Abstract: The aim of the study was to establish the strength and direction of the relationship between daily temperature of river water and air with the use of selected estimation methods. The relationship was assessed for the River Noteć and its tributaries (Western Poland), using the cross-correlation function and Granger causality. The study established cause-and-effect relations for “water–air” and “air–water” directions of influence. It was confirmed that forecasting the pattern of flowing water temperature from changes in air temperature yields better results when done based on data from the previous day. Results of modelling the relationship between data series with the use of the linear and natural cubic splines models confirmed the presence of a nonlinear relation. It was also established that there is a statistically significant correlation of random fluctuations for both temperature series on the same days. This made it possible to confirm the occurrence of short-term connections between water and air temperature. The results can be used to determine the qualities of thermal regimes and to predict temperature of river waters in the conditions of climate change. PubDate: 2019-04-05

Abstract: Saturated hydraulic conductivity (Ks) describes the water movement through saturated porous media. The hydraulic conductivity of streambed varies spatially owing to the variations in sediment distribution profiles all along the course of the stream. The artificial intelligence (AI) based spatial modeling schemes were instituted and tested to predict the spatial patterns of streambed hydraulic conductivity. The geographical coordinates (i.e., latitude and longitude) of the sampled locations from where the in situ hydraulic conductivity measurements were determined were used as model inputs to predict streambed Ks over spatial scale using artificial neural network (ANN), adaptive neuro-fuzzy inference system (ANFIS) and support vector machine (SVM) paradigms. The statistical measures computed by using the actual versus predicted streambed Ks values of individual models were comparatively evaluated. The AI-based spatial models provided superior spatial Ks prediction efficiencies with respect to both the strategies/schemes considered. The model efficiencies of spatial modeling scheme 1 (i.e., Strategy 1) were better compared to Strategy 2 due to the incorporation of more number of sampling points for model training. For instance, the SVM model with NSE = 0.941 (Strategy 1) and NSE = 0.895 (Strategy 2) were the best among all the models for 2016 data. Based on the scatter plots and Taylor diagrams plotted, the SVM model predictions were found to be much efficient even though, the ANFIS predictions were less biased. Although ANN and ANFIS models provided a satisfactory level of predictions, the SVM model provided virtuous streambed Ks patterns owing to its inherent capability to adapt to input data that are non-monotone and nonlinearly separable. The tuning of SVM parameters via 3D grid search was responsible for higher efficiencies of SVM models. PubDate: 2019-04-03

Abstract: West Africa plays key roles in global climate and shows one of the strongest variations in hydro-climatic conditions. As it turns out, the region appears to be underrepresented in the existing compendium of Earth science and hydrology-focused journal papers when it comes to significant discussion on terrestrial hydrology and freshwater science. This prominent gap is largely precipitated by increasing number of constraints that include lack of considerable and robust investments in gauge measurements for meteorological and hydrological applications, poor funding of research institutions and other disincentives, among other factors. In this manuscript, the challenges and problems in large-scale terrestrial hydrology-focused investigation in West Africa are reviewed. Using a dossier of some recent contributions in the field of remote sensing hydrology, this review also highlights some of the progress in terrestrial hydrology and the opportunities that exist for hydro-geodetic research in West Africa that leverage on sustained investments in satellite geodetic missions. It is noted that West Africa is still a pristine environment for hydrology-focused research and can benefit from recent advancements in sophisticated space agency programs such as the Gravity Recovery and Climate Experiment, which undoubtedly has revolutionized terrestrial hydrology research around the world for nearly two decades. Given the poor density of gauge stations and limited ground observations, hydrological research in West Africa is expected to benefit more from independent space observations and multi-resolution data. This is because the lack of sufficient in-situ data for the parameterizations and adequate initialization of outputs from hydrological models and reanalysis data for hydrological applications results in poor representation of the West African land surface and hydrological state variables. To further improve our contemporary understanding of West Africa’s terrestrial hydrology, the continued evaluation/validation of these observations and space-borne measurements is advocated. PubDate: 2019-04-01

