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Publisher: Springer-Verlag (Total: 2351 journals)

 Acta Geodaetica et GeophysicaJournal Prestige (SJR): 0.305 Citation Impact (citeScore): 1Number of Followers: 2      Hybrid journal (It can contain Open Access articles) ISSN (Print) 2213-5812 - ISSN (Online) 2213-5820 Published by Springer-Verlag  [2351 journals]
• Examination of the validity of the computed intermediate apparent
resistivity points in the Wenner and offset Wenner configuration of
sounding
• Authors: Miloud Chermali; Fouzi Bellalem; Mohamed Walid Belgroun; Amar Boudella; Mohand Ouabdallah Bounif
Abstract: The Wenner and offset Wenner array is among the quite recent configurations used to assess and reduce the disturbing lateral effect in resistivity soundings. Even if this system could be considered as one of the most efficient configurations for this purpose so far, the restricted number of measuring points makes its vertical resolution limited. To fix this limitation, Barker found out a specific equation by which resistance values at points halfway between the actual measuring ones are computed without being measured. This aim was reached by combining expressions of electric potentials at various electrode spacings. For the same purpose, three other equations were worked out and tested. For a single sounding, resistance values were computed at intermediate points by the mean of these equations. Observational errors were also calculated using Barker’s formulae. The computed resistance values were found to be contaminated by these errors, in varying degrees to the extent that some of them were lacking reliability. Furthermore, at each electrode spacing, the differences between the interpolated and the assumed resistivity values on a straight line joining the actual measuring points were calculated. After normalizing these differences to their corresponding averages, the RMS of these normalized differences were computed for a set of soundings using the four equations. Finally, a comparison of the obtained results with the errors of measurements from the reliability of the computed resistance values was made. This comparison allowed classifying these equations from the reliability of the intermediate resistivity values perspective. In addition, Barker’s choice of one of these equations as the one that gives the most satisfactory results is justified.
PubDate: 2018-10-11
DOI: 10.1007/s40328-018-0236-x

• Nonextensive and distance-based entropy analysis on the influence of
sunspot variability in magnetospheric dynamics
• Authors: Sumesh Gopinath; P. R. Prince
Abstract: In the present study, information theoretic distance-based entropies have been employed for a better understanding of nonlinear features of the magnetosphere using proxies such as AE and Dst indices. Among the various distance-based entropies, approximate and sample entropies are considered as potential quantifiers which could track the nonlinear variations of the magnetospheric system. The generalized nonextensive Tsallis q-entropy and Fisher’s information measure are used to study the nonextensive entropy and complexity respectively of the magnetospheric dynamics. For the analysis, 1-min AE and Dst indices are considered during the period 1985–2007. The results indicate that nonlinearity and nonextensive entropy of Dst index are solar activity dependent. But, the nonlinearity and nonextensive measures of AE index are not having any solar activity dependence. This implies that, other than the modulating solar wind, certain other complex phenomena of internal origin are having influence on the dynamics of geomagnetic activity in the auroral zone.
PubDate: 2018-09-19
DOI: 10.1007/s40328-018-0235-y

• Topo-Transylvania: a multidisciplinary Earth science initiative in Central
Europe to tackle local and global challenges
• Authors: Liviu Matenco
PubDate: 2018-08-24
DOI: 10.1007/s40328-018-0234-z

