Issue Of Geophysics Research Articles

Introduction to the magnetotellurics special issue of exploration geophysics

The geophysical technique of magnetotellurics (MT) was first described in 1953 and the associated technique of geomagnetic depth sounding (GDS) in 1959. Both methodologies have had a long history in Australia both for academic research and resource exploration. Since the early 1990s with advances in digital data storage, 2D inversion codes and 3D inversion codes from the 2010s, there has been a rapid increase in the number of MT surveys across Australia. Regional MT programs around Australia and since 2013 the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) have steadily mapped the 3D resistivity of the Australian continent. To complement the regional AusLAMP MT sites numerous additional transects, and broadband MT grids have been deployed providing remarkable new insights into the tectonic evolution of the Australian lithosphere and provide the link to crustal mineral resources. In this special edition, ten papers explore different aspects of MT research in Australia over the last decade.

Developing neural network analysis technology for the resolution of issues in oil and gas geophysics

Developing neural network analysis technology for the resolution of issues in oil and gas geophysics

A robust numerical method based on a deep-learning operator for solving the 2D acoustic wave equation

The numerical solution of a wave equation plays a crucial role in computational geophysics problems, which forms the foundation of inverse problems and directly impacts the high-precision imaging results of earth models. However, common numerical methods often lead to significant computational and storage requirements. Due to the heavy reliance on forward-modeling methods in inversion techniques, particularly full-waveform inversion, enhancing the computational efficiency and reducing the storage demands of traditional numerical methods have become key issues in computational geophysics. We develop the deep Lax-Wendroff correction (DeepLWC) method, a deep-learning-based numerical format for solving 2D hyperbolic wave equations. DeepLWC combines the advantages of traditional numerical schemes with a deep neural network. We provide a detailed comparison of this method with the representative traditional Lax-Wendroff correction method. Our numerical results indicate that the DeepLWC significantly improves the calculation speed (by more than 10 times) and reduces the space needed for storage by more than 10,000 times compared with traditional numerical methods. In contrast to the more popular physics-informed neural network method, DeepLWC maximizes the advantages of traditional mathematical methods in solving partial differential equations and uses a new sampling approach, leading to improved accuracy and faster computations. It is particularly worth pointing out that DeepLWC introduces a novel research paradigm for numerical equation solving, which can be combined with various traditional numerical methods, enabling acceleration and reduction in the storage requirements of conventional approaches.

О возможной связи между магнитными бурями и землетрясениями в определенных тектонических условиях (на примере о. Сахалин)

The paper considers topical issues of geophysics related to the possible influence of disturbances in the magnetosphere on seismicity. The study was conducted based on a detailed catalog of seismic events in southern Sakhalin for the period from 2003 to 2023. The paper aims to test the assumption that such an influence can manifest itself in individual seismogenic zones during their proximity to discharge. The testing was carried out in randomly selected segments of the West Sakhalin (WSF) and Central Sakhalin (CSF) faults. The coincidence of the moments of some seismic events (with M > 2.7) and magnetic storms with a high index (G1 and higher) was revealed in these segments. The LURR (load-unload response ratio) method was used to identify periods when fault segments were in a subcritical stress-strain state. It was shown that the main part of the coincidences occurred during the periods of increased abnormal activity of the LURR parameter.

Modern Problems of Experimental Mineralogy, Petrology, and Geochemistry

Abstract —This Special issue of Russian Geology and Geophysics is a collection of papers on current problems of experimental mineralogy, petrology, and geochemistry discussed at the XVIII Russian Conference on Experimental Mineralogy (5–10 September 2022, Vinogradov Institute of Geochemistry, Irkutsk). The scope of considered issues ranges from laboratory modeling of mineral formation processes in different tectonic settings to technical mineralogy. The reported experiments are run at pressures and temperatures corresponding to crustal and mantle conditions.

Geophysics Bright Spots

Welcome to the latest installment of Geophysics Bright Spots. There are a number of interesting research articles in the recent issue of Geophysics. Here is a list of articles that piqued the editors' interests.

