bluuebunny/crossref_metadata_2025 huggingface dataset:
Collective behavior of asperities before large stick-slip events
Authors: Shu Weiwei , Lengliné Olivier , Schmittbuhl Jean
Published: February 2023

The multi-scale roughness of a fault interface is responsible for multiple asperities that establish a complex and discrete set of real contacts. Since asperities control the initiation and evolution of the fault slip, it is important to explore the intrinsic relationships between the collective behavior of local asperities and the frictional stability of the global fault system. However, such a mechanism is still elusive due to the difficulty of imaging an exhaustive spatiotemporal variability of a fault interface at depth, and the limited computational efficiency of the numerical models with heterogeneity over a large time and space domain. Here we propose a novel analog experimental approach, which allows us to capture the temporal evolution of the slip of each asperity on a faulting interface. We link the collective behavior of asperities with the mechanical response of the whole fault interface. We find that many destabilizing events at the local asperity scale occurred in the frictional strengthening stage which is conventionally considered as the stable regime of a fault. We compute the interseismic coupling to evaluate the slipping behaviors of asperities during the fault strengthening stage. Based on a high-resolution topographical map of the fault surface, we evidence that the interseismic coupling is not only dependent on the normal load and the peak height of asperity but also can be affected by the interactions between asperities through the embedding soft matrix. Furthermore, we quantify the spatiotemporal interactions of asperities as slip episodes. The significant characteristics and scaling-laws observed in natural earthquakes, such as the magnitude-frequency distribution and the moment-duration scaling, are reproduced through the catalog of slip episodes to demonstrate the effective upscaling. We give geophysical implications for the physics and mechanics of natural faults and discuss some limitations of our experimental setup.
Modes of decadal variability in observed Arctic sea-ice concentration
Authors: Dörr Jakob , Årthun Marius , Bonan David B. , Wills Robert C. J.
Published: February 2023

The Arctic sea ice cover is strongly influenced by internal variability on decadal time scales, affecting both short-term trends and the timing of the first ice-free summer. Several mechanisms of variability have been proposed, but the contributions of distinct modes of decadal variability to regional and pan-Arctic sea-ice trends has not been quantified in a consistent manner. The relative contribution of forced and unforced variability in observed Arctic sea ice changes also remains poorly quantified. Here, we identify the dominant patterns of winter and summer decadal Arctic sea-ice variability in the satellite record and their underlying mechanisms using a novel technique called low-frequency component analysis. The identified patterns account for most of the observed regional sea ice variability and trends, and thus help to disentangle the role of forced and unforced sea ice changes since 1979. In particular, we separate a mode of decadal ocean-atmosphere-sea ice variability, with an anomalous atmospheric circulation over the central Arctic, that accounts for approximately 30-50% of the accelerated decline in pan-Arctic summer sea-ice area between 2000 and 2012. For winter, we find that internal variability has so far dominated decadal trends in the Bering Sea, while it plays a smaller role in the Barents and Kara Seas. These results, which detail the first purely observation-based estimate of the contribution of internal variability to decadal trends in sea ice, suggest a lower estimate of the internal variability contribution than most model-based assessments.
Material footprint assessment of hydropower plants
Authors: Shao Ling , Pan Yunlong , Chu Yuwen , Wu Zi
Published: February 2023

Hydropower is the largest renewable source of electricity generation. However, the construction and operation of hydropower plants may cause significant material footprints. This study provides a systems accounting framework for evaluating the life-cycle material footprint of a hydropower plant. It is based on the hybrid method as a combination of the process analysis and the input-output analysis. A case study for a typical pumped storage hydropower plant (NPSHP) is carried out to demonstrate the framework. 12 metals (bauxite and aluminum ores, copper ores, gold ores, iron ores, lead ores, nickel ores, PGM ores, silver ores, tin ores, uranium and thorium ores, zinc ores, and other non-ferrous metal ores) and 8 minerals (building stones, chemical and fertilizer minerals, clays and kaolin, gravel and sand, limestone & gypsum & chalk & dolomite, salt, slate, and other minerals) are included.  The results can be helpful to promote a sustainable energy transition by incorporating material planetary boundaries into renewable energy systems.
Why is El Nino warm?
Authors: Fueglistaler Stephan , Resplandy Laure , Hogikyan Allison
Published: February 2023

El Nino years stand out in the global average temperature time series as record-warm years. The coupled atmosphere-ocean dynamics leading to warming in the climatologically cold equatorial Eastern Pacific are well understood, but cannot be the cause for the very strong signal in global average temperarture. The latter must be caused by an increase in subcloud Moist Static Energy (MSE) in the domain of highest subcloud MSE where atmospheric deep convection couples the surface, boundary layer and free troposphere. Transformation of the data from geographical space to sea-surface temperature (SST) percentiles eliminates the large spatial see-saws in all variables arising from the geographic reorganization of the general circulation, and brings to light the mechanism: While in the Eastern Pacific region oceanic heat uptake is reduced (corresponding to a heat flux out of the ocean), the deep convective domain sees a heat flux from the atmosphere into the ocean. We show that this heat flux into the ocean at the high end of SSTs - the opposite of the canonical perspective of a warming due to a heat flux from the ocean to the atmosphere - is mechanically forced: surface wind speeds are lower in regions of active deep convection than in ENSO neutral (and La Nina) years. The resulting reduced evaporation leads to the increase in subcloud MSE that causes the global temperature signal.
A spatially explicit uncertainty analysis of the air-sea CO2 flux from observations
Authors: Jersild Annika , Landschützer Peter
Published: February 2023

