposed algorithms, the model comes with space and time dependent uncertainty estimates. The new model ArchKalmag14k shows less variation in the large scale degrees than comparable models. Local predictions represent the underlying data and agree with comparable models, if the location is sampled well. Uncertainties are bigger for earlier times and in regions of sparse data coverage. We also use ArchKalmag14k to analyze the appearance and evolution of the South Atlantic anomaly together with reverse flux patches at the core mantle boundary, considering the model uncertainties. While we find good agreement with earlier models for recent times, our model suggests a different evolution of intensity minima prior to 1650 CE. In general, our results suggest that prior to 6000 BCE the data is not sufficient to support global models.
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 31
    Publication Date: 2022-01-26
    Description: The wet tropospheric correction (WTC) retrieved from the onboard calibration microwave radiometer (CMR) of Haiyang-2A (HY-2A) is critical in monitoring the global sea level. However, the CMR WTC became significantly biased from June 2017 due to the failure of the 18.7-GHz band, which caused massive errors in the sea surface height (SSH) measurements. We investigate the accuracy of the CMR WTC derived from the two remaining bands to address this problem. A comprehensive evaluation using multisource data demonstrates that the dual-band + backscattering coefficient (BC) algorithm achieves comparable accuracy to the three-band algorithm, and it does not suffer from any large errors when the equipment works well. Hence, we calibrated the HY-2A CMR data with the dual-band + BC algorithm when the 18.7-GHz band failed, and the accuracy of the CMR WTC is improved from 2.34 to 1.39 cm compared with European Center for Medium-Range Weather Forecasts (ECMWF) ERA5 data. In addition, the SSH measurements are improved significantly by a maximum of 2 cm in mean value using the dual-band + BC WTC during the failure period of HY-2A CMR. Compared with Jason-3 SSH measurements, the HY-2A with dual-band + BC shows a slightly larger difference than HY-2A with three-band by 0.1 cm in rms. This method prolongs the operational lifetime of the HY-2A CMR and could be used in the reprocessing of HY-2A observations.
    Type: info:eu-repo/semantics/article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 32
    Publication Date: 2022-01-26
    Description: Water-rock interactions are relevant to planetary habitability, influencing mineralogical diversity and the production of organic molecules. We examine carbonates and silicates in the martian meteorite Allan Hills 84001 (ALH 84001), using colocated nanoscale analyses, to characterize the nature of water-rock reactions on early Mars. We find complex refractory organic material associated with mineral assemblages that formed by mineral carbonation and serpentinization reactions. The organic molecules are colocated with nanophase magnetite; both formed in situ during water-rock interactions on Mars. Two potentially distinct mechanisms of abiotic organic synthesis operated on early Mars during the late Noachian period (3.9 to 4.1 billion years ago).
    Type: info:eu-repo/semantics/article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 33
    Publication Date: 2022-01-26
    Description: A regional harmonic spline geomagnetic main field model, Southern Africa Core Field Model (SACFM-3), is derived from Swarm satellite and ground-based data for the southern African region, in the eastern part of the South Atlantic Anomaly (SAA) where the field intensity continues to decrease. Using SACFM-3 and the global CHAOS-6-×9 model, a detailed study was conducted to shed light on the high spatial and temporal geomagnetic field variations over Southern Africa between 2014 and 2019. The results show a steady decrease of the radial component Z in almost the entire region. In 2019, its rate of decrease in the western part of the region has reached high values, 76 nT/year and 78 nT/year at Tsumeb and Keetmanshoop magnetic observatories, respectively. For some areas in the western part of the region the radial component Z and field intensity F have decreased in strength, from 1.0 to 1.3% and from 0.9 to 1.2%, respectively, between the epochs 2014.5 and 2019.5. There is a noticeable decrease of the field intensity from the south-western coast of South Africa expanding towards the north and eastern regions. The results show that the SAA area is continuing to grow in the region. Abrupt changes in the linear secular variation in 2016 and 2017 are confirmed in the region using ground-based data, and the X component shows an abrupt change in the secular variation in 2018 at four magnetic observatories (Hermanus, Hartebeesthoek, Tsumeb and Keetmanshoop) that needs further investigation. The regional model SACFM-3 reflects to some extent these fast core field variations in the Z component at Hermanus, Hartebeesthoek and Keetmanshoop observatories.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 34
    Publication Date: 2022-01-26
    Language: English
    Type: info:eu-repo/semantics/other
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 35
    Publication Date: 2022-01-26
    Description: High-altitude ecosystems react sensitively to hydroclimatic triggers. Here we evaluated the ecological and hydrological changes in a glacier-influenced lake (Hala Hu, China) since the last glacial. Rapid fluctuations of aquatic biomarker concentrations, ratios, and hydrogen isotope values, from 15 to 14,000 and 8 to 5000 years before present, provided evidence for aquatic regime shifts and changes in lake hydrology. In contrast, most negative hydrogen isotope values of terrestrial biomarkers were observed between 9 and 7,000 years before present. This shows that shifts of vapour sources and increased precipitation amounts were not relevant drivers behind ecosystem changes in the studied lake. Instead, receding glaciers and increased meltwater discharge, driven by higher temperatures, caused the pronounced ecological responses. The shifts within phytoplankton communities in the Late Glacial and mid Holocene illustrate the vulnerability of comparable ecosystems to climatic and hydrological changes. This is relevant to assess future ecological responses to global warming.
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 36
    Publication Date: 2022-01-26
    Description: Reliable, accurate, and timely information about oceans is important for many applications, including water resource management, hydrological cycle monitoring, environmental studies, agricultural and ecosystem health applications, economy, and the overall health of the environment. In this regard, remote sensing (RS) systems offer exceptional advantages for mapping and monitoring various oceanographic parameters with acceptable temporal and spatial resolutions over the oceans and coastal areas. So far, different methods have been developed to study oceans using various RS systems. This urges the necessity of having review studies that comprehensively discuss various RS systems, including passive and active sensors, and their advantages and limitations for ocean applications. In this article, the goal is to review most RS systems and approaches that have been worked on marine applications. This review paper is divided into two parts. Part 1 is dedicated to the passive RS systems for ocean studies. As such, four primary passive systems, including optical, thermal infrared radiometers, microwave radiometers, and Global Navigation Satellite Systems, are comprehensively discussed. Additionally, this article summarizes the main passive RS sensors and satellites, which have been utilized for different oceanographic applications. Finally, various oceanographic parameters, which can be retrieved from the data acquired by passive RS systems, along with the corresponding methods, are discussed.
