Applied Sciences

Research

22 pages, 8364 KiB

Open AccessArticle

Investigation on Spatial Transformation and Proportional Coefficient of Vehicle-Mounted Transient Electromagnetic Detection Environments in Operational Tunnels

by Jinhua Xu, Shaohua Liu, Huaqiu Zhou, Rikai Zhang, Bo Wang, Yikang Xu and Wangping Qian

Appl. Sci. 2022, 12(18), 9303; https://doi.org/10.3390/app12189303 - 16 Sep 2022

Cited by 1 | Viewed by 1211

Abstract

The vehicle-mounted transient electromagnetic method (VMTEM) has been proposed to detect tunnel internal defects in operational tunnels based on the ideal space state. However, the space environment of tunnel surrounding rock is different compared with conventional application fields, so the interpretation of detection [...] Read more.

The vehicle-mounted transient electromagnetic method (VMTEM) has been proposed to detect tunnel internal defects in operational tunnels based on the ideal space state. However, the space environment of tunnel surrounding rock is different compared with conventional application fields, so the interpretation of detection data has certain inadaptability and unreliability. In this paper, three typical space states involved in the detection process of operational tunnels were analyzed. The diffusion law of the transient electromagnetic response signal under the condition of three typical space states was carried out, the proportional coefficient of different space states was determined, and the spatial transformation problem was also determined. Meanwhile, the results obtained by the numerical simulation calculation and numerical derivation calculation were verified by laboratory experiments. The results showed that the correction coefficient of full space to half space was 2.50, and that of three-quarters space to half space was 1.42. The detection process in operational tunnels involves the mutual transformation process of three typical space states. The critical distance that the spatial transformation does not affect is 300 m. In addition, the results of laboratory experiments verified the typical space proportional coefficient and spatial transformation phenomenon well. The results can provide essential ideas for the subsequent space correction of the detection environment in operational tunnels. Full article

(This article belongs to the Special Issue Integration of Methods in Applied Geophysics)

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13 pages, 4072 KiB

Open AccessArticle

AVO-Friendly Velocity Analysis Based on the High-Resolution PCA-Weighted Semblance

by Chunlin Zhang, Liyong Fan, Guiting Chen and Jijun Li

Appl. Sci. 2022, 12(12), 6098; https://doi.org/10.3390/app12126098 - 15 Jun 2022

Cited by 3 | Viewed by 1680

Abstract

Velocity analysis using the semblance spectrum can provide an effective velocity model for advanced seismic imaging technology, in which the picking accuracy of velocity analysis is significantly affected by the resolution of the semblance spectrum. However, the peak broadening of the conventional semblance [...] Read more.

Velocity analysis using the semblance spectrum can provide an effective velocity model for advanced seismic imaging technology, in which the picking accuracy of velocity analysis is significantly affected by the resolution of the semblance spectrum. However, the peak broadening of the conventional semblance spectrum leads to picking uncertainty, and it cannot deal with the amplitude-variation-with-offset (AVO) phenomenon. The well-known AB semblance can process the AVO anomalies, but it has a lower resolution compared with conventional semblance. To improve the resolution of the AB semblance spectrum, we propose a new weighted AB semblance based on principal component analysis (PCA). The principal components or eigenvalues of seismic events are highly sensitive to the components with spatial coherence. Thus, we utilized the principal components of the normal moveout (NMO)-corrected seismic events with different scanning velocities to construct a weighting function. The new function not only has a high resolution for velocity scanning, but it is also a friendly method for the AVO phenomenon. Numerical experiments with the synthetic and field seismic data sets proved that the new method significantly improves resolution and can provide more accurate picked velocities compared with conventional methods. Full article

(This article belongs to the Special Issue Integration of Methods in Applied Geophysics)

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19 pages, 4262 KiB

Open AccessArticle

The Response Mechanism of Borehole Shear-Horizontal Transverse-Electric Seismoelectric Waves to Fluid Salinity

by Weihao Wang, Wenyang Gao, Jinxia Liu, Tribikram Kundu and Zhiwen Cui

Appl. Sci. 2022, 12(10), 5132; https://doi.org/10.3390/app12105132 - 19 May 2022

Cited by 1 | Viewed by 1338

Abstract

The converted electric field in the seismoelectric effect can be used to monitor the salinity of the reservoir. Compared to some conventional excitation methods (e.g., Monopole source), the response law of borehole shear-horizontal transverse-electric (SH-TE) seismoelectric waves to fluid salinity is unique. In [...] Read more.