• Patterns and trends of time–space evolution of Neogene volcanism in the
Carpathian–Pannonian region: a review
• Authors: Alexandru Szakács; Zoltán Pécskay; Ágnes Gál
Abstract: Based on a self-consistent K–Ar database completed with up-to-date geochronological information, this review paper addresses the general time–space evolution of Neogene magmatism in the Carpathian–Pannonian region, aiming at identifying significant patterns and trends. Grouped according to petrochemical criteria (felsic and intermediate calc-alkaline, alkaline) and major geotectonic units (Carpathian and intra-Carpathian, in turn divided into ALCAPA and TISZA-DACIA lithospheric blocks), the dated rocks reveal distinct evolution patterns. The intra-Carpathian area is characterized by (1) scattered, areal Eastward shifting magmatism, more developed on the ALCAPA block, involving felsic and intermediate calc-alkaline magmas in the early stage of evolution (21–7 My) and alkaline magmas in the later stages (11 to < 1 My), and (2) long-lasting magmatic activity spatially focused in an area ca. 200 km across located on the ALCAPA block, shifting in time from felsic to intermediate calc-alkaline and finally to alkaline compositions. We suggest that a mantle plume-type thermal anomaly was acting at the site of focused magmatism contributing to the development of higher volume areal-type magmatism in the same block, as compared with the later activated colder and more brittle TISZA-DACIA block. The Carpathian magmatism in turn displays two distinct time–space evolution patterns: (1) a long-lasting and slowly eastward migrating intermediate calc-alkaline magmatic front, active in the 15–9 My time interval along most of the Carpathian thrust-and-fold belt, generated in a subduction environment, and (2) a time-transient magmatism along the South-easternmost Carpathian segment, in the 11 to < 0.1 Ma time interval, whose purely subduction-related origin is questionable. Beyond these evolution patterns, two regional CPR-wide trends have also been identified: (1) the general Eastward shift of magmatic activity in time, irrespective of the chemical type, and (2) the convergence of magmatism in both time and space towards the South-eastern corner of the CPR (i.e. the Carpathian bend area in Romania), currently the geodynamically most active (and most hazardous) area of the whole CPR, including the Vrancea seismic structure. Eastward directed asthenospheric flow, possibly related to the inferred mantle plume responsible for the focused time-persistent volcanism on the ALCAPA block, might be considered as being at the origin of these evolutionary trends.
PubDate: 2018-08-09
DOI: 10.1007/s40328-018-0230-3

• Ionospheric temporal variations over the region of Turkey: a study based
on long-time TEC observations
• Authors: Erman Şentürk; Murat Selim Çepni
Abstract: In this study, daily mean vertical total electron content (VTEC) and daily mean 2-h VTEC values were obtained from Center for Orbit Determination in Europe–Global Ionosphere Maps (CODE–GIM) data over the region of Turkey between January 1, 2003, and December 31, 2016. The time interval is sufficient to reflect temporal changes of the ionosphere. The daily mean VTEC data was used to analyze the space weather effects on the VTEC variability and daily mean 2-h VTEC data was utilized to see the pattern of the diurnal, monthly, seasonal and yearly variation of VTEC values. The highest correlation was found between VTEC and F10.7 (r = 0.83). Totally, 40 major geomagnetic storms were identified that 45% of the storms are caused a decrease and 55% of the storms are caused an increase in VTEC variation. The maximum VTEC is shown at 13:00 LT and the minimum VTEC is shown at 03:00 LT according to diurnal variation of the 14-year mean 2-h VTEC. The maximum VTEC is shown on April and the minimum VTEC is shown on July according to diurnal variation of monthly mean VTEC. Diurnal variation of seasonal mean VTEC and its standard deviations are higher in equinox than solstices. Diurnal variation of yearly mean VTEC has a significant change from low to high solar activity periods.
PubDate: 2018-08-09
DOI: 10.1007/s40328-018-0233-0

• Determination and interpolation of parameters for precise conversion of
GNSS wet zenith delay to precipitable water vapor in Turkey
• Authors: Ilke Deniz; Gokhan Gurbuz; Cetin Mekik
Abstract: Studies of estimating precipitable water vapor (PWV) from continuous Global Navigation Satellite System (GNSS) stations with high temporal and spatial resolution continuously have become popular in recent years. In this estimation process, the weighted mean temperature (Tm) and the conversion parameter (Q) are the most important parameters to convert tropospheric zenith delay (ZTD) to PWV. In this study, Tm and Q time series are derived by assessing 4103 profile observations of eight Turkish radiosonde stations (RS) for approximately one year. The Tm − Ts linear regression model is developed. In analogy to Tm − Ts model, the Q values are modelled based on different combinations of surface temperature (Ts), station latitude (θ), station height (H) and day of the year (DOY). To test the validity of these models, the GNSS derived PWV (PWVGNSS) values are computed from the GNSS data of just over a year for the Istanbul and Ankara RS-GNSS stations using the most precise Tm and Q models, and later they are compared with the PWVRS values. The mean of the differences obtained for the Ankara and Istanbul stations are found to be 1.4–1.6 mm with a standard deviation of 1.7–1.8 mm, respectively. Moreover, modelling and interpolating meteorological parameters such as temperature, pressure, as well as PWV and ZTD are tested using the spherical harmonic functions (SHF). The results indicate that SHF can be safely and accurately used for modelling and interpolating meteorological parameters and ZTD.
PubDate: 2018-08-07
DOI: 10.1007/s40328-018-0232-1