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 37
    Publication Date: 2022-01-28
    Description: Ground motion with strong‐velocity pulses can cause significant damage to buildings and structures at certain periods; hence, knowing the period and velocity amplitude of such pulses is critical for earthquake structural engineering. However, the physical factors relating the scaling of pulse periods with magnitude are poorly understood. In this study, we investigate moderate but damaging earthquakes (⁠Mw 6–7) and characterize ground‐motion pulses using the method of Shahi and Baker (2014) while considering the potential static‐offset effects. We confirm that the within‐event variability of the pulses is large. The identified pulses in this study are mostly from strike‐slip‐like earthquakes. We further perform simulations using the frequency–wavenumber algorithm to investigate the causes of the variability of the pulse periods within and between events for moderate strike‐slip earthquakes. We test the effect of fault dips, and the impact of the asperity locations and sizes. The simulations reveal that the asperity properties have a high impact on the pulse periods and amplitudes at nearby stations. Our results emphasize the importance of asperity characteristics, in addition to earthquake magnitudes for the occurrence and properties of pulses produced by the forward directivity effect. We finally quantify and discuss within‐ and between‐event variabilities of pulse properties at short distances.
    Language: English
    Type: info:eu-repo/semantics/article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 38
    Publication Date: 2022-01-28
    Description: Fault zones are major sources of hazard for many populated regions around the world. Earthquakes still occur unanticipated, and research has started to observe fault properties with increasing spatial and temporal resolution, having the goal of detecting signs of stress accumulation and strength weakening that may anticipate the rupture. The common practice is monitoring source parameters retrieved from measurements; however, model dependence and strong uncertainty propagation hamper their usage for small and microearthquakes. Here, we decipher the ground motion (i.e., ground shaking) variability associated with microseismicity detected by dense seismic networks at a near-fault observatory in Irpinia, Southern Italy, and obtain an unprecedentedly sharp picture of the fault properties evolution both in time and space. We discuss the link between the ground-motion intensity and the source parameters of the considered microseismicity, showing a coherent spatial distribution of the ground-motion intensity with that of corner frequency, stress drop, and radiation efficiency. Our analysis reveals that the ground-motion intensity presents an annual cycle in agreement with independent geodetic displacement observations from two Global Navigation Satellite System stations in the area. The temporal and spatial analyses also reveal a heterogeneous behavior of adjacent fault segments in a high seismic risk Italian area. Concerning the temporal evolution of fault properties, we highlight that the fault segment where the 1980 Ms 6.9 Irpinia earthquake nucleated shows changes in the event-specific signature of ground-motion signals since 2013, suggesting changes in their frictional properties. This evidence, combined with complementary information on the earthquake frequency–magnitude distribution, reveals differences in fault segment response to tectonic loading, suggesting rupture scenarios of future moderate and large earthquakes for seismic hazard assessment.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 39
    Publication Date: 2022-01-28
    Description: Seismic event detection and phase picking are the base of many seismological workflows. In recent years, several publications demonstrated that deep learning approaches significantly outperform classical approaches, achieving human-like performance under certain circumstances. However, as studies differ in the datasets and evaluation tasks, it is unclear how the different approaches compare to each other. Furthermore, there are no systematic studies about model performance in cross-domain scenarios, i.e., when applied to data with different characteristics. Here, we address these questions by conducting a large-scale benchmark. We compare six previously published deep learning models on eight datasets covering local to teleseismic distances and on three tasks: event detection, phase identification and onset time picking. Furthermore, we compare the results to a classical Baer-Kradolfer picker. Overall, we observe the best performance for EQTransformer, GPD and PhaseNet, with a small advantage for EQTransformer on teleseismic data. Furthermore, we conduct a cross-domain study, analyzing model performance on datasets they were not trained on. We show that trained models can be transferred between regions with only mild performance degradation, but models trained on regional data do not transfer well to teleseismic data. As deep learning for detection and picking is a rapidly evolving field, we ensured extensibility of our benchmark by building our code on standardized frameworks and making it openly accessible. This allows model developers to easily evaluate new models or performance on new datasets. Furthermore, we make all trained models available through the SeisBench framework, giving end-users an easy way to apply these models.
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 40
    Publication Date: 2022-01-19
    Description: Time-variable gravity measurements from the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) missions have opened up a new avenue of opportunities for studying large-scale mass redistribution and transport in the Earth system. Over the past 19 years, GRACE/GRACE-FO time-variable gravity measurements have been widely used to study mass variations in different components of the Earth system, including the hydrosphere, ocean, cryosphere, and solid Earth, and significantly improved our understanding of long-term variability of the climate system. We carry out a comprehensive review of GRACE/GRACE-FO satellite gravimetry, time-variable gravity fields, data processing methods, and major applications in several different fields, including terrestrial water storage change, global ocean mass variation, ice sheets and glaciers mass balance, and deformation of the solid Earth. We discuss in detail several major challenges we need to face when using GRACE/GRACE-FO time-variable gravity measurements to study mass changes, and how we should address them. We also discuss the potential of satellite gravimetry in detecting gravitational changes that are believed to originate from the deep Earth. The extended record of GRACE/GRACE-FO gravity series, with expected continuous improvements in the coming years, will lead to a broader range of applications and improve our understanding of both climate change and the Earth system.
    Language: English
    Type: info:eu-repo/semantics/article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 41
    Publication Date: 2022-01-19
    Description: Long-term excessive groundwater exploitation for agricultural, domestic and stock applications has resulted in substantial ground subsidence in Arizona, USA, and especially in the Willcox Groundwater Basin. The land subsidence rate of the Willcox Basin has not declined but has rather increased in recent years, posing a threat to infrastructure, aquifer systems, and ecological environments. In this study, we first investigate the spatiotemporal characteristics of land subsidence in the Willcox Groundwater Basin using an interferometric synthetic aperture radar (InSAR) time series analytical approach with L-band ALOS and C-band Sentinel-1 SAR data acquired from 2006 to 2020. The overall deformation patterns are characterized by two major zones of subsidence, with the mean subsidence rate increasing with time from 2006 to 2020. An approach based on independent component analysis (ICA) was adopted to separate the mixed InSAR time series signal into a set of independent signals. The application of ICA to the Willcox Basin not only revealed that two different spatiotemporal deformation features exist in the basin but also filtered the residual errors in InSAR observations to enhance the deformation time series. Integrating the InSAR deformation and groundwater level data, the response of the aquifer skeletal system to the change in hydraulic head was quantified, and the hydromechanical properties of the aquifer system were characterized. Historical spatiotemporal storage loss from 1990 to 2020 was also estimated using InSAR measurements, hydraulic head and estimated skeletal storativity. Understanding the characteristics of land surface deformation and quantifying the response of aquifer systems in the Willcox Basin and other groundwater basins elsewhere are important in managing groundwater exploitation to sustain the mechanical health and integrity of aquifer systems.