The converted electric field in the seismoelectric effect can be used to monitor the salinity of the reservoir. Compared to some conventional excitation methods (e.g., Monopole source), the response law of borehole shear-horizontal transverse-electric (SH-TE) seismoelectric waves to fluid salinity is unique. In order to explore its physical mechanism, we study the influence of fluid salinity on borehole SH-TE wave fields in this paper. First, to analyze the effect of salinity on the electric field, we simulate the response for different salinity levels inside and outside the borehole. Then we study the wave fields in case of a radial salinity discontinuity outside the borehole, and simulate the interface response by the secant integral method. Finally, we show the feasibility of using the borehole SH-TE wavefields to estimate the salinity interface position combining the slowness-time coherence (STC) method. The results show that the electric field amplitude changes monotonously with the pore fluid salinity level. However, the borehole fluid salinity has almost no effect on the electric field. This is caused by the excitation method and the low frequency of the sound source. An interface converted electromagnetic wave response is generated when an SH wave passes through the salinity discontinuity interface. The interface position estimation examples show that the borehole SH-TE wave field is a potential method to evaluate the behavior and the location of the interface next to the borehole. Full article

(This article belongs to the Special Issue Integration of Methods in Applied Geophysics)

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20 pages, 9133 KiB

Open AccessArticle

Geophysical Imaging of the Critical Zone along the Eastern Betic Shear Zone (EBSZ), SE Iberian Peninsula

by Handoyo Handoyo, Juan Alcalde, Irene DeFelipe, Imma Palomeras, Raquel Martín-Banda, Julián García-Mayordomo, David Martí, José J. Martínez-Díaz, Juan Miguel Insua-Arévalo, Teresa Teixidó, Ignacio Marzán and Ramon Carbonell

Appl. Sci. 2022, 12(7), 3398; https://doi.org/10.3390/app12073398 - 27 Mar 2022

Cited by 2 | Viewed by 3277

Abstract

The critical zone (CZ) represents the most-shallow subsurface, where the bio-, hydro-, and geospheres interact with anthropogenic activity. To characterize the thickness and lateral variations of the CZ, here we focus on the Eastern Betic Shear Zone (EBSZ), one of the most tectonically [...] Read more.

The critical zone (CZ) represents the most-shallow subsurface, where the bio-, hydro-, and geospheres interact with anthropogenic activity. To characterize the thickness and lateral variations of the CZ, here we focus on the Eastern Betic Shear Zone (EBSZ), one of the most tectonically active regions in the Iberian Peninsula. Within the EBSZ, the Guadalentín Depression is a highly populated area with intensive agricultural activity, where the characterization of the CZ would provide valuable assets for land use management and seismic hazard assessments. To achieve this, we have conducted an interdisciplinary geophysical study along the eastern border of the Guadalentín Depression to characterize the CZ and the architecture of the shallow subsurface. The datasets used include Electrical Resistivity Tomography (ERT), first-arrival travel time seismic tomography, and multichannel analysis of surface waves (MASW). The geophysical datasets combined help to constrain the high-resolution structure of the subsurface and image active fault systems along four transects. The resulting geophysical models have allowed us to interpret the first ~150 m of the subsurface and has revealed: (i) the variable thickness of the CZ; (ii) the CZ relationship between the fault zone and topographic slope; and (iii) the differences in CZ thickness associated with the geological units. Our results provide a method for studying the shallow subsurface of active faults, complementing previous geological models based on paleo-seismological trenches, and can be used to improve the CZ assessment of tectonically active regions. Full article

(This article belongs to the Special Issue Integration of Methods in Applied Geophysics)

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19 pages, 7519 KiB

Open AccessArticle

Data Quality Assessment of Time-Variable Surface Microgravity Surveys in the Southeastern Tibetan Plateau

by Qiuyue Zheng, Xiuyi Yao, Shi Chen, Jinling Yang, Dong Liu and Zhengyu Chen

Appl. Sci. 2022, 12(7), 3310; https://doi.org/10.3390/app12073310 - 24 Mar 2022

Cited by 1 | Viewed by 1596

Abstract

Ground-based time-variable gravimetry with high accuracy is an important approach in monitoring geodynamic processes. The uncertainty of instruments including scale factor (SF) and drift rate are the primary factors affect the quality of observation data. Differing from the conventional gravity adjustment procedure, this [...] Read more.

