Special Issue "Advances in Applied Geophysics"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Earth Sciences and Geography".

Deadline for manuscript submissions: 31 December 2021.

Special Issue Editors

Prof. Dr. Filippos Vallianatos
E-Mail Website1 Website2
Guest Editor
Professor of Geophysics-Applied Geophysics, Department of Geophysics-Geothermics, Faculty of Geology and Geoenvironment, School of Sciences National and Kapodistrian University of Athens, Panepistimiopolis, Zografos, 157 84 Athens, Greece
Interests: geophysics; earth physics; seismology; applied geophysics
Special Issues, Collections and Topics in MDPI journals
Dr. Vassilis Sakkas
E-Mail
Co-Guest Editor
Department of Geophysics-Geothermics, Faculty of Geology and Geoenvironment, School of Sciences National and Kapodistrian University of Athens, Panepistimiopolis, Zografos, 157 84 Athens, Greece
Interests: geophysics; space applications in geophysics; satellite geodesy (GNSS); satellite interferometry

Special Issue Information

Dear Colleagues,

In the context of the increasing demand for knowledge of the physical properties of the Earth’s crust with geophysical measurements, the development of new approaches for the characterization of the Earth’s crust is a crucial issue.

The focus of this Special Issue of applied sciences is seismic and electromagnetic exploration, magnetotellurics, archeogeophysics, petrophysics, inversion techniques, satellite techniques to study the Earth’s surface, and instrument development, as applied to support our image of the Earth’s crust. In addition, during the two last decades, the use of geophysical techniques for addressing environmental, engineering, and hydrogeological issues has developed significantly, since geophysical prospection can provide additional and fine information about the underground medium.

This Special Issue aims to bring together the most recent works on the application of geophysical methods for the imaging of the Earth’s crust along with the possible environmental, engineering, and hydrogeological applications, for the fine characterization of the near surface structure.

Without being exhaustive, the concerned methods are seismics, electromagnetics (e.g., magnetotellurics, time–domain electromagnetics, radar), active electrical methods (e.g., electrical resistivity tomography and induced polarization) or passive electrical methods (spontaneous potential), nuclear magnetic resonance, and even microgravimetry. Contributions focusing on the petrophysical laws, along with the application of modern satellite technique, such as satellite geodesy, interferometry, gravity etc., which may be combined with classical geophysical and seismological methods for the solution of geophysical problems are also welcome.

Prof. Dr. Filippos Vallianatos
Dr. Vassilis Sakkas
Guest Editors

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 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

  • geophysical imaging
  • earth’s crust
  • seismics
  • geoelectromagnetism
  • electrical methods
  • environmental and engineering geophysics
  • satellite techniques
  • geodesy
  • interferometry
  • gravity

Published Papers (18 papers)