    Language: English
    Type: info:eu-repo/semantics/article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 42
    Publication Date: 2022-01-19
    Description: Earthquake site responses or site effects are the modifications of surface geology to seismic waves. How well can we predict the site effects (average over many earthquakes) at individual sites so far? To address this question, we tested and compared the effectiveness of different estimation techniques in predicting the outcrop Fourier site responses separated using the general inversion technique (GIT) from recordings. Techniques being evaluated are (a) the empirical correction to the horizontal-to-vertical spectral ratio of earthquakes (c-HVSR), (b) one-dimensional ground response analysis (GRA), and (c) the square-root-impedance (SRI) method (also called the quarter-wavelength approach). Our results show that c-HVSR can capture significantly more site-specific features in site responses than both GRA and SRI in the aggregate, especially at relatively high frequencies. c-HVSR achieves a “good match” in spectral shape at ∼80%–90% of 145 testing sites, whereas GRA and SRI fail at most sites. GRA and SRI results have a high level of parametric and/or modeling errors which can be constrained, to some extent, by collecting on-site recordings.
    Language: English
    Type: info:eu-repo/semantics/article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 43
    Publication Date: 2022-01-19
    Description: This dataset provides friction data from ring-shear tests (RST) on twice broken rice used in the GEC Laboratory in CY Cergy Paris University in stick-slip experiments. They were obtained by Sarah Visage as part of her doctoral training (funded by the ANR DISRUPT programme) during an invitation at the Helmholtz Laboratory for Tectonic Modelling (HelTec) at the GFZ German Research Centre for Geosciences in Potsdam. Like any granular material, the twice broken rice is characterized by several internal friction coefficients μ and cohesions C, classicaly qualified as dynamic, static, and reactivation coefficients. In adition, since the rice exhibits a stick slip behaviour, the various shear - velocity or shear-displacement curves exhibit high frequency oscillations and we therefore define maximum, minimum, and mean values corresponding respectively to the curve peaks, curve troughs and smoothed curve.
    Language: English
    Type: info:eu-repo/semantics/workingPaper
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 44
    Publication Date: 2022-01-19
    Description: Bastnäsite [REE(CO3)F] is the main mineral of REE ore deposits in carbonatites. Synthetic bastnäsite-like compounds have been precipitated from aqueous solutions by many different methods but previous attempts to model magmatic crystallization of bastnäsite from hydrous calciocarbonatite melts were unsuccessful. Here we present the first experimental evidence that bastnäsite and two other REE carbonates, burbankite and lukechangite, can crystallize from carbonatite melt in the synthetic system La(CO3)F – CaCO3 – Na2CO3 at temperatures between 580 and 850 °C and pressure 100 MPa. The experiments on starting mixtures of reagent-grade CaCO3, Na2CO3, La2(CO3)3 and LaF3 were carried out in cold-seal rapid-quench pressure vessels. The studied system is an isobaric pseudoternary join of a quinary system where CO2 and fluorides act as independent components. Liquidus phases in the run products are calcite,nyerereite, Na carbonate, bastnäsite, burbankite solid solution (Na,Ca)3(Ca,La)3(CO3)5 and lukechangite Na3La2(CO3)4F. Calcite and bastnäsite form a eutectic in the boundary join La(CO3)F – CaCO3 at 780 ± 20 °C and 58 wt% La(CO3)F. Phase equilibria in the boundary join La(CO3)F – Na2CO3 are complicated by peritectic reaction between Ca-free endmember of burbankite solid solution petersenite (Pet) and lukechangite (Luk) with liquid (L): Na4La2(CO3)5 (Pet) + NaF (L) = Na3La2(CO3)4F (Luk) + Na2CO3 (Nc) The righthand-side assemblage becomes stable below 600 ± 20 °C. In ternary mixtures, bastnäsite (Bst), burbankite (Bur) and calcite (Cc) are involved in another peritectic reaction: 2 La(CO3)F (Bst) + CaCO3 (Cc) + 2 Na2CO3 (L) = Na2CaLa2(CO3)5 (Bur) + 2 NaF (L) Burbankite in equilibrium with calcite replaces bastnäsite below 730 ± 20 °C. Stable solidus assemblages in the pseudoternary system are: basnäsite-burbankite-fluorite-calcite, basnäsite-burbankite-fluorite-lukechangite, bastnäsite-burbankite-lukechagite, burbankite-lukechangite-3 nyerereite-calcite and burbankite-lukechangite-nyerereite-natrite. Addition of 10 wt% Ca3(PO4)2 to one of the ternary mixtures resulted in massive crystallization of La-bearing apatite and monazite, and complete disappearance of bastnäsite and burbankite. Our results confirm that REE-bearing phosphates are much more stable than carbonates and fluorocarbonates. Therefore, primary crystallization of the latter from common carbonatite magmas is unlikely. Possible exceptions are carbonatites at Mountain Pass that are characterized by very low P2O5 concentrations (usually at or below 0.5 wt%) and extremely high REE contents in the order of a few weight percent or more. In other carbonatites, bastnäsite and burbankite probably crystallized from highly concentrated alkaline carbonate-chloride brines that have been found in melt inclusions and are thought to be responsible for widespread fenitization around carbonatite bodies.
    Language: English
    Type: info:eu-repo/semantics/article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 45
    Publication Date: 2022-01-19
    Description: The role of seasonality is indisputable in climate and ecosystem dynamics. Seasonal temperature and precipitation variability are of vital importance for the availability of food, water, shelter, migration routes, and raw materials. Thus, understanding past climatic and environmental changes at seasonal scale is equally important for unearthing the history and for predicting the future of human societies under global warming scenarios. Alas, in palaeoenvironmental research, the term ‘seasonality change’ is often used liberally without scrutiny or explanation as to which seasonal parameter has changed and how. Here we provide fundamentals of climate seasonality and break it down into external (insolation changes) and internal (atmospheric CO2 concentration) forcing, and regional and local and modulating factors (continentality, altitude, large-scale atmospheric circulation patterns). Further, we present a brief overview of the archives with potentially annual/seasonal resolution (historical and instrumental records, marine invertebrate growth increments, stalagmites, tree rings, lake sediments, permafrost, cave ice, and ice cores) and discuss archive-specific challenges and opportunities, and how these limit or foster the use of specific archives in archaeological research. Next, we address the need for adequate data-quality checks, involving both archive-specific nature (e.g., limited sampling resolution or seasonal sampling bias) and analytical uncertainties. To this end, we present a broad spectrum of carefully selected statistical methods which can be applied to analyze annually- and seasonally-resolved time series. We close the manuscript by proposing a framework for transparent communication of seasonality-related research across different communities.