Ground-based time-variable gravimetry with high accuracy is an important approach in monitoring geodynamic processes. The uncertainty of instruments including scale factor (SF) and drift rate are the primary factors affect the quality of observation data. Differing from the conventional gravity adjustment procedure, this study adopted the modified Bayesian gravity adjustment (MBGA) method, which accounts for the nonlinear drift rate, and where the SF is considered as one of the hyperparameters estimated using Akaike’s Bayesian information criterion. Based on the terrestrial time-variable gravity datasets (2018–2020) from the southeastern Tibetan Plateau, errors caused by nonlinear drift rate and SF were processed quantitatively through analysis of the gravity difference (GD) residuals and the mutual difference of the GD. Additionally, cross validation from absolute gravity (AG) values was also applied. Results suggest that: (1) the drift rate of relavive instruments show nonlinear characteristics, and owing to their different spring features, the drift rate of CG-5 is much larger than that of LCR-G gravimeters; (2) the average bias between the original and optimized SF of the CG-5 gravimeters is approximately 169 ppm, while that of the LCR-G is no more than 63 ppm; (3) comparison of the differences in gravity values (GV) suggests that the uncertainty caused by the nonlinear drift rate is smaller than that attributable to SF. Overall, the novel approach adopted in this study was found effective in removing errors, and shown to be adaptive and robust for large-scale hybrid surface gravity campaign which providing high accuracy gravity data for the geoscience research. Full article

(This article belongs to the Special Issue Integration of Methods in Applied Geophysics)

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15 pages, 3197 KiB

Open AccessArticle

Three-Dimensional Modeling of the Xichang Crust in Sichuan, China by Machine Learning

by Li-Wen Gong, Huai Zhang, Shi Chen and Li-Juan Chen

Appl. Sci. 2022, 12(6), 2955; https://doi.org/10.3390/app12062955 - 14 Mar 2022

Cited by 5 | Viewed by 2209

Abstract

Seismicity and distribution of earthquakes can provide active fault structural information on the crust at a regional scale. The morphology of faults can be derived from the epicentral distribution of micro-earthquakes. In this study, we combined both the relocated earthquake catalogue and related [...] Read more.

Seismicity and distribution of earthquakes can provide active fault structural information on the crust at a regional scale. The morphology of faults can be derived from the epicentral distribution of micro-earthquakes. In this study, we combined both the relocated earthquake catalogue and related preliminary geophysical information for 3D modeling of the crust in the Xichang area, Sichuan province, China. The fault morphology and deep crustal structure were automatically extracted by the machine learning approach, such as the supervised classification and cluster analysis methods. This new 3D crustal model includes the seismic velocity distribution, fault planes in 3D and 3D seismicity. There are many earthquake clusters located in the folded basement and low-velocity zone. Our model revealed the topological relation between the folded basement and faults. Our work show the crustal model derived is supported by the earthquake clusters which in turn controls the morphological characteristics of the crystalline basement in this area. Our use of machine learning techniques can not only be used to predict the refined fault geometry, but also to combine the seismic velocity structure with the known geological information. This 3D crustal model can also be used for geodynamic analysis and simulation of strong motionseismic waves. Full article

(This article belongs to the Special Issue Integration of Methods in Applied Geophysics)

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13 pages, 3664 KiB

Open AccessArticle

A New Stochastic Process of Prestack Inversion for Rock Property Estimation

by Long Yin, Sheng Zhang, Kun Xiang, Yongqiang Ma, Yongzhen Ji, Ke Chen and Dongyu Zheng

Appl. Sci. 2022, 12(5), 2392; https://doi.org/10.3390/app12052392 - 25 Feb 2022

Viewed by 1183

Abstract

In order to enrich the current prestack stochastic inversion theory, we propose a prestack stochastic inversion method based on adaptive particle swarm optimization combined with Markov chain Monte Carlo (MCMC). The MCMC could provide a stochastic optimization approach, and, with the APSO, have [...] Read more.

In order to enrich the current prestack stochastic inversion theory, we propose a prestack stochastic inversion method based on adaptive particle swarm optimization combined with Markov chain Monte Carlo (MCMC). The MCMC could provide a stochastic optimization approach, and, with the APSO, have a better performance in global optimization methods. This method uses logging data to define a preprocessed model space. It also uses Bayesian statistics and Markov chains with a state transition matrix to update and evolve each generation population in the data domain, then adaptive particle swarm optimization is used to find the global optimal value in the finite model space. The method overcomes the problem of over-fitting deterministic inversion and improves the efficiency of stochastic inversion. Meanwhile, the fusion of multiple sources of information can reduce the non-uniqueness of solutions and improve the inversion accuracy. We derive the APSO algorithm in detail, give the specific workflow of prestack stochastic inversion, and verify the validity of the inversion theory through the inversion test of two-dimensional prestack data in real areas. Full article

