Geophysical Fields Research Articles

PHYSICAL EFFECTS OF THE POWERFUL TONGA VOLCANO EXPLOSION IN THE EARTH – ATMOSPHERE – IONOSPHERE – MAGNETOSPHERE SYSTEM ON JANUARY 15, 2022

PHYSICAL EFFECTS OF THE POWERFUL TONGA VOLCANO EXPLOSION IN THE EARTH – ATMOSPHERE – IONOSPHERE – MAGNETOSPHERE SYSTEM ON JANUARY 15, 2022

Geophysical research of underground hydraulic structures, old Glubochinsky water tunnel case study

Research objective is to study the features of geophysical fields and parameters in the area of the artificial underground water tunnel and estimate the capabilities of geophysical methods of identifying hidden underground industrial facilities. Methods of research. Measurements of self-potential signals (SP) were carried out using nonpolarizing electrodes and an electrical exploration receiver. The magnetic exploration was carried out by a proton magnetometer. Electrotomography was carried out using multielectrode electrical survey equipment with a Schlumberger symmetrical scheme of surveys. The microseismic background was recorded using an autonomous seismic station. The georadar survey was carried out using the SIR-3000 ground penetrating radar and antennas with the frequencies of 100 MHz and 270 MHz. Results. Based on the survey results, graphs of magnetic and self-potential fields, electrotomographic and microseismic sections, and radarogram were built on the research profile. The research has shown different levels of the magnetic field and the SP in the area of volcanic rocks and dikes of gabbro-dolerites occurrence. A significant increase in microseismic noise was observed with an increase in the weathering crust thickness. A local decrease in the SP potential, abnormally high values of specific electrical resistivity and intensive reflections of radio waves from the tunnel top were recorded above the underground water tunnel. Conclusions. Qualitative and quantitative geophysical characteristics were obtained in the area of the old underground water tunnel. The research showed different levels of the magnetic field and spontaneous polarization potentials in the occurrence area of rocks of different composition. A significant increase in microseismic noise was recorded with an increase in the weathering crust thickness. Geophysical signs of the boundaries between geological structures and artificial underground objects are revealed. The exact position and depth of the old underground tunnel of Glubochinsky hydraulic structures was determined.

Interpretation of transient electromagnetic data using zero-level curves

Geophysical data has long been used to gain insight into the geologic structure and composition of the subsurface. The geometrical characteristics of geophysical data, such as the locations of the minimum, maximum, and zero-crossings, gives insight into the subsurface based on the physics of the measured geophysical field. These characteristics provide a preliminary understanding of subsurface properties without performing expensive 3D inversions. When examining the zero-level curve (or zero-crossings) of magnetic data collected at the surface, one finds that the zero-level curve corresponds to a conic section with properties related to the location and orientation of a subsurface magnetic dipole. The zero-level curve can be inverted using a least-squares fitting to find a corresponding magnetic dipole location and direction in the subsurface. This understanding is extended in our work to time-domain electromagnetics, where current is induced and flows inside a confined conductor. The induced current creates a magnetic dipole in the subsurface conductor that can be characterized by the zero-level curve. As the current decays, the magnetic dipole in the conductor changes. At times directly after the transmitter is turned off, the direction of current flow depends primarily on the geometry of the transmitter and conductor. As time advances, the current flow tends towards the long-axis of the conductor, and the magnetic dipole aligns perpendicularly to that long axes. Inverting the zero-level curve of the electromagnetic data at every time channel of interest enables the tracking of the magnetic dipole through time, giving insight to the orientation and location of the conductor. We examine the method of interpreting zero-level curves using synthetic examples. We also apply it to field data measured over a compact volcanogenic massive sulfide deposit at the Lalor Mine site in Canada, and demonstrate that the geometrical information obtained is consistent with the results from previous studies in the area.

НАУКА И ПОЭЗИЯ: К 90-ЛЕТИЮ АЛЕКСАНДРА ГОРОДНИЦКОГО

A brief summary of the life path and main scientific works in the field of geology and geophysics of the ocean A. M. Gorodnitsky – geophysicist, doctor of geological and mineralogical sciences (1982), professor (1991), academician of the Russian Academy of Natural Sciences (1993), Honored Scientist of the Russian Federation (2005), chief researcher of the Laboratory of Geophysical Fields, an interesting and versatile gifted person – also widely known as a poet, songwriter and marine painter.