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Research

Article
Improved Workflow for Fault Detection and Extraction Using Seismic Attributes and Orientation Clustering
Appl. Sci. 2021, 11(18), 8734; https://doi.org/10.3390/app11188734 - 19 Sep 2021
Viewed by 506
Abstract
Faults represent important analytical targets for the identification of perceptual ground motions and associated seismic hazards. In particular, during oil production, important data such as the path and flow rate of fluid flows can be obtained from information on fault location and their [...] Read more.
Faults represent important analytical targets for the identification of perceptual ground motions and associated seismic hazards. In particular, during oil production, important data such as the path and flow rate of fluid flows can be obtained from information on fault location and their connectivity. Seismic attributes are conventional methods used for fault detection, whereby information obtained from seismic data are analyzed using various property processing methods. The analyzed data eventually provide information on fault properties and imaging of fault surfaces. In this study, we propose an efficient workflow for fault detection and extraction of requisite information to construct a fault surface model using 3D seismic cubes. This workflow not only improves the ability to detect faults but also distinguishes the edges of a fault more clearly, even with the application of fewer attributes compared to conventional workflows. Thus, the computing time of attribute processing is reduced, and fault surface cubes are generated more rapidly. In addition, the reduction in input variables reduces the effect of the interpreter’s subjective intervention on the results. Furthermore, the clustering method can be applied to the azimuth and dip of the fault to be extracted from the complexly intertwined fault faces and subsequently imaged. The application of the proposed workflow to field data obtained from the Vincentian oil field in Australia resulted in a significant reduction in noise compared to conventional methods. It also led to clearer and continuous edge detection and extraction. Full article
(This article belongs to the Special Issue Advances in Applied Geophysics)
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Article
Variations in Wedge Earthquake Distribution along the Strike Underlain by Thermally Controlled Hydrated Megathrusts
Appl. Sci. 2021, 11(16), 7268; https://doi.org/10.3390/app11167268 - 06 Aug 2021
Cited by 1 | Viewed by 394
Abstract
Accretionary wedge earthquakes usually occur in the overriding crust close to the trench or above the cold nose of the mantle wedge. However, the mechanism and temperature properties related to the slab dip angle remain poorly understood. Based on 3D thermal models to [...] Read more.
Accretionary wedge earthquakes usually occur in the overriding crust close to the trench or above the cold nose of the mantle wedge. However, the mechanism and temperature properties related to the slab dip angle remain poorly understood. Based on 3D thermal models to estimate the subduction wedge plate temperature and structure, we investigate the distribution of wedge earthquakes in Alaska, which has a varying slab dip angle along the trench. The horizontal distance of wedge-earthquake hypocenters significantly increases from the Aleutian Islands to south–central Alaska due to a transition from steep subduction to flat subduction. Slab dehydration inside the subducted Pacific plate indicates a simultaneous change in the distances between the intraslab metamorphic fronts and the Alaskan Trench at various depths, which is associated with the flattening of the Pacific plate eastward along the strike. The across-arc width of the wedge-earthquake source zone is consistent with the across-arc width of the surface high topography above the fully dehydrated megathrust, and the fluid upwelling spontaneously influences wedge seismotectonics and orogenesis. Full article
(This article belongs to the Special Issue Advances in Applied Geophysics)
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Article
Two-Dimensional Full-Waveform Joint Inversion of Surface Waves Using Phases and Z/H Ratios
Appl. Sci. 2021, 11(15), 6712; https://doi.org/10.3390/app11156712 - 22 Jul 2021
Viewed by 361
Abstract
Surface-wave dispersion and the Z/H ratio are important parameters used to resolve the Earth’s structure, especially for S-wave velocity. Several previous studies have explored using joint inversion of these two datasets. However, all of these studies used a 1-D depth-sensitivity kernel, which lacks [...] Read more.
Surface-wave dispersion and the Z/H ratio are important parameters used to resolve the Earth’s structure, especially for S-wave velocity. Several previous studies have explored using joint inversion of these two datasets. However, all of these studies used a 1-D depth-sensitivity kernel, which lacks precision when the structure is laterally heterogeneous. Adjoint tomography (i.e., full-waveform inversion) is a state-of-the-art imaging method with a high resolution. It can obtain better-resolved lithospheric structures beyond the resolving ability of traditional ray-based travel-time tomography. In this study, we present a systematic investigation of the 2D sensitivities of the surface wave phase and Z/H ratio using the adjoint-state method. The forward-modeling experiments indicated that the 2D phase and Z/H ratio had different sensitivities to the S-wave velocity. Thus, a full-waveform joint-inversion scheme of surface waves with phases and a Z/H ratio was proposed to take advantage of their complementary sensitivities to the Earth’s structure. Both applications to synthetic data sets in large- and small-scale inversions demonstrated the advantage of the joint inversion over the individual inversions, allowing for the creation of a more unified S-wave velocity model. The proposed joint-inversion scheme offers a computationally efficient and inexpensive alternative to imaging fine-scale shallow structures beneath a 2D seismic array. Full article