Geophysics Bright Spots

Welcome to the latest installment of Geophysics Bright Spots. There are a number of interesting research articles in the recent issue of Geophysics. Here is an article that piqued the editors’ interests.

S-wave velocity prediction using physical model-driven Gaussian process regression: A case study of tight sandstone reservoir

Knowing S-wave velocity is critical to characterize the tight sandstone reservoir owing to its insensitive elastic responses. However, it is challenging to precisely acquire S-wave information due to the high cost and technical difficulties. Here, beyond the conventional model- and statistical data-driven methods, we propose a numerical scheme based on Gaussian process regression (GPR) to predict the S-wave velocity with P-wave velocity and lithologic parameters as input. The GPR is a nonparametric kernel-based probabilistic model, which is explicitly defined by the mean and covariance functions. Compared with other machine-learning methods even the deep learning method, the GPR is a small data-based machine learning method, which is significant for geophysical issues. In addition, through training a small data set, the GPR-based scheme not only accurately estimates S-wave velocity but also quantifies the uncertainty of the results. Compared with conventional methods such as the Castagna relations, the comprehensive formula, and the bidirectional long short-term memory, the S-wave velocity predicted by GPR is more accurate in terms of the mean-squared error, root-mean-squared error, average relative error, and correlation coefficient. The field data test demonstrates that the proposed GPR-based scheme is superior and can be satisfactorily implemented for logging data.

Geophysics Bright Spots

Welcome to the latest installment of Geophysics Bright Spots. There are a number of interesting research articles in the last two issues of Geophysics. Here is a list of what piqued the editors' interests.

Geophysics Bright Spots

Welcome to the latest installment of Geophysics Bright Spots. Here are a few of the research articles from the last two issues of Geophysics that piqued the editors' interests.

ГЕОДИНАМІКА

Determining the physical parameters of geomaterials under high temperature and pressure conditions is necessary in connection with the fundamental issues of geology and geophysics. It is also aimed at solving applied problems, such as establishing relationships between physical parameters and chemical components of rocks under the earthly conditions of temperature and pressure. The purpose of the paper is to study the peculiarities of the influence of chemical components on the elastic and density properties of igneous and metamorphic rocks of the continental and oceanic lithosphere under high temperature and pressure conditions. The elastic and density characteristics of the rocks of the continental and oceanic lithosphere were determined by the ultrasonic pulse method. The experiments were carried out in a high-pressure solid-phase installation of a cylinder-piston type. The technique provides for the simultaneous determination of the longitudinal and transverse waves velocity and density in the course of one experiment on one rock sample at high temperature and pressure conditions up to 1.5-2.0 GPa. Based on an experimental study of the elastic and density properties of the rocks of the continental and oceanic lithosphere, the research revealed a qualitative connection between these parameters and chemical composition of the samples under high temperature and pressure conditions. It is first established that the studied rocks demonstrate regional dependence in the influence of oxides on the elastic wave velocity and density magnitude. Therefore they increase with the growing pressure in some areas, and decrease in others. This phenomenon is explained by the difference in the atomic structure of matter. It was revealed that in the section of the lithosphere, the speed and density of elastic waves increase with depth. Moreover, chemical composition of rocks changes from acid to medium, basic, and, finally, ultrabasic composition. The relationship of the chemical composition of rocks and minerals with elastic and density properties makes it possible to directly search for solid minerals.

Geophysics Bright Spots

Welcome to the latest installment of Geophysics Bright Spots. There are a number of interesting research articles in the last two issues of Geophysics. Here is a list of what piqued the editors' interests.