60 Years and Beyond of Reviews of Geophysics

AbstractReviews of Geophysics is an AGU journal, first established in February 1963. It is a hybrid open access invitation‐only journal that publishes comprehensive review articles across various disciplines within the Earth and Space Sciences. The selection criteria are rigorous and many submissions are declined without review. The journal is the highest ranked in the fields of Geochemistry and Geophysics, with a high Journal Impact Factor (JIF2021 = 24.9), which is indicative of its high visibility and influence within the scientific community. The journal's published review papers, beyond a mere summary of literature, provide crucial context for current work, and establish the framework for comprehensive understanding of research progress, challenges, and interconnections between different communities, so that research may be appreciated by a broad audience. We emphasize the importance of publishing studies that provide a comprehensive overview and synthesis of the current state of knowledge in a field, especially in the case of geophysics, where knowledge is rapidly developing, increasing and becoming more specialized.

Towards an ensemble-based evaluation of land surface models in light of uncertain forcings and observations

Abstract. Quantification of uncertainty in fluxes of energy, water, and CO2 simulated by land surface models (LSMs) remains a challenge. LSMs are typically driven with, and tuned for, a specified meteorological forcing data set and a specified set of geophysical fields. Here, using two data sets each for meteorological forcing and land cover representation (in which the increase in crop area over the historical period is implemented in the same way), as well as two model structures (with and without coupling of carbon and nitrogen cycles), the uncertainty in simulated results over the historical period is quantified for the Canadian Land Surface Scheme Including Biogeochemical Cycles (CLASSIC) model. The resulting eight (2×2×2) model simulations are evaluated using an in-house model evaluation framework that uses multiple observation-based data sets for a range of quantities. The simulated area burned, fire CO2 emissions, soil carbon mass, vegetation carbon mass, runoff, heterotrophic respiration, gross primary productivity, and sensible heat flux show the largest spread across the eight simulations relative to their global ensemble mean values. Simulated net atmosphere–land CO2 flux, a critical determinant of the performance of LSMs, is found to be largely independent of the simulated pre-industrial vegetation and soil carbon mass, although our framework represents the historical increase in crop area in the same way in both land cover representations. This indicates that models can provide reliable estimates of the strength of the land carbon sink despite some biases in carbon stocks. Results show that evaluating an ensemble of model results against multiple observations disentangles model deficiencies from uncertainties in model inputs, observation-based data, and model configuration.

Structural Description of Geophysical Random Fields with Non-Gaussian Statistics

Structural Description of Geophysical Random Fields with Non-Gaussian Statistics

Effect of two temperature and nonlocality in an isotropic thermoelastic thick circular plate without energy dissipation

This paper is related to the study of two temperature parameter effect for the axisymmetric deformation in a two-dimensional nonlocal homogeneous isotropic thick circular plate without energy dissipation. The plate is subjected to a cubical thermal source with a unit magnitude normal force. Laplace and Hankel transforms have been used to find the analytical solutions to the problem. The expressions for physical quantities such as displacement components, stress components and conductive temperature have been obtained in the transformed domain. The resulting quantities in the physical domain have been obtained with the use of inversion technique. The numerical simulated results have been depicted graphically for studying the effect of nonlocal parameter along with two temperature on the components of displacements, stresses and conductive temperature. The results obtained in this paper can be very useful for the researchers working in the field of nonlocal theory of thermoelasticity, in the fields of geophysics and various other scientific fields.

Diamond-bearing lithosphere of the Siberian platform (based on geophysical data). Precambrian heredity, Paleoproterozoic plume magmatism, diamond content of the Anabar tectonic province

In the first part of the article [15], we presented the results of the analysis of the structural relationship of prospective areas and tectonic zonation of the Siberian Platform (SP). Here we demonstrate the reflection of the heredity of structural-material complexes (SMC) of the Precambrian basement of the SP to the Paleoproterozoic mantle-plume events in the geophysical fields. The analysis of the attributes of the prospective areas, as images of the SMC of the deep Precambrian, made it possible to determine the area of maximum thermal-mantle impact on the SP Precambrian lithosphere of the Early Proterozoic superplume, as well as its presumed center in the northwestern segment of the SP. The spatial distribution of the attributes, revealing the correlation of the components with the prospecting areas, contributed to the refinement of the position of the system of orthogonal lineaments on the SP, in general, corresponding to the framework reported in Basharin’s work [3]. The published geological and geophysical materials and the results of processing geophysical data showed that the deep structure of the central part of the Anabar tectonic province (AN) has the attributes characteristic of the Archean diamondiferous cratons. This can indicate the presence of a diamondiferous lithospheric root within AN. The southwestern segment of AN corresponds with the position of the Angara-Vilyui ore belt (AVRP) [2], which, along with other data, can allow us to extend the ore belt in the northeast direction, as well as recognize it in the rank of the Siberian diamond province. The prospects for the discovery of new industrial-diamond-bearing kimberlite fields are associated with the territory of the AN, the positions of the diamond-bearing lithospheric root, zones of deep crustal-mantle faults within it and its boundaries.