Abstract: The current past has seen a sensational increment in the utilization of satellites for the applications like navigation, entertainment, media transmission, remote sensing, mobile communications, weather forecasting, defense and other purposes. These applications are assigned in the microwave and millimeter wave bands, which offer higher information transfer possibility in lesser time and use very small antennas and devices by ensuring secured and effective communications. However, beyond the 10 GHz range of frequencies these applications are generally subjected to signal losses due to various atmospheric parameters like rain, clouds, fog, hail ice and other applicable phenomena. The main factor for the signal degradation is the rainfall. The attenuation caused by rain increases with frequency, as there is increased absorption of the RF energy at higher frequencies due to water drops present along the path of the transmission; hence, the signal attenuation is more in higher-frequency bands. The other factors that induce losses in the signal are the clouds, gases present in the lower atmosphere and the different layers in the atmosphere that cause scintillation and the system losses and cable losses. This survey article abridges all outcomes related to propagation impairments and attenuation aspects at microwave and millimeter wave frequencies covering the studies of various researchers in last three decades. In addition, few of the models developed by various researchers were listed along with model parameters which are useful for the propagation engineers and others who are interested in this specialization. PubDate: 2019-04-01

Abstract: On 5 April 2017, an Mw6.1 earthquake occurred about 50 km NE of the city of Fariman, northeast Iran. Several hundreds of aftershocks including two M > 5 events followed the main shock. The quake struck numerous towns and villages across the region, killed one person, and injured tens of people. Many schools and universities were evacuated around the epicentral area, and a lot of people left their residences for a few days. The northeastward motion of the central Iran toward Eurasia influences the epicentral region. Regional movements occur by shortening on the northwest-trending reverse faults. We studied teleseismic source parameters of this earthquake by applying different moment tensor decomposition methods including grid search for the nodal planes of the best double couple; linear inversion for a deviatoric moment tensor; grid search for the best double-couple moment tensor; grid search for the best deviatoric moment tensor; and grid search for the best full moment. Based on the moment tensors, the event occurred on a reverse fault following the regional compressional motion. The results of this study will provide useful information for future regional seismotectonic investigations and are of significant use for applications such as regional seismic hazard evaluations. PubDate: 2019-04-01

Abstract: The geophysical electromagnetic (EM) theories are commonly based on the assumption that the conductivity of underground media is frequency independent. However, due to the existence of induced polarization (IP) effect, many earth materials are dispersive, and their electrical conductivity varies significantly with frequency. Therefore, the conventional numerical techniques are not proper for EM forward modeling in general dispersive medium. We present a new algorithm for modeling three-dimensional (3D) EM data containing IP phenomena in frequency domain by using an edge-based finite element algorithm. In this research, we describe the dispersion behavior of earth media by using a Cole–Cole complex conductivity model. Our algorithm not only models land and airborne EM surveys but also provides more flexibility in describing the surface topography with irregular hexahedral grids. We have validated the developed algorithm using an analytic solution over a half-space model with and without IP effect. The capabilities of our code were demonstrated by modeling coupled EM induction and IP responses in controlled-source audio magnetotelluric (CSAMT) and airborne electromagnetic (AEM) examples. This algorithm will have important guiding significance for survey planning in the dispersive areas, and it could be taken as a forward solver for practical 3D inversion incorporated IP parameters. PubDate: 2019-04-01

Abstract: To solve quantitative interpretation problems in coal-bed methane logging, deep learning is introduced in this study. Coal-bed methane logging data and laboratory results are used to establish a deep belief network (DBN) to compute coal-bed methane content. Network parameter effects on calculations are examined. The calculations of DBN, statistical probabilistic method and Langmuir equation are compared. Results show that, first, the precision and speed of DBN calculation should determine the restricted Boltzmann machine’s quantity. Second, the hidden layer neuron quantity must align with calculation accuracy and stability. Third, the ReLU function is the best for logging data; the Sigmoid function and Linear function are second; and the Softmax function has no effect. Fourth, the cross-entropy function is superior to MSE function. Fifth, RBMs make DBN more accuracy than BPNN. Furthermore, DBN calculation accuracy and stability are better than those of statistical probabilistic method and Langmuir equation. PubDate: 2019-04-01

