Heterogeneous data management and modeling for the gravimetric geoid model: a review study in Pakistan

Arabian Journal of Geosciences - The gravimetric geoid model can be used as vertical reference in surveying and other related technologies. It is being developed by NESCOM in collaboration with the...     

EGY-HGM2016: an improved hybrid local geoid model for Egypt based on the combination of GOCE-based geopotential model with gravimetric and GNSS/levelling measurements

An improved hybrid gravimetric geoid model for Egypt, EGY-HGM2016, has been recently computed implementing the least-squares collocation (LSC) method through the remove-compute-restore (RCR) procedure. The computation of EGY-HGM2016 involves different datasets in terms of gravity anomalies determined from the GOCE (gravity field and steady-state ocean circulation explorer)-based global geopotential model (SPW-R4) up to d/o 200 and EGM2008 from d/o 201 to 720 combined with terrestrial gravity datasets in terms of 2140 gravity field anomalies and about 121,480 marine surface gravity anomalies. In addition, orthometric heights from 17 GPS/levelling measurements have been considered during the modelling process to improve the determination of the hybrid gravimetric geoid over the Egyptian region. The EGY-HGM2016 model estimated over Egypt provides geoid heights that are ranging from 7.677 to 21.095 m with a standard deviation (st. dev.) of about 2.534 m in the northwest of the country excluding the involvement of the orthometric heights from GPS/levelling measurements. When the later dataset is considered during the implementation of LSC process, hybrid residual height anomalies ranging from ?1.5 to +0.9 m, with a mean of 0.22 m and a st. dev. of 0.17 m, are obtained. Comparison of the predicted hybrid gravimetric geoid with the corresponding ones obtained from EGM2008, GOCE-based SPW R4 model, and GPS/levelling reveals considerable improvements of our EGY-HGM2016 model over Egypt.     

频谱分析法在反演造山带地形高差演化中的应用——以中国大别山、米仓山和美国内华达山脉为例

近年来迅速发展的低温热年代学已极大改善了人们对地壳内(1～6 km)隆升和剥蚀过程的认识.然而在实际工作中,样品的采集除了受到气候、地理环境等恶劣条件的制约以外,在对低温热年代学数据进行解释或以此计算造山带的隆升剥露速率时,使用的一些有关近地表热结构的假定条件通常是不科学的,如将易受地表起伏影响的地热等温线形态考虑成水...     

The ideal-typical sequence model: Its applicability to the development of transport in Saudi Arabia,the Sudan and other Middle Eastern countries

This paper is an attempt to apply the Ideal-Typical Sequence Model which was produced by Taaffe, Morrill and Gould (1963) to the development of modern transport in Saudi Arabia, the Sudan, and other Middle Eastern countries. The model and its principles are explained and then reference was made to studies produced in this connection. The finding of this paper is that the model is broadly applicable to modern transport development in Saudi Arabia but not to the Sudan, although the three principles of penetration, inter-connection and continuous process are applicable in both countries. Some modifications concerning the direction, number of the penetration lines and the motives behind the construction of those lines are made in this paper which are thought to make the model of general application to all under-developed countries irrespective of their geographical characteristics.     

Liquid bridge contribution to shear behavior of unsaturated soil: modeling and application to a micromechanics model

Acta Geotechnica - Liquid bridges in unsaturated soils attach to grain contacts and contribute to strengthening microscopic bonding forces, which leads to macroscopic high strength and stiffness...     

Insights into the deformation and failure characteristic of a slope due to excavation through multi-field monitoring: a model test

Acta Geotechnica - Multi-field information monitoring is useful to better understand the deformation and failure behaviour of landslides. Therefore, in this study, a physical slope model under...     