(This article belongs to the Special Issue Advances in Applied Geophysics)
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Article
Impact of Post-Earthquake Seismic Waves on the Terrestrial Environment
Appl. Sci. 2021, 11(14), 6606; https://doi.org/10.3390/app11146606 - 18 Jul 2021
Viewed by 494
Abstract
When an earthquake occurs, it is not only the crustal material in the seismic zone that moves violently; the seismic waves of the earthquake with certain level of energy can act on the crust over large areas, producing remote effects that affect the [...] Read more.
When an earthquake occurs, it is not only the crustal material in the seismic zone that moves violently; the seismic waves of the earthquake with certain level of energy can act on the crust over large areas, producing remote effects that affect the living environment. According to the records of the long-term observation station of Chinese Continental Scientific Drilling, the effects of near-surface crust caused by the post-earthquake seismic waves include the following four aspects: (1) the pore fissure loosening; (2) the pore pressure rising and groundwater upwelling; (3) gas releasing; and (4) exothermic reaction. The effects of groundwater upwelling, gas releasing and exothermic reaction may be superimposed on the process of global warming, which has a certain impact on the terrestrial environment and requires further studies. Full article
(This article belongs to the Special Issue Advances in Applied Geophysics)
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Article
Lp-Norm Inversion of Gravity Data Using Adaptive Differential Evolution
Appl. Sci. 2021, 11(14), 6485; https://doi.org/10.3390/app11146485 - 14 Jul 2021
Viewed by 417
Abstract
As a popular population based heuristic evolutionary algorithm, differential evolution (DE) has been widely applied in various science and engineering problems. Similar to other global nonlinear algorithms, such as genetic algorithm, simulated annealing, particle swarm optimization, etc., the DE algorithm is mostly applied [...] Read more.
As a popular population based heuristic evolutionary algorithm, differential evolution (DE) has been widely applied in various science and engineering problems. Similar to other global nonlinear algorithms, such as genetic algorithm, simulated annealing, particle swarm optimization, etc., the DE algorithm is mostly applied to resolve the parametric inverse problem, but has few applications in physical property inversion. According to our knowledge, this is the first time DE has been applied in obtaining the physical property distribution of gravity data due to causative sources embedded in the subsurface. In this work, the search direction of DE is guided by better vectors, enhancing the exploration efficiency of the mutation strategy. Besides, to reduce the over-stochastic of the DE algorithm, the perturbation directions in mutation operations are smoothed by using a weighted moving average smoothing technique, and the Lp-norm regularization term is implemented to sharpen the boundary of density distribution. Meanwhile, in the search process of DE, the effect of Lp-norm regularization term is controlled in an adaptive manner, which can always have an impact on the data misfit function. In the synthetic anomaly case, both noise-free and noisy data sets are considered. For the field case, gravity anomalies originating from the Shihe iron ore deposit in China were inverted and interpreted. The reconstructed density distribution is in good agreement with the one obtained by drill-hole information. Based on the tests in the present study, one can conclude that the Lp-norm inversion using DE is a useful tool for physical property distribution using gravity anomalies. Full article
(This article belongs to the Special Issue Advances in Applied Geophysics)
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Article
Computation of Optimized Electrode Arrays for 3-D Electrical Resistivity Tomography Surveys
Appl. Sci. 2021, 11(14), 6394; https://doi.org/10.3390/app11146394 - 11 Jul 2021
Viewed by 469
Abstract
The present study explores the applicability and effectiveness of an optimization technique applied to electrical resistivity tomography data. The procedure is based on the Jacobian matrix, where the most sensitive measurements are selected from a comprehensive data set to enhance the least resolvable [...] Read more.
