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Variations in conductivity in the near-surface, such as the presence of small and localized three-dimensional (3D) bodies, cause a galvanic distortion in direct current (DC), so the measured appare...

This study measures the relationship between labor productivity and national competitiveness. Through the shift- share analysis method, the paper has separated labor productivity into three factors: static shift effect, dynamic shift effect and endogeneous effect. Next, in combination with the Granger causality test, the paper examines the relationship between the factors constituting labor productivity and competitiveness during the period from 2005 to 2017. Research data is collected from General Statistics Office and annual global competitiveness reports. The results show that the interaction between labor productivity with global competitiveness index (GCI) in Vietnam has similar variation. Nevertheless, when separating labor productivity into three effects, this relationship shows more clearly that the impact of labor productivity on GCI scores is mainly caused by endogeneous effect, not by static shift effect or dynamic shift effect. Therefore, in order to improve its competitiveness, Vietnam should focus on a number of solutions: reforming the education system towards developing thinking capacity and creative capacity; fostering industrial manners to create dynamic and flexible workers; building the State with sufficient capacity to implement consistent and transparent policies; formulating policies to attract all economic sectors so that they actively participate in the field of human resource training for the country.

This chapter examines the relationship between the Dutch Disease, the Baumol Cost Disease and Labour Productivity. It uses shift share analysis to assess the breakdown of labour productivity into three parts: intra-industry productivity, static shift share and dynamic shift share effects. The chapter establishes that in the context of the Dutch Disease an asymptotic stagnancy sets into economy and the growth of the slowest growing (services) sector that compromises the overall growth of the economy. In the period 1999–2008, the main addition to overall labour productivity in T&T occurred on account of changes in sectoral labour productivity in the BT sector. In the period 2009–2016, the main reason for the fall in labour productivity was the decline in the share of the BT sector in total employment.

An efficient joint two-dimensional direct current resistivity (DCR) and magnetotelluric (MT) inversion, referred to as WSJointInv2D-MT-DCR, was developed with FORTRAN 95 based on the data space Occam's inversion algorithm. Our joint inversion software can be used to invert just the MT data or the DCR data, or invert both data sets simultaneously to get the electrical resistivity structures. Since both MT and DCR surveys yield the same resistivity structures, the two data types enhance each other leading to a better interpretation. Two synthetic and a real field survey are used here to demonstrate that the joint DCR and MT surveys can help constrain each other to reduce the ambiguities occurring when inverting the DCR or MT alone. The DCR data increases the lateral resolution of the near surface structures while the MT data reveals the deeper structures. When the MT apparent resistivity suffers from the static shift, the DCR apparent resistivity can serve as a replacement for the estimation of the static shift factor using the joint inversion. In addition, we also used these examples to show the efficiency of our joint inversion code. With the availability of our new joint inversion software, we expect the number of joint DCR and MT surveys to increase in the future. Joint inversion software for 2D magnetotelluric and direct current resistivity.Both data help enhance each other reducing the ambiguities of the interpretation.The software is free for academic uses.

A new inversion method using marine magnetotellurics is proposed based on previous studies using the nonlinear conjugate gradient method. A numerical example is used to verify the inversion algorithm and program. The inversion model and response resemble the synthetic model. Some technologies have been added to the inversion algorithm: parallel structure, terrain inversion and static shift correction.