Magnetic and radiometric signatures over a Proterozoic massive sulfide setting of northern fringe of Dalma Volcanics,eastern India: An implication to metallogeny

Magnetic and radiometric surveys were carried out over a felsic dominated rifted margin of Proterozoic volcanic terrain of a mobile belt in the eastern India. The studies were made in blocks I and II of 0.65 sq km and 0.70 sq km respectively over a previously identified conductor in the northern fringe of Dalma Volcanics (DVs). In general, both the blocks show high magnetic signature associated with sulfide mineralisation. The interpretation of magnetic data suggests that nature of the causative source is mainly horizontal cylinder in both the blocks. The depth to the top of the causative source is about 25 m in both the blocks and extends upto 60 m in block I and 40m in block II. Gamma count rate exhibits about a factor of two to three enhancements above the field background for both the blocks. The obtained iso-rad maps are similar to uranium and copper belt in the Singhbhum shear zone south of the study area. The anomalous radiometric signature of the residual soil/rock of the area indicates towards hydrothermal alteration. The detailed magnetic surveys and preliminary iso-rads results seems quite encouraging and may be attributed to VMS setting in the area and potential sulfide mineralisation with uranium mineral association in the DVs province.     

Methodology for the assessment and classification of regional vulnerability to natural hazards in China: the application of a DEA model

This paper presents a new method for quantifying vulnerability to natural hazards in China. As an important area of vulnerability research, quantitative assessment of vulnerability has raised much focus in academia. Presently, scholars have proposed a variety of methods for quantitative assessment, which usually create an index of overall vulnerability from a suite of indicators, based on the understanding of the cause or mechanism of vulnerability. However, due to the complex nature of vulnerability, this approach caused some arguments on the indicator selection and the weight set for subindices. A data envelopment analysis?Cbased model for the assessment of the regional vulnerability to natural disasters is presented here to improve upon the traditional methods, and a new approach for the classification of vulnerability is proposed. The vulnerability to natural hazards in China??s mainland is illustrated as a case study. The result shows that the overall level of vulnerability to natural hazards in mainland China is high. The geographic pattern shows that vulnerability is highest in western China, followed by diminishing vulnerability in central China, and lowest vulnerability levels in eastern China. There is a negative correlation between the level of vulnerability and the level of regional economic development.     

Turbidites and iron formations, Beardmore-Geraldton, Ontario: application of a combined ramp/fan model to Archaean clastic and chemical sedimentation

Sandy turbidites, grain flows, conglomeratic mass-flows and oxide-facies iron formation are present in the late Archaean Beardmore-Geraldton terrain, a metasedimentary belt which extends for at least 80 km in an E-W direction. The marine portion of this basin contains four lithofacies associations (LA): (1) Thinbedded, iron formation-clastic sediment association. This association represents a continuum of deposit types containing iron formation; subtypes are defined on the basis of bedding attributes and the proportion of iron formation to sand/silt. (2) Thin-bedded, turbidite-dominated association. These sediments consist mostly of silt/sand beds which either show no vertical trends, or thin and fine upwards over a few metres. (3) Medium-bedded, turbidite-dominated association. Most of these sediments are medium to coarsegrained, vertically unstructured sand sequences with occasional structured intervals. (4) Thick-bedded association. This is dominated by poorly graded sands up to 7–8 m in thickness. Sand beds are characterised by a thin basal zone of coarse sand and pebbles, a large central interval containing a mixture of medium and coarse sand, and a thin upper zone of fine sand/silt. The overall depositional system was initiated by transport of sediment by braided streams to the strand area where it accumulated in distributary mouth bars. We infer a nearshore break in slope, locally with large channels (LA 4) extending from close to the strand line across deltaic surfaces to the deeper portions of submarine fans (structured portions of LA 3). However, many deltaic surfaces probably were not tapped by major channels, but merged downslope into a submarine ramp. Sediment was transported across the ramp by slump events and sheet-like grain flows (unstructured portions of LA 3). Iron formation and LA 2 sediments probably accumulated both in upper-mid ramp areas with low sediment delivery rates, and distal to fan-ramp successions. As major streams on the braid plain changed position, associated submarine channels and slump-fed ramp deposits also would have shifted laterally. This produced overlap of different facies associations in both the fan and ramp environments, which may explain why observed vertical trends in bedding are limited to several metres. We suggest that on narrow, active Archaean cratonic margins, additional non-regular processes such as variations in sediment supply related to periods of heightened pyroclastic activity, and seismic activity associated with the arc, also contributed to the lack of vertically structured sequences. Turbidite sequences in such environments in general may contain important contributions from both submarine ramp and submarine fan sedimentation.     

