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Near-Surface Geophysics: A Remote Sensing Tool for the Shallow Subsurface

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A special issue of Remote Sensing (ISSN 2072-4292). This special issue belongs to the section "Remote Sensing in Geology, Geomorphology and Hydrology".

Deadline for manuscript submissions: closed (20 October 2022) | Viewed by 29965

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Special Issue Editors

Prof. Dr. Gian Piero Deidda

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Guest Editor

Department of Civil, Environmental Engineering and Architecture, University of Cagliari, 09123 Cagliari, Italy
Interests: environmental and engineering geophysics; seismic data acquisition and processing; electromagnetic data inversion techniques

Dr. Mahjoub Himi

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Guest Editor

Department of Mineralogy, Petrology and Applied Geology, Faculty of Earth Science, University of Barcelona, 08028 Barcelona, Spain
Interests: environmental geophysics; optimization; modeling; site selection
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Cassiani Giorgio

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Guest Editor

Department of Geosciences, University of Padova, 35131 Padova, Italy
Interests: environmental and engineering geophysics; hydrogeophysics; hydrological and hydrogeological modeling; geophysical soil mapping; seismological micro-scale zoning and other soil dynamics

Special Issue Information

Dear Colleagues,

Detailed knowledge of the upper few meters of the Earth’s crust, where humans continuously interact with natural Earth systems, is of paramount importance to sustainable economic development. In the last few decades, we have witnessed an ever-growing demand for innovative technologies and less-invasive, cost-effective investigation methods able to provide quasi real-time, accurate, and detailed knowledge of the natural system. One method that meets these requirements is near-surface geophysics.

Human interaction with the near-surface Earth generates anthropic objects and artefacts, spatial and temporal changes in physical parameters of the soil, and processes that provide signatures that can be detected, sensed, and monitored with a suite of geophysical methods (seismics, ground-penetrating radar, DC resistivity, time-domain and frequency-domain electromagnetic induction, gravity, and magnetics) known as near-surface geophysics. This method includes (but is not limited to) imaging of shallow geological formations, geological resources, and environmental problems, monitoring groundwaters, the detection of contaminated sites for remedial clean-up of hazardous waste materials, mapping salinity, soil water content, and/or other physical soil properties, and surveying for civil engineering, archaeological, and forensic projects.

Near-surface geophysics mostly uses ground-based methods and only partly uses proximal and/or remote sensing methods. In the broadest sense, however, since it uses sensors on or above the Earth’s surface to sense objects and phenomena in the subsurface, near-surface geophysics can be considered to be a remote sensing tool.

This Special Issue of Remote Sensing aims to provide an overview of recent advances in near-surface geophysics, with a special focus on case studies demonstrating its potential in environmental, hydrogeological, and engineering investigations, especially when geophysical methods are used in conjunction with other proximal and/or remote sensing techniques. Papers on novel data acquisition procedures and innovative distributed sensors, enabling rapid area coverage and allowing for the collection of a large volume of data, are welcome. We are also looking for contributions showing the added value of combined approaches to complex 3D characterization and modeling of surface and subsurface targets and/or processes. Joint interpretation (inversion) of multiple data types, either within a deterministic or geostatistical framework, is also of interest. In addition, contributions on our understanding of the dynamic links (relationships) between geophysical properties and physicochemical properties of subsurface materials will also be appreciated.

Prof. Dr. Gian Piero Deidda
Prof. Dr. Mahjoub Himi
Prof. Dr. Cassiani Giorgio
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Remote Sensing is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

applied geophysics
environmental geophysics
proximal and remote sensing
near-surface geophysics and remote sensing
monitoring
data acquisition
data processing and analysis
data integration
modeling and inversion
joint inversion
petrophysics
soil mapping.

Published Papers (13 papers)

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Research

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36 pages, 10911 KiB

Open AccessArticle

Forward Electromagnetic Induction Modelling in a Multilayered Half-Space: An Open-Source Software Tool

by Gian Piero Deidda, Patricia Díaz de Alba, Federica Pes and Giuseppe Rodriguez

Remote Sens. 2023, 15(7), 1772; https://doi.org/10.3390/rs15071772 - 26 Mar 2023

Cited by 2 | Viewed by 2388

Abstract

Electromagnetic induction (EMI) techniques are widely used in geophysical surveying. Their success is mainly due to their easy and fast data acquisition, but the effectiveness of data inversion is strongly influenced by the quality of sensed data, resulting from suiting the device configuration to the physical features of the survey site. Forward modelling is an essential tool to optimize this aspect and design a successful surveying campaign. In this paper, a new software tool for forward EMI modelling is introduced. It extends and complements an existing open-source package for EMI data inversion, and includes an interactive graphical user interface. Its use is explained by a theoretical introduction and demonstrated through a simulated case study. The nonlinear data inversion issue is briefly discussed and the inversion module of the package is extended by a new regularized minimal-norm algorithm. Full article