The ocean is a critical component of the global carbon budget. With a carbon reservoir substantially larger than the atmosphere's and an air-sea carbon flux absorbing approximately 25% of anthropogenic carbon annually, understanding and quantifying the air-sea carbon dioxide (CO2) flux and ocean carbon storage is essential for climate research. With this in mind, we developed a two-step neural network approach (SOM-FFN) to reconstruct the partial pressure of carbon dioxide (pCO2) at a 1°x1° resolution, providing an important global observational resource. Uncertainties in neural network and other interpolation techniques are, however, still substantial and remain poorly quantified, especially for remote or infrequently sampled regions. These uncertainties, which include mapping or extrapolation uncertainties as well as uncertainties in wind and gas transfer formulations, have a significant effect on our ability to balance regional and global carbon budgets. Therefore, we are reporting on the development of a two dimensional (longitude and latitude) gridded uncertainty product, available publicly alongside our standard neural network air-sea CO2 flux output from the SOM-FFN method. This dataset will pave the way for a better guided use of the computed air-sea CO2 fluxes and their regional uncertainties, taking into account major sources of air-sea CO2 flux uncertainty. Early analysis presented here allows for identification of regions of higher uncertainty, such as high latitude open ocean, and points to areas within the flux calculation where uncertainty must be further constrained in order to contribute to improving balance of regional carbon budgets in support of the UN stocktake.
TROPOMI Monitoring of NO2 Sources and Spread during the Beirut 2020 Seaport Ammonium Nitrate Explosion
Authors: El-Kork Nayla , Farahat Ashraf
Published: February 2023

TROPOMI Monitoring of NO2 Sources and Spread during the Beirut 2020 Seaport  Ammonium Nitrate Explosion Nayla El-Kork1,2, Ashraf Farahat31Space and Planetary Science Center, Khalifa University,P.O. Box 127788, Abu Dhabi, United Arab Emirates;nayla.elkork@ku.ac.ae 2Department of Physics, Khalifa University, P.O. Box 127788, Abu Dhabi, United Arab Emirates;3Department of Physics, College of Engineering and Physics, King Fahd University of Petroleum, & Minerals, Dhahran 31261, Saudi Arabia.; ashraf.farahat@kfupm.edu.sa Ammonium nitrate (NH₄NO₃) is a white crystalline solid chemical compound consisting of ions of ammonium and is commonly used as a high-nitrogen garden and farm fertilizer. Ammonium nitrate can trigger explosions if exposed to a temperature above 190 °C. More than thirty ammonium nitrate accidents have occurred since the beginning of the 19th century, including explosions in the United Kingdom (1916), Germany (1921), the United States (1942, 1947, and 2013), France (2001), and China (2015).  The most recent massive explosion occurred on August 4, 2020, in Beirut, Lebanon. The explosion killed over 200 people, injured about 7,000, damaged significant properties in Beirut, and loaded large amounts of particulate matter, dust, and toxic gases into the atmosphere. In this work, we use NO2 measurements from the Level 2 NO2 TROPOspheric Monitoring Instrument (TROPOMI), onboard S5P (100 – 700 nm) to investigate the generation of the toxic NO2 gas during the Beirut explosion. Interestingly a high NO2 emission over Beirut was observed from 28 July – 3 August 2020, a few days before the Beirut blast, with the highest emission on 28 July. This high NO2 background is attributed to many reasons: vehicle and ship emissions and the armed conflict in Syria. To confirm the possible effects of vehicles and ships in increasing NO2 loading in the atmosphere, the NO2 emission from Cairo, Egypt (known for its high population and high traffic volume); Nicosia, Cyprus (known for its low population and low traffic volume); and Suez Canal, Egypt (known for its high ship traffic and high traffic volume) are compared to Beirut NO2 emissions. Meanwhile, to understand the spatiotemporal distribution of NO2 (before, during, and after the explosion), the emission is examined in seven locations with four coastal (Beirut, Jounieh, Batron, and Tripoli) and three inland cities (Ehden, Baalbek, and Ain El Bnaiyyeh) in Lebanon. Results indicate that although NO2 was emitted during the Beirut blast, its amount was not significantly high, and it only affected some of the coastal locations within 20 – 25 km of Beirut, while it did not seem to affect the inland regions. The reported NO2 emission from the explosion could be overestimated, as there is an already high NO2 background in Beirut from vehicles, ships, and the armed conflict in Syria.   
Response of the Snowball Earth Climate to Orbital Forcing at High CO2 Level
Authors: Wu Jiacheng , Liu Yonggang
Published: February 2023