Abstract: The present study analyzes the efficiency of local intermittency measure based on wavelet transforms in identifying solar flare effects on magnetograms. If we observe the flare-time features in geomagnetic components, most often, disturbances associated with other solar phenomena will enhance or mask the solar flare signatures. Similarly, diurnal and high-latitude geomagnetic variabilities will suppress solar flare effects on magnetograms. The measurements of amplitudes taken directly from temporal variations of weak geomagnetic components have certain limitations regarding the identification of the proper base and peak values from which the deviation due to solar flare has to be measured. In such situations, local intermittency measure based on cross-wavelet analysis can be employed which could remarkably identify the flare effects, even if the signatures are weak or masked by other disturbance effects. The present study shows that local intermittency measure based on wavelet analysis could act as an alternate quantification technique for analyzing solar flare effects on geomagnetic activity. PubDate: 2019-04-01

Abstract: The original version of this article unfortunately contained a mistake: The affiliation of Deepak Chamlagain was incorrect: Department of Geology, Trichandra M. Campus, Tribhuvan University, Kathmandu, Nepal. PubDate: 2019-03-11

Abstract: There is an exceptional opportunity of achieving simultaneous and complementary data from a multitude of geoscience and environmental near-earth orbiting artificial satellites to study phenomena related to the climate change. These satellite missions provide the information about the various phenomena, such as sea level change, ice melting, soil moisture variation, temperature changes and earth surface deformations. In this study, we focus on permafrost thawing and its associated gravity change (in terms of the groundwater storage), and organic material changes using the gravity recovery and climate experiment (GRACE) data and other satellite- and ground-based observations. The estimation of permafrost changes requires combining information from various sources, particularly using the gravity field change, surface temperature change, and glacial isostatic adjustment. The most significant factor for a careful monitoring of the permafrost thawing is the fact that this process could be responsible for releasing an additional enormous amount of greenhouse gases emitted to the atmosphere, most importantly to mention carbon dioxide (CO2) and methane that are currently stored in the frozen ground. The results of a preliminary numerical analysis reveal a possible existence of a high correlation between the secular trends of greenhouse gases (CO2), temperature and equivalent water thickness (in permafrost active layer) in the selected regions. Furthermore, according to our estimates based on processing the GRACE data, the groundwater storage attributed due to permafrost thawing increased at the annual rates of 3.4, 3.8, 4.4 and 4.0 cm, respectively, in Siberia, North Alaska and Canada (Yukon and Hudson Bay). Despite a rather preliminary character of our results, these findings indicate that the methodology developed and applied in this study should be further improved by incorporating the in situ permafrost measurements. PubDate: 2019-03-07

Abstract: The knowledge of Q is desirable for improving seismic resolution, facilitating amplitude analysis and seismic interpretation. The most commonly used methods for Q estimation are the frequency-spectrum-based methods. Generally, these methods are based on the plane wave theory assuming that the transmission/reflection loss is frequency independent. This assumption is reasonable in the far-field situation and makes the transmission/reflection coefficient irrelevant with the Q estimation result. However, in the near-surface context, this assumption is invalid because the seismic wave propagates in the form of spherical wave in the real seismic surveys and the spherical-wave transmission/reflection coefficient is frequency dependent. As a result, deviation will exist. In this paper, the influence of the spherical-wave effect on the Q estimation in the near-surface context was proved in both synthetic data and field data for the first time, and it was found that the deviation due to the spherical-wave effect is of order comparable to the intrinsic attenuation. The compensation method based on the forward modeling is then proposed to correct this deviation, and the effectiveness of the proposed method is proved by the reasonable estimated results of both synthetic data and field data example. These results raise caution for the interpretation of the extracted Q in the near-surface context if they do not account for the spherical-wave effect and point to the necessity of incorporating a frequency-dependent term in the frequency-spectrum-based method when applied to the Q estimation in the near surface. PubDate: 2019-03-06

Abstract: Flooding events are rising across European watercourses because of changing climatic conditions and anthropogenic pressure. To deal with these events, the European Floods Directive requires the development of flood risk management plans regularly updated every 6 years, where areas affected by flood risk and relative management strategies should be identified. Along the Directive, sediment transport and morphological changes in freshwater environments like rivers are only marginally considered, leading to a possibly wrong estimate of the impact of floods in the case of watercourses in which sediment transport represents a fundamental component. Using the Secchia River in Italy as a case study, the paper compares two numerical simulations performed with the freeware iRIC suite, imposing the same boundary conditions but comparing fixed and mobile bed. The obtained results pinpoint the importance of considering sediment transport in drawing flooding scenarios for alluvial sandy rivers. As suggested by this example, for the incoming revisions of the flood risk management plans, forecasted by 2021, water managers should account for the dynamic behaviour of surface watercourses, considering sediments not only as a driver of pollutants but also as a key aspect that shapes the environment and should be considered in modelling future scenarios and drawing associated management strategies. PubDate: 2019-03-04