(This article belongs to the Special Issue Near-Surface Geophysics: A Remote Sensing Tool for the Shallow Subsurface)

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16 pages, 13521 KiB

Open AccessArticle

Multi-Mode Surface Wave Tomography of a Water-Rich Layer of the Jizhong Depression Using Beamforming at a Dense Array

by Qingyu Wu, Qiusheng Li, Xiangyun Hu, Zhanwu Lu, Wenhui Li, Xiaoran Wang and Guangwen Wang

Remote Sens. 2023, 15(1), 40; https://doi.org/10.3390/rs15010040 - 22 Dec 2022

Viewed by 1474

Abstract

Urban structure imaging using noise-based techniques has rapidly developed in recent years. Given the complexity of the cross-correlation function in high-frequency signals, here, the beamforming (BF) method was used to analyze one data set taken from a dense array in the Jizhong Depression and obtain multi-mode dispersion curves. Multi-mode surface waves improved inversion stability, reduced non-uniqueness, and yielded a one-dimensional shear wave (S-wave) velocity model. Interpolation yielded a high-resolution three-dimensional (3D) S-wave velocity model for the study area. The model shows that velocity gradually changed in the horizontal direction and greatly increased in the vertical direction, which is largely consistent with changes in the sedimentary environment related to the continuous subsidence of the Jizhong Depression since the Quaternary. A low-velocity anomaly at a depth of ~300–400 m was revealed and determined to be caused by either a deep-buried ancient river course or low-lying area. This study demonstrates the potential of the BF method for processing dense array data sets of urban exploration. The high-resolution 3D S-wave velocity model provides a new reference for studying the Quaternary structure of the Jizhong Depression, as well as groundwater resources, urban infrastructure, and underground spaces. Full article

(This article belongs to the Special Issue Near-Surface Geophysics: A Remote Sensing Tool for the Shallow Subsurface)

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17 pages, 5890 KiB

Open AccessArticle

Application of Resistivity and Seismic Refraction Tomography for Landslide Stability Assessment in Vallcebre, Spanish Pyrenees

by Mahjoub Himi, Mickel Anton, Alex Sendrós, Clàudia Abancó, Maurizio Ercoli, Raúl Lovera, Gian Piero Deidda, Aritz Urruela, Lluís Rivero and Albert Casas

Remote Sens. 2022, 14(24), 6333; https://doi.org/10.3390/rs14246333 - 14 Dec 2022

Cited by 4 | Viewed by 2560

Abstract

Geophysical surveys are a noninvasive reliable tool to improve geological models without requiring extensive in situ borehole campaigns. The usage of seismic refraction tomography (SRT), electrical resistivity tomography (ERT) and borehole data for calibrating is very appropriate to define landslide body geometries; however, it is still only used occasionally. We present here the case of a Spanish Pyrenees slow-moving landslide, where ERT, SRT and lithological log data were integrated to obtain a geological three-dimensional model. The high contrasts of P-wave velocity and electrical resistivity values of the upper materials (colluvial debris and clayey siltstone) provided accurate information on the geometry of the materials involved in the landslide body, as well as the sliding surface. Geophysical prospecting allowed us to identify the critical sliding surface over a large area and at a reduced cost and, therefore, gives the geophysical method an advantage over borehole data. The three-dimensional model was used to carry out stability analyses of a landslide in 2D and 3D, which, coherently with previous studies, reveal that the lower part is more unstable than the upper units. Full article

(This article belongs to the Special Issue Near-Surface Geophysics: A Remote Sensing Tool for the Shallow Subsurface)

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19 pages, 5888 KiB

Open AccessArticle

Electro-Magnetic Geophysical Dynamics under Conservation and Conventional Farming

by Alberto Carrera, Matteo Longo, Ilaria Piccoli, Benjamin Mary, Giorgio Cassiani and Francesco Morari

Remote Sens. 2022, 14(24), 6243; https://doi.org/10.3390/rs14246243 - 09 Dec 2022