The present study explores the applicability and effectiveness of an optimization technique applied to electrical resistivity tomography data. The procedure is based on the Jacobian matrix, where the most sensitive measurements are selected from a comprehensive data set to enhance the least resolvable parameters of the reconstructed model. Two existing inversion programs in two and three dimensions are modified to incorporate this new approach. Both of them are selecting the optimum data from an initial comprehensive data set which is comprised of merged conventional arrays. With the two-dimensional (2-D) optimization approach, the most sensitive measurements are selected from a 2-D survey profile and then a clone of the resulting optimum profile reproduces a three-dimensional (3-D) optimum data set composed of equally spaced parallel lines. In a different approach, with the 3-D optimization technique, the optimum data are selected from a 3-D data set of equally spaced individual parallel lines. Both approaches are compared with Stummer’s optimization technique which is based on the resolution matrix. The Jacobian optimization approach has the advantage of selecting the optimum data set without the need for the solution of the inversion problem since the Jacobian matrix is calculated as part of the forward resistivity problem, thus being faster from previous published approached based on the calculation of the sensitivity matrix. Synthetic 3-D data based on the extension of previous published works for the 2-D optimization case and field data from two case studies in Greece are tested, thus verifying the validity of the present study, where fewer measurements from the initial data set (about 15–50%) are able to reconstruct a model similar with the one produced from the original comprehensive data set. Full article
(This article belongs to the Special Issue Advances in Applied Geophysics)
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Article
Mean Dynamic Topography Modeling Based on Optimal Interpolation from Satellite Gravimetry and Altimetry Data
Appl. Sci. 2021, 11(11), 5286; https://doi.org/10.3390/app11115286 - 07 Jun 2021
Viewed by 511
Abstract
Mean dynamic topography (MDT) is crucial for research in oceanography and climatology. The optimal interpolation method (OIM) is applied to MDT modeling, where the error variance–covariance information of the observations is established. The global geopotential model (GGM) derived from GOCE (Gravity Field and [...] Read more.
Mean dynamic topography (MDT) is crucial for research in oceanography and climatology. The optimal interpolation method (OIM) is applied to MDT modeling, where the error variance–covariance information of the observations is established. The global geopotential model (GGM) derived from GOCE (Gravity Field and Steady-State Ocean Circulation Explorer) gravity data and the mean sea surface model derived from satellite altimetry data are combined to construct MDT. Numerical experiments in the Kuroshio over Japan show that the use of recently released GOCE-derived GGM derives a better MDT compared to the previous models. The MDT solution computed based on the sixth-generation model illustrates a lower level of root mean square error (77.0 mm) compared with the ocean reanalysis data, which is 2.4 mm (5.4 mm) smaller than that derived from the fifth-generation (fourth-generation) model. This illustrates that the accumulation of GOCE data and updated data preprocessing methods can be beneficial for MDT recovery. Moreover, the results show that the OIM outperforms the Gaussian filtering approach, where the geostrophic velocity derived from the OIM method has a smaller misfit against the buoy data, by a magnitude of 10 mm/s (17 mm/s) when the zonal (meridional) component is validated. This is mainly due to the error information of input data being used in the optimal interpolation method, which may obtain more reasonable weights of observations than the Gaussian filtering method. Full article
(This article belongs to the Special Issue Advances in Applied Geophysics)
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Article
Multiscale Post-Seismic Deformation Based on cGNSS Time Series Following the 2015 Lefkas (W. Greece) Mw6.5 Earthquake
Appl. Sci. 2021, 11(11), 4817; https://doi.org/10.3390/app11114817 - 24 May 2021
Cited by 1 | Viewed by 404
Abstract
In the present work, a multiscale post-seismic relaxation mechanism, based on the existence of a distribution in relaxation time, is presented. Assuming an Arrhenius dependence of the relaxation time with uniform distributed activation energy in a mesoscopic scale, a generic logarithmic-type relaxation in [...] Read more.
In the present work, a multiscale post-seismic relaxation mechanism, based on the existence of a distribution in relaxation time, is presented. Assuming an Arrhenius dependence of the relaxation time with uniform distributed activation energy in a mesoscopic scale, a generic logarithmic-type relaxation in a macroscopic scale results. The model was applied in the case of the strong 2015 Lefkas Mw6.5 (W. Greece) earthquake, where continuous GNSS (cGNSS) time series were recorded in a station located in the near vicinity of the epicentral area. The application of the present approach to the Lefkas event fits the observed displacements implied by a distribution of relaxation times in the range τmin ≈ 3.5 days to τmax ≈ 350 days. Full article
(This article belongs to the Special Issue Advances in Applied Geophysics)
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Article
Detection of Preferential Water Flow by Electrical Resistivity Tomography and Self-Potential Method