Abstract: Given that more than 90% of earthquake fatalities occur in rural environments, one has to rethink how to protect the population. With most rural buildings being one- and two-story dwellings, the earthquake closet (EC) offers an affordable solution as a protection unit. Two recent earthquakes with nearly 100,000 fatalities each are used for estimating the lives that could be saved and how much this would cost. The cost of constructing an EC in a single-family home is taken to be $500–$600 in developing countries. For the “statistical value of life” $1 million is used, a minimum amount given in the literature. The cost of hospitalization is derived from reports after an earthquake. The number of fatalities and injured avoided is estimated for an example earthquake each in China and Pakistan. The estimated dollar savings resulting in large earthquakes reach $18.3 billion at a cost of $1.3 billion, and $10 billion at a cost of $0.5 billion, respectively, in the two examples. PubDate: 2019-03-04

Abstract: Ground vibration is one of the most undesirable effects induced by blasting operations in open-pit mines, and it can cause damage to surrounding structures. Therefore, predicting ground vibration is important to reduce the environmental effects of mine blasting. In this study, an eXtreme gradient boosting (XGBoost) model was developed to predict peak particle velocity (PPV) induced by blasting in Deo Nai open-pit coal mine in Vietnam. Three models, namely, support vector machine (SVM), random forest (RF), and k-nearest neighbor (KNN), were also applied for comparison with XGBoost. To employ these models, 146 datasets from 146 blasting events in Deo Nai mine were used. Performance of the predictive models was evaluated using root-mean-squared error (RMSE) and coefficient of determination (R2). The results indicated that the developed XGBoost model with RMSE = 1.554, R2 = 0.955 on training datasets, and RMSE = 1.742, R2 = 0.952 on testing datasets exhibited higher performance than the SVM, RF, and KNN models. Thus, XGBoost is a robust algorithm for building a PPV predictive model. The proposed algorithm can be applied to other open-pit coal mines with conditions similar to those in Deo Nai. PubDate: 2019-02-25

Abstract: Western Anatolia has been formed by the motions of the African plate, Arabian plate and Hellenic Subduction zone. The Hellenic Subduction zone, which has high seismicity, is the main tectonic feature of the eastern Mediterranean Sea related to the subduction of the African Plate beneath the Aegean Sea Plate. The Hellenic Subduction zone has a complex lithospheric structure and shows complex differences in the Aegean Sea in terms of continental crust thickness and mantle velocity. In the study area, the directions of Global Positioning System (GPS) velocity vectors which are towards SE change towards S from North of Western Anatolia to Hellenic Subduction zone. It is thought that the factor which controls this mechanism is the shear force or subduction zone located in Aegean Sea. Western Anatolia region, which is located in Western Anatolia Extensional province, includes several morphologically significant N–S trending active normal faults. Besides, the NE–SW and NW–SE trending faults, which their kinematic features change from north to south, are very effective on the tectonic regime of the region. Additionally, for determining the boundaries of these tectonic elements, the Complete Spherical Bouguer (CSB) gravity anomaly of study area was calculated by using World Gravity Map (WGM2012) model. Moreover, in historical and instrumental studies, the high seismicity of the study area is remarkable. It is thought that this case is also related with the mechanism which oriented the GPS velocity vectors to southward. Consequently, the dominant kinematic structure of the region was classified by combining the GPS velocity vectors computed for Izmir and its surroundings bounded by Western Anatolia, Aegean Sea and Eastern Mediterranean and the CSB gravity anomaly. Finally, the results were interpreted together with focal depth distributions of earthquakes and Bouguer gravity data. PubDate: 2019-02-23