Cited by 2 | Viewed by 1214

Abstract

In the context of global warming, agriculture faces severe challenges such as water scarcity and soil erosion. Key to achieving soil sustainability is the choice of farming practices, the consequences of which are generally site-specific. In this study, the ability of Electrical Resistivity Tomography (ERT) and Electro Magnetic Induction (EMI) methods were assessed for monitoring the effects of conventional (CONV) and conservation (CONS) agricultural practices. The aim is to highlight differences in soil water distribution caused by both short- and long-term effects of the two different practices. Results demonstrated that both ERT and EMI provided sufficient information to distinguish between the effects of CONV and CONS, while traditional direct measurements, being punctual techniques, lacked sufficient spatial resolution. The ERT transects showed that the soil was much more homogeneous as a result of CONS practices, resulting in a higher sensitivity to changes in the water content. Conversely, due to the heterogeneous soil structure under CONV, water distribution was more irregular and difficult to predict. Similar patterns were also observed with the EMI surveys, with a strong link to spatial variability. Finally, we conclude that for CONV soil, the accessible water for the plant is clearly controlled by the soil heterogeneities rather than by the forcing atmospheric conditions. This study is a first step towards paving the way for more refined hydrology models to identify which soil parameters are key to controlling spatial and temporal changes in soil water content. Full article

(This article belongs to the Special Issue Near-Surface Geophysics: A Remote Sensing Tool for the Shallow Subsurface)

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19 pages, 5381 KiB

Open AccessArticle

Mineral Exploration Potential Estimation Using 3D Inversion: A Comparison of Three Different Norms

by Tao Chen and Guibin Zhang

Remote Sens. 2022, 14(11), 2537; https://doi.org/10.3390/rs14112537 - 25 May 2022

Cited by 4 | Viewed by 1873

Abstract

Gravity data have been frequently used in researching the subsurface to map the 3D geometry of the density structure, which is considered the basis for further interpretations, such as the estimation of exploration potential in mineral exploration. The gravity inversion, practically employed to map the density structure, can be achieved by different methods. The method based on Tikhonov regularization is the most commonly used among them. Usually, the subsurface is discretized into a set of cells or voxels. To recover a stable and reliable solution, constraints are introduced into the Tikhonov regularization. One constrained inversion introduces a quadratic penalty (L₂ norm) into the inversion, which imposes smooth features on the recovered model. Another gravity inversion, known as sparse inversion, imposes compactness and sharp boundaries on the recovered density structure. Specifically, the L₁ norm and L₀ norm are favored for such a purpose. This work evaluates the merits of the gravity data inversion in cooperation with different model norms and their applicability in exploration potential estimation. Because these norms promote different features in the recovered models, the reconstructed 3D density structure reveals different geometric features of the ore deposit. We use two types of synthetic data for evaluating the performances of the inversion with different norms. Numerical results demonstrate that L₀ norm-based inversion provides high-resolution recovered models and offers reliable estimates of exploration potential with minimal deviation from theoretical mass compared to inversions equipped with the other two norms. Finally, we use the gravity data collected over the iron ore deposit at the Dida mining area in Jilin province (Northeast China) for the application. It is estimated that the exploration potential of the iron ore deposits is about 3.2 million tons. Full article

(This article belongs to the Special Issue Near-Surface Geophysics: A Remote Sensing Tool for the Shallow Subsurface)

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18 pages, 9179 KiB

Open AccessArticle

Geophysical Study of the Diendorf-Boskovice Fault System (Austria)

by Valeria Paoletti, Esther Hintersberger, Ingrid Schattauer, Maurizio Milano, Gian Piero Deidda and Robert Supper

Remote Sens. 2022, 14(8), 1807; https://doi.org/10.3390/rs14081807 - 08 Apr 2022

Cited by 4 | Viewed by 1777

Abstract

We describe here the results of the characterization of subsurface structures in an area of the south-eastern edge of the Bohemian Massif, in Austria by high-resolution geophysical survey techniques and advanced analysis methods of potential fields. The employed methods included potential field multiscale techniques for source-edge location and characterization of sources at depth. Our results confirmed the presence of already known structures: the location of the Diendorf Fault and the Moldanubian Shearzone are clearly recognized in the data at the same location as on the geological maps, even where the Diendorf fault is covered with sediments of the Molasse Basin. In addition, we detected several geological contacts between different rock types in the Bohemian Massif west of the Diendorf Fault. From our results, we were also able to quickly identify and image, without a priori information, previously unknown structures, such as faults with-depth-to-the top of about 500 m and magmatic intrusions about 400 m deep. Full article