(This article belongs to the Special Issue Integration of Methods in Applied Geophysics)

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18 pages, 5641 KiB

Open AccessArticle

Borehole Geophysical Joint Inversion to Fully Evaluate Shaly Sandstone Formations

by Alireza Shahin, Michael T. Myers and Lori A. Hathon

Appl. Sci. 2022, 12(3), 1255; https://doi.org/10.3390/app12031255 - 25 Jan 2022

Cited by 3 | Viewed by 2223

Abstract

Simultaneous inversion of sonic, density, and electrical resistivity borehole-derived well logs, has been addressed in literature in recent years. However, this problem is not broadly studied for dual-porosity sandstone formations. In addition, most authors presumed salinity and matrix properties as known parameters in [...] Read more.

Simultaneous inversion of sonic, density, and electrical resistivity borehole-derived well logs, has been addressed in literature in recent years. However, this problem is not broadly studied for dual-porosity sandstone formations. In addition, most authors presumed salinity and matrix properties as known parameters in their studies. We integrate the conservation of mass to model density, a differential effective medium theory for elastic modeling, and a laboratory-supported model for electrical resistivity of dual-porosity sandstones. Utilizing this methodology, we simulate electrical resistivity, sonic, and density well-log data. We develop a stochastic global search engine to jointly invert petrophysical properties. We build a dual-porosity formation with associated petrophysical properties and show the proposed workflow accurately replicates true well-log responses in the oil column, water leg, and transition zone. Local petrophysical properties (microporosity, intergranular porosity, total porosity, and water saturation) and global model parameters (salinity, matrix properties, critical porosity, resistivity lithology exponents, and sonic length scales for different pore networks) are all well recovered. The developed multiphysics calibrated rock models will assist petrophysicists and seismic analysts to identify and distinguish sandstone facies characteristics from well-log and prestack seismic data. Full article

(This article belongs to the Special Issue Integration of Methods in Applied Geophysics)

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26 pages, 10194 KiB

Open AccessFeature PaperArticle

ERT and GPR Prospecting Applied to Unsaturated and Subwater Analogue Archaeological Site in a Full Scale Laboratory

by Luigi Capozzoli, Valeria Giampaolo, Gregory De Martino, Felice Perciante, Vincenzo Lapenna and Enzo Rizzo

Appl. Sci. 2022, 12(3), 1126; https://doi.org/10.3390/app12031126 - 21 Jan 2022

Cited by 6 | Viewed by 2370

Abstract

Geophysical techniques are widely applied in the archaeological field to highlight variations of the physical behaviour of the subsoil due to the presence of ancient and buried remains., Considerable efforts are required to understand the complexity of the relationship between archaeological features and [...] Read more.

Geophysical techniques are widely applied in the archaeological field to highlight variations of the physical behaviour of the subsoil due to the presence of ancient and buried remains., Considerable efforts are required to understand the complexity of the relationship between archaeological features and their geophysical response where saturated conditions occur. In the case of lacustrine and wetland scenarios, geophysical contrasts or electromagnetic signal attenuation effects drastically reduce the capabilities of the geophysical methodologies for the detection of structures in such conditions. To identify the capability of the electrical and electromagnetic methods in different water-saturated scenarios, an experimental activity was performed at the Hydrogeosite CNR laboratory. The test allowed us to analyze the limits and potentialities of an innovative approach based on the combined use of the ground-penetrating radar and 2D and 3D electrical resistivity tomographies. Results showed the effectiveness of the ground-penetrating radar for detecting archaeological remains also in quasi-saturated and underwater scenarios despite the em signal attenuation phenomena; whilst the results obtained involving the resistivity tomographies offered a new perspective for the archaeological purposes due to the use of the loop–loop shaped array. Moreover, the radar signal attenuation, resolution and depth of investigation do not allow to fully characterize the archaeological site as in the case of the scenarios with a limited geophysical contrast (i.e., water-saturated and arid scenarios). The experimental tests show that these limits can be only partially mitigated through the integration of the geophysical methodologies and further efforts are necessary for improving the results obtainable with an integrated use of the adopted geophysical methodologies. Full article

(This article belongs to the Special Issue Integration of Methods in Applied Geophysics)

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17 pages, 4897 KiB

Open AccessArticle

Robust L_p-Norm Inversion for High-Resolution Fluid Contents from Nuclear Magnetic Resonance Measurements

by Houzhu Zhang and Jinhong Chen

Appl. Sci. 2021, 11(23), 11298; https://doi.org/10.3390/app112311298 - 29 Nov 2021

Cited by 1 | Viewed by 1220

Abstract

Fluid content computed from nuclear magnetic resonance (NMR) has proved to be an accurate and reliable tool for petrophysical property estimation. To overcome the limitations of conventional NMR measurements, high spatial resolution NMR (HSR-NMR) has been introduced to achieve the desired resolution for [...] Read more.