Результаты вероятностно-корреляционного анализа геолого-геофизических данных на территории Скифской и Прикаспийской морфоструктур для оценки перспектив нефтегазоносных областей

The articleconsiders method application results ofcorrelation analysis of gravitational and magnetic field data, heat flux values, data of decoding satellite images measured in the regions of the Pre-Caspian and Scythian large concentric morphological structures of the central type. As a result, using the correlation method, a complex of various geophysical fields in these regions was analyzed. Local concentric morphological structures with high values of the gravitational field and heat flow promising for the search of new oil and gas fields were identified.

Rock brittleness index inversion method with constraints of seismic and well logs via a CNN-GRU fusion network based on the spatiotemporal attention mechanism

Rock brittleness is an important parameter for evaluating the fracability of the unconventional oil and gas reservoirs such as tight sandstone and shale oil. Compared with the laboratory measurement, rock brittleness in 3D stratum using the joint inversion of seismic and well logs is more significant for oil exploration and development, but the resolution of the inversion results is low due to the narrowly effective bandwidth of seismic data. Deep neural network (DNN) can establish the complex nonlinear mapping relationship between input and output data to improve the resolution of inversion results, but it has the problem of unstable prediction results in the case of insufficient training samples in the geophysical field. Aiming at the problem, firstly, the ratio of Young ‘s modulus to Poisson ‘s ratio is defined as the rock brittleness index, and an AVO approximation equation with brittleness index is derived, thus establishing the convolution model between the rock brittleness index and seismic data. Secondly, an objective function containing the loss of logging data, seismic data and low-frequency components obtained by the inverse distance weighted interpolation of seismic and well logs is proposed to improve the spatial constraints of seismic and well logs. Then, the spatiotemporal attention mechanism is fused with the convolutional neural network (CNN) and gate recurrent unit (GRU) network to improve the sensitivity of the network proposed to important spatiotemporal characteristics. Finally, a DNN based on the double constraints of convolution model and data is established to solve the inversion stability in the case of small samples. The inversion results of the geological model with sand body superposition and pinchout and the tight sandstone reservoir in Junggar Basin verify that the generalization and prediction accuracy of the network proposed.

Introduction to this special section: Full-waveform inversion

The estimation of the parameters of a mathematical model by data-fitting procedures goes back more than 200 years. Mathematics historians seem to agree to credit C. F. Gauss for the introduction of this idea ( Gauss, 2011 ). In the field of exploration geophysics, Lailly (1983) and Tarantola (1984) were the first to propose the use of data-fitting techniques to estimate model parameters that control the propagation of waves in the subsurface. The concept of full-waveform inversion (FWI) was born.

Structural Description of Geophysical Random Fields with Non-Gaussian Statistics

The article considers an approach to the description of random fields as a set of intense structures with random parameters. Such structures are observed both in optical fields propagating in inhomogeneous media and in fields of hydrodynamic origin and are formed because of focusing of radiation or deformation of flows. The article discusses the filtration methods and the evolution of such structures. Different modes of structures, modes of periodic and stochastic oscillations, are described.

Geological-Geophysical and Oceanographic Researches in the Sea of Japan, the Tatar Strait 79th Cruise of the R/V “<i>Professor Gagarinsky</i>”

The paper presents brief results of comprehensive studies of the waters of the Tatar Strait and the Sea of Japan, obtained on the 79th cruise of the R/V “Professor Gagarinsky” in May–June 2022. The distribution of geophysical fields was obtained, the block’s divisibility of the bottom of the water area was confirmed and the new data on the distribution of gases in the sedimentary thickness, bottom and surface water was obtained. The electrokinetic parameters of microorganisms for evaluating their relationship with methane concentration was obtained, micropalentological analysis of sedimentary deposits was performed.