(This article belongs to the Special Issue Near-Surface Geophysics: A Remote Sensing Tool for the Shallow Subsurface)

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13 pages, 5113 KiB

Open AccessArticle

Modeling and Inversion of Airborne and Semi-Airborne Transient Electromagnetic Data with Inexact Transmitter and Receiver Geometries

by Tao Chen and Dikun Yang

Remote Sens. 2022, 14(4), 915; https://doi.org/10.3390/rs14040915 - 14 Feb 2022

Cited by 3 | Viewed by 1932

Abstract

Airborne and semi-airborne transient electromagnetic (TEM) surveys have high efficiency but may suffer from systematic errors due to the inexact shape, position, and orientation of the transmitter and receiver, which can deviate from the nominal design because of complex terrain, platform instability, or external forces. Without considering actual survey geometry, modeling and inversion can bias the interpretation of results. We develop a universal approach to layered earth capable of modeling arbitrarily complex transmitter and receiver geometry used in airborne and semi-airborne surveys. Our algorithm decomposes an airborne loop or grounded wire source to a set of x-, y-, or z-oriented electric dipoles. An arbitrarily oriented receiver coil is simulated by projecting three-component data to the actual direction of receiving. In airborne TEM, the transmitter loop and receiver coil are often bound together on a rigid frame and tilt during the flight. Our simulations and synthetic inversion show that such a tilt may reduce responses relative to the data obtained with the nominal geometry; an inversion without considering the tilt can underestimate near-surface conductivity. In semi-airborne TEM, the transmitter wire on the surface can be crooked, and the airborne receiver coil can also tilt. Our modeling shows that the simulated data can change significantly if the actual transmitter and receiver geometry does not exactly follow the nominal survey design; if not appropriately accounted for, such an error may distort the recovered conductivity model. Finally, the benefit of our algorithm is demonstrated by an airborne TEM field data inversion of groundwater problems with the tilt angle of the transmitter–receiver frame accurately modeled. Our work provides a tool for improving the resolution of airborne and semi-airborne TEM in near-surface conductivity characterization. Full article

(This article belongs to the Special Issue Near-Surface Geophysics: A Remote Sensing Tool for the Shallow Subsurface)

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29 pages, 10619 KiB

Open AccessArticle

Frequency-Domain Electromagnetic Mapping of an Abandoned Waste Disposal Site: A Case in Sardinia (Italy)

by Gian Piero Deidda, Mahjoub Himi, Ilaria Barone, Giorgio Cassiani and Albert Casas Ponsati

Remote Sens. 2022, 14(4), 878; https://doi.org/10.3390/rs14040878 - 12 Feb 2022

Cited by 7 | Viewed by 2540

Abstract

For decades, bad practices in municipal and industrial waste management have had negative environmental impacts, generating high health risks for people and the environment. The use of badly designed, not engineered, and not well-operated landfills has, around the world, produced a large number of potentially contaminated sites, for which there are urgent needs to assess the actual risk and to proceed, in case, with reclamation activities. One of these sites, an abandoned waste disposal site located near a Site of Community Importance on the central-eastern coast of Sardinia (Italy), is the subject of the case history described in this work. As a part of a multi-method geophysical characterisation, a frequency-domain electromagnetic (FDEM) mapping survey was carried out with the specific aim of detecting the presence of buried materials (waste) and of delineating the lateral extent of the landfill by identifying the electrical conductivity anomalies produced, for the most part, by the conductive waste fill. Using an EM31 device in the vertical-dipole configuration, at a height of 0.9 m above the ground, both quadrature and in-phase electromagnetic responses were collected over a 7-hectare area with elevation varying between 6 m and 2.8 m above sea level. After removing the measurements identified as data coming from any recognisable surface man-made features within the survey area or near its perimeter, the filtered quadrature response (expressed as apparent conductivity) ranged from 5.5 mS/m to about 188.6 mS/m. All values are beyond the low induction number (LIN) condition and valid for the classical EM31 mapping, thus requiring advanced data processing. To obtain undistorted, meaningful, and interpretable high-resolution maps, measured data have been processed to correct the bias, introduced by the nonlinearity of the device, as a function of height above ground and the topography. The comparative analysis of the apparent conductivity map, obtained by the properly processed EM31 data and some aerial photos that clearly documented the site history, has allowed unequivocal delineation of the landfill extent, in good agreement with the results obtained with other geophysical methods (not described in this paper) and with the ground truthing data provided by three boreholes, which were core-drilled at the end of the study at three locations selected on the basis of the apparent conductivity map. Full article