В ходе эксперимента FENICS-2014 по глубинному зондированию литосферы Фенноскандинавского щита выполнены частотные зондирования (ЧЗ) с контролируемым источником в комплексе с магнитотеллурическими зондированиями. В качестве контролируемого источника поля использовались две взаимно ортогональные заземленные воздушные линии электропередачи (ВЛ), питаемые от генератора Энергия-2 . Разработанный специально для зондирований с ВЛ генератор Энергия-2 мощностью 200 кВт с выходным напряжением до 1000 В позволяет формировать в линии ток произвольной формы. В диапазоне частот зондирований 0,01-200 Гц генератор обеспечил амплитуду тока в линиях от 250 до 30 А, что позволило исследовать электропроводность литосферы в диапазоне глубин от нескольких сотен метров до 100 км на разносах от источника до 860 км. Описаны методика и результаты углубленной обработки данных зондирований. Углубленная обработка проводилась для определения погрешности измерений сигнала путем вычисления статистических оценок по нескольким фрагментам записи на данной частоте. Для этого рассматривались синхронные записи силы тока в источнике и измеряемых компонент поля для каждого из используемых фрагментов записи. В каждом из фрагментов выполнялся спектральный анализ авто- и взаимных корреляционных функций наблюдаемых компонент поля и силы тока в источнике. Для каждой частоты тока источника определялись измеренное значение и погрешность измерений амплитуд наблюдаемых компонент поля, фазовых сдвигов между компонентами поля и амплитуды силы тока в источнике. Выполнен теоретический анализ учета величины статического сдвига кривых ЧЗ для электрических компонент поля и эффективного импеданса от контролируемого источника по отношению к кривым для магнитных составляющих. Представлена методика учета статических искажений для кривых ЧЗ, осложненных действием волновода Земля - ионосфера и тока смещения Максвелла в воздухе. В результате углубленной обработки данных уточнены параметры нормального разреза для литосферы до глубины 80-100 км., In the course of FENICS-2014 experiment on deep sounding of the lithosphere in the Fennoscandian shield area, deep controlled source audio-frequency magnetotelluric (CSAMT) soundings in combination with magnetotelluric soundings were performed. As powerful controlled sources of different polarization, two mutually orthogonal grounded overhead transmission lines (OHL) powered by the Energy-2 generator were used. Specially designed for deep soundings by using an OHL, the 200 kW generator with output voltage up to 1000 V allows to generate an arbitrary waveform. In the soundings frequency range of 0,01-200 Hz it provided the amplitude of the current from 250 to 30 A. As a result, the electrical conductivity of the lithosphere has been investigated in the depth range from a few hundred meters to 100 km at up to 860 km separation from the source. The method and results of advanced processing of the soundings data are described. The aim of advanced data processing was to determine the signal measurement error by calculating statistical estimates for several recording fragments at a given frequency. For this purpose, synchronous records of the source current strength and the measured field components, for each of recording fragments, were considered. Spectral analysis of the auto- and cross-correlation functions of the observed field components and the source current strength was performed for each of the recording fragments. The measurement error of the amplitudes of the observed field components, the phase shifts between the field components and the source current amplitude were determined by the root-mean-square deviation of the measured values for each fragment of the record, from the mean value of all records for a given frequency. The theoretical analysis of possibility to determine the static shift of the CSAMT curves for electric field components and for effective impedance, relative to the curves for magnetic field components, was performed. The method for correcting the static shift, complicated by the effect of the Earth - ionosphere waveguide and of displacement currents, was presented. As a result of the advanced data processing the structure of normal conductivity profile to a depth of 80-100 km was refined., №5(8) (2020)

Karst cavity mapping is attracting great interest from engineering geologists because of its relation to the dangerous geohazards faced during engineering construction. Ground-based geophysical methods still face challenges in karst mapping, and concealed karst cavities potentially pose threats to tunnel construction in southwest China. Given the significant contrast in electrical resistivity between karst cavities and their host rocks, geoelectrical methods are widely used for mapping these cavities. We have developed a successful case history of mapping karst cavities on a planned railway route using controlled-source audio magnetotellurics (CSAMT). Scalar CSAMT, with frequencies ranging from 0.5 to 8192 Hz, was used for field data acquisition. A full-frequency domain apparent resistivity correction method was used for near-field corrections. Electromagnetic array profiling (EMAP) filtering was used for topographic and static shift corrections, and the Bostick conversion was used for data interpretation. Our study indicated that the results of the Bostick conversion with EMAP filtering were more acceptable than the results of rapid relaxation inversion and nonlinear conjugate gradient inversion in this case. The G Tunnel is a key tunnel along the Gui-Guang high-speed railway in southwest China. Initial geophysical and engineering geologic results suggest that the bedrock of the survey section of the G Tunnel route is sandstone. A CSAMT survey with three inline sections and three crossline sections over the tunnel route was conducted in two phases to verify the rock conditions of the tunnel route. A concealed karst cavity with a low-resistivity anomaly was found on the tunnel route and was verified by the borehole. Data from the CSAMT survey significantly refined our understanding of the subsurface engineering geologic conditions along the tunnel route.