Appl. Sci. 2021, 11(9), 4224; https://doi.org/10.3390/app11094224 - 06 May 2021
Cited by 1 | Viewed by 537
Abstract
This study explores the hydrogeological conditions of a landslide-prone hillslope in the Upper Mosel valley, Luxembourg. The investigation program included the monitoring of piezometer wells, hydrogeological field tests, analysis of drillcore records, and geophysical surveys. Monitoring and field testing in some of the [...] Read more.
This study explores the hydrogeological conditions of a landslide-prone hillslope in the Upper Mosel valley, Luxembourg. The investigation program included the monitoring of piezometer wells, hydrogeological field tests, analysis of drillcore records, and geophysical surveys. Monitoring and field testing in some of the observation wells indicated very pronounced preferential flow. Electrical resistivity tomography (ERT) and self-potential geophysical methods were employed in the study area for exploration of the morphology of preferential flowpaths. Possible signals associated with flowing groundwater in the subsurface were detected; however, they were diffusively spread over a relatively large zone, which did not allow for the determination of an exact morphology of the conduit. Analysis of drillcore records indicated that flowpaths are caused by the dissolution of thin gypsum interlayers in marls. For better understanding of the site’s hydrogeological settings, a 3D hydrogeological model was compiled. By applying different subsurface flow mechanisms, a hydrogeological model with thin, laterally extending flowpaths embedded in a porous media matrix showed the best correspondence with field observations. Simulated groundwater heads in a preferential flow conduit exactly corresponded with the observed heads in the piezometer wells. This study illustrates how hydrogeological monitoring and geophysical surveys in conjunction with the newest hydrogeological models allow for better conceptualization and parametrization of preferential flow. Full article
(This article belongs to the Special Issue Advances in Applied Geophysics)
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Article
Uncertainty of the 2D Resistivity Survey on the Subsurface Cavities
Appl. Sci. 2021, 11(7), 3143; https://doi.org/10.3390/app11073143 - 01 Apr 2021
Cited by 2 | Viewed by 539
Abstract
We examined the uncertainty of the two-dimensional (2D) resistivity method using conceptual cavity models. The experimental cavity study was conducted to validate numerical model results. Spatial resolution and sensitivity to resistivity perturbations were also assessed using checkerboard tests. Conceptual models were simulated to [...] Read more.
We examined the uncertainty of the two-dimensional (2D) resistivity method using conceptual cavity models. The experimental cavity study was conducted to validate numerical model results. Spatial resolution and sensitivity to resistivity perturbations were also assessed using checkerboard tests. Conceptual models were simulated to generate synthetic resistivity data for dipole-dipole (DD), pole-dipole (PD), Wenner–Schlumberger (WS), and pole-pole (PP) arrays. The synthetically measured resistivity data were inverted to obtain the geoelectric models. The highest anomaly effect (1.46) and variance (24,400 Ω·m) in resistivity data were recovered by the DD array, whereas the PP array obtained the lowest anomaly effect (0.60) and variance (2401 Ω·m) for the shallowest target cavity set at 2.2 m depth. The anomaly effect and variance showed direct dependency on the quality of the inverted models. The DD array provided the highest model resolution that shows relatively distinct anomaly geometries. In contrast, the PD and WS arrays recovered good resolutions, but it is challenging to determine the correct anomaly geometries with them. The PP array reproduced the lowest resolution with less precise anomaly geometries. Moreover, all the tested arrays showed high sensitivity to the resistivity contrasts at shallow depth. The DD and WS arrays displayed the higher sensitivity to the resistivity perturbations compared to the PD and PP arrays. The inverted models showed a reduction in sensitivity, model resolution, and accuracy at deeper depths, creating ambiguity in resistivity model interpretations. Despite these uncertainties, our modeling specified that two-dimensional resistivity imaging is a potential technique to study subsurface cavities. We inferred that the DD array is the most appropriate for cavity surveys. The PD and WS arrays are adequate, while the PP array is the least suitable for cavity studies. Full article
(This article belongs to the Special Issue Advances in Applied Geophysics)
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Article
Seismic Data Interpretation and Petrophysical Analysis of Kabirwala Area Tola (01) Well, Central Indus Basin, Pakistan
Appl. Sci. 2021, 11(7), 2911; https://doi.org/10.3390/app11072911 - 24 Mar 2021
Cited by 2 | Viewed by 608
Abstract
Well logging is a significant procedure that assists geophysicists and geologists with making predictions regarding boreholes and efficiently utilizing and optimizing the drilling process. The current study area is positioned in the Punjab Territory of Pakistan, and the geographic coordinates are 30020′10 N [...] Read more.