It is commonly accepted that the Milankovitch cycles have modulated the glacial-interglacial cycles during the Quaternary Period. However, how the climate during the Neoproterozoic snowball Earth events, the most extreme glaciations that have occurred on Earth, was affected by the orbital forcings remains largely unclear. Especially, whether the snowball Earth deglaciation might occur more easily at some orbital configurations than others is an important question. Here a coupled atmosphere-land model (CAM3 and CLM3) is used to investigate the response of temperature and hydrological cycle during a snowball Earth to this forcing at an atmospheric CO2 level of ~0.1 bar. To simplify the analysis, we have chosen to remove the continents. The results show that the climate is very different under different orbital configurations. The globally averaged annual surface temperature can differ by 2.4 °C while the difference in the monthly mean can reach 3.7 °C in the subtropical region. Surprisingly, we find that the Milankovitch theory does not only work in the extratropical region but also in the tropics; the snow thickness in the tropical region is inversely proportional to the summer insolation received in this region. After adding an explicit meltpond module, we find that the threshold CO2 that is needed to trigger the deglaciation may be reduced from 0.12 bar (low eccentricity) to 0.07 bar (high eccentricity). Moreover, the summer insolation in the tropics is more important than that in the subtropical region for the formation of a perennial meltwater belt. Hence, we conclude that the orbital forcing is important to the snowball Earth climate at its late stage and would assist Earth to get out of this state when the eccentricity was high.
Reassessment of the Phanerozoic net crustal growth: U–Pb and Hf zircon data for the Central Asian Orogenic Belt
Authors: Ganbat Ariuntsetseg , Tsujimori Tatsuki , Pastor-Galán Daniel , Webb Alexander
Published: February 2023

The Central Asian Orogenic Belt (CAOB) consists of several continental blocks, was assembled during the Phanerozoic, and preserves large volumes of Phanerozoic granitoids with juvenile Nd and Hf isotope characteristics, and thus regarded as the largest site of Phanerozoic continental growth on Earth. Nonetheless, it remains disputed whether the significant crustal additions occurred during the Phanerozoic. We compiled available zircon U–Pb geochronological and Hf-in-zircon isotopic data for granitoids from the orogenic segments of CAOB. Using this data, we estimated the percentage of juvenile versus evolved crustal portions in different Phanerozoic time slices of the CAOB.     The areal distribution of Hf isotopic information shows a younging trend in the Hf model age and radiogenic Hf values from northeast to southwest. For many orogenic segments of the CAOB, the range of hafnium isotope signatures for the granitoids shifted towards more radiogenic compositions over time. We interpret these findings to indicate that the lower crust and lithospheric mantle beneath the CAOB continental blocks were largely removed during continuous oceanic subduction and replaced by juvenile crust. Melts of this crust display the radiogenic hafnium signature. The juvenile versus evolved crustal portion estimations in different time slices show that the crustal growth has taken place in a steady-state mode, and the rate of the radiogenic crustal generation is close to overall global averaged rates of crust generation. It follows that Phanerozoic net crustal growth in accretionary orogens, as exemplified by the CAOB, may have been overestimated as it has been compensated by crustal destruction.
Application of Multi-attribute fusion Technology in Channel Sand Body Recognition and Boundary Characterization : A Case Study of the Gangzhong Oil Field in Bohai Bay Basin
Authors: Zhou Dawen
Published: February 2023

Fan delta is an important reservoir for hydrocarbon accumulation.The channel sand bodies of fan-delta front facies are narrow , and the lithologic assemblage changes quickly in space and is sensitive to water depth changes. It is a key and challenging task to accurately identify and characterize the channel with seismic data under the condition of few Wells. In this study, we selected the fan delta deposits of the Shahejie Formation in the Gangzhong area of the Bohai Bay Basin, China as an example to explore the method to accurately characterize the channel in the fan delta system by using seismic multi-attribute fusion technology.Six types of thirty-eight seismic attributes reflecting different geological information are extracted for river channel identification in the target area, and the most sensitive attributes to geological conditions are selected in each class of attributes. The physical meaning of various attributes is analyzed to identify the differences between different river structures. The multi-attribute clustering analysis based on FCM algorithm is used to reduce data dimension and reduce redundancy. Three seismic attributes that reflect the boundaries of geological bodies and lithological characteristics are selected for RGB fusion to highlight the overall characteristics of river distribution in this area, and enhance the characterization of the boundaries of channel sand body. It provides practical value for the next favorable target prediction of channel sand body.
How marine insurance causes damage with insurers aiding and abetting it!
Authors: Gupta Praveen
Published: February 2023