Fluid content computed from nuclear magnetic resonance (NMR) has proved to be an accurate and reliable tool for petrophysical property estimation. To overcome the limitations of conventional NMR measurements, high spatial resolution NMR (HSR-NMR) has been introduced to achieve the desired resolution for cores of any size. However, inversion of fluid contents from HSR-NMR data suffers from nonreliable measurements at the ends of the detection coil due to the heterogeneities of the magnetic fields caused by the relatively small size of the coil. A robust L_p-norm inversion algorithm, developed for geophysical inverse problems, has been implemented and applied on the inversion of NMR measurements. The estimated fluid content from L_p inversion matches well with the kerogen content in the cores both visually and quantitively. The resolution of the inverted fluid contents is as high as 1 inch. Further testing on the raw data with large derivations demonstrated that reliable results can only be achieved by using L_p inversion with low p’s values within the range of (1, 1.1). Full article

(This article belongs to the Special Issue Integration of Methods in Applied Geophysics)

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15 pages, 4030 KiB

Open AccessArticle

Integration of ERT, IP and SP Methods in Hard Rock Engineering

by Peng Shao, Yanjun Shang, Muhammad Hasan, Xuetao Yi and He Meng

Appl. Sci. 2021, 11(22), 10752; https://doi.org/10.3390/app112210752 - 15 Nov 2021

Cited by 7 | Viewed by 2681

Abstract

Investigation of a hard rock site for the development of engineered structures mainly depends on the delineation of weathered and unweathered rock, and the fractures/faults. Traditionally, borehole tests are used in such investigations. However, such approaches are expensive and time-consuming, require more equipment, [...] Read more.

Investigation of a hard rock site for the development of engineered structures mainly depends on the delineation of weathered and unweathered rock, and the fractures/faults. Traditionally, borehole tests are used in such investigations. However, such approaches are expensive and time-consuming, require more equipment, cannot be conducted in steep topographic areas, and provide low coverage of the area with point measurements only. Conversely, geophysical methods are non-invasive, economical, and provide large coverage of an area through both vertical and lateral imaging of the subsurface. The geophysical method, electrical resistivity tomography (ERT), can reduce a significant number of expensive drilling tests in geotechnical investigations. However, a geophysical method alone may provide ambiguity in the interpretation of the subsurface, such as electrical resistivity cannot differentiate between water and clay content. Such uncertainty can be improved by the integration of ERT with induced polarization (IP). Similarly, self-potential (SP) can be integrated with other geophysical methods to delineate the groundwater flow. In this contribution, we integrated three geophysical methods (ERT, IP and SP) to delineate the weathered and unweathered rock including the weathered/unweathered transition zone, to detect the fractures/faults, and to map the groundwater flow. Based on ERT, IP and SP results, we develop a geophysical conceptual site model which can be used by site engineers to interpret/implement the findings for build-out. Our approach fills the gaps between the well data and geological model and suggests the most suitable places for the development of engineered structures in the hard rock terrains. Full article

(This article belongs to the Special Issue Integration of Methods in Applied Geophysics)

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11 pages, 4356 KiB

Open AccessArticle

An Improved GPR Method Based on BP and RPCA for Tunnel Lining Defects Detection and Its Application in Qiyue Mountain Tunnel, China

by Dongli Li and Echuan Yan

Appl. Sci. 2021, 11(21), 10234; https://doi.org/10.3390/app112110234 - 1 Nov 2021

Cited by 4 | Viewed by 1765

Abstract

Tunnel lining defects are one of the most common problems that tunnels experience during operation, and they can pose severe safety risks. The most popular nondestructive testing method for detecting tunnel lining defects is ground penetrating radar (GPR), one of the basic geophysical [...] Read more.