We present a novel approach where time-domain electromagnetic (TEM) data are transformed and subsequently used in two-dimensional (2-D) magnetotelluric inversion of the determinant of the impedance tensor. The main idea is to integrate TEM with magnetotelluric (MT) data to produce subsurface electrical resistivity models. Specifically, we show that 2-D MT data inversion of the determinant of the impedance tensor supported by inclusion of TEM–MT-transformed data has superior resolution at the near surface and at the same time static shift afflicting the MT data can be addressed. Thus, the approach allows for practical express integration of TEM data with MT measurements as opposed to a full combined 3-D inversion, which requires significant resources. The approach is successfully applied in the Mygdonian sedimentary basin located in Northern Greece. In addition to TEM and MT data, also controlled source — and radiomagnetotelluric data are available from the Mygdonian basin, which have been subjected to 2-D analysis previously. We have extended the analysis to a full 3-D inversion using ModEM code. All obtained models are analysed and are in a good agreement.

To solve the problem of correction of magnetotelluric (MT) static shift, we quantise factors that influence geological environments and observation conditions and study MT static shift according to 3D MT numerical forward modelling and field tests with real data collection. We find that static shift distortions affect both the apparent resistivity and the impedance phase. The distortion results are also related to the frequency. On the basis of synthetic and real data analysis, we propose the concept of generalised static shift resistivity (GSSR) and a new method for correcting MT static shift. The approach is verified by studying 2D inversion models using synthetic and real data.

Through a large number of magnetotelluric (MT) observations conducted in a study area, one can obtain regional one-dimensional (1-D) features of the subsurface electrical conductivity structure simply by taking the geometric average of determinant invariants of observed impedances. This method was proposed by Berdichevsky and coworkers, which is based on the expectation that distortion effects due to near-surface electrical heterogeneities will be statistically smoothed out. A good estimation of a regional mean 1-D model is useful, especially in recent years, to be used as a priori (or a starting) model in 3-D inversion. However, the original theory was derived before the establishment of the present knowledge on galvanic distortion. This paper, therefore, reexamines the meaning of the Berdichevsky average by using the conventional formulation of galvanic distortion. A simple derivation shows that the determinant invariant of distorted impedance and its Berdichevsky average is always downward biased by the distortion parameters of shear and splitting. This means that the regional mean 1-D model obtained from the Berdichevsky average tends to be more conductive. As an alternative rotational invariant, the sum of the squared elements (ssq) invariant is found to be less affected by bias from distortion parameters; thus, we conclude that its geometric average would be more suitable for estimating the regional structure. We find that the combination of determinant and ssq invariants provides parameters useful in dealing with a set of distorted MT impedances.

Small-scale near-surface galvanic scatters are known to be a bane when using natural field EM data to get quantitative information about the subsurface resistivity structure. Specifically, on magnetotelluric measurements, the effect of local surficial inhomogeneities is almost inevitable and produces a static shift in the measured apparent resistivities over the whole range of sampled frequencies. We present here the methodology used to account for static shift effects and make a correct interpretation of the resistivity distribution in a region beneath the northeastern part of the volcanic-covered Parana basin, SE Brazil. Within this region are located the ground electrodes of the Rio Madeira HVDC transmission system (Bipoles I and II). The available data includes geophysical soundings made for the electrodes site selection before their installation and data acquired in the subsequent commissioning measurements after their construction (electrode resistance, soil surface potentials and pipe-to-soil potentials). Iterative calculations for the simultaneous adjustment of the measured electrode resistance and the local geoelectric model were developed, based on the commissioning data of the electrode. The accuracy of the adjusted geoelectric model was confirmed by the excellent fit obtained for the measured and calculated pipe-to-soil potentials at Gasbol, the Bolivia-Brazil gas pipeline located 26 km away from the electrode.