Marine insurers: cargo, shipping (hull and P&I) while insuring their insureds, aid and abet ocean biodiversity damage and climate change. In the process they are also a threat to the related planetary boundaries.While marine insurance is a direct threat to the well-being of our oceans, insurers of land-based assets - with multiple forms of discharges - also critically and adversely impact the oceans need to be taken into account.The author will highlight an overview on what these damages are, the possible corrective actions required, seek the insights from the participants and ideally agree upon a plan of action to mitigate this threat.
High Resolution Simulations of European Air Quality in 2050 Following Different CMIP6 Climate Change Mitigation Pathways
Authors: Clayton Connor J. , McQuaid James B. , Marsh Daniel R. , Turnock Steven T. , Graham Ailish M. , Pringle Kirsty J. , Kumar Rajesh
Published: February 2023

Air quality co-benefits are expected to occur with greater climate mitigation, however climate mitigation is not expected to occur in isolation of other socio-economic changes. Although modelling studies investigating these co-benefits are common, limited work uses the recently developed “Shared Socioeconomic Pathways” which factor in the different patterns of climate mitigation, socioeconomic development and pollution control. Additionally, as the SSPs were designed for climate model ensembles, such as CMIP6, existing work usually uses global climate or earth system models with interactive chemistry simulated at relatively coarse horizontal resolution. These computational trade-offs may impact how effectively they model air quality at human exposure-relevant scales and may miss differing trends seen only at subregional scales.We have used the anthropogenic emissions inputs from different SSPs which have different mitigation patterns applied to climate change and air pollution in 2050 to drive a specialised Atmospheric Chemistry model (WRF-Chemv4.2) at 30km resolution over Europe. We compare these to a 2014 control simulation. We present the validation of this model setup, which suggests an overestimation of surface PM2.5 concentrations, largely driven by overestimated NO3 aerosol, but good agreement with O3 observations. We find that while significant potential for air quality co-benefits exists, these effects are non-linear, with both PM2.5 and O3 worsening in some locations and scenarios despite increased pollution control compared to the present. We also find notable spatial heterogeneity in the change of PM2.5 and O3 across Europe in some scenarios.  Overall, however the results show that across Europe, scenarios with greater mitigation of climate change and air pollution show improvements in air quality that could lead to benefits to human health. 
Atmospheric Drivers of Rainfall Events in the Republic of Djibouti
Authors: Mohamed Waberi Moussa , Camberlin Pierre , Pohl Benjamin , Assowe Omar
Published: February 2023

The Republic of Djibouti is a small country (23 200 km²) in East Africa, characterised by an arid context coupled with a high variability of rainfall that generates flash floods causing severe damage to the population and infrastructure. The mechanisms controlling climate dynamics in Djibouti and the Eastern Africa region remain poorly understood. In this study, we document the atmospheric mechanisms associated with extreme rainfall events in the Republic of Djibouti. To that end, we use at the daily timescale rain-gauge data (a network of 36 stations on the period 2013-2020), satellite-based rainfall estimates (CHIRPS, IMERG, MSWEP and RFE) and atmospheric reanalyses (ERA5), selected over their common period 2001-2020.A multivariate Hierarchical Ascendant Classification of rainy days in Djibouti (≥ 10% of grid-points exceeding 1 mm.day-1, according to all four satellite products) reveal 4 clusters (intense rainfall, moderate rainfall, rainy in the southwest, rainy in the east) which differentiate from each other by the intensity and spatial extent of rainfall. These clusters show a non-homogeneous seasonal distribution, occurring mainly in the March-April-May (MAM) and July-August-September (JAS) seasons, and more rarely in October-November-December (OND). The atmospheric circulation anomaly patterns associated with the clusters are quite similar and highly season-dependent. In MAM most clusters display an anomalous trough over the Red Sea from 700 hPa to 200 hPa. In JAS, an anomalous low over the southern Red Sea drives a thicker than normal monsoon flow at 700 hPa (especially for the southwest cluster), while upper northerlies prevail at 200 hPa. In OND, most rainy events result from moisture advection from the Western Indian Ocean favoured by positive phases of the Indian Ocean Dipole. Some highly unusual atmospheric circulation patterns, which are not depicted by the above classification (e.g., associated with tropical cyclones), also result in intense rainfall events in the Republic of Djibouti.
Entropy-based early detection of critical transitions in spatial vegetation fields
Authors: Tirabassi Giulio , Masoller Cristina
Published: February 2023