Well logging is a significant procedure that assists geophysicists and geologists with making predictions regarding boreholes and efficiently utilizing and optimizing the drilling process. The current study area is positioned in the Punjab Territory of Pakistan, and the geographic coordinates are 30020′10 N and 70043′30 E. The objective of the current research work was to interpret the subsurface structure and reservoir characteristics of the Kabirwala area Tola (01) well, which is located in the Punjab platform, Central Indus Basin, utilizing 2D seismic and well log data. Formation evaluation for hydrocarbon potential using the reservoir properties is performed in this study. For the marked zone of interest, the study also focuses on evaluating the average water saturation, average total porosity, average effective porosity, and net pay thickness. The results of the study show a spotted horizon stone with respect to time and depth as follows: Dunghan formation, 0.9 s and 1080.46 m; Cretaceous Samana Suk formation, 0.96 s and 1174.05 m; Datta formation, 1.08 s and 1400 m; and Warcha formation, 1.24 s and 1810 m. Based on the interpretation of well logs, the purpose of petrophysical analysis was to identify hydrocarbon-bearing zones in the study area. Gamma ray, spontaneous potential, resistivity, neutron, and density log data were utilized. The high zone present in the east–west part of the contour maps may be a possible location of hydrocarbon entrapment, which is further confirmed by the presence of the Tola-01 well. Full article
(This article belongs to the Special Issue Advances in Applied Geophysics)
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Article
Application of the Segmented Correlation Technology in Seismic Communication with Morse Code
Appl. Sci. 2021, 11(4), 1947; https://doi.org/10.3390/app11041947 - 23 Feb 2021
Viewed by 452
Abstract
Seismic communication might promise to revolutionize the theory of seismic waves. However, one of the greatest challenges to its widespread adoption is the difficulty of signal extraction because the seismic waves in the vibration environments, such as seas, streets, city centers and subways, [...] Read more.
Seismic communication might promise to revolutionize the theory of seismic waves. However, one of the greatest challenges to its widespread adoption is the difficulty of signal extraction because the seismic waves in the vibration environments, such as seas, streets, city centers and subways, are very complex. Here, we employ segmented correlation technology with Morse code (SCTMC), which extracts the target signal by cutting the collected data into a series of segments and makes these segments cross-correlate with the decoded signal to process the collected data. To test the effectiveness of the technology, a seismic communication system composed of vibroseis sources and geophones was built in an environment full of other vibration signals. Most notably, it improves the signal-to-noise ratio (SNR), extending the relay distance and suppressing other vibration signals by using technology to deal with seismic data generated by the system. Full article
(This article belongs to the Special Issue Advances in Applied Geophysics)
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Article
Ambient Noise Measurements to Constrain the Geological Structure of the Güevéjar Landslide (S Spain)
Appl. Sci. 2021, 11(4), 1454; https://doi.org/10.3390/app11041454 - 05 Feb 2021
Cited by 2 | Viewed by 746
Abstract
The reactivation of very large landslides may cause severe damage to society. Its prevention and management requires detailed information on the geometry and structure of these landslides, but the use of standard techniques (boreholes) may be prohibitive from an economic point of view. [...] Read more.
The reactivation of very large landslides may cause severe damage to society. Its prevention and management requires detailed information on the geometry and structure of these landslides, but the use of standard techniques (boreholes) may be prohibitive from an economic point of view. To overcome these difficulties, geophysical techniques are of special interest because they allow for studying very large areas at a reasonable cost. In this paper, we present a case study wherein the analysis of ambient noise allowed us to produce a model of a large landslide near Granada (southern Spain). The geometry and location of the failure zone, as well as the assessment of the state of involved materials, were estimated by combining two available boreholes and different geophysical techniques (downhole tests and the spectral analysis of ambient noise, horizontal to vertical spectral ratios (HVSR) and the frequency-wavenumber (f-k) methods). The results have allowed us to differentiate between values within the landslide mass with respect to those of stable materials, and to perform for the first time a comprehensive geological model of this unstable mass. Differences were also observed within the landslide mass (earth flow vs. slide zones), which are attributed to differences in the degree of alteration and the disturbance of the internal structure of materials constituting the landslide mass. These results show that techniques based on the measurement of ambient noise are of special interest for studying very large, highly remolded landslide masses. Full article
(This article belongs to the Special Issue Advances in Applied Geophysics)
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Article