• Spatial relation of surface faults and crustal seismicity: a first
comparison in the region of Switzerland
• Authors: György Hetényi; Jean-Luc Epard; Leonardo Colavitti; Alexandre H. Hirzel; Dániel Kiss; Benoît Petri; Matteo Scarponi; Stefan M. Schmalholz; Shiba Subedi
Abstract: The deformation pattern in active orogens is in general diffuse and distributed, and is expressed by spatially scattered seismicity and fault network. We select two relating datasets in the region encompassing Switzerland and analyse how they compare with each other. The datasets are not complete but are the best datasets currently available which fully cover the investigated area at a uniform scale. The distribution of distances from each earthquake to the nearest fault suggests that about two-thirds of the seismicity occurs near faults, yet about 10% occurs far from known faults. These numbers are stable for various selections of earthquakes and even when considering location uncertainties. Earthquake magnitudes in the catalogue are smaller than what could be expected from faults lengths. This suggests that the deep fracture pattern is more segmented than the superficial one, or mostly partial rupture during earthquakes, and (partly) the impropriety of the scaling law. Statistics on the distances from each fault to the nearest earthquake reveal that all supposedly-active faults in Switzerland have experienced a typically felt (magnitude 2.5 or larger) event, and only one out of six has not done so in the past four decades. Future applications of the presented approach to more complete or comprehensive fault databases may result in revised numbers regarding the connection between deep and superficial fracture patterns, representative of the stress regime of the region. The public and educational message: (1) in the region of Switzerland, earthquakes can happen in areas without known or mapped faults; (2) not all faults produce earthquakes within a human lifetime, but they seem to do so over long times.
PubDate: 2018-08-06
DOI: 10.1007/s40328-018-0229-9

• Upper mantle xenoliths as sources of geophysical information: the Perşani
Mts. area as a case study
• Authors: István Kovács; Levente Patkó; György Falus; László Előd Aradi; Gyöngyvér Szanyi; Zoltán Gráczer; Csaba Szabó
Abstract: The aim is to give an overview on how geochemical and petrological data, obtained from upper mantle xenoliths, could be utilized to provide information on the geophysical properties of the upper mantle at their origin. First we demonstrate how a tentative lithospheric column may be constructed based on the equilibrium temperature of upper mantle xenoliths and the area specific depth-temperature curves. Then it is described how the speed of seismic waves at the given pressure and temperature conditions could be calculated from the modal composition and geochemistry of major rock forming minerals of upper mantle xenoliths (e.g. olivine and orthopyroxene). It is also discussed how the lattice preferred orientation of minerals in upper mantle xenoliths provides information on the seismic anisotropy of the upper mantle, and how this information could be used to calculate the orientation and thickness of the anisotropic layer in the upper mantle if one anisotropic layer is assumed. Structural hydroxyl (or most commonly referred to as ‘water’) incorporated in nominally anhydrous minerals plays a critical role in determining the electrical conductivity and rheology of the upper mantle. Finally, it is presented how electrical conductivity and effective viscosity of the upper mantle could be approximated based on the structural hydroxyl content in olivine, the most abundant mineral constituent of the upper mantle. Our study area, the Perşani Mountains is situated in the Carpathian Bend area (Romania) which is geologically one of the most active areas in Europe. Abundant upper mantle xenoliths from the Perşani Mountains (Eastern Carpathians) will serve as examples how meaningful geophysical information can be obtained for the upper mantle. Furthermore, it is shown how these pieces of information may be utilized in interpreting geophysical and geodynamic challenges of this area.
PubDate: 2018-08-06
DOI: 10.1007/s40328-018-0231-2