In semiarid regions, vegetated ecosystems can display abrupt and unexpected changes, i.e., transitions to different states, due to drifting or time-varying parameters, with severe consequences for the ecosystem and the communities depending on it. Despite intensive research, the early identification of an approaching critical point from observations is still an open challenge. Many data analysis techniques have been proposed, but their performance depends on the system and on the characteristics of the observed data (the resolution, the level of noise, the existence of unobserved variables, etc.). Here, we propose an entropy-based approach to identify an upcoming transition in spatiotemporal data. We apply this approach to observational vegetation data and simulations from two models of vegetation dynamics to infer the arrival of an abrupt shift to an arid state. We show that the permutation entropy (PE) computed from the probabilities of two-dimensional ordinal patterns may provide an early warning indicator of an approaching tipping point, as it may display a maximum (or minimum) before decreasing (or increasing) as the transition approaches. Like other spatial early warning indicators, the spatial permutation entropy does not need a time series of the system dynamics, and it is suited for spatially extended systems evolving on long time scales, like vegetation plots. We quantify its performance and show that, depending on the system and data, the performance can be better, similar or worse than the spatial correlation. Hence, we propose the spatial PE as an additional indicator to try to anticipate regime shifts in vegetated ecosystems.Tirabassi, G., & Masoller, C. (2023). Entropy-based early detection of critical transitions in spatial vegetation fields. Proceedings of the National Academy of Sciences, 120(1), e2215667120.
Palaeoenvironmental reconstruction of the Mio-Pliocene succession of the Miscano River: insights on sedimentation after the Messinian salinity crisis in the southern Apennines
Authors: Infante Andrea , Aiello Giuseppe , Barra Diana , Ciarcia Sabatino , Di Donato Valentino , Morabito Simona , Prinzi Ernesto Paolo , Vitale Stefano
Published: February 2023

We present a study of a Mio-Pliocene marine to a continental clastic sedimentary succession of the southern Apennines Foreland Basin System well exposed in the Miscano River in the Irpinia sector of the chain. These well-bedded wedge-top basin deposits host a significant angular unconformity between a post-evaporitic succession (uppermost Messinian-lowermost Pliocene), developed on top of the evaporite deposits related to the Messinian Salinity Crisis, and an overlying upper part of the Zanclean sediments. The unconformity witnesses a major tectonic shortening stage of the southern Apennines characterized by out-of-sequence thrusting that involved the Mio-Pliocene wedge-top basin deposits. Meio-microfaunal and nannofloral fossil assemblages were analyzed to define the depositional environments and biostratigraphy of the two successions. In addition, benthic foraminiferal and ostracod assemblages were studied in detail, and their autochthonous/allochthonous provenience was discussed from a paleoecological point of view. The relative response of these assemblages to environmental parameters, such as salinity, oxygenation, paleobathymetry and climatic changes, allowed us to reconstruct the paleoenvironmental evolution of these wedge-top basin deposits.
New method of directional spectrum estimation accounting for ambient shearing currents
Authors: Toledo Yaron , Soffer Rotem , Kit Eliezer
Published: February 2023

Realistic currents in seas and oceans are almost always changing in depth thus indicating on the presence of shear in the mean ambient flow. However, analysis methodologies interpreting directional wave data gathered by in-situ measurement devices such as: buoys, pressure gauges and Acoustic Doppler Current Profilers (ADCPs) utilize potential irrotational flow theory which cannot account for the rotational shearing currents. The effects of shearing currents on the wave direction estimations were studied on synthetic ADCP data of waves propagating in a predetermined spread. The synthetic data was generated employing the Rayleigh Boundary Value Problem (BVP) and a selected ambient current profile. The potential data processing led to significant errors in wave directional spread estimation for common shearing currents (~10°  in mean wave direction for the presented example). This finding is of great importance, as it addresses the influence of an ambient current profile on wave propagation direction. The obtained results suggest that there is an uncertainty with the confidence of any wave directional spread ever presented by in-situ wave measurement devices.
A new methodology was developed for estimating directional wave spectra based on rotational flow physics by acquiring new terms emanate from wave-shearing current interaction governing equations. This included a derivation of new numerical transfer functions for the fluid’s physical properties based on the Rayleigh BVP. Then, by applying classical cross- and auto-spectral analysis on time-series data sets, the directional spread function was numerically reconstructed. The newly derived data processing methodology was applied to the same synthetic ADCP data sets. It was found to be capable of reconstructing the spread with great accuracy (0.4° in mean wave direction for the presented example). In addition, to modeling and synthetic data, field measurement data from several campaigns were also analyzed showing the importance of accounting for the vertical shear. This makes it a prominent methodology for estimating directional wave spectra in realistic oceanic conditions.
Evaluation of the Geographical Accessibility to Medical Services, Taking into Account the Environmental and Infrastructural Factors
Authors: Kvirkvelia Bela , Elizbarashvili Shalva , Kimeridze Maia , Khuntselia Tamar , Chikhradze Nino
Published: February 2023