Appropriate sampling strategy and analytical methodology to address contamination by industry: Part 1. Conceptual model of a sampling design and sampling types

This paper presents the results of a literature review on the conceptual model of a sampling design and the different types of samples that can be used to characterize the nature and the extent of contamination at a specific site. The main findings stress the importance of sampling for obtaining relevant sample types and subsequent-qualitative results. The proposed sampling design can be used for environmental studies where, the efficient use of time, money, and human resources are very critical. A good quality sampling design should meet the needs of the study with a minimum expenditure of resources.     

A numerical model of trace-element coprecipitation in a physicochemical calcification system: Application to coral biomineralization and trace-element ‘vital effects’

A mixed equilibrium/kinetic steady-state numerical model of coral calcification has been developed to test whether a physicochemical calcification mechanism is able to account for recent geochemical observations, in particular correlated trace-element variations presented in a companion paper [Sinclair, D.J., 2005. Correlated trace-element ‘vital effects’ in tropical corals: a new tool for probing biomineralization chemistry. Geochim. Cosmochim. Acta69 (13), 3265-3284]. The model simulates trace-element partitioning from a CaCO₃ supersaturated extracellular calcifying fluid (ECF) which has been modified by enzymatic input of Ca²⁺ and removal of 2H⁺ by CaATPase. CO₂ input is modelled as a diffusion process, while the ECF is continuously replenished by fresh seawater, which is the sole source of minor and trace-elements (TEs). Trace-element species fully equilibrate in the ECF, and selected trace-element species kinetically compete with Ca²⁺ or at the surface of the growing crystal. Each simulation is run to steady-state, and results are presented for a grid of CaATPase ion pumping rates and seawater replenishment rates. The dominant feature of the model output occurs when CaATPase ion pumping is high while seawater replenishment rates are low. At this point, CO₂ diffusion reaches its maximum, C input becomes limiting, buffering capacity is reduced and the pH of the system rises dramatically; significantly affecting the TE composition of the skeleton. At more modest pumping rates, the model reproduces the relative amplitudes of trace-element variations and slopes of the mutually positive correlations between B, Sr and U observed by Sinclair [Sinclair, D.J., 2005. Correlated trace-element ‘vital effects’ in tropical corals: a new tool for probing biomineralization chemistry. Geochim. Cosmochim. Acta69 (13), 3265-3284], but does not reproduce the negative correlations with Mg. The best fit between model and observation occurs when the coral simultaneously increases ion pumping and seawater replenishment rates: a strategy which allows rapid calcification while avoiding dangerously high pH variations. The model predicts that calcification occurs at only moderate pH elevations (8.3-8.4) with seasonal TE variations being explained by a shift of only 0.3 pH units. The model does not reproduce the full amplitude of diurnal pH variations observed recently. Sensitivity tests show that the model output is relatively insensitive to changes in the composition of the fluid from which the ECF is drawn (such as might occur if photosynthesis or active C transport mechanisms significantly modify the penultimate fluid source). Further research, however, is needed to establish the consequences of active transport of TEs and anions to the calcifying site.     

SHIA_Landslide: a distributed conceptual and physically based model to forecast the temporal and spatial occurrence of shallow landslides triggered by rainfall in tropical and mountainous basins