• Employing the Bayesian data fusion to estimate the fundamental frequency
of site by means of microtremor data
Abstract: The fundamental site frequency is one of the most important characteristics of the subsoil. Despite the different methods to calculate fundamental frequency, using microtremors resulted from weak ground motion is one of the fastest and cheapest approaches. Unfortunately, the effects of local transient perturbations on microtremor data increase the uncertainty in the estimation of fundamental frequency. In this paper, to solve this problem, the Bayesian data fusion method has been proposed and used to estimate the fundamental frequency of site. In this method the results of the different data windows have been fused to estimate the fundamental frequency more accurately and with less uncertainty. The advantage of this method is that it does not need any extra filtering to remove the transient perturbations’ effects except a simple band-pass filter to remove the out of range frequency components. The method has been applied to microtremor data recorded in the city of Meybod in central Iran. The comparison between the results of this approach and those obtained from the other methods indicate that the proposed method has a better performance and could be applied easily.
PubDate: 2018-08-02
DOI: 10.1007/s40328-018-0227-y

• Probing tectonic processes with space geodesy in the south Carpathians:
insights from archive SAR data
• Authors: Eszter Szűcs; István Bozsó; István János Kovács; László Bányai; Ágnes Gál; Alexandru Szakács; Viktor Wesztergom
Abstract: The Carpathian bend is amongst the tectonically most active areas in Europe where intraplate subduction triggers sub-crustal earthquakes releasing significant amount of seismic energy in a well-defined seismic zone. To constrain the deep processes by exploiting their linkage to the surface processes an accurate knowledge of surface deformations is required. Detection of small-magnitude tectonic processes with high reliability is a challenge in which the recent space geodetic techniques may bright a breakthrough. In this study we used the archive ENVISAT data set of the European Space Agency to investigate the feasibility limit of detecting crustal deformations in the region of the south Carpathian bend, where past geodetic observations failed to unravel the tectonic processes with high details. Despite the inherent limitations of radar interferometry our results show that coherent velocity field can be estimated with a magnitude of few mm/year. The vertical displacement field suggests subsidence in the Brasov basin which is in agreement with former studies, however radar interferometry can provide a more detailed picture.
PubDate: 2018-08-01
DOI: 10.1007/s40328-018-0228-x

• Detection of high and moderate crustal strain zones in Uttarakhand
Himalaya, India
• Authors: Rakesh K. Dumka; Bahadur Singh Kotlia; Girish Ch. Kothyari; Joydeep Paikrey; Siddharth Dimri
Abstract: We present geodetically estimated crustal strain rates in Uttarakhand Himalaya, a region which has long been considered as a part of seismic gap. We processed and analyzed the GPS data, acquired from the sites enveloping all the litho-tectonic units from the Sub Himalaya in the south to the Tethys Himalaya in the north together with the major Himalayan thrust/fault systems. On the basis of the obtained dataset, we conclude that the maximum amount of crustal shortening takes place towards the hinterland in the vicinity of Main Central Thrust and Inner Lesser Himalaya which is also in agreement with high seismic activity in these sectors. The GPS velocities of the sites (Indian reference frame) show significant variation from the sub-Himalaya to the Tethys Himalaya. The Sub and Inner Lesser Himalayan parts exhibit low deformation rate in contrast to the maximum amount of deformation in the Inner Lesser and Higher Himalayan segments. The strain analysis reveals lateral variation with high strain zones (HSZ) and moderate strain zones (MSZ) within the compressional regime in the Uttarakhand Himalaya. The strain rate of 0.45 and 0.25 micro-strain/year is observed in the HSZ and MSZ respectively. By comparing the strain rate with the seismicity pattern for the past five decades, we suggest that the earthquakes in the HSZ are related with ramp structure of the MHT, whereas, part of accumulated strain in the MSZ is being released in form of the present day seismic activity.
PubDate: 2018-07-23
DOI: 10.1007/s40328-018-0226-z