In this study we present what environment and infrastructure factors should be considered when evaluating geographical accessibility to medical services in developing countries.Access to medical services is a versatile and complex concept and includes geographical, temporal, financial and other factors. Geographical factors are considered as the basis for access to medical services. Geographical access to medical services means deployment of medical institutions within certain radius or time required for travel to the medical institution and the number of services compared to the number of potential customers. The World Health Organization gives preference to the travel time needed to reach the service compared to the distance to evaluate geographical accessibility.As a rule, while researching the geographical access to medical services in the world, it is generally accepted that every person is in the same average travel conditions and has appropriate transportation means. A change in the travel time, such as weather conditions, road and transport availability and other variable factors, are not taken into consideration.However, under the global warming conditions, the frequency and intensity of extreme hydrometeorological events are significantly increased and are likely to be increased further in future. Rain, snowfall, extreme temperature, hurricanes, etc. create emergencies, affect travel time and, thus, hamper geographical access. Moreover, in high mountainous regions, there are frequent landslides, mudflows, rockfalls, avalanches, etc. Developed countries are more willing to respond to such challenges and are quick to react. However, it is a significant problem in developing countries and often the rural areas are torn apart and isolated for many hours and even whole winter.Thus, when evaluating geographical accessibility to medical service in developing countries it is crucial to take into account the risks of extreme geological and hydrometeorological phenomena on the roads, availability of road infrastructure, transport system. This approach will enable detailed modelling of real problems and their inclusion in the health care development plan. This can bring significant social-economic benefits.This work was supported by Shota Rustaveli National Science Foundation of Georgia (SRNSFG), Grant № FR-19-14993.
Prediction of the maximum compressive horizontal principal stress directions of medium to deep shale gas in the Nanchuan region, China
Authors: Yang Ruiqing , Yang Fengli , Hu Panpan
Published: February 2023

 AbstractThe Nanchuan region is located on the southeastern margin of the Sichuan Basin, South China. Silurian Wufeng-Longmaxi Formation, buried between 2000-4500m deep in this area, is an important shale gas-producing formation. Influenced by multi-phase tectonic action during Mesozoic- Cenozoic [1], the maximum compressive horizontal principal stress (σHmax) directions are complex and the orientation changes rapidly (55°-135°). Therefore, effectively predicting the maximum compressive horizontal principal stress (σHmax) is important for improving the shale gas production capacity and optimizing the fracturing scheme development.In this paper, the SHELLS finite element stress field modeling [2] was introduced and used to understand the above problems. Based on the increased and improved resolution of its program, and faults topography, heat flow, petrophysical parameters, and boundary conditions in the shale gas target layer, the σHmax directions in the study area were modeled and calculated. The prediction results show that σHmax directions in the Nanchuan region vary multi-directionally (0-180°), and are consistent with 11 of the 13 drilled wells, with only two drilled wells having minor differences (Figure 1). 85% of the predicted wells are consistent with the measured wells, achieving significant geological results and laying the foundation for the effective development of shale gas production capacity and optimized fracturing schemes in the area.Keywords: Stress field modeling, maximum compressive horizontal principal stress directions, shale gas, mid-deep, the Nanchuan regionFigure 1 σHmax directions in the Nanchuan region compared to actual drillingReferences:[1] Tang J G., Wang K M., Qin D C., Zhang Y., Feng T., 2021. Tectonic deformation and its constraints to shale gas accumulation in the Nanchuan area, southeastern Sichuan. Bulletin of Geological Science and Technology. 40(5), 11-21. ( in Chinese version).[2] Bird, P., 1999. Thin-plate and thin-shell finite-element programs for forward dynamic modeling of plate deformation and faulting 1. Comput. Geosci. 25, 383–394.
Finding Argoland: reconstructing a lost continent in SE Asia
Authors: Advokaat Eldert , van Hinsbergen Douwe
Published: February 2023

Can continents get lost? The geological textbooks predict that when continents enter subduction zones, subduction either stops, or part of the crust is scraped off and preserved in orogens. A possible exception has been the conceptual continent of Argoland. Argoland must have been broken off the NW Australian margin in the Late Jurassic and migrated north to end up somewhere in SE Asia, but the previously identified fragments that may form candidates are too small to represent all of Argoland, and the geology shows that they were once separated by oceanic basins that are much older than the Late Jurassic. We compiled the orogenic architecture and the geologic record of SE Asia and the NW Australian margin. We identified Gondwana-derived units that collectively may represent Argoland. These fragments are found between relics of Late Triassic to Middle Jurassic oceanic basins that all pre-date the break-up of Argoland. We systematically restore deformation within SE Asia in the upper plate system above the Sunda trench, use this to estimate where Gondwana-derived fragments accreted at the Sundaland (Eurasian) margin in the Cretaceous, and subsequently reconstruct their tectonic transport back to the Australian-Greater Indian margin. Our reconstruction shows that Argoland originated at the northwest Australian margin between the Bird’s Head in the east and Wallaby-Zenith Fracture Zone in the west, south of which it bordered Greater India. We show that the lithospheric fragment that broke off northwest Australia in the Late Jurassic was a collage of continental fragments and intervening oceanic basins.
Hail in the Kvemo Kartli Region (Georgia)
Authors: Elizbarashvili Elizbar , Elizbarashvili Mariam , Kvirkvelia bela
Published: February 2023