Landslides are a main cause of human and economic losses worldwide. For this reason, landslide hazard assessment and the capacity to predict this phenomenon have been topics of great interest within the scientific community for the implementation of early warning systems. Although several models have been proposed to forecast shallow landslides triggered by rainfall, few models have incorporated geotechnical factors into a complete hydrological model of a basin that can simulate the storage and movement of rainwater through the soil profile. These basin and full hydrological models have adopted a physically based approach. This paper develops a conceptual and physically based model called open and distributed hydrological simulation and landslides—SHIA_Landslide (Simulación HIdrológica Abierta, or SHIA, in Spanish)—that is supported by geotechnical and hydrological features occurring on a basin-wide scale in tropical and mountainous terrains. SHIA_Landslide is an original and significant contribution that offers a new perspective with which to analyse shallow landslide processes by incorporating a comprehensive distributed hydrological tank model that includes water storage in the soil coupled with a classical analysis of infinite slope stability under saturated conditions. SHIA_Landslide can be distinguished by the following: (i) its capacity to capture surface topography and effects concerning the subsurface flow; (ii) its use of digital terrain model (DTM) to establish the relationships among cells, geomorphological parameters, slope angle, direction, etc.; (iii) its continuous simulation of rainfall data over long periods and event simulations of specific storms; (iv) its consideration of the effects of horizontal and vertical flow; and (vi) its inclusion of a hydrologically complete water process that allows for hydrological calibration. SHIA_Landslide can be combined with real-time rainfall data and implemented in early warning systems.     

A statistical model to relate pyrite oxidation and oxygen transport within a coal waste pile: case study,Alborz Sharghi,northeast of Iran

This paper presents a statistical model for predicting pyrite fraction remaining in a coal waste pile at the Alborz Sharghi coal mine located at northeast of Iran. This model calculates the fraction of pyrite remaining using mole fraction of oxygen diffused into the pore spaces of the pile and the pile depth. Comparison of the statistical outputs revealed that a second-order polynomial expression with respect to oxygen mole fraction and depth provides a better correspondence to the field measurements for the fraction of pyrite remaining with a RMSE of 0.089231. Besides, two statistical relationships have been proposed for the remaining pyrite fraction and the mole fraction of oxygen versus the pile depth. A quadratic polynomial shows the best correlation of the field measured data. The suggested models were successfully validated with the acceptable confidence levels of 92 and 90 % for remaining pyrite and oxygen using a new data set which revealed the fact that they can be applied in similar situations. Both statistical analysis and field data indicate that the pyrite oxidation process is limited to the shallower depths of the waste pile where the mole fraction of oxygen decreased rapidly.     

Accuracy of a pre-trained sentiment analysis (SA) classification model on tweets related to emergency response and early recovery assessment: the case of 2019 Albanian earthquake

Traditionally, earthquake impact assessments have been made via fieldwork by non-governmental organisations (NGO's) sponsored data collection; however, this approach is time-consuming, expensive and often limited. Recently, social media (SM) has become a valuable tool for quickly collecting large amounts of first-hand data after a disaster and shows great potential for decision-making. Nevertheless, extracting meaningful information from SM is an ongoing area of research. This paper tests the accuracy of the pre-trained sentiment analysis (SA) model developed by the no-code machine learning platform MonkeyLearn using the text data related to the emergency response and early recovery phase of the three major earthquakes that struck Albania on the 26th November 2019. These events caused 51 deaths, 3000 injuries and extensive damage. We obtained 695 tweets with the hashtags: #Albania #AlbanianEarthquake, and #albanianearthquake from the 26th November 2019 to the 3rd February 2020. We used these data to test the accuracy of the pre-trained SA classification model developed by MonkeyLearn to identify polarity in text data. This test explores the feasibility to automate the classification process to extract meaningful information from text data from SM in real-time in the future. We tested the no-code machine learning platform's performance using a confusion matrix. We obtained an overall accuracy (ACC) of 63% and a misclassification rate of 37%. We conclude that the ACC of the unsupervised classification is sufficient for a preliminary assessment, but further research is needed to determine if the accuracy is improved by customising the training model of the machine learning platform.