A study for delineating geothermal system of prospect area “P” has been done by using multi-dimensional modeling of magnetotelluric data. Physiographycally, geothermal prospect of “P” area is located at non-volcanic Banda inner arc hosted by Malihan Sekis rock complex with Perm-Trias age. The existance of geothermal system in this area is indicated by the presence of thermal manifestations in form of 6 chloride-bicarbonate hot springs with temperature in the the range of 37-67oC, and pH of 6-7. The development of geothermal system is most probably associated with strong tectonic activity caused by the collision between Seram island plate and Australian plate that ignite the occurence of intrussive body as heat source. In order to know the subsurface information of prospect area, magnetotelluric (MT) survey has been done. The processing of MT data was started from time-series data, continued by noise filtering, rotation of strike orientation and static shift correction to obtain better MT curve. The data were then being inversed by means of 1-Dimensional, 2-Dimensional and 3-Dimensional inversion methods. Reservoir temperature is estimated to be around 160-180 oC and classified as moderate temperature. The result of MT data inversions shows the presence of conductive layer (300 ?m) with updome shape appears underneath the manifestations occurence (MAP1, MAP2, MAP4, and MAP5), indicating that the heat source is located in northern part and elongate to souteast direction. The conceptual model of geothermal system was built based on integrated interpretation of geological, geochemical and geophysical data. The prospect area and recommendation of drilling location is estimated to be ± 3 km2 around upflow zone.Keywords: Prospect zone, geothermal system, magnetotelluric method, multi-dimension modeling

The presence of shallow conductive heterogeneities can cause static shift in controlled source audio-frequency magnetotellurics (CSAMT) apparent resistivity sounding curves. This is observed as a shift along the apparent resistivity axis in double logarithmic coordinates. Such effect can cause difficulties in CSAMT data interpretation. In this letter, we established a new method to identify and correct the CSAMT static shift based on the high-resolution Radon transformation. We took advantage of the property that the static shift of apparent resistivity curves behaves as a point in the Radon domain. We presented 3-D synthetic study to demonstrate that the static shift can be effectively removed from the apparent resistivity curve. However, due to the low resolution and precision, the traditional Radon transform can generate ``scissor-tail'' and then, the static shift may not be completely removed. We proposed to use a new high-resolution Radon transform by improving the regularization matrix using the least squares inversion. Our numerical simulation shows that by using this high-resolution Radon transform, the static shift converges accurately to a point without showing the ``scissor-tail.'' In the application to field CSAMT data, the high-resolution Radon transform method was able to correct the static shift effectively; thus, it can improve the precision and accuracy in data interpretation.

The results of deep induction sounding in Ukraine made in the twenty-first century with the participation of the author have been summarized, including also a number of data obtained in the previous decades. The apparent resistivity and magnetic transfer function on the territories of western Ukraine and eastern Poland have been analyzed. The articulation of these data with the regional magnetic variation soundings allowed taking into account the influence of a static shift of areal interpretation of magnetotelluric resistivity results, which increased the reliability of interpretation. The analysis of induction sounding performed with 1D, 2D, and 3D inversions of magnetic transfer functions allowed localizing the crustal anomalies. The results are discussed.

Frequency-domain controlled-source electromagnetic surveys can be negatively affected by near-surface geologic features, resulting in static shifts in the observed electric field amplitude data. We propose using an equivalent source method to denoise electric field data from frequency-domain controlled-source electromagnetic (CSEM) surveys. The equivalent source method can either be applied individually to data from each measured frequency or simultaneously to data from all frequencies measured. We demonstrate the effectiveness of the method by denoising an individual synthetic CSEM survey with data contaminated with noise from near-surface conductive bodies, as well as a synthetic time-lapse survey representing resistivity changes in a target due to, for instance, [Formula: see text] sequestration. We also apply the equivalent source method to denoise a set of controlled-source audio-magnetotelluric data affected by static shift from a field survey in western China.

The problem of quantitative three-dimensional interpretation of the magnetotelluric (MT) data ranks among the most difficult problems in electromagnetic (EM) geophysics. Our paper presents a new rigorous numerical method for MT inversion, based on the integral equations technique. An important feature of the proposed method is the calculation of the Frechet derivative with the aid of a quasi-analytical approximation with an inhomogeneous background. This approach simplifies the algorithm of inversion and requires only a single forward modeling on each iteration. We have also developed a method for a joint inversion of MT and magnetovariational (MV) data. We show in the present paper that the joint inversion of MT impedances and the Wiese-Parkinson vectors can automatically allow for the static shift in the observed data, which is caused by the geoelectric inhomogeneities contained in the near-surface layer.