Network Metadata (NETTA) : Sistem Monitoring Jaringan Dan Metadata UPT BMKG Dengan Notifikasi Berbasis Telegram

ABSTRACT
 
 BMKG has a role to disseminate geo-hydrometeorological information in the fields of Meteorology, Climatology and Geophysics. The dissemination process requires data from BMKG operational equipment spread across 183 Technical Implementation Units (UPT) throughout Indonesia. The recorded data must be collected and disseminated using a communication network. The existing network monitoring system currently at BMKG uses the PRTG monitoring application but can only be accessed by central employees. Thus, a system that can be accessed by regional employees to see the condition of the communication network in each UPT is needed, so that it can support operations. This paper discusses monitoring system and communication network metadata design with notifications using telegrams that can be adapted for operations at BMKG called NetTa (Network Metadata). The system consists of a network monitoring dashboard, provider rental metadata dashboard, network monitoring notifications via Telegram bots. The system operates in real time and can be accessed from anywhere using a smartphone and PC. The results of functional testing show that monitoring system of all existing features on the system can be accessed according to the design. Telegram notifications can provide network device status as well as warnings if there is a communication network interruption based on the monitored sensor code
 
 Keywords : Monitoring, Network, UPT BMKG, Telegram, Metadata

The prospects of integrated use of high-precision geometric and GNSS leveling for studying neotectonic processes at geodynamic polygons

This article presents the development of a methodology for determining the deviation of straight lines using high-precision leveling and GNSS measurements, its estimated accuracy, and the justification of technological parameters for constructing geodynamic testing grounds. This problem is essential in the geodetic and geophysical fields since changes in the shape of the equipotential surface may indicate a redistribution of mass in the Earth's crust and other natural phenomena. Studying this problem using the proposed methodology can provide insight into the main geological processes, gravitational potentials, and neotectonic processes. Monitoring of changes and deformation of the Earth's surface is of great importance for understanding solid processes on the Earth, especially those caused or intensified by anthropogenic activities, which currently pose global challenges to humanity. The study presents the analysis of the existing methods for determining the change in the shape of the equipotential surface. It substantiates the advantages of using high-precision leveling and GNSS measurements to ensure the accuracy and reliability of the results. The calculation formulas for estimating the accuracy of determining the deviation of straight lines with the possibility of studying the shape of equipotential surfaces with millimeter accuracy are proposed. The methodology and technological parameters have been developed, which can be used to determine the change in the deviation of a straight line on geodynamic polygons with an accuracy of 0.1-0.2". Also, the possibility of using the research results to determine changes in the shape of equipotential surfaces is theoretically substantiated. Namely, changes in their radii of curvature are associated with the possibility of predicting neotectonic processes according to modern scientific hypotheses. Keywords: deviation of straight lines; global navigation satellite systems; geometric leveling; orthometric excesses; geoid, geodetic heights.

Concrete Autoencoder for the Reconstruction of Sea Temperature Field from Sparse Measurements

This paper presents a new method for finding the optimal positions for sensors used to reconstruct geophysical fields from sparse measurements. The method is composed of two stages. In the first stage, we estimate the spatial variability of the physical field by approximating its information entropy using the Conditional Pixel CNN network. In the second stage, the entropy is used to initialize the distribution of optimal sensor locations, which is then optimized using the Concrete Autoencoder architecture with the straight-through gradient estimator for the binary mask and with adversarial loss. This allows us to simultaneously minimize the number of sensors and maximize reconstruction accuracy. We apply our method to the global ocean under-surface temperature field and demonstrate its effectiveness on fields with up to a million grid cells. Additionally, we find that the information entropy field has a clear physical interpretation related to the mixing between cold and warm currents.

A geophysically constrained crustal element map of East Antarctica between Enderby Land and Princess Elizabeth Land