Viscoelastic Model and Synthetic Seismic Data of Eastern Rub’Al-Khali
Appl. Sci. 2021, 11(4), 1401; https://doi.org/10.3390/app11041401 - 04 Feb 2021
Cited by 1 | Viewed by 575
Abstract
The Rub’ Al-Khali basin in Saudi Arabia remains unexplored and lacks data availability due to its remoteness and the challenging nature of its terrain. Thus far, there are neither digital geologic models nor synthetic seismic data from this specific area accessible for testing [...] Read more.
The Rub’ Al-Khali basin in Saudi Arabia remains unexplored and lacks data availability due to its remoteness and the challenging nature of its terrain. Thus far, there are neither digital geologic models nor synthetic seismic data from this specific area accessible for testing research techniques and analysis. In this study, we build a 2D viscoelastic model of the eastern part of the Rub’ Al-Khali basin and generate a corresponding dual-component seismic data set. We compile high-resolution depth models of compressional- and shear-wave velocities, density, as well as compressional- and shear-wave quality factors from published data. The compiled models span Neoproterozoic basement up to Quaternary sand dunes. We then use the finite-difference technique to model the propagation of seismic waves in the compiled viscoelastic medium of eastern Rub’ Al-Khali desert. In particular, we generate vertical and horizontal components of the shot gathers with accuracy to the fourth and second orders in space and time, respectively. The viscoelastic models and synthetic seismic datasets are made available in an open-source site for prospective re-searchers who desire to use them for their research. Users of these datasets are urged to make their findings also accessible to the geoscience community as a way of keeping track of developments related to the Rub’ Al-Khali desert. Full article
(This article belongs to the Special Issue Advances in Applied Geophysics)
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Article
lp Norm Smooth Inversion of Magnetic Anomaly Based on Improved Adaptive Differential Evolution
Appl. Sci. 2021, 11(3), 1072; https://doi.org/10.3390/app11031072 - 25 Jan 2021
Cited by 1 | Viewed by 466
Abstract
Due to the approved applicability of differential evolution (DE) in geophysical problems, the algorithm has been widely concerned. The DE algorithms are mostly applied to solve the geophysical parametric estimation based on specific models, but they are rarely used in solving the physical [...] Read more.
Due to the approved applicability of differential evolution (DE) in geophysical problems, the algorithm has been widely concerned. The DE algorithms are mostly applied to solve the geophysical parametric estimation based on specific models, but they are rarely used in solving the physical property inverse problem of geophysical data. In this paper, an improved adaptive differential evolution is proposed to solve the lp norm magnetic inversion of 2D data, in which the perturbation direction in the mutation strategy is smoothed by using the moving average technique. Besides, a new way of updating the regularization coefficient is introduced to balance the effect of the model constraint adaptively. The inversion results of synthetic models demonstrate that the presented method can obtain a smoother solution and delineate the distributions of abnormal bodies better. In the field example of Zaohuoxi iron ore deposits in China, the reconstructed magnetic source distribution is in good agreement with the one inferred from drilling information. The result shows that the proposed method offers a valuable tool for magnetic anomaly inversion. Full article
(This article belongs to the Special Issue Advances in Applied Geophysics)
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Article
3D Gravity Inversion on Unstructured Grids
Appl. Sci. 2021, 11(2), 722; https://doi.org/10.3390/app11020722 - 13 Jan 2021
Cited by 1 | Viewed by 756
Abstract
Compared with structured grids, unstructured grids are more flexible to model arbitrarily shaped structures. However, based on unstructured grids, gravity inversion results would be discontinuous and hollow because of cell volume and depth variations. To solve this problem, we first analyzed the gradient [...] Read more.
Compared with structured grids, unstructured grids are more flexible to model arbitrarily shaped structures. However, based on unstructured grids, gravity inversion results would be discontinuous and hollow because of cell volume and depth variations. To solve this problem, we first analyzed the gradient of objective function in gradient-based inversion methods, and a new gradient scheme of objective function is developed, which is a derivative with respect to weighted model parameters. The new gradient scheme can more effectively solve the problem with lacking depth resolution than the traditional inversions, and the improvement is not affected by the regularization parameters. Besides, an improved fuzzy c-means clustering combined with spatial constraints is developed to measure property distribution of inverted models in both spatial domain and parameter domain simultaneously. The new inversion method can yield a more internal continuous model, as it encourages cells and their adjacent cells to tend to the same property value. At last, the smooth constraint inversion, the focusing inversion, and the improved fuzzy c-means clustering inversion on unstructured grids are tested on synthetic and measured gravity data to compare and demonstrate the algorithms proposed in this paper. Full article