Pathways of further development of the dynamic correction technique suggested by E. Fainberg are discussed. This technique allows the correction of magnetotelluric (MT) and magnetovariational (MV) data distorted by subsurface irregularities within a broad range of frequencies beyond the static shift interval. This paper addresses new algorithms for the dynamic correction of tensor MT and MV response functions. Moreover, experiments on the dynamic correction of MT and MV data calculated for models containing heterogeneities in sedimentary cover and infinite or half-infinite conductive crustal prism are described. Model experiments show that the dynamic correction can ensure sufficient accuracy of the input data for the reliable solution of the inverse problem of magnetotellurics.

SUMMARY Magnetotelluric (MT) data have been acquired across the Samail Ophiolite, Oman mountains, along a 115 km transect in January 2005. Twenty-five MT stations were deployed approximately every 4 km along a profile perpendicular to the coastline near Muscat. The profile extends from the Huw'l/Meeh subwindow in the northwestern part of the profile and crosses the Saih Hatat window, a Tertiary domal culmination that folds a major NE-facing recumbent fold nappe, and ends along the southern boundary between the Dasir and Ibra ophiolite blocks. The survey aimed to investigate the tectonic evolution of the emplacement of the Samail Ophiolite by delineating major faults and geological boundaries on a crustal scale. The data shows complex behaviour with the influence of static shift effects and anomalously high phases exceeding 90°. Phase tensor analysis and 3-D forward modelling hint that the upper plate–lower plate (UP–LP) shear zone has a 3-D effect on the data in the northern part of the profile. Rotated MT impedances were inverted using a 2-D code. Major resistivity interfaces coincide with the location of the UP–LP shear zone near the surface, and dip towards the Arabian margin suggesting a southwest orientated underthrusting prior to the ophiolite emplacement. The para-autochthonous and less deformed upper plate is a resistor, whereas the strongly deformed lower plate is more conductive.

Besides the field acquisition of magnetotelluric is nearly 3D exploration level, the 3D data process and inversion have shortcomings. But our 3D inversion system has effectively resolved the problems of static shift and inversion efficiency. The system contains static shift correction, initial model design and inversion functions. In addition, the magnetotelluric data of the Middle and Lower Reaches of Tangtze Metallogenic were used to verify the system and confirm that 3D MT is an effective method for deep exploration. Keywords—magnetotelluric; static shift; correction; 3D inversion; system

We present and test a new method to correct for the static shift affecting magnetotelluric (MT) apparent resistivity sounding curves. We use geostatistical analysis of apparent resistivity and phase data for selected periods. For each period, we first estimate and model the experimental variograms and cross variogram between phase and apparent resistivity. We then use the geostatistical model to estimate, by cokriging, the corrected apparent resistivities using the measured phases and apparent resistivities. The static shift factor is obtained as the difference between the logarithm of the corrected and measured apparent resistivities. We retain as final static shift estimates the ones for the period displaying the best correlation with the estimates at all periods. We present a 3D synthetic case study showing that the static shift is retrieved quite precisely when the static shift factors are uniformly distributed around zero. If the static shift distribution has a nonzero mean, we obtained best results when an apparent resistivity data subset can be identified a priori as unaffected by static shift and cokriging is done using only this subset. The method has been successfully tested on the synthetic COPROD-2S2 2D MT data set and on a 3D-survey data set from Las Cañadas Caldera (Tenerife, Canary Islands) severely affected by static shift.

Static shift performance evaluation index and optimization measures for manual transmission in passenger car were analyzed. The objective evaluation applied to static shift performance was proposed based on subjective evaluation requirement. The optimization method for static shift performance was proposed as well. To verify the effectiveness of relevant conclusion and the reliability of relevant analysis methods, the static shift performance for manual transmission in passenger car was analyzed through simulation and testing.

The magnetotelluric (MT) method has been applied to the determination of the deep resistivity structure of the northeastern margin of the Parnaiba Basin. Transient electromagnetic (TEM) and MT data were collected in early 1999 along a 95 km long N–S line, extending from the coast across the projected subcrop position of a discontinuous fault found to the west of the study area that is believed to be a possible basin-bounding fault. The MT data were processed to yield the TE- and TM-mode responses and then corrected for static shift using central-loop and single-loop TEM data, respectively. Regularized 2D MT inversion was subsequently undertaken using a structured initial model with the near-surface constrained by TEM inversion results. As a consistency check, we performed another set of 2D inversions using different smooth initial models. The various optimal 2D inversion models show clearly the presence of a major basement trough, over 2 km deep, located about 70 km from the coast. We interpret it as possibly marking the main basin margin and suggest that it may have implications for groundwater resource development in the area.