(This article belongs to the Special Issue Near-Surface Geophysics: A Remote Sensing Tool for the Shallow Subsurface)

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19 pages, 7374 KiB

Open AccessArticle

Sub-Bottom Sediment Classification Using Reliable Instantaneous Frequency Calculation and Relaxation Time Estimation

by Shaobo Li, Jianhu Zhao, Hongmei Zhang and Siheng Qu

Remote Sens. 2021, 13(23), 4809; https://doi.org/10.3390/rs13234809 - 27 Nov 2021

Cited by 5 | Viewed by 1604

Abstract

The shift in IF (instantaneous frequency) series and the corresponding relaxation time have the potential to characterize sediment properties. However, these attributes derived from SBP (sub-bottom profiler) data are seldom used for offshore site investigations because of the unsoundness in attribute calculation. To overcome this problem, a new reliable method combining VMD (variational mode decomposition) and WVD (Wigner–Ville distribution), as well as relaxation time, is presented. Since the number of modes in classical VMD should be provided in advance, a modified VMD algorithm, MVMD (modified variational mode decomposition), is proposed here, where the distribution of the frequency domain of modes is taken into account to automatically determine the number of modes. Through the relaxation time model, the IF data of a series of pings calculated through MVMD-WVD are transformed into a relaxation time map. A robust estimation algorithm is applied to the relaxation time map to reduce the effects of interferences and obtain robust relaxation times. The final relaxation time data are used to determine the sediment types. Real data from SBP experiments, as well as borehole sampling and geotechnical analysis results, verified the good performance of the proposed method. Full article

(This article belongs to the Special Issue Near-Surface Geophysics: A Remote Sensing Tool for the Shallow Subsurface)

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17 pages, 145700 KiB

Open AccessArticle

IAS: A New Novel Phase-Based Filter for Detection of Unexploded Ordnances

by Ismael M. Ibraheem, Hasan Aladad, Mohamad Faek Alnaser and Randell Stephenson

Remote Sens. 2021, 13(21), 4345; https://doi.org/10.3390/rs13214345 - 28 Oct 2021

Cited by 11 | Viewed by 2518

Abstract

A new phase-based filter (called improved analytical signal (IAS)) is introduced to detect buried unexploded ordnance (UXO) precisely from magnetic fields using the arcsine function of the ratio of the first-order vertical derivative of the analytical signal to the first-order derivatives of the x-, y-, and z-components of the analytical signal. The calculations are computed in the frequency domain and then transformed back into the space domain using the inverse Fourier transform. The filter has been tested on magnetic data collected at a test site with UXO bodies of variable orientation. It was also validated on magnetic data measured at a former army artillery range in Slovakia. The results show that the IAS filter not only revealed better imaging of the UXO bodies compared to the other commonly used filters but also produced a high-resolution image with much less influence of noise. Full article

(This article belongs to the Special Issue Near-Surface Geophysics: A Remote Sensing Tool for the Shallow Subsurface)

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19 pages, 6234 KiB

Open AccessArticle

An Integrated Horizon Picking Method for Obtaining the Main and Detailed Reflectors on Sub-Bottom Profiler Sonar Image

by Shaobo Li, Jianhu Zhao, Hongmei Zhang and Siheng Qu

Remote Sens. 2021, 13(15), 2959; https://doi.org/10.3390/rs13152959 - 28 Jul 2021

Cited by 4 | Viewed by 2280

Abstract

A sub-bottom profiler (SBP) can capture the sediment interfaces and properties of different types of sediment. Horizon picking from SBP images is one of the most crucial steps in marine sub-bottom sediment interpretation. However, traditional horizon picking methods are good at obtaining the main horizons representing the main reflectors while ignoring the detailed horizons. While detailed horizons are the prime objective, many tiny structures caused by interference echoes will also be picked. To overcome this limitation, an integrated horizon picking method for obtaining the main and detailed horizons simultaneously is proposed in this paper. A total of three main process steps: the diffusion filtering method, the enhancement filtering method as well as the local phase calculation method, are used to help obtain the main and detailed horizons. The diffusion filtering method smooths the SBP images and preserves reflectors. Enhancement filtering can eliminate outliers and enhance reflectors. The local phase can be used to highlight all of the reflections and help in the choosing of detailed horizons. A series of experiments were then performed to validate the effectiveness of the proposed method, and good performances were achieved. Full article