The research aimed at studying the characteristics of hail in the Kvemo Kartli region (Georgia). Hail (30%) is the most frequent natural hydrometeorological event in the territory of Georgia after flash floods (37%). Hail is typical for the Kvemo Kartli region, where agricultural production is the leading industry. It damages farm lands. The study of hail is very important for the development and introduction of hail prevention methods in the region.We used the observation materials of 7 weather stations of the region for the years of 1961-2022, a catalog was compiled and the following characteristics of hailfall were calculated: probability, number of days, intensity, frequency, duration, and distribution areas.Hail is observed in the warm spell of the year; especially active processes develop in spring and the first half of summer, which are associated with convective clouds.The highest number of hailfall days in the region is 12-14 days a year. In the Kvemo Kartli region, hail damage the territory with an area of ​​1 to 5 square kilometers in 38% of its cases; in 33% of cases, it damages an area of ​​less than 1 km2. An area of ​​more than 5 km2 is damaged in approximately 30% of cases of hail. Rarely, hail damages much larger areas, for example, more than 50 km2 is damaged in 3% of cases. The average duration of hailfall is 9-10 minutes. In 60% of cases, hailfall lasts less than 5 minutes, in 80% of cases, the duration of hailfall is less than 10 minutes. In 3% of cases, hail can last for an hour and a half.Thus, the main climatic characteristics of hail in the Kvemo Kartli region have been identified.The research results can be used to reduce the negative impact of hail and implement measures to prevent hail.This work was supported by Shota Rustaveli National Science Foundation of Georgia (SRNSFG) Grant № FR-19-14993.
Characterization of ambient seismic noise sources for long term monitoring of a sea dike: preliminary results of the SEEWALL project.
Authors: Lehujeur Maximilien , Kahrizi Amin , Abraham Odile , Michel Loic , Bardainne Thomas , Lescoat Antoine , Vivin Lila , Blanchais Julien , Boulay Christopher , Devie Thibaud , Palma-Lopes Sérgio , Durand Olivier , Gugole Gautier
Published: February 2023

Protection against sea submersion is a key point for the management of coastal areas. Operators need tools to monitor the aging of the sea dikes in order to reduce the risk of catastrophic events such as the Xynthia storm that occurred in 2010 (west of France). Long-term monitoring of these structures can be done using the ambient seismic noise produced by a combination of natural sources (e.g. the impact of swell on the structure, water currents, the wind force on ground-anchored constructions, etc.) and/or nearby anthropogenic sources (e.g. road/pedestrian traffic, coastal activities, etc.).Continuous ambient noise recordings can be used for monitoring structures by detecting small variations in seismic velocities related to localized degradations that cannot be detected visually. However, this monitoring technique requires sufficient energy in the proper frequency range for the intended application (typically at wavelengths of the order of the size of the structure or less). Additionally, the distribution of the sources must be relatively stable over time in order to interpret the velocity variations explicitly. The case of sea dikes is particularly challenging as the seismic noise is highly variable due various factors, like the water height variations during the tidal cycle, the variations in tidal intensity during the year, or the effects of the climatic conditions on the direction and intensity of the swell.This study is conducted in the framework of the SEEWALL project, which aims to develop a system for monitoring sea dikes using ambient seismic sources. A dike located on the Noirmoutier Island (France) has been instrumented with permanent accelerometers along with several geophysical and meteorological probes which have been recording continuously for about one year. This contribution focuses on the identification of the essential properties of the ambient seismic noise recorded in this setting and seeks to evaluate how these properties affect our ability to measure temporal variations of the seismic waves velocity. In other words, our objective is to identify the noise sources that contribute most favorably to the approximated empirical Green’s functions and/or that are highly repeatable over time, in order to develop methods that can be applied to various dikes and to optimize the type and amount of seismic data required to monitor such structures.
Role of background moisture in dictating the Intraseasonal Rainfall over Bay of Bengal
Authors: Kottapalli Aditya , Pn Vinayachandran
Published: February 2023

The northward propagating intraseasonal Oscillation (ISO) is one of the dominant modes of tropical variability during Boreal summers. Several mechanisms have been proposed to explain northward propagation. Yet the factors that decide the ISO rainfall over a particular region remains elusive. in this  study we show that the ISO rainfall anomalies weaken across the south Bay of Bengal (SBoB) before they re-strengthen over the north Bay of Bengal (NBoB). We use the moisture budget to understand the reason for the same. We find that the horizontal moisture flux convergence predominantly controls the ISO rainfall anomalies over the two regions. Further analyses reveal that the convergence of background moisture by the ISO wind perturbations decides the ISO rainfall structure. We hypothesize that the weaker rainfall anomalies in the SBoB result from the weaker background column relative humidity and moisture, which do not allow the initial dynamic perturbations to grow as fast as they do in an environment with stronger background relative humidity and moisture (NBoB). 
Variation of global compound heatwaves and their associations with climate variability
Authors: Zhang Kun , Li Jinbao , Ng Michael K. , Tai Amos P. K. , Wu Jin
Published: February 2023