SUMMARY The static shift caused by near-surface conductors poses a significant challenge in magnetotelluric (MT) inversion. We present a technique to remove the static shifts in MT data by using the equivalent source technique. This method is based on the assumption that all the data are measured on or above the surface. Since static shifts across multiple stations at the same frequency are in general uncorrelated, they can be identified and removed by constructing an equivalent source layer that reproduces only the coherent signal in the data observed at multiple stations. Here we use a synthetic three-dimensional model to demonstrate the technique and demonstrate the effectiveness of the method using field data sets in the presentation.

In this paper, the effect of plastic casing and hand, on 2.4 GHz PCB antenna used in wireless mouse is investigated thoroughly from measurement. A systematic observation from measurement reveals two types of shift in the resonance of PCB antenna. The resonance shift caused by plastic casing is referred to as Static Shift, and is relatively easy to correct for. The resonance shift caused by hand is referred to as Dynamic Shift, and is detrimental for the performance of antenna in the final product. However, measurement concludes that, Dynamic Shift is significantly nullified for antenna placed around 4 mm away from edge of casing. This data when used effectively, while PCB floor planning is expected to improve the overall performance of the product, particularly for products used in dynamic environment like wireless mouse, presenter, keyboard.

Amplitudes are used to constrain refraction models. This study demonstrates that the refraction time section generated through the convolution of forward and reverse refraction traces together with a static shift facilitates the convenient recognition of amplitude variations related to changes in refractor wavespeed. For large contrasts in wavespeeds between the upper layer and the refractor, the head coefficient is approximately proportional to the ratio of the specific acoustic impedances. Since the convolution operation effectively multiplies the amplitudes of the forward and reverse arrivals, the convolved amplitudes are proportional to the square of this ratio. In general, the higher the contrast in the refractor wavespeed and/or density, the lower the amplitude. The regions recognized in the wavespeed analysis function correlate with those determined with amplitudes, thereby providing an additional constraint on inversion with model‐based approaches.

Foram realizadas 43 sondagens magnetotelúricas, totalizando oito seções, na parte central da bacia sedimentar do São Francisco, região Norte do estado de Minas Gerais. Este estudo visou mapear a estrutura geoelétrica da bacia. O levantamento foi superposto a 10 linhas sísmicas, cobrindo 11.000 km² de área. O espaçamento entre as sondagens foi irregular e a freqüência utilizada variou de 0,001 até 400 Hz, permitindo investigar até 60 km de profundidade. Os dados foram corrigidos do efeito de deslocamento estático através da mediana da resistividade do primeiro condutor. Utilizou-se um invariante do tensor impedância para interpretar a estrutura geoelétrica da bacia. Apresenta-se neste trabalho o resultado de uma seção geoelétrica obtida através de inversão 1D. Foi identificada uma seqüência de horizontes condutivos e resistivos, correspondentes ao pacote sedimentar e o topo do embasamento geoelétrico, que caracterizam a bacia do São Francisco. Além disso, identificou-se uma zona condutiva e outra resistiva a profundidades crustais. Os resultados apresentaram uma boa concordância com os dados sísmicos e gravimétricos, enquanto a concordância com o perfil de eletrorresistividade do poço existente na área de investigação foi apenas razoável. Forty-three magnetotelluric (MT) soundings were undertaken along eight profiles at the central portion of the São Francisco Sedimentary Basin, northern region of Minas Gerais State. The study aimed at the mapping of the geoelectrical structure of the basin. The MT profiles were deployed along ten seismic lines covering 11,0000 km² of total area. The MT soundings were irregularly spaced and covered the frequency range from 0.001Hz to 400 Hz, probing the electric structure from the surface to a maximum depth of 60 km. The MT data affected by static shift were corrected by fixing the resistivity value (given by the median) of the first observed conductor. The geoelectric interpretation was based on a rotationally invariant impedance response function. We identified a sequence of conductive and resistive layers, which are related to the sedimentary sequence observed in the São Francisco Basin and its crystalline basement. The results show good agreement with seismic and gravimetric data while showing just a fair agreement with available electrical well log information.