Abstract: While working on practical problems related to the spread of thermal pollution in rivers, we face difficulties related to the collection of necessary data. However, we would like to predict the increase in water temperature at the best accuracy to forecast possible threats to the environment. What level of accuracy is necessary and which processes that influence the water temperature change have to be taken into account are usually problematic. Those problems, with special stress on water–air heat exchange in practical applications in the so-called mid-field region in rivers, which is very important for the environmental impact assessment, constitute the main subject of the present article. The article also summarises the existing knowledge and practice on water–air heat exchange calculations in practical applications. PubDate: 2019-02-20

Abstract: In this paper, the impact of maximum flow uncertainty on flood hazard zone is analyzed. Two factors are taken into account: (1) the method for determination of maximum flows and (2) the limited length of the data series available for calculations. The importance of this problem is a consequence of the implementation of the EU Flood Directive in all EU member states. The factors mentioned seem to be among the most important elements responsible for potential uncertainty and inaccuracy of the developed flood hazard maps. Two methods are analyzed, namely the quantiles method and the maximum likelihood method. The maximum flows are estimated for the Wronki gauge station located in the reach of the Warta river. This simple river system is located in the central part of Poland. The length of the available data is 44 years. Hence, the series of the lengths 40, 30 and 20 years are tested and compared with reference calculations for 44 years. The hydrodynamic model HEC-RAS is used to calculate water surface profiles in steady state flow. The Python scripting language is applied for automation of HEC-RAS calculations and processing of final results in the form of inundation maps. The number of trials for each factor is not huge to keep the presented methodology useful in practice. The chosen measure of uncertainty is the range of variability for maximum flow values as well as inundation areas. The estimated values stressed the great importance of the factors analyzed for the uncertainty of the maximum flows as well as inundation areas. The impact of the data series length on the maximum flows is straightforward; a shorter data series gives a wider range of variability. However, the dependencies between other factors are more complex. Hence, the application of methodology based on the simulation and GIS data processing for assessment of this problem seems to be quite a good approach. PubDate: 2019-02-13

Abstract: The 2015 M7.8 Gorkha earthquake has moved the upper, unbroken, part of the Main Himalayan Thrust (MHT) and the neighboring sections of this fault closer to failure. Using the program and data set of QLARM, which has been correct in fatality estimates of past Himalayan earthquakes, we estimate quantitatively the numbers of fatalities, injured and strongly affected people when assumed ruptures along these two sections will happen. In the Kathmandu up-dip scenario with M8.1, we estimate that more than 100,000 people may perish, about half a million may be injured, and 19 million are likely to be affected strongly, if we assume the high virtual attenuation observed for the 2015 Gorkha earthquake exists here also. Likewise, if the 100 km underthrusting segment west of Gorkha ruptures, we quantitatively estimate that 12,000–62,000 people may perish and 4 million to 8 million will be strongly affected, in a down-dip (lower half of the thrust plane) and an up-dip rupture (upper half) scenario, respectively. If the up-dip part of the MHT cannot rupture by itself, and greater earthquakes are required to generate the several meters of displacement observed in trenches across the MHT, then our estimates are minima. PubDate: 2019-02-11

Abstract: Soft and hard interbedded rocks show obvious time-dependent deformation after deep tunnel excavations, and it is therefore necessary to research the mechanical behavior of the layered rock. However, it is hard to obtain ideal transversely isotropic rocks in fields, so rock-like specimens were poured by using artificial materials. Cyclic loading–unloading creep experiments were performed on the artificial layered cemented specimens with various layer angles (0°, 30°, 60° and 90°) at a 20 MPa confinement. Time-independent deformations and time-dependent deformations of the rock-like specimens were distinguished to investigate the visco-elasto-plastic deformation characteristics. Instantaneous elastic strain and instantaneous plastic strain had linear correlations with stress ratio, whereas creep strain, including visco-elastic strain and visco-plastic strain, increased nonlinearly with an increasing stress ratio. The specimens with a small layer angle had more noticeable time-independent and time-dependent deformations and larger steady-state creep rates than those of the specimens with a large layer angle. Attenuation creep and secondary creep could be observed at relative low stress levels, whereas accelerating creep until failure occurred at the creep failure stress level. The time for creep failure can be predicated according to the axial steady-state creep rate or volumetric creep curve. Damage in the rock-like specimens showed linear correlation with the stress ratio. Dip angle has a significant effect on the creep failure mode under cyclic loading–unloading conditions. PubDate: 2019-02-09