Tunnel lining defects are one of the most common problems that tunnels experience during operation, and they can pose severe safety risks. The most popular nondestructive testing method for detecting tunnel lining defects is ground penetrating radar (GPR), one of the basic geophysical applications. However, detection responses might differ significantly from the real shape of tunnel lining defects, making it challenging to identify and interpret. When data quality is poor, interpretation and identification become more challenging, resulting in a high cost of tunnel repairs. The improved back projection (BP) imaging and robust principal component analysis (RPCA) are used in this work to offer a GPR data processing method. Even in the event of poor data quality, our method could recover GPR responses, allowing the shapes and locations of tunnel lining flaws to be clearly depicted. With BP imaging, this approach recovers the tunnel defects’ responses to better forms and positions, and with RPCA, it further isolates the target imaging from clutters. Several synthetic data demonstrate that the approach presented in this work may successfully repair and extract the positions and forms of lining defects, making them easier to identify and comprehend. Furthermore, our technique was used to GPR data gathered from the Qiyue Mountain Tunnel in China, yielding more accurate findings than the traditional method, which was validated by the actual scenario to illustrate the efficiency of our method on real data. Full article

(This article belongs to the Special Issue Integration of Methods in Applied Geophysics)

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14 pages, 6583 KiB

Open AccessArticle

Crustal Electrical Structure of the Zhaheba Complex Imaged by Magnetotelluric Data and Its Tectonic Implications

by Pingchuan Zhang, Changqing Yu and Xiangzhi Zeng

Appl. Sci. 2021, 11(21), 10013; https://doi.org/10.3390/app112110013 - 26 Oct 2021

Cited by 1 | Viewed by 1409

Abstract

A Magnetotelluric profile stretching northward from the Wulungu Depression (on the northern margin of the Junggar Basin) to the Dulate arc (crossing the Zhaheba–Aermantai ophiolite belt) was carried out in an attempt to probe the crustal structure and properties of the East Junggar, [...] Read more.

A Magnetotelluric profile stretching northward from the Wulungu Depression (on the northern margin of the Junggar Basin) to the Dulate arc (crossing the Zhaheba–Aermantai ophiolite belt) was carried out in an attempt to probe the crustal structure and properties of the East Junggar, NW China. Along the profile, the inversion model was used to determine the electrical structure of the crust and uppermost mantle. The results revealed that the crust of the eastern Junggar Basin is composed of the shallow low resistivity layer and underlying high resistivity bodies. There is a crustal detachment in the basement: the upper layer is a Hercynian folded basement and the lower is a Precambrian basement. The Zhaheba complex is characterized by relatively high resistivity, with a thickness of ~5 km, the bottom controlled by the Zhaheba–Aermantai fault. The crust of the Yemaquan arc is composed of the residual continental crust, characterized by stable resistance. The exposed intrusive rocks are characterized by irregular resistors. The crust of the Dulate arc is characterized by relatively low resistivity. The shallow low resistivity layers represent the Zhaheba depression composed of the Devonian-Permian volcanic and sedimentary rocks. The crustal conductive anomalies are related to the magmatism and mechanism of metal deposits in the post-collision period. Full article

(This article belongs to the Special Issue Integration of Methods in Applied Geophysics)

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23 pages, 10678 KiB

Open AccessArticle

An Empirical Correlation between the Residual Gravity Anomaly and the H/V Predominant Period in Urban Areas and Its Dependence on Geology in Andean Forearc Basins

by José Maringue, Esteban Sáez and Gonzalo Yañez

Appl. Sci. 2021, 11(20), 9462; https://doi.org/10.3390/app11209462 - 12 Oct 2021

Cited by 3 | Viewed by 1753

Abstract

The study of site amplification effects is crucial to assess earthquake hazards that can produce great damage in urban structures. In this context, the gravity and the ambient noise horizontal-to-vertical spectral ratio (H/V) are two of the most used geophysical methods to study [...] Read more.

The study of site amplification effects is crucial to assess earthquake hazards that can produce great damage in urban structures. In this context, the gravity and the ambient noise horizontal-to-vertical spectral ratio (H/V) are two of the most used geophysical methods to study the properties of the subsoil, which are essential to estimate seismic amplification. Even though these methods have been used complementarily, a correlation between them has not been thoroughly studied. Understanding this correlation and how it depends on geology could be important to use one method as an estimator of the other and to make a distinction between the seismic and gravimetric basement. In this research, a comparison between the residual gravity anomaly and the H/V predominant period is performed using a long dataset from different projects on sedimentary basins in a group of the most important cities in Chile. To simplify the geological information, a seismic classification is used for soils, which considers the Vs30 and the predominant period of vibration (T0). The results of this comparison show a direct correlation between both parameters, the higher the negative residual gravity anomaly the higher the H/V predominant period. This correlation improves when only soft soils are considered, increasing the R2 value in more than a 50% in all the individual cities with respect to the overall correlation. When all the cities are considered, the R2 value for soft soils increases up to 0.87. These results suggest that the ideal geological background for this correlation is when a soft soil layer overlies a homogeneous bedrock. Heterogeneities in the bedrock and in the soil column add dispersion to the correlation. Additionally, the comparison between the depth to basement inferred by both methods show differences of less than 15% in soft sites; in denser sites, the difference increases up to 30% and the definition of a clear H/V peak is more difficult. In general, the gravimetric basement is deeper than the seismic one. However, gravimetric depths to basement can be under/over-estimated in zones with a heterogeneous soil column. Full article