Current Issues of Tectonics, Paleogeography, Geodynamic Evolution, and Mineral Resources of the Continental Margins of the Russian Arctic

AbstractThe special issue is focused on the problems of tectonics, paleogeography, geodynamic evolution, and mineral resources of the continental margins of the Russian Arctic. This topic is relevant, since the knowledge of the geologic structure of the Arctic Ocean and its formation and evolution can solve many global problems of geology and important regional problems, including the formation of oil- and gas-bearing sedimentary basins as well as prospecting for, and development of, diamonds and deposits of nonferrous, noble, rare-earth, and other minerals. In previous issues of Russian Geology and Geophysics, considerable attention was paid to the geology and oil and gas potential of the Arctic. In this special issue, emphasis is placed on the tectonics, stratigraphy, paleogeography, and petrology of the Arctic continental margins of Russia, the development of tectonic and geodynamic models for key structures, and diamond content and metallogeny of Arctic zones of the Siberian Platform, Chukotka, and the Kola Peninsula.

Geophysics Bright Spots

Welcome to the latest installment of Geophysics Bright Spots. There are a number of interesting research articles in the latest issue of Geophysics. Here is a list of what piqued the editors’ interests.

Design of a Low‐Cost Electrical Resistivity Meter for Near Surface Surveys

AbstractA programmable automated electrical resistivity meter was designed and constructed. The device was created to perform near surface studies, particularly for archaeogeophysical target characterization. Real field and laboratory model studies can be performed changing the current input of the device. The equipment consists of two independent devices, each one with its own microcontroller platform. They are interconnected through serial data transfer protocol. The first device, works as a resistivity meter where the ABMN electrode positions are programmed and permits the interaction with the user. The second one, connects the current and voltage channels to the programmed electrode positions. A physical model and field measurements were performed with different electrode configurations such as Dipole‐Dipole, Werner‐Schlumberger and Wenner γ112 in order to verify the performance of the automated electrical resistivity meter. The measurements give mean relative standard deviation values between 0.6% and 5.5% and data inversion convergence between 1.3% and 7.2%. Even though this open source and low cost electrical resistivity meter was design primarily for archaeogeophysical studies, it could be adapted to other geophysical issues such as contamination plumes detection and characterization, tunnel detection, etc.

Geophysics Bright Spots

Welcome to the latest installment of Geophysics Bright Spots. There are a number of interesting research articles in the latest issue of Geophysics. Here is a list of what piqued the editors' interests.

Geophysics Bright Spots

Welcome to the latest installment of Geophysics Bright Spots. There are a number of interesting articles in the latest issue of Geophysics. Here is a list of what piqued the editors' interests.

Comparison of three methods for computing the gravitational attraction of tesseroids at satellite altitude

Global gravity modelling is one of the most important issues in geophysics and geodesy. Because a tesseroid model comprises the curvature of the Earth, the computation methods for the gravitational potential of tesseroids and its first-order derivatives in spherical coordinates are attracting great attention in recent years. In this paper we deal with the numerical evaluation of the radial component of the gravitational attraction generated by tesseroid masses at satellite height with the Gauss-Legendre quadrature (GLQ), the Taylor series expansion (TSE) and the prism approximation (PA) methods. Forward modelling of tesseroids of 1° × 1° and 5′ × 5′ are performed by three computation methods and the comparison between them are made in terms of computational efficiency and accuracy. The numerical results show that the GLQ of order 5 can provide the adequate accuracy for the gravity modelling of 1° × 1° tesseroids at satellite height. The GLQ of order 2 and TSE methods are superior to the PA approach in both computational accuracy and efficiency. The satellite height has important impact on the accuracy of the GLQ and TSE, whereas it has no effect on the PA method. In addition, we developed combined GLQ approach and combined TSE method, respectively, for global gravity modelling based on 1° × 1° and 5′ × 5′ tesseroids. Apart from the synthetic tesseroids, 1° × 1° data from the CRUST1.0 global crustal model and 5′ × 5′ rock-equivalent topographic data from the Earth2014 model are used to validate two combined methods. The numerical results show that these two combined methods can balance the computational accuracy and efficiency.

Geophysics Bright Spots

Welcome to the latest installment of Geophysics Bright Spots. Below are articles that the editors found interesting in the latest issue of Geophysics.

Geophysics Bright Spots

Welcome to the latest installment of Geophysics Bright Spots. Below is an article that the editors found interesting in the latest issue of Geophysics. Although this list contains only one article, you will find many other interesting articles in the issue.