    Type: info:eu-repo/semantics/article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 46
    Publication Date: 2022-01-19
    Description: In a recent editorial in the journal Nature Sustainability, the editors raised the concern that journal submissions on water studies appear too similar. The gist of the editorial: “too many publications and not enough ideas.” In this response, we contest this notion, and point to the numerous new ideas that result from taking a broader view of the water science field. Drawing inspiration from a recently hosted conference geared at transcending traditional disciplinary silos and forging new paradigms for water research, we are, in fact, enthusiastic and optimistic about the ways scientists are investigating political, economic, historical, and cultural intersections toward more just and sustainable human-water relations and ways of knowing.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 47
    Publication Date: 2022-01-19
    Description: Brillouin spectroscopy at room temperature and pressure up to 40 GPa documents nearly identical elasticity and refractive index of amorphous CaSiO3 created by two different methods: temperature-quenching the melt at ambient pressure, and pressure-amorphizing crystalline wollastonite at room temperature. We find reproducible hysteresis of 0 to 8% on pressure cycling that is small relative to the 30% to 60% changes in shear and longitudinal wave velocities over this pressure range. Together with observed changes in refractive index and previous results from Raman spectroscopy, these measurements reveal a continuous and reversible change in atomic-packing induced by pressure. Unlike many other silicate glasses, amorphous CaSiO3 exhibits highly reproducible properties, behaving smoothly and reversibly under pressure cycling and possessing similar structure and elasticity regardless of synthesis paths for the starting material, which suggests that the amorphous solid may mimic the liquid over the pressure range investigated.
    Language: English
    Type: info:eu-repo/semantics/article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 48
    Publication Date: 2022-01-19
    Description: Zur Förderung des Dialogs zur NFDI in der Helmholtz-Gemeinschaft veranstaltete das Helmholtz Open Science Office am 8. Dezember 2021 ein zweites virtuelles Helmholtz Open Science Forum unter dem Motto „Helmholtz in der Nationalen Forschungsdateninfrastruktur (NFDI)“. Alle Mitarbeitenden der Helmholtz-Gemeinschaft waren eingeladen, sich an dem zentrenübergreifenden Austausch zu beteiligen. Aufbauend auf das erste Forum im Mai 2021 lag der Schwerpunkt der Veranstaltung auf der Identifikation und Diskussion von Helmholtzspezifischen Themen und Aktivitäten bei der Realisierung der NFDI.
    Language: German
    Type: info:eu-repo/semantics/report
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 49
    Publication Date: 2022-01-19
    Description: Consistent calibration and monitoring is a basic prerequisite for providing a reliable time series of global and regional sea-level variations from altimetry. The precisions of sea-level measurements and regional biases for six altimeter missions (Jason-1/2/3, Envisat, Saral, Sentinel-3A) are assessed in this study at 11 GNSS-controlled tide gauge stations in the German Bight (SE North Sea) for the period 2002 to 2019. The gauges are partly located at the open water, and partly at the coast close to mudflats. The altimetry is extracted at virtual stations with distances from 2 to 24 km from the gauges. The processing is optimized for the region and adjusted for the comparison with instantaneous tide gauge readings. An empirical correction is developed to account for mean height gradients and slight differences of the tidal dynamics between the gauge and altimetry, which improves the agreement between the two data sets by 15–75%. The precision of the altimeters depends on the location and mission and ranges from 1.8 to 3.7 cm if the precision of the gauges is 2 cm. The accuracy of the regional mission biases is strongly dependent on the mean sea surface heights near the stations. The most consistent biases are obtained based on the CLS2011 model with mission-dependent accuracies from 1.3 to 3.4 cm. Hence, the GNSS-controlled tide gauges operated operationally by the German Waterway and Shipping Administration (WSV) might complement the calibration and monitoring activities at dedicated CalVal stations.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 50
    Publication Date: 2022-01-19
    Description: Upper-plate normal faults along forearcs often accumulate slip during 〉Mw 6 earthquakes. Such normal faults traverse the forearc of the Hellenic Subduction System (HSS) in Greece and are the focus of this study. Here, we use detailed field-mapping and analysis of high-resolution Digital Elevation Models (DEMs) to study 42 active normal faults on the islands of Kythira and Antikythira in the Aegean Sea. Onshore fault kinematic data are complemented by seabed bathymetry mapping of ten offshore faults that extend along the Kythira-Antikythira Strait (KAS). We find that normal faults in the KAS have lengths of ∼1–58 km and scarps ranging in height from 1.5 m to 2.8 km, accommodating, during the Quaternary, trench-orthogonal (NE-SW) extension of ∼2.46 ± 1.53 mm/a. Twenty-eight of these faults have ruptured since the Last Glacial Maximum, with their postglacial (16 ± 2 ka) displacement rates (0.19–1.25 mm/a) exceeding their Quaternary (≤0.7–3 Ma) rates (0.03–0.37 mm/a) by more than one order of magnitude. Rate variability, which is more pronounced on short (〈8 km) faults, is thought to arise due to temporally clustered paleoearthquakes on individual KAS faults. When displacement accumulation is considered across the entire onshore fault network, rate variability between the two time-intervals examined decreases significantly (2.79 ± 0.41 vs 1.29 ± 0.99 mm/a), a feature that suggests that earthquake clustering in the KAS may occur over ≤16 ka timescales.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 51
    Publication Date: 2022-01-19
    Description: The release of greenhouse gases from the large organic carbon stock in permafrost deposits in the circumarctic regions may accelerate global warming upon thaw. The extent of this positive climate feedback is thought to be largely controlled by the microbial degradability of the organic matter preserved in these sediments. In addition, weathering and oxidation processes may release inorganic carbon preserved in permafrost sediments as CO2, which is generally not accounted for. We used 13C and 14C analysis and isotopic mass balances to differentiate and quantify organic and inorganic carbon released as CO2 in the field from an active retrogressive thaw slump of Pleistocene-age Yedoma and during a 1.5-years incubation experiment. The results reveal that the dominant source of the CO2 released from freshly thawed Yedoma exposed as thaw mound is Pleistocene-age organic matter (48–80%) and to a lesser extent modern organic substrate (3–34%). A significant portion of the CO2 originated from inorganic carbon in the Yedoma (17–26%). The mixing of young, active layer material with Yedoma at a site on the slump floor led to the preferential mineralization of this young organic carbon source. Admixtures of younger organic substrates in the Yedoma thaw mound were small and thus rapidly consumed as shown by lower contributions to the CO2 produced during few weeks of aerobic incubation at 4°C corresponding to approximately one thaw season. Future CO2 fluxes from the freshly thawed Yedoma will contain higher proportions of ancient inorganic (22%) and organic carbon (61–78%) as suggested by the results at the end, after 1.5 years of incubation. The increasing contribution of inorganic carbon during the incubation is favored by the accumulation of organic acids from microbial organic matter degradation resulting in lower pH values and, in consequence, in inorganic carbon dissolution. Because part of the inorganic carbon pool is assumed to be of pedogenic origin, these emissions would ultimately not alter carbon budgets. The results of this study highlight the preferential degradation of younger organic substrates in freshly thawed Yedoma, if available, and a substantial release of CO2 from inorganic sources.
