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Earth and environmental sciences cover all planetary and Earth science aspects, including solid Earth processes, development of Earth, environmental issues, ecology, marine and freshwater systems, as well as the human interaction with these systems.
Earth and Environmental Sciences
In this study we introduce new rock physical models which describe the pressure dependence of seismic velocity and quality factor. The models are based on the idea (accepted in the literature) that microcracks in rocks are opened and closed under the change of pressure. The models were applied to acoustic P wave velocity data measured on core samples originated from oil-drilling wells (27 samples) and also seismic velocity and quality factor data sets published in international literature. During the measurements the pulse transmission and the spectral ratio techniques were used. Measurements were carried out at various incremental pressures and parameters of the models were determined by linearized inversion methods. The calculated data matched accurately with measured data proving that the new rock physical models apply well in practice.
The paper discusses the characteristics and feasibility of a multilayer kinematic refraction inversion method that is applicable to estimate the — even laterally changing — parameters of a geological model in the simultaneous evaluation of refraction data. The studied method has been developed at the Department of Geophysics of the University of Miskolc for the interpretation of parameters (layer thicknesses and seismic velocities) using series expansion based on adequately chosen basis functions. Besides revealing its resolution properties, ambiguity studies are also presented on synthetic data sets. In the terminology of refraction inversion uncertain and ambiguous results are frequently encountered problems in multilayer cases when all parameters (or all coefficients describing the parameters) are estimated simultaneously in the same inversion procedure. Results of resolution and ambiguity analyses of synthetic data sets and field examples are shown in this study.
Nowadays, GPS is the best positioning system with its constellation, but number of GLONASS satellites increased to the required number, with launched new ones, for positioning. With recent revitalization of GLONASS, a great number of high precision GLONASS and GPS/GLONASS receivers have been produced. In this paper, baselines of two networks have been analyzed in order to assess the usability of GLONASS on global positioning. In both networks, repeatabilities of results were investigated by using GPS, GLONASS and GPS/GLONASS data. Results revealed that repeatabilities of all baselines by using GLONASS observations are not consistent when compared to the GPS and GPS/GLONASS.
Estimation of precipitable water vapor (PWV) in the atmosphere using ground based GPS (Global Positioning System) data requires an appropriate model for computation of zenith hydrostatic delay (ZHD). Presented herein is a site-specific ZHD model (SSM) for a station at New Delhi, India. The model has been developed by regressing one-year atmospheric vertical profile data collected through radiosonde. The model based on surface atmospheric pressure at the station, has been validated invoking data of three more years. The ZHD values estimated through the model disagree at the 0.3 mm level with ZHD values obtained from raytracing of radiosonde data. Further, Saastamoinen ZHD model provides an error about 0.23 mm rms while about 0.19 mm by the developed model (SSM). Thus, developed SSM can be used for precise estimation of PWV.
Soft computing techniques are widely used for the applications on most of the nonlinear problems related to the real world. Earth’s most of the nonlinear characteristics exhibit the uncertainty problem that has to be interpreted with most of the advanced soft computing tools. Here the three layer electrical resistivity data has taken for interpreting the subsurface parameters of the earth using Adaptive Neuro-Fuzzy inference (ANFIS) technique. ANFIS can be predictably used for most of the nonlinear problems. Its membership functions and rules with adjustable parameters will help the interpretation technique with less error percentage results. In the present study, the program is specially designed for the interpretation of three layer electrical resistivity data. The network model is successful in training with large number of data sets available. Interpretation using ANFIS technique will give the promising results with good accuracy. With much less error percentage, the program supports all types of three layer electrical resistivity data more than a conventional method can do. Typical problems with parameter estimation can be done more efficiently with this ANFIS program.
Nowadays, the Continuously Operating Reference Station (CORS) network, combined with network RTK corrections (NRTK solution), is a widely used technique for high-accuracy positioning in real time. This “active” network realizes a reference frame and propagates it to the users. In border regions the coherence between the reference frames propagated by neighboring active networks is a critical problem. In this study the test results of post-processed and simultaneous NRTK positions at six test points located in the border region between Portugal and the Community of Andalusia, in the south west of the Iberian Peninsula, are presented. The analysis is based on two GNSS active networks present in this border region, namely RENEP (Portugal) and RAP (Community of Andalusia, Spain), a national and a local RTK network respectively, with similar characteristics. Upon comparing the post-processed position for each test point, as estimated with respect to each of the two active networks analyzed, the discrepancies found in 3D were less than 2 centimeters. The results of network-based RTK positioning were found to be successful within a 2 cm precision level in the east and north components and 4 cm for the up component. The results also confirm that the NRTK positioning accuracy is about 2 cm in horizontal and 4 cm in vertical, which can satisfy the requirement of real-time positioning users at a centimetric accuracy level, even in border regions considering extrapolated NRTK solutions.
The multifractal analysis is applied to the study of geomechanical monitoring time series. Estimation of singularity spectra parameters within moving time window for this monitoring time series provides a possibility for splitting the history of observations into few adjacent fragments which could reflect e.g. hidden different states of the rock massif in the vicinity of measuring station. In this contribution, analysis of time series of measured distances is presented. A laser distance meter is used for measuring the height of a large chamber in the medieval Jeroným Mine (Czech Republic). This time series separation into individual segments using singularity spectra parameters is important for possible comprehensive analysis of data in individual time periods and/or between individual time periods.
The Earth topographic masses are compensated by an isostatic adjustment. According to the isostatic hypothesis a mountain is compensated by mass deficiency beneath it, where the crust is floating on the viscous mantle. For study of the impact of the compensating mass on the topographic mass a crustal thickness (Moho boundary) model is needed. A new gravimetric-isostatic model to estimate the Moho depth, Vening Meinesz-Moritz model, and two well-known Moho models (CRUST2.0 and Airy-Heiskanen) are used in this study. All topographic masses cannot be compensated by simple isostatic assumption then other compensation mechanism should be considered. In fact small topographic masses can be supported by elasticity of the larger masses and deeper Earth’s layers. We discuss this issue applying spatial and spectral analyses in this study. Here we are going to investigate influence of the crustal thickness and its density in compensating the topographic potential. This study shows that the compensating potential is larger than the topographic potential in low-frequencies vs. in high-frequencies which are smaller. The study also illustrates that the Vening Meinesz-Moritz model compensates the topographic potential better than other models, which is more suitable for interpolation of the gravity field in comparison with two other models. In this study, two methods are presented to determine the percentage of the compensation of the topographic potential by the isostatic model. Numerical studies show that about 75% and 57% of the topographic potentials are compensated by the potential beneath it in Iran and Tibet. In addition, correlation analysis shows that there is linear relation between the topographic above the sea level and underlying topographic masses in the lowfrequencies in the crustal models. Our investigation shows that about 580±7.4 metre (in average) of the topographic heights are not compensated by variable the crustal root and density.