(This article belongs to the Special Issue Advances in Applied Geophysics)
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Article
Prediction of Shale Gas Reservoirs Using Fluid Mobility Attribute Driven by Post-Stack Seismic Data: A Case Study from Southern China
Appl. Sci. 2021, 11(1), 219; https://doi.org/10.3390/app11010219 - 28 Dec 2020
Cited by 1 | Viewed by 575
Abstract
Paleozoic marine shale gas resources in Southern China present broad prospects for exploration and development. However, previous research has mostly focused on the shale in the Sichuan Basin. The research target of this study is expanded to the Lower Silurian Longmaxi shale outside [...] Read more.
Paleozoic marine shale gas resources in Southern China present broad prospects for exploration and development. However, previous research has mostly focused on the shale in the Sichuan Basin. The research target of this study is expanded to the Lower Silurian Longmaxi shale outside the Sichuan Basin. A prediction scheme of shale gas reservoirs through the frequency-dependent seismic attribute technology is developed to reduce drilling risks of shale gas related to complex geological structure and low exploration level. Extracting frequency-dependent seismic attribute is inseparable from spectral decomposition technology, whereby the matching pursuit algorithm is commonly used. However, frequency interference in MP results in an erroneous time-frequency (TF) spectrum and affects the accuracy of seismic attribute. Firstly, a novel spectral decomposition technology is proposed to minimize the effect of frequency interference by integrating the MP and the ensemble empirical mode decomposition (EEMD). Synthetic and real data tests indicate that the proposed spectral decomposition technology provides a TF spectrum with higher accuracy and resolution than traditional MP. Then, a seismic fluid mobility attribute, extracted from the post-stack seismic data through the proposed spectral decomposition technology, is applied to characterize the shale reservoirs. The application result indicates that the seismic fluid mobility attribute can describe the spatial distribution of shale gas reservoirs well without well control. Based on the seismic fluid mobility attribute section, we have learned that the shale gas enrich areas are located near the bottom of the Longmaxi Formation. The inverted velocity data are also introduced to further verify the reliability of seismic fluid mobility. Finally, the thickness map of gas-bearing shale reservoirs in the Longmaxi Formation is obtained by combining the seismic fluid mobility attribute with the inverted velocity data, and two favorable exploration areas are suggested by analyzing the thickness, structure, and burial depth. The present work can not only be used to evaluate shale gas resources in the early stage of exploration, but also help to design the landing point and trajectory of directional drilling in the development stage. Full article
(This article belongs to the Special Issue Advances in Applied Geophysics)
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Article
Seismic AVOA Inversion for Weak Anisotropy Parameters and Fracture Density in a Monoclinic Medium
Appl. Sci. 2020, 10(15), 5136; https://doi.org/10.3390/app10155136 - 26 Jul 2020
Cited by 2 | Viewed by 689
Abstract
In shale gas development, fracture density is an important lithologic parameter to properly characterize reservoir reconstruction, establish a fracturing scheme, and calculate porosity and permeability. The traditional methods usually assume that the fracture reservoir is one set of aligned vertical fractures, embedded in [...] Read more.
In shale gas development, fracture density is an important lithologic parameter to properly characterize reservoir reconstruction, establish a fracturing scheme, and calculate porosity and permeability. The traditional methods usually assume that the fracture reservoir is one set of aligned vertical fractures, embedded in an isotropic background, and estimate some alternative parameters associated with fracture density. Thus, the low accuracy caused by this simplified model, and the intrinsic errors caused by the indirect substitution, affect the estimation of fracture density. In this paper, the fractured rock of monoclinic symmetry assumes two non-orthogonal vertical fracture sets, embedded in a transversely isotropic background. Firstly, assuming that the fracture radius, width, and orientation are known, a new form of P-wave reflection coefficient, in terms of weak anisotropy (WA) parameters and fracture density, was obtained by substituting the stiffness coefficients of vertical transverse isotropic (VTI) background, normal, and tangential fracture compliances. Then, a linear amplitude versus offset and azimuth (AVOA) inversion method, of WA parameters and fracture density, was constructed by using Bayesian theory. Tests on synthetic data showed that WA parameters, and fracture density, are stably estimated in the case of seismic data containing a moderate noise, which can provide a reliable tool in fracture prediction. Full article
(This article belongs to the Special Issue Advances in Applied Geophysics)
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