(This article belongs to the Special Issue Integration of Methods in Applied Geophysics)

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16 pages, 5498 KiB

Open AccessArticle

Application of Integrated Geophysical Methods for Site Suitability of Research Infrastructures (RIs) in China

by Yan-Jun Shang, Chang-Gen Yang, Wei-Jun Jin, Yan-Wei Chen, Muhammad Hasan, Yue Wang, Kun Li, Da-Ming Lin and Min Zhou

Appl. Sci. 2021, 11(18), 8666; https://doi.org/10.3390/app11188666 - 17 Sep 2021

Cited by 7 | Viewed by 2428

Abstract

Research Infrastructures (RIs) are essential to achieve excellence in innovative scientific research. However, because of limited land availability and specific geological requirements, evaluating the viability of a site for a new RI can be a challenging task. Stringent safety construction requirements include developing [...] Read more.

Research Infrastructures (RIs) are essential to achieve excellence in innovative scientific research. However, because of limited land availability and specific geological requirements, evaluating the viability of a site for a new RI can be a challenging task. Stringent safety construction requirements include developing site-specific architectural and geoengineering solutions, minimizing construction disturbances, and reinforcing rock and soil in a timely fashion. For successful development of the RIs in China, such as the Daya Bay Neutrino Laboratory (DBNL) and the China Spallation Neutron Source (CSNS), an integrated approach of joint geophysical methods including the electrical resistivity tomography (ERT), controlled-source audio-frequency magneto telluric (CSAMT)), gravity and seismic refraction methods, and geological mapping and surveys were carried out. Geophysical parameters, such as electrical resistivity, density, and seismic velocity, show inverse proportion to the degree of rock fracturing or weathering. The results show that the low values of geophysical parameters suggest the weathered/fractured rock, while high values reveal the fresh bedrock. The Engineering Geological Suitability Index (EGSI) value can represent the individual EGSI values at a constant and summed over varying depths. EGSI methodology is an improvement on the existing siting process and has been applied to CSNS. Our integrated approach provides clearer insight into the subsurface for site suitability of RIs in challenging geological engineering conditions and removes any ambiguity caused by a single geophysical parameter. The obtained geological knowledge of the area not only provides engineers with much-needed information about the construction conditions of a potential site but also gives scientists the opportunity to explore the local geology. In this study, we demonstrate our innovative approach for siting RIs, as demonstrated by the synthetic evaluation of the site location and utilization for two established RIs (DBNL and CSNS). Full article

(This article belongs to the Special Issue Integration of Methods in Applied Geophysics)

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21 pages, 112676 KiB

Open AccessArticle

Use of Seismic Spectral Decomposition, Phase, and Relative Geologic Age as Attributes to Improve Quantitative Porosity Prediction in the Daqing Field, China

by David Mora Calderon, John P. Castagna, Ramses Meza, Shumin Chen and Renqi Jiang

Appl. Sci. 2021, 11(17), 8034; https://doi.org/10.3390/app11178034 - 30 Aug 2021

Cited by 4 | Viewed by 2262

Abstract

The high production potential of the Daqing oilfield in China is recognized for seismically thin sand bodies that usually are not resolved with conventional seismic data. The present study assesses the usefulness of applying seismic multi-attribute analysis to bandwidth extended data in resolving [...] Read more.