Recent widespread heatwaves have broken local temperature records over the world. Large and intense heatwaves not only change the land surface biophysical environment in terms of temperature rise and water shortage, but also endanger our natural and human ecosystems by increasing health risks. Compared to the independent daytime or nighttime heatwave, the compound heatwave often yield higher hot extremes and even pose greater hazard to human and ecosystem health, as it prevents humans or ecosystems recovering from previous hot temperatures if the extreme hot occur in both day and night. However, factors shaping their spatiotemporal patterns on a global scale remain poorly understood, as do their links with large-scale interannual climatic variability. Here, with the air temperatures from multiple global datasets (e.g., ERA5L, CPC, MERRA2, and JRA55), we quantified the frequency and intensity patterns of compound heatwaves over 1980–2019 and analyzed their associations with modes of climate variability. Our results show a significant increasing trend of compound heatwave occurrences on a global scale, with the global average frequency and intensity increased by 90% and 32%, respectively, in 2010–2019 relative to 1980–1989. Specifically, Arctic and mid-latitudes of the Northern Hemisphere have seen the greatest increases in heatwave frequency and intensity over the last four decades, which may be connected to the amplifying influence of Arctic warming as well as human activity. The interannual variability of tropical compound heatwaves is dominated by ENSO occurrences from the previous year to the present year. And, the PDO and AMO modes dominate the interannual variability of extremely high temperatures in the majority of the mid-latitudes. In contrast, the interannual variability of compound heatwaves in the Arctic is most strongly tied to the AO and NAO in the winter of the present year, but it is most directly associated with the AAO and SAM in the Antarctic, which has an 8–9-month lag impact. This work will increase our knowledge of the global patterns and mechanisms of compound heatwaves in a multi-decadal context, hence enhancing our ability to predict hot extremes. 
Modelling weathering-induced progressive rock slope failures
Authors: Wang Liang , Loew Simon , Lei Qinghua
Published: February 2023

Rock slopes usually exhibit progressive failure phenomena over a long period of time under the active Earth surface environment involving complex geological, mechanical, hydrological, and chemical interactions. Among these processes, weathering has been recognised as a ubiquitous and important factor that drives slope destabilisation. Rock masses in a slope may experience weathering-induced strength degradation of variable degrees depending on the morphology, lithology, depth, fracturing, and time, which can lead to the emergence of various rock slope failure patterns, e.g. planar and rotational slides, slumps, topples, and rock falls. After failure, the slope may transition from slow deformation to catastrophic collapse characterised by rapidly moving material flows of fragmented rocks. These complex processes are driven by various mechanisms operating across different timescales, which pose a great challenge for modelling the entire history of rockslide evolution. In this study, we develop a unified computational framework for simulating the pre- and post-failure behaviour of rock slopes subject to long-term weathering processes. This framework includes the following key features: (i) a coupled weathering-damage model is developed to capture the interplay of weathering-induced strength loss and damage-related strain softening; (ii) pre-existing faults are represented explicitly as thin weakness zones; (iii) an implicit time integration scheme is adopted to simulate the slope evolutionary behaviour across multiple timescales; (iv) a frictional velocity-weakening law is incorporated to capture the development of rapid mass flows; (v) the particle finite element technique is used to track the small to large deformation/motion of rock masses. We show that our model can realistically simulate the pre-failure progressive rock slope destabilisation, the catastrophic rock mass failure, and the post-failure transient runout, demonstrating the capability of our model in realistically capturing the initiation, evolution, and consequence of weathered rock slope failures. Our results provide useful insights into the interplay of natural weathering and brittle damage in rockslide evolution and the control of geological structures on pre- and post-failure patterns of rock slopes.
Temporal water table dynamics derived from optical satellite data
Authors: Burdun Iuliia , Bechtold Michel , Aurela Mika , De Lannoy Gabrielle , Desai Ankur R. , Humphreys Elyn , Kareksela Santtu , Komisarenko Viacheslav , Liimatainen Maarit , Marttila Hannu , Minkkinen Kari , Nilsson Mats B. , Ojanen Paavo , Salko Sini-Selina , Tuittila Eeva-Stiina , Uuemaa Evelyn , Rautiainen Miina
Published: February 2023

Water table constitutes a master control of the general biogeochemistry in northern peatlands. The performance of peatland simulations in global ecosystem models is strongly hampered by the accuracy of the water table predictions. We examined the applicability of the Optical TRApezoid Model (OPTRAM) to monitor the temporal fluctuations in water table over 53 intact, restored, and drained northern peatlands in Finland, Estonia, Sweden, Canada, and the USA from 2018 through 2021. Various OPTRAM were computed based on Sentinel-2 data with the Google Earth Engine cloud platform. We found that (i) the choice of vegetation index utilised in OPTRAM does not significantly affect OPTRAM performance; (ii) the tree cover density is a significant factor controlling the sensitivity of OPTRAM to water table dynamics; (iii) the relationship between water table and OPTRAM often disappears for deep water tables. Based on an anomaly analysis, we further found that OPTRAM seems to be in particular suitable to monitor long-term (i.e., interannual) water table variability while the performance for short-term changes (e.g., response to individual rain events) was lower. Overall, our results support the application of OPTRAM to monitor water table dynamics in intact and restored northern peatlands with low tree cover density when the water table is shallow to moderately deep.