(This article belongs to the Special Issue Near-Surface Geophysics: A Remote Sensing Tool for the Shallow Subsurface)

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27 pages, 18416 KiB

Open AccessArticle

Multi-Scale Geophysical Methodologies Applied to Image Archaeological Ruins at Various Depths in Highly Terraneous Sites

by Amin Ibrahim, Khaled S. Gemail, Kamal Abdelrahman, Naif Al-Otaibi, Elkhedr Ibrahim and Saada A. Saada

Remote Sens. 2021, 13(11), 2055; https://doi.org/10.3390/rs13112055 - 23 May 2021

Cited by 5 | Viewed by 3192

Abstract

Among all geophysical techniques, electrical resistivity and magnetic surveying as an integrative approach has been used widely for archaeological prospection at different scales of investigations. In this study, DC resistivity (1D vertical sounding and/2D/3D ERT) and magnetic surveys (total and gradient) as a multi-scale approach was applied in a highly terraneous archaeological site (Tell) with a case study to characterize and image the various archaeological assets at different depths with different spatial resolutions. Four critical zones of great interest within the considered Tell were surveyed. At the heart of the study area, three layers were depicted clearly from 1D resistivity sounding. A thick conductive zone of mostly clay is sandwiched between two resistive layers. The topmost layer contains construction debris (dated back to the Islamic Era), whereas the deeper layer could be related to Gezira sand on which the probable Pharaonic temple was constructed. A long 2D ERT profile using Wenner Beta (WB) and Dipole–Dipole (DD) arrays with a 5-m electrode spacing identified shallow high resistivity anomalies that could be related to construction ruins from fired bricks. Additionally, it succeeded in imaging the turtleback-shaped deeper resistive layer of mostly sand. At an elevated rim to the east and west of the Tell, total and vertical magnetic gradient maps clearly delineated different archaeological structures: the walls of the rooms of ancient Islamic settlers and the walls of water tanks from the Byzantine Era. Magnetic modeling assuming 2.5-dimensional magnetic models constrained by the 2D ERT inversion models could be used to create a realistic representation of the buried structures. Toward the northern part of the Tell, the joint application of the quasi-3D ERT inversion scheme and the magnetic survey revealed an anomaly of a well-defined geometric shape of an archaeological interest thought to be a crypt or water cistern based on nearby archaeological evidence. The overall results of the geophysical survey integrated with the image of some partially excavated parts provided the archaeologists with a comprehensive and realistic view of the subsurface antiquities at the study area. Full article

(This article belongs to the Special Issue Near-Surface Geophysics: A Remote Sensing Tool for the Shallow Subsurface)

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15 pages, 7290 KiB

Open AccessTechnical Note

High-Precision Depth Domain Migration Method in Imaging of 3D Seismic Data in Coalfield

by Jianguang Han, Bingluo Gu, Guanghui Zhu and Zhiwei Liu

Remote Sens. 2022, 14(12), 2850; https://doi.org/10.3390/rs14122850 - 14 Jun 2022

Cited by 1 | Viewed by 1585

Abstract

Fault structures developed in coal seams, which are often associated with roof collapse, water inrush, gas outburst, and other accidents, are common geological hazards in coal exploration and development. The accurate detection of micro-structures such as small faults has always been a research focus to ensure safety in coalfields. Three-dimensional (3D) seismic research is one of the most efficient methods for obtaining the structural characteristics of coal areas and identify small faults in coal seams, but it is difficult for traditional seismic data imaging technologies to meet the high-precision demand of current coal exploration. Aiming at the characteristics of 3D seismic data in coalfields, we calculated the difference coefficients based on the optimized inversion algorithm and proposed a variable-density acoustic equation optimized with a temporal–spatial staggered-grid finite difference forward algorithm. On this basis, by combining normalized cross-correlation imaging conditions and GPU/CPU collaborative parallel processing technology, we developed an efficient and high-precision 3D reverse time migration method suitable for 3D seismic data in coalfields. Numerical tests verified the accuracy and efficiency of the proposed migration method for the imaging of coal-measure strata with small fault structures and could effectively identify 5 m small faults in the coal seam. The migration test of 3D seismic data in real coalfields showed that our 3D reverse time migration method has good practicability for high-precision imaging of 3D seismic data in coalfields and is an effective method for the precise imaging of small faults in coal measures. Full article

(This article belongs to the Special Issue Near-Surface Geophysics: A Remote Sensing Tool for the Shallow Subsurface)

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