The high production potential of the Daqing oilfield in China is recognized for seismically thin sand bodies that usually are not resolved with conventional seismic data. The present study assesses the usefulness of applying seismic multi-attribute analysis to bandwidth extended data in resolving and making inferences about these thin layers. In thin layers, tuning can obscure relationships between seismic amplitude and rock properties. In such cases, the seismic phase varies with the layer impedance and may hence aid in reservoir characterization. A seismically derived relative geologic age may also be a useful attribute in predicting rock properties because it helps define the stratigraphic position of a layer. When utilized in multi-attribute analysis in the Daqing field, spectral decomposition amplitude, phase, and a relative geological age attribute to improved prediction of well log effective porosity from seismic data and are preferentially selected by stepwise regression. The study follows standard methodology by implementing seismic multi-attribute analysis and discusses the improvement of applying it to bandwidth extended data. This will include a combination of attributes such as relative geologic age, phase, amplitude, and the magnitude components of spectrally decomposed data. Full article

(This article belongs to the Special Issue Integration of Methods in Applied Geophysics)

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19 pages, 7877 KiB

Open AccessArticle

Multi-Parametric Imaging of Etruscan Chamber Tombs: Grotte Di Castro Case Study (Italy)

by Vincenzo Sapia, Valerio Materni, Federico Florindo, Marco Marchetti, Andrea Gasparini, Nunzia Voltattorni, Riccardo Civico, Fabio Giannattasio, Luca Miconi, Maria Flavia Marabottini and Stefano Urbini

Appl. Sci. 2021, 11(17), 7875; https://doi.org/10.3390/app11177875 - 26 Aug 2021

Cited by 2 | Viewed by 1927

Abstract

A multi-parametric approach that involves the use of different geophysical methods coupled with geochemical data allowed us to identify undiscovered archeological burials in a funerary area of the Grotte di Castro Etruscan settlement. In particular, we tested the suitability of the capacitive resistivity [...] Read more.

A multi-parametric approach that involves the use of different geophysical methods coupled with geochemical data allowed us to identify undiscovered archeological burials in a funerary area of the Grotte di Castro Etruscan settlement. In particular, we tested the suitability of the capacitive resistivity method and the presence of Radon in soil for the identification of burials calibrating their outcomes over coincident survey profiles with standard geophysical techniques routinely applied for archaeological prospections. Soil Radon data were acquired both in a grid and along a profile to highlight anomalous gas concentrations, whereas electrical resistivity and ground-penetrating radar measurements were conducted on overlapping profiles to depict the electrical and electromagnetic subsurface distribution. Data integration showed a series of anomalies, suggesting the presence of multiple burials starting from a depth of approximately 1.5 m below the terrain surface. Slight anomalies of Radon in the soil were found to correspond to most of the recovered geophysical ones. Our results pointed out the effectiveness of geophysical method integration in archeological prospecting with the novelty of the joint use of Radon in soil measurements and capacitive resistivity tomography. The latter provided reliable results and can be considered as a standalone technique in archaeological surveys. Full article

(This article belongs to the Special Issue Integration of Methods in Applied Geophysics)

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17 pages, 106629 KiB

Open AccessArticle

Automated Fault Detection and Extraction under Gas Chimneys Using Hybrid Discontinuity Attributes

by Qazi Sohail Imran, Numair A. Siddiqui, Abdul Halim Abdul Latiff, Yasir Bashir, Muhammad Khan, Kamran Qureshi, Abd Al-Salam Al-Masgari, Nisar Ahmed and Muhammad Jamil

Appl. Sci. 2021, 11(16), 7218; https://doi.org/10.3390/app11167218 - 5 Aug 2021

Cited by 13 | Viewed by 4193

Abstract

3D-seismic data have increasingly shifted seismic interpretation work from a horizons-based to a volume-based focus over the past decade. The size of the identification and mapping work has therefore become difficult and requires faster and better tools. Faults, for instance, are one of [...] Read more.

3D-seismic data have increasingly shifted seismic interpretation work from a horizons-based to a volume-based focus over the past decade. The size of the identification and mapping work has therefore become difficult and requires faster and better tools. Faults, for instance, are one of the most significant features of subsurface geology interpreted from seismic data. Detailed fault interpretation is very important in reservoir characterization and modeling. The conventional manual fault picking is a time-consuming and inefficient process. It becomes more challenging and error-prone when dealing with poor quality seismic data under gas chimneys. Several seismic attributes are available for faults and discontinuity detection and are applied with varying degrees of success. We present a hybrid workflow that combines a semblance-based fault likelihood attribute with a conventional ant-tracking attribute. This innovative workflow generates optimized discontinuity volumes for fault detection and automatic extraction. The data optimization and conditioning processes are applied to suppress random and coherent noise first, and then a combination of seismic attributes is generated and co-rendered to enhance the discontinuities. The result is the volume with razor sharp discontinuities which are tracked and extracted automatically. Contrary to several available fault tracking techniques that use local seismic continuity like coherency attributes, our hybrid method is based on directed semblance, which incorporates aspects of