• On the tectono-stratigraphic evolution and hydrocarbon systems of
extensional back-arc basins: inferences from 2D basin modelling from the
Pannonian basin
• Authors: Attila Bartha; Attila Balázs; Árpád Szalay
Abstract: Two-dimensional basin modelling was carried out in the Pannonian basin of Central Europe to investigate the Miocene extension, post-rift evolution, and subsequent basin inversion and associated sedimentation. A tectono-sedimentary evolutionary model was constrained by seismic and well data. The simulated basin and petroleum systems model performed with petroleum systems modelling software package integrates the spatial and temporal variations of episodes of subsidence and uplift, sedimentation and erosion, and the dynamics of biogenic and thermogenic gas generation, migration, accumulation and loss. This high-resolution approach analysed the impact of the shelf-margin slope progradation and sequential sediment loading on mechanical compaction, pore pressure development, source rock maturation and hydrocarbon charge. Generation and migration processes were genetically controlled by the deposition of the SSE-ward prograding Pannonian (s.l.) shelf-margin slope sediments, and repeated tectonic inversions along the Mid-Hungarian Fault Zone. We tested different maturation kinetic models and compared the impact of different generation reaction schemes on charge. Biogenic gas generation was associated with the deposition of almost the entire sedimentary succession in the studied Jászság and Békés sub-basins. However, the preservation of the gases was limited in time and space. Most of the thermogenic gas was generated by the deepwater marls in the Békés sub-basin, whereas the depocentre of the Jászság sub-basin, mainly filled with Miocene rhyolites or rhyolitic tuffs connected to the intense volcanic activity, prevented the generation of significant amounts of hydrocarbon there.
PubDate: 2018-07-20
DOI: 10.1007/s40328-018-0225-0

• Active tectonic deformation and associated earthquakes: a case
study—South West Carpathians Bend zone
• Authors: M. Popa; I. Munteanu; F. Borleanu; E. Oros; M. Radulian; C. Dinu
Abstract: Active tectonic deformation is continuously shaping the landscape in the Alpine Orogenic system. Earthquakes are clear proves of neotectonic deformation process. In the Romanian Carpathians the most active deformation is recorded in the South Eastern Carpathian Bend Zone. Nevertheless, seismicity associated to latest orogenic stage of active deformation is not limited to this area. Other seismic regions, like the South West Carpathians Bend Zone, were identified. Recently, several earthquake sequences were recorded in the Caransebes-Mehadia (CMB) and Hateg basins (HB). These sedimentary basins developed over the South Carpathians, Getic/Supra Getic and Danubian basement napes, their evolution being related with the N-ward tectonic transport of the Carpathian Orogen, in the current position, during the Paleogene-Quaternary times. The aim of the present study is to perform a thorough analysis of the earthquakes recorded in these two basins in correlation with the observed geological structure to better understand and constrain the neotectonic processes affecting the SW Carpathians Bend Zone. The focal mechanisms determined for HB show a predominant strike-slip faulting component with the principal axes oriented approximately NW–SE (compression) and NE–SW (extension), a reorientation from the N-S one described for the Pliocene–Pleistocene phase. The focal mechanisms in CMB imply N–S extension with normal or strike-slip faulting. We argue that the present day tectonic processes are not restricted to the SE Carpathians Bend zone, as previously inferred. Instead they affect a much larger area of the Carpathian Orogen, like the SW Carpathians Bend zone.
PubDate: 2018-07-18
DOI: 10.1007/s40328-018-0224-1

• Salt dome boundary detection in seismic image via resolution enhancement
by the improved NFG method
• Authors: M. Soleimani; H. Aghajani; S. Heydari-Nejad
Abstract: Accurate geological modeling of subsurface structures with all available geophysical data is a challenging task in geo-exploration studies. Concern in precise modeling will increase by increasing geological complexity of subsurface structures such as salt dome. Integrating various sources of geophysical data will reduce uncertainty in geological modeling in complex media. In this study, we introduce an integrated strategy for more appropriate detection of salt boundary in seismic image, by applying the normalized full gradient (NFG) method, used in processing of potential field data. In the proposed strategy, we initially, analyzed sensitivity of the NFG parameters by derivation of a synthetic model. Parameter analysis and optimization showed dependency of geometrical properties of the geological target to the harmonic number in the NFG method. Afterwards, seismic traces were processed by the NFG method. Results showed increase in vertical resolution of seismic envelope compared to the result of the well-known Hilbert Transform. The proposed strategy was applied on a synthetic seismic data contains complex salt model. Results have shown that application of the proposed strategy produced higher resolution seismic image compared to the Hilbert Transform method. The method also was applied on a field seismic data with a complex salt dome from southwest of Kazakhstan. Seismic image obtained by the integration procedure could better exhibit body of the salt dome, as well as better interpretation of faults, layer boundary truncation, salt bottom and subsalt layers. Thus, it was concluded that the proposed strategy could be considered as an alternative to resolve some of ambiguities in geological interpretation of seismic data in complex geological settings.
PubDate: 2018-07-09
DOI: 10.1007/s40328-018-0222-3