East Antarctica along with Greater India played a vital role in the accretion and breakup of the Indo-Antarctic landmasses during the supercontinents Nuna, Rodinia and Gondwana. Without geophysical potential field methods, interpreting the architecture of the ice-covered geological provinces of Antarctica is impossible. We present here a crustal element map of East Antarctica between Enderby Land and Princess Elizabeth Land (Indo-Antarctica tectonic element) using aerogeophysical data interpretation. The data reveal distinct anastomosing geophysical provinces that correlate with sparse geological data. Our crustal element map shows the Oygarden Province and the Northern and Southern Rayner provinces are arcuate belts that wrap around the Archean Napier Province. These provinces represent the remnants of an accretionary tectonic margin, which evolved between ca 1300 Ma and 900 Ma. The arcuate geometry of these Meso- to Neoproterozoic provinces formed during the collision with the Napier Province, which represents a microcontinent. This collision triggered widespread extension and ultra-high temperature metamorphism in the Northern and Southern Rayner provinces. The southernmost provinces include the Fisher Province, Lambert Province and a transition zone. The provinces are truncated by a suture zone with the Archean Ruker Province, following north-dipping subduction during the Meso- to Neoproterozoic. Our interpretation provides a template upon which to correlate geological provinces with the terranes on the conjugate eastern Indian margin. KEY POINTS An aeromagnetic interpretation is given for Enderby Land and Princess Elizabeth Land of East Antarctica. Napier Province is a microcontinent that collided with the Rayner Province during a ca 1000 Ma orogenic event. A new interpretation of potential field data suggests anastomosing provinces accreted as part of a collisional event. New structures/piercing points are identified at the Mawson Coast and in Kemp Land.

Geomagnetic and FDEM Methods in the Roman Archaeological Site of Bocca Delle Menate (Comacchio, Italy)

The increasing use of geophysical investigations for archaeological purposes is now provided also by Italian reforms about preventive archaeology. They allow not only the discovery or the spatial definition of possible buried archaeological evidence, but they are also able to define the state of preservation of ancient structures. The Bocca delle Menate archaeological site is in Comacchio village territory, situated in Ferrara provence (Emilia Romagna region, Italy). The archeological site provides important evidence of the Roman presence in the Po Delta (Italy). The Roman villa was excavated between 1958 and 1959, during the reclaiming works in the Mezzano Valley (Comacchio, Ferrara). An archaeological preliminary survey and a geophysical field trip using Geomagnetic and Frequency Domain Electromagnetic Methods were carried out, following the aim to identify the planimetry of the villa previously excavated and eventually newly discovered archaeological remains. The geomagnetic results detected the archaeological buried structures, even if the original disposition of them is not completely highlighted. The electromagnetic method was able to depict the geological and geomorphological background surrounding the Roman villa. The obtained results highlighted that the applied geophysical methods are excellent tools for the preservation, protection, and monitoring of archaeological heritage previously excavated, adding to their already known importance as best tools for new archaeological buried remains detections.

Neogene-Quaternary response of the Novohradské hory Mts. (Czech Republic) fluvial systems to tectonics – Analyses of morphotectonics, stream-length index and structural geology

Based on comparison of morphotectonic analysis results with the SL index analysis, airborne geophysical measurements and field geological and structural data, possible Miocene to Holocene development of the landscape relief of Novohradské Mts. (southern Moldanubian Zone; Bohemian Massif) with a significant contribution of active faulting is interpreted.We suppose a polyphase reactivation of pre-existing faults under (a) the Miocene-Pliocene stress-field (regional ∼ NNW–SSE extension) as (oblique) normal faults trending ∼ SW–NE to ∼NW–SE were responsible for the subsidence of the Třeboň Basin and Kaplice Furrow and (b) the Pliocene to Holocene stress-field (Shmax = 146°) when horizontal in the ∼NNW–SSE direction with possible activity of the prevailing ∼ NNE-SSW trending faults as a sinistral strike-slips or weak reverse oblique-slip movement. The second set of subvertical ∼ WNW–ESE faults was predominantly reactivated in a dextral strike-slip regime or as gentle reverse oblique-slip faults. These Miocene to Holocene events reflect the coupling between the East-Alpine–Carpathian segment and its northern foreland, mainly due to northward motion of the African and the Arabian lithospheric plates.The core of the Novohradské hory Mts. experienced a significant uplift compared to the neighboring areas of the Kaplice Furrow and the Třeboň Basin. The most significant uplift has been found near Rychnov nad Malší, and on the tectonic border between the Kaplice Furrow and the Bukovský hřbet Ridge. This uplift took place during the late Pliocene and Pleistocene, after the sedimentation of lacustrine sediments in the Kaplice Furrow. Although the combination of GIS, morphotectonic and geophysical analyses with validation by field structural data does not provide the final proof of young tectonic activity, we conclude that there is strong indication of Neogene-Quaternary reactivation of several faults in the Novohradské Hory Mts. Based on similar morphological features, it can be supposed that many areas in the Alpine Foreland and Bohemian Massif underwent similar tectonic evolution during the Miocene to Holocene era.