     

A geochemical and geophysical approach to derive a conceptual circulation model of CO2-rich mineral waters: A case study of Vilarelho da Raia, northern Portugal

The Vilarelho da Raia-Chaves region, located in northern Portugal adjacent to the Spanish border, is characterized by both hot and cold CO₂-rich mineral waters issuing from springs and drilled wells. The present paper updates the conceptual circulation model of the Vilarelho da Raia cold CO₂-rich mineral waters. Vilarelho da Raia mineral waters, dominated by Na and HCO₃ ions, have formed mainly by interaction with CO₂ of deep-seated mantle origin. The δ ¹⁸O, δ ²H and ³H values indicate that these waters are the result of meteoric waters infiltrating into Larouco Mountain, NW of Vilarelho da Raia, circulating at shallow depths in granitic rocks and moving into Vilarelho da Raia area. The conceptual geochemical and geophysical circulation model indicates that the hot and cold CO₂-rich mineral waters of Chaves (76 °C) and Vilarelho da Raia (17 °C) should be considered manifestations of similar but not the same geohydrological systems. Electronic Publication     

The development of a multi-surface soil speciation model for Cd (II) and Pb (II): Comparison of two approaches for metal adsorption to clay fractions

The mobility of toxic metals in soils or sediments is of great concern to scientists and environmentalists since it directly affects the bioavailability of metals and their movement to surface and ground waters. In this study, a multi-surface soil speciation model for Cd (II) and Pb (II) was developed to predict the partition of metals on various soil solid components (e.g. soil organic matter (SOM), oxide mineral, and clay mineral). In previous study, the sorption of metal cations on SOM and oxide minerals has been evaluated by thermodynamically based surface complexation model. However, metal binding to soil clay fractions was normally treated in a simplistic manner: only cation exchange reactions were considered and exchange coefficient was assumed unity. In this study, the binding of metals onto clays was described by a two-site surface sorption model (a basal surface site and an edge site). The model was checked by predicting the adsorption behavior of Cd (II) and Pb (II) onto three selected Chinese soils as a function of pH and ionic strengths. Results showed that the proposed model more accurately predicted the metal adsorption on soils under studied condition, especially in low ionic strength condition, suggesting that adsorption of metals to soil clay fractions need to be considered more carefully when modeling the partition of trace elements in soils. The developed soil speciation model will be useful when evaluating the movement and bioavailability of toxic metals in soil environment.     

Ostwald ripening as a possible mechanism for zircon overgrowth formation during anatexis: theoretical constraints,a numerical model,and its application to pelitic migmatites of the Tickalara Metamorphics,northwestern Australia

A fundamental dichotomy exists between the low solubility of zircon in peraluminous melt predicted by experimental and geochemical studies and the large volume proportions of zircon overgrowths formed during high-temperature metamorphism and anatexis that are revealed by cathodoluminescence imaging. We investigate the potential of Ostwald ripening as a possible mechanism for overgrowth formation by presenting a numerical solution to the continuity equation governing open system, diffusion rate-limited Ostwald ripening in a zircon-saturated melt. Application of the model to a typical (log-normal) initial zircon crystal size distribution (CSD) suggests that despite uncertainties associated with the interfacial free energy of zircon, significant grain coarsening is possible via this mechanism under geological conditions and time scales relevant to high-grade metamorphism. Primary influences on the rate at which Ostwald ripening proceeds are (i) the temperature of the system, (ii) the duration of the time interval for which the system is above its solidus, and (iii) the nature of the initial (premelting) zircon CSD.To test the viability of the model, we examine zircon CSDs from three high-grade pelitic migmatites of the Tickalara Metamorphics (northwestern Australia), assuming that zircon crystals hosted by melanosome biotite were permanently occluded from the melt (and therefore approximate the premelting CSD). The model predicts that within 1 to 2 Ma, these biotite-hosted zircon CSDs will evolve into the observed leucosome-hosted zircon CSDs via melt-present Ostwald ripening, under geological conditions applicable to peak metamorphism.Although we have not conclusively demonstrated that Ostwald ripening contributed to changes in zircon CSDs during anatexis of the Tickalara metapelites, our results suggest that Ostwald ripening is a viable mechanism for zircon volume transfer in a zircon-saturated melt and capable of playing a significant role in overgrowth formation in rocks where the total volume of zircon overgrowths substantially exceeds the concentration of zircon dissolvable in the coexisting melt.