• Deformation of static datum: Turkish CORS network (TUSAGA-Aktif) is
considered
• Authors: Sermet Öğütcü
Abstract: The geocentric datum of Turkish CORS Network (TUSAGA-Aktif) is a semi-kinematic datum realized with respect to the International Terrestrial Reference Frame (ITRF 96) at the reference epoch of 1 January 2005 (2005.00). This realization was maintained by ITRF no net rotation (NNR) velocities of CORS stations. Up-to-date ITRF NNR velocities were determined by General Command of Mapping in Turkey using 7 years of CORS stations data from 2008 to 2015. In accordance with Turkish surveying regulation, there are two types of coordinate computation of the control points performed with Global Navigation Satellite System relative positioning technique based on the datum. Coordinates of the first-order and the second-order control points are computed in semi-kinematic datum, whereas the third-order control points are computed in static datum. Generally, CORS stations of TUSAGA-Aktif are used as fiducial stations for coordinate computation of these control points. In this study, baseline deformation effect of static datum on the three-dimensional position of the points are investigated. 20 CORS stations within TUSAGA-Aktif were chosen to simulate the rover and the fiducial stations. The results show that relative displacement from the reference epoch (2005.00) between the rover-fiducial stations at the measurement time and the positioning error of the rover station are in a good agreement. The differences are in the order of mm to cm level. The results also show that when more than one fiducial station used in static datum processing, mean relative displacement between the rover-fiducial stations at the measurement time and the positioning error of the rover are also in a good agreement. The results emphasized that, velocities of the fiducial stations should be known by the users for conducting static datum processing with minimum baseline deformation as much as possible.
PubDate: 2018-06-27
DOI: 10.1007/s40328-018-0223-2

• A generalized V S –N correlation using various regression analysis
and genetic algorithm
• Authors: Amit Shiuly; Narayan Roy
Abstract: Shear wave velocity (VS) is an important parameter from geotechnical earthquake engineering perspective. In the absence of the direct measurement of VS, VS–N correlation serves an alternative for evaluating the shear wave velocity (VS) from standard penetration resistance value (SPT-N) at a particular region. In the present study, an attempt has been made to propose generalized VS–N correlation from the globally available correlations for all soil and specific soil type using various regression procedures and genetic algorithm (GA). Various regression procedures along with GA have been used to assess the sensitivity of generalized VS–N correlations in connection with regression methodology. 1D ground response analysis has been carried out at two bore-hole locations in Kolkata city using the VS obtained from generated correlations and site specific response spectra have been generated at those two locations. Finally, performance of some typical buildings have been studied by nonlinear static analysis procedure using those site specific response spectra developed for proposed VS–N relationships for all type of soil and specific type of soil. The performance of the considered typical buildings has been represented in terms of base shear and roof displacement. Chi square ( $$\chi^{2}$$ ) test has also been conducted to check the confidence level of base shear and roof displacement obtained by using various developed VS–N relationships varies with the results obtained using available site specific relationships proposed by Nath (2016), and it reveals that VS–N relationships developed by GA perform better than the VS–N relationships developed by other regression method.
PubDate: 2018-06-19
DOI: 10.1007/s40328-018-0220-5

• Latitudinal variation of F-region ionospheric response during three
strongest geomagnetic storms of 2015
• Authors: Bapan Paul; Barin Kumar De; Anirban Guha
Abstract: The latitudinal ionospheric response of the three strongest geomagnetic storms of 2015 of the current solar cycle 24 during 16–19 March 2015, 21–24 June 2015 and 19–22 December 2015 is investigated using the total electron content data derived from a latitudinal chain of Global Positioning System (GPS) receivers extending from 70°N to 70°S. The storm time perturbations of the ionosphere during main and recovery phase is presented by the GPS derived vertical total electron content (VTEC) data which is further supported by ionospheric F region critical frequency (foF2) and F region peak height (hmF2) data. We observed symmetrical hemispheric response of the ionosphere during the strongest 17th March (St. Patrick’s Day) storm whereas asymmetrical hemispheric response of the ionosphere during 22nd June and 20th December storm over the Asian-Australian sector. The observations are explained by the combined transport of background inter-hemispheric seasonal wind and storm time disturbed meridional wind and by the global thermospheric compositional variation [O/N2] data.
PubDate: 2018-06-11
DOI: 10.1007/s40328-018-0221-4