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 52
    Publication Date: 2021-12-13
    Description: It has been proposed that at short timescales of 102–105 yr, climatic variability can explain variations in sediment flux, but in orogens with pronounced climatic gradients rate changes caused by the oscillating efficiency in rainfall, runoff, and/or sediment transport and deposition are still not well-constrained. To explore landscape responses under variable climatic forcing, we evaluate time windows of prevailing sediment aggradation and related paleo-erosion rates from the southern flanks of the Dhauladhar Range in the western Himalaya. We compare past and present 10Be-derived erosion rates of well-dated Late Pleistocene fluvial landforms and modern river sediments and reconstruct the sediment aggradation and incision history based on new luminescence data. Our results document significant variations in erosion rates ranging from 0.1 to 3.4 mm/yr over the Late Pleistocene. We find that, during times of weak monsoon intensity, the moderately steep areas (hillslope angles of 27 ± 13°) erode at lower rates of 0.1–0.4 mm/yr compared to steeper (〉40°) crestal regions of the Dhauladhar Range that erode at 0.8−1.3 mm/yr. In contrast, during several millennia of stronger monsoon intensity, both the moderately steep and high slope areas record higher erosion rates (〉1-3.4 mm/yr). Lithological clast-count analysis shows that this increase of erosion is focused in the moderately steep areas, where Lesser Himalayan rocks are exposed. Our data thus highlight the highly non-linear response of climatic forcing on landscape evolution and suggest complex depositional processes and sedimentary signals in downstream areas.
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 53
    Publication Date: 2021-12-13
    Description: Reflectance spectroscopy in the visible-infrared and shortwave infrared (450–2500 nm) wavelength region is a rapid, cost-effective and non-destructive method that can be used to monitor heavy metal (PTE, potential toxic elements) contaminated areas. Due to the PTE pollution that has accumulated in the course of wastewater treatment, the existence of Technosols presents an environmental problem, a potential source for PTE uptake by vegetation, or even the release of PTEs into groundwater. In this study, multivariate procedures using Partial Least Squares Regression (PLSR) and Random Forest Regression (RFR) are applied to quantify relationships between soil heavy metal concentration (Cr, Cu, Ni, Zn) and reflectance data of highly contaminated Technosols from a former sewage farm near Berlin, Germany. Laboratory measurements of 110 soil samples in four different preparation steps were acquired with HySpex hyperspectral cameras. The impact of the different preparation steps, namely “oven-dried”, “sieved”, “ground”, “LOI”, was evaluated for its potential to enhance the method performance or to reduce the time-consuming soil sample preparation. Furthermore, different spectral pre-processing methods were evaluated regarding improvements of spectral modelling performance and their ability to minimise noise and multiple scattering effects. Considering the optimal coefficient of determination (R2), PLSR shows an improving performance and accuracy with increasing preparation steps such as ground or LOI for all metals of interest (R2_Cr: 0.52–0.78; R2_Cu: 0.36–0.73; R2_Ni: 0.19–0.42 and R2_Zn: 0.41–0.74). RFR shows a weaker estimation performance for all metals, even when using higher sample preparation levels (R2_Cr: 0.36–0.62; R2_Cu: 0.17–0.72; R2_Ni: 0.20–0.35 and R2_Zn: 0.26–0.67). The results show that an application of methods such as PLSR for the prediction of PTE concentration in Technosols is still a challenge but provides more robust estimations than the user-friendly RFR method. Additionally, this study shows that PTE estimation performance in heterogeneous soil samples can be improved by increased laboratory soil preparation steps and further spectral pre-processing steps.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 54
    Publication Date: 2022-01-17
    Description: Holocene history of the Indian monsoon reconstruction using environmental magnetism has emerged as an effective paleoclimate proxy with its fast, efficient, and repeatable measuring procedures. In this chapter, we have made an attempt to provide a broad synthesis of the available sediment magnetic records obtained from the loess-paleosols (central Himalaya), lake (western India), delta and lagoon sequences (eastern coast Godavari and Iskapalli). Variations in magnetomineralogical S-ratio values of sediment archives were combined and stacked as a surrogate for Holocene paleomonsoon change. High S-ratio results from low weathering rates were attributed to more wet conditions, while low S-ratios were related to dry conditions from intense low temperature oxidation. Combining the S-ratio data from diverse environments collectively revealed three broad climate phases with minor oscillations during the past 20 ka. These are (i) a step-wise intensification of the SW monsoon since the Last Glacial Maximum with its peak level at ∼9.0 ka, (ii) the prevalence of a prolonged dry spell along the eastern coast and western India at ∼3.5 ka that led to the collapse of the Harappan civilization, and (iii) reduction of monsoon rainfall during the period of global cooling events such as Last Glacial Maximum, Younger Dryas, and Little Ice Age. We observed that instead of the concentration-specific magnetic susceptibility (χ), the combined remanence S-ratio seems to be a more sensitive proxy responding to the monsoon variability both at centennial and millennial time scales.
    Type: info:eu-repo/semantics/bookPart
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 55
    Publication Date: 2022-01-17
    Description: A dense seismological array and profile reveal the deep structure across the Longmenshan from the Songpan-Ganzi terrane of the Tibetan plateau to the Sichuan basin. Receiver function and tomographic images reveal that the Pengguan Complex which cores the Longmenshan in the region where the Ms. 8 Wenchuan earthquake of 2008 occurred, is marked by high velocities in the upper 15 km of the crust. At about 15 km depth both P- and S-wave velocities decrease at a flat-lying boundary around which the aftershock hypocentres of the Wenchuan earthquake are concentrated. Thus, this boundary may be a faulted interface or detachment, marking the base of the Pengguan Complex. Moho depths change significantly in going from the Tibetan plateau to the Sichuan basin. At the location of the dense profile a Moho step occurs, located about 50 km NW of the surface trace of the Yingxiu-Beichuan fault (YBF). The boundary at about 15 km depth below the Pengguan Complex seems to deepen at around the Wenchuan-Maoxian fault (WMF) by about 3 km and merge to the NW with another interface at about 18 km depth. This interface, NW of the WMF, which correlates with the top of a zone of high conductivity is interpreted to represent the top of the Tibetan mid-crustal low velocity, high conductivity zone. The tomographic image indicates that the boundary between the low velocities of the Songpan-Ganzi terrane and the high velocities of the Sichuan basin in the middle and lower crust occurs NW of the surface trace of the YBF. Thus, it is proposed that a zone extending from the WMF at about 15 km depth to the Moho step about 25 km further NW marks the boundary between the Tibetan plateau and the Sichuan basin in the middle and lower crust.
    Language: English
    Type: info:eu-repo/semantics/article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 56
    Publication Date: 2022-01-17
    Description: DeepGreen wurde vom 01.08.2018 bis zum 30.06.2021 in einer zweiten Projektphase von der Deutschen Forschungsgemeinschaft (DFG) gefördert. DeepGreen unterstützt Bibliotheken als Dienstleister für Hochschulen, außeruniversitäre Forschungseinrichtungen und die dort tätigen Wissenschaftler:innen dabei, Publikationen auf Open-Access-Repositorien frei zugänglich zu machen und fördert das Zusammenspiel von wissenschaftlichen Einrichtungen und Verlagen. An der zweiten Projektphase waren der Kooperative Bibliotheksverbund Berlin-Brandenburg, die Bayerische Staatsbibliothek, der Bibliotheksverbund Bayern, die Universitätsbibliotheken der Friedrich-Alexander-Universität Erlangen-Nürnberg und der Technischen Universität Berlin und das Helmholtz Open Science Office beteiligt. In dem Projekt wurde erfolgreich eine technische und organisatorische Lösung zur automatisierten Verteilung von Artikeldaten wissenschaftlicher Verlage an institutionelle und fachliche Repositorien entwickelt. In der zweiten Projektphase lag der Fokus auf der Erprobung der Datendrehscheibe in der Praxis und der Ausweitung auf weitere Datenabnehmer und weitere Verlage. Im Anschluss an die DFG-geförderte Projektlaufzeit ist DeepGreen in einen zweijährigen Pilotbetrieb übergegangen. Ziel des Pilotbetriebs ist es, den Übergang in einen bundesweiten Real-Betrieb vorzubereiten.
    Type: info:eu-repo/semantics/report
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 57
    Publication Date: 2022-01-17
    Description: The assimilation of global navigation satellite system (GNSS) data has been proven to have a positive impact on weather forecasts. However, the impact is limited due to the fact that solely the zenith total delays (ZTDs) or integrated water vapor (IWV) derived from the GPS satellite constellation are utilized. Assimilation of more advanced products, such as slant total delays (STDs), from several satellite systems may lead to improved forecasts. This study shows a preparation step for the assimilation, i.e., the analysis of the multi-GNSS tropospheric advanced parameters: ZTDs, tropospheric gradients and STDs. Three solutions are taken into consideration: GPS-only, GPS–GLONASS (GR) and GPS–GLONASS–Galileo (GRE). The GNSS estimates are calculated using the operational EPOS.P8 software developed at GFZ. The ZTDs retrieved with this software are currently being operationally assimilated by weather services, while the STDs and tropospheric gradients are being tested for this purpose. The obtained parameters are compared with the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA5 reanalysis. The results show that all three GNSS solutions show similar level of agreement with the ERA5 model. For ZTDs, the agreement with ERA5 results in biases of approx. 2 mm and standard deviations (SDs) of 8.5 mm. The statistics are slightly better for the GRE solution compared to the other solutions. For tropospheric gradients, the biases are negligible, and SDs are equal to approx. 0.4 mm. The statistics are almost identical for all three GNSS solutions. For STDs, the agreement from all three solutions is very similar; however it is slightly better for GPS only. The average bias with respect to ERA5 equals approx. 4 mm, with SDs of approx. 26 mm. The biases are only slightly reduced for the Galileo-only estimates from the GRE solution. This study shows that all systems provide data of comparable quality. However, the advantage of combining several GNSS systems in the operational data assimilation is the geometry improvement by adding more observations, especially for low elevation and azimuth angles.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 58
    Publication Date: 2022-01-17
    Description: Knowledge of groundwater flow is of high relevance for groundwater management or the planning of different subsurface utilizations such as deep geothermal facilities. While numerical models can help to understand the hydrodynamics of the targeted reservoir, their predictive capabilities are limited by the assumptions made in their setup. Among others, the choice of appropriate hydraulic boundary conditions, adopted to represent the regional to local flow dynamics in the simulation run, is of crucial importance for the final modelling result. In this work, we systematically address this problematic in the area of the central part of the Upper Rhine Graben. We quantify how and to which degree different upper boundary conditions and vertical cross-boundary fluid movement influence the calculated deep fluid flow conditions in the area under study. Robust results, which are insensitive to the choice of boundary condition, are: (i) a regional groundwater flow component descending from the graben shoulders to rise at its centre and (ii) the presence of heterogeneous hydraulic potentials at the rift shoulders. Contrarily, results affected by the chosen boundary conditions are: (i) calculated flow velocities, (ii) the absolute position of the upflow axis, and (iii) the evolving local flow dynamics. If, in general, the investigated area is part of a supra-regional flow system—like the central Upper Rhine Graben is part of the entire Upper Rhine Graben—the inflow and outflow across vertical model boundaries need to be considered.
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 59
    Publication Date: 2021-10-22
    Description: Strong anisotropy of seismic velocity in the Earth's crust poses serious challenges for seismic imaging. Where in situ seismic properties are not available, the anisotropy can be determined from velocity analysis of surface and borehole seismic profiles. This is well established for dense, long-offset reflection seismic data. However, it is unknown how applicable this approach is for sparse seismic reflection data with low fold and short offsets in anisotropic metamorphic rocks. Here, we show that anisotropy parameters can be determined from a sparse 3-D data set at the COSC-1 borehole site in the Swedish Caledonides and that the results agree well with the seismic anisotropy parameters determined from seismic laboratory measurements on core samples. Applying these anisotropy parameters during 3-D seismic imaging improves the seismic image of the high-amplitude reflections especially in the vicinity of the lower part of the borehole. Strong reflections in the resulting seismic data show good correlation with the borehole-derived lithology. Our results aid the interpretation and extrapolation of the seismic stratigraphy of the Lower Seve Nappe in Jämtland and other parts in the Caledonides.
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 60
    facet.materialart.
    Unknown
    In:  Acoustic Emission Testing | Springer Tracts in Civil Engineering
    Publication Date: 2021-08-17
    Description: In-situ acoustic emission (AE) monitoring is carried out in mines, tunnels and underground laboratories in the context of structural health monitoring, in decameter-scale research projects investigating the physics of earthquake nucleation and propagation and in research projects looking into the seismo-hydro-mechanical response of the rock mass in the context of hydraulic stimulations or nuclear waste storage. In addition surface applications e.g. monitoring rock faces of large construction sites, rock fall areas and rock slopes are documented in the literature. In geomechanical investigations in-situ AE monitoring provides information regarding the stability of underground cavities, the state of stress and the integrity of the rock mass. The analysis of AE events recorded in-situ allows to bridge the observational gap between the studies of faulting processes in laboratory and studies of larger natural and induced earthquakes. This chapter provides an overview of various projects involving in-situ AE monitoring underground with a focus on recent achievements in the field. In-situ AE monitoring networks are able to record AE activity from distances up to 200 m, but the monitoring limits depend strongly on the extension of the network, geological and tectonic conditions. Very small seismic events with source sizes on approximately decimeter to millimeter scale are detected. In conclusion in-situ AE monitoring is a useful tool to observe instabilities in rock long before any damage becomes directly visible and is indispensable in high-resolution observations of rock volume deformation in decameter in-situ rock experiments.
    Type: info:eu-repo/semantics/bookPart
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 61
    Publication Date: 2021-09-30
    Description: Well-constrained earthquake depth estimations are important for seismic hazard determination. As local networks of the East-African Rift are usually too sparse for reliable depth estimations, we used detections of pP and sP phase arrivals (the so-called depth phases) at teleseismic distance to constrain earthquake depths in this region. We rely on a fully automatic Cepstral analysis approach, first validated at the global scale using the ISC-EHB catalogue, then applied on the East-African seismicity. We investigated 9575 earthquakes from magnitude 2 since 2005 which allows us to constrain the depth estimation of 584 events with magnitude mainly above 3.5, complemented by 139 reliable depth estimations from previous studies based on teleseismic data as well. To ensure a final catalogue as complete as possible, we also identified from regional catalogues 113 earthquakes assumed to be well constrained, based on network geometry empirical criteria. Thanks to this study, we finally propose new earthquake depth distributions for the seismic source zonation defined by Poggi et al., in order to estimate the seismic hazard of the East African Rift region. Including those new distributions in the source models leads to significant changes of seismic hazard assessments results.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 62
    Publication Date: 2021-09-27
    Description: The formally named SP lava flow is a quartz-, olivine- and pyroxene-bearing basalt flow that is preserved in the desert climate of northern Arizona, USA. The flow is independently dated with an 40Ar/39Ar age of 72 ± 4 ka (2σ) and has undergone negligible erosion and/or burial, making its surface an ideal site for direct calibration of cosmogenic nuclide production rates. Production rates for cosmogenic 26Al have been determined from SP flow quartz in this study and are combined with production rates for 10Be, 14C, and 21Ne (Fenton et al., 2019) to yield a suite of production rate ratios. The error-weighted mean, sea-level, high latitude (SLHL) total reference production rate of 26Al is 25.8 ± 2.5 at/g/yr (2σx; standard error) using time-independent Lal (1991)/Stone (2000)(St) scaling factors. The St scaled spallogenic 26Al rate is 25.0 ± 2.4 at/g/yr integrated over the past 72 ka. This rate overlaps within 2σ uncertainty with other St-scaled production rates in the literature. SLHL spallogenic 26Al production rates in SPICE quartz (SP Flow Production-Rate Inter-Calibration Site for Cosmogenic-Nuclide Evaluations) are nominally lower if time-dependent Sf, Sa, and Lm scaling factors are used, yielding values of 22.9 ± 2.2 at/g/yr, 22.6 ± 2.2 at/g/yr, and 24.1 ± 2.2 at/g/yr (2σx), respectively. All 26Al production rates in SP flow quartz overlap within 2σ uncertainty, regardless of time independent or time dependent scaling. Production rate ratios for cosmogenic 26Al/10Be, 26Al/14C, and 26Al/21Ne are based on the total, local production rates of each cosmogenic nuclide, independent of scaling models, and have error-weighted means (±2σx; standard error) of 6.7 ± 0.6, 2.23 ± 0.20, and 1.51 ± 0.13, respectively. This study suggests that, similar to cosmogenic 21Ne and 10Be production rates in SP flow quartz, production rates of cosmogenic 26Al in quartz do not significantly increase when integrated over 72 ka, a time span which includes the period of decreased magnetic strength from 20 to 50 ka.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 63
    Publication Date: 2021-12-15
    Description: GNSS Reflectometry (GNSS-R) is a novel remote sensing technique for the monitoring of geophysical parameters using reflected GNSS signals from the Earth's surface. Ocean wind speed monitoring is the main objective of the recently launched Cyclone GNSS (CyGNSS), a GNSS-R constellation of eight microsatellites, launched in late 2016. In this study, the capability of deep learning, especially, for an operational wind speed data derivation from the measured Delay-Doppler Maps (DDMs) is characterized. CyGNSSnet is based on convolutional layers for the feature extraction from bistatic radar cross section (BRCS) DDMs, along with fully connected layers for processing ancillary technical and higher-level input parameters. The best architecture is determined on a validation set and is evaluated over a completely blind dataset from a different time span than that of the training data to validate the generality of the model for operational usage. After a data quality control, CyGNSSnet results in an RMSE of 1.36 m/s leading to a significant improvement by 28% in comparison to the officially operational retrieval algorithm. The RMSE is the lowest among those seen in the literature for any conventional or machine learning-based algorithm. The benefits of the convolutional layers, the advantages and weaknesses of the model are discussed. CyGNSSnet offers efficient processing of GNSS-R measurements for high-quality global ocean winds.
    Type: info:eu-repo/semantics/article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 64
    Publication Date: 2021-12-15
    Description: 1-D site response analysis dominates earthquake engineering practice, while local 2-D/3-D models are often required at sites where the site response is complex. For such sites, the 1-D representation of the soil column can account neither for topographic effects or dipping layers nor for locally generated horizontally propagating surface waves. It then remains a crucial task to identify whether the site response can be modelled sufficiently precisely by 1-D analysis. In this study we develop a method to classify sites according to their 1-D or 2-D/3-D nature. This classification scheme is based on the analysis of surface earthquake recordings and the evaluation of the variability and similarity of the horizontal Fourier spectra. The taxonomy is focused on capturing significant directional dependencies and interevent variabilities indicating a more probable 2-D/3-D structure around the site causing the ground motion to be more variable. While no significant correlation of the 1-D/3-D site index with environmental parameters and site proxies seems to exist, a reduction in the within-site (singlestation) variability is found. The reduction is largest (up to 20 per cent) for purely 1-D sites. Although the taxonomy system is developed using surface stations of the KiK-net network in Japan as considerable additional information is available, it can also be applied to any (non-downhole array) site.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 65
    Publication Date: 2021-12-15
    Description: Severe droughts caused unprecedented impacts on grasslands in Central Europe in 2018 and 2019. Yet, spatially varying drought impacts on grasslands remain poorly understood as they are driven by complex interactions of environmental conditions and land management. Sentinel-2 time series offer untapped potential for improving grassland monitoring during droughts with the required spatial and temporal detail. In this study, we quantified drought effects in a major Central European grassland region from 2017 to 2020 using a regression-based unmixing framework. The Sentinel-2-based intra-annual time series of photosynthetic vegetation (PV), non-photosynthetic vegetation (NPV), and soil fractional cover provide easily interpretable quantities relevant for understanding drought effects on grasslands. Fractional cover estimates from Sentinel-2 matched in-situ conditions observed during field visits. The comparison to a multitemporal reference dataset showed the best agreement for PV cover (MAE = 7.2%). Agreement was lower for soil and NPV, but we observed positive relationships between fractional cover from Sentinel-2 and the reference data with MAE = 10.1% and MAE = 15.4% for soil and NPV, respectively. Based on the fractional cover estimates, we derived a Normalized Difference Fraction Index (NDFI) time series contrasting NPV and soil cover relative to PV. In line with meteorological and soil moisture drought indices, and with the Normalized Difference Vegetation Index (NDVI), NDFI time series showed the most severe drought impacts in 2018, followed by less severe, but persisting effects in 2019. Drought-specific metrics from NDFI time series revealed a high spatial variability of onset, duration, impact, and end of drought effects on grasslands. Evaluating drought metrics on different soil types, we found that grasslands on less productive, sandy Cambisols were strongly affected by the drought in 2018 and 2019. In comparison, grasslands on Gleysols and Histosols were less severely impacted suggesting a higher drought resistance of these grasslands. Our study emphasizes that the high temporal and spatial detail of Sentinel-2 time series is mandatory for capturing relevant vegetation dynamics in Central European lowland grasslands under drought.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 66
    Publication Date: 2021-12-17
    Description: For 5 nm thin Nb films adhered to a rigid substrate, hydrogen absorption leads to ultrahigh mechanical stress of about -8 GPa. This is related to a purely elastic behaviour. The high mechanical stress destabilizes phases and even suppresses conventional two-phase regions known for the Nb-H bulk system. These unique thin film properties can be preserved to thicker films, by lateral confinement. Nb-Fe films provide a laterally confined columnar domain structure of well-separated α-Nb(Fe) and μ-FeNb phases. While the α-Nb(Fe) absorbs hydrogen at low chemical potentials, the μ-FeNb phase does not, separating the two phases into a hydrogen active and a hydrogen passive one. The behaviour of 75 nm Nb-Fe films was studied by in situ mechanical stress measurements, in situ x-ray diffraction and transmission electron microscopy. With increasing Fe-content, Nb-Fe films show a strong increase in the yield stress upon hydrogen absorption. This allows for an extended elastic range and high maximum stress values of -4.6 GPa, for 75 nm Nb-Fe films. X-ray diffraction pattern collected upon hydrogen loading of Nb-Fe films show peak shifts and intermediate peak broadening. This indicates the presence of a two-phase region and preservation of the lattice coherency between the α-Nb(Fe)-H phase and the hydride phase. Peak shifts indicate a reduced vertical expansion of the hydrogen absorbing α-Nb(Fe) lattice. This is attributed to the presence of the µ-FeNb phase. FEM simulations on Nb-Fe-H films confirm reduced overall expansions and lateral stresses, when compared to pure Nb-H films. High vertical stresses arise upon H-loading due to the link between the two Nb-Fe phases. These stresses are tensile for µ-FeNb and compressive for the α-Nb(Fe) domains and also reach values of several GPa. Conservation of the exceptional thin film properties to thicker films by lateral confinement is suggested to be a powerful strategy for many different applications like sensor technologies or energy storage.
    Type: info:eu-repo/semantics/article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 67
    Publication Date: 2021-12-17
    Description: The replacement of magnetite by hematite is commonly observed in various geologic systems. In contrast to the formation of hematite by a solid-state oxidation, numerous experimental results have demonstrated that it can also occur by a redox-independent dissolution-reprecipitation reaction. However, the orientation relationship and the intermediate products between magnetite and hematite remain unknown during the redox-independent replacement. In this work, high-resolution transmission electron microscopy (TEM) was used to investigate porous hematite from the Baishiya skarn deposit, East Kunlun orogenic belt, aiming to build a refined growth model applicable to the replacement of magnetite by hematite in natural hydrothermal systems. Initially, hydrothermal leaching of Fe2+ from magnetite led to the formation of ferrihydrite that transformed to goethite and hematite nanocrystals successively. Oriented attachment of pseudocubic hematite nanoparticles induced by Cl along specific crystallographic directions formed hematite mesocrystals on the exposed dodecahedral facets of magnetite, leading to an orientation relationship between magnetite and adjacent hematite (i.e., (110)magnetite || (012)hematite), which is different from that of oxidation (i.e., (110)magnetite || (110)hematite). However, oriented attachment can be imperfect in some instances, and dislocations of adjacent nanoparticles result. The dislocations in the hematite mesocrystals have acted as a closed space to capture the remaining ferrihydrite. When the Si concentration in ferrihydrite was sufficient, the solid-state conversion of the remaining ferrihydrite to hematite was blocked. We propose that repeated dissolution and reprecipitation of hematite mesocrystals (i.e., defective crystals) are required to remove Si, and thereby form defect-free hematite crystals, providing a genetic link between the widespread hematitisation and related multistage fluid infiltration in some of the world's richest deposits (e.g., Olympic Dam and Bayan Obo deposits). This is the first time that Si and Cl have been verified to act as key factors to shape the hematite growth pathway during the ore-forming processes, challenging the ‘ion-by-ion’ growth model that has underpinned our knowledge of mineral solubility, nucleation, and mass transfer from nano- to micron-scales in natural hydrothermal systems.
    Type: info:eu-repo/semantics/article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 68
    Publication Date: 2021-12-17
    Description: Micellization is one of the most challenging promotion mechanisms of surfactants for gas hydrate formation. Surfactants have been reported as the most efficient promoters for the formation of gas hydrates; however, their mechanism of action is not yet clear. The literature review reveals a major gap in the current knowledge for clarifying the effect of micellization on clathrate hydrate formation. Previous studies have mostly focused on hydrate formation in the presence of a special category of compounds that can form micelles, i.e., surfactants (in most cases, sodium dodecyl sulfate (SDS)). However, structures more complex than SDS have not been extensively studied. In other words, the changes in the surfactants’ molecular structure significantly alter their activity in the hydrate formation process. The current study aims to fill this gap by investigating a novel additive, i.e., waterborne polyurea/urethanes (WPUU), which can generate micelles at the hydrate forming temperature. The experimental results show that WPUUs have a surfactant property and form micelles at the hydrate forming temperature. Nonetheless, no promotion effect on methane hydrate formation was observed. The results of the molecular dynamic simulation confirm that WPUU inhibits gas hydrate formation due to its stronger proton-accepting hydrogen bond compared to water molecules. The results indicate that depending on the molecular structure of the additives, their micelles could have an inhibition effect on methane hydrate formation. Our findings present a molecular foundation to guide the molecular design of efficient hydrate inhibitors and promoters for flow assurance and gas storage applications. Moreover, they provide new insight into the inhibition mechanism of kinetic hydrate inhibitors.