• Developing a global model for the conversion of zenith wet tropospheric
delays to integrated water vapour
• Authors: Juni Ildikó; Rózsa Szabolcs
Abstract: The tropospheric wet delay is a significant systematic error of GNSS positioning, nevertheless it carries important information to meteorologists. It is closely related to the integrated water vapour that is the upper limit of precipitable water. The zenith wet delay can be converted to the integrated water vapour using a simple conversion factor. This conversion factor can be determined with the empirical formulae derived from radiosonde observations. In the past decades, numerous models were derived for this purpose, but all of these models rely on radiosonde observations stemming from a limited area of the globe. Although these models are valid for the area, where the underlying radiosonde observations were measured, there are several examples that these empirical formulae are used to validate GNSS based integrated water vapour estimations all over the globe. Our aim is to create a global model for the conversion of the zenith tropospheric delay to the integrated water vapour for realtime and nearrealtime applications using globally available Numerical Weather Models (NWM). Thus our model takes into consideration the fact that the model parameters strongly depend on the geographical location. 10 years of monthly mean ECMWF (European Center for Medium-Range Weather Forecast) dataset were used for the derivation of the model parameters in a grid with the resolution of 1° × 1°. The empirical coefficients of the developed models depend on two input parameters, namely the geographical location and the surface temperature measured at the station. Thus, the new models can be used for both realtime and near-realtime GNSS meteorological applications. The developed models were validated using 6 years of independent global ECMWF monthly mean analysis datasets (2011–2016). The results showed, that the application of the original models outside the area of the underlying radiosonde data sets can result in a relative systematic error of 7–8% in the estimation of the conversion factor as well as the estimated IWV values.
PubDate: 2018-04-19
DOI: 10.1007/s40328-018-0215-2

• The application of a combination of weighted least-squares and
autoregressive methods in predictions of polar motion parameters
• Authors: Fei Wu; Kazhong Deng; Guobin Chang; Qianxin Wang
Abstract: This study employs a combination of weighted least-squares extrapolation and an autoregressive model to produce medium-term predictions of polar motion (PM) parameters. The precisions of PM parameters extracted from earth orientation parameter (EOP) products are applied to determine the weight matrix. This study employs the EOP products released by the analysis center of the ‘International Global Navigation Satellite System Service and International Earth Rotation and Reference Systems Service’ needs to be modified to ‘International Global Navigation Satellite System Service (IGS) and International Earth Rotation and Reference Systems Service (IERS)’ as primary data. The polar motion parameters and their precisions are extracted from the EOP products to predict the changes in polar motion over spans of 1–360 days. Compared with the combination of least-squares and autoregressive model, this method shows considerable improvement in the prediction of PM parameters.
PubDate: 2018-03-19
DOI: 10.1007/s40328-018-0214-3

• Metropolis algorithm driven factor analysis for lithological
characterization of shallow marine sediments
• Authors: A. Abordán; N. P. Szabó
Abstract: Factor analysis of well logging data can be effectively applied to calculate shale volume in hydrocarbon formations. A global optimization approach is developed to improve the result of traditional factor analysis by reducing the misfit between the observed well logs and theoretical data calculated by the factor model. Formation shaliness is directly calculated from the factor scores by a nonlinear regression relation, which is consistent in the studied area in Alaska, USA. The added advantage of the implementation of the Simulated Annealing method is the estimation of the theoretical values of nuclear, sonic, electrical as well as caliper well-logging data. The results of globally optimized factor analysis are compared and verified by independent estimates of self-potential log-based deterministic modeling. The suggested method is tested in two different shaly-sand formations in the North Aleutian Basin of Alaska and the comparative study shows that the assumed nonlinear connection between the factor scores and shale volume is applicable with the same regression constants in different burial depths. The study shows that factor analysis solved by the random search technique provides an independent in situ estimate to shale content along arbitrary depth intervals of a borehole, which may improve the geological model of the hydrocarbon structure in the investigated area.
PubDate: 2018-01-06
DOI: 10.1007/s40328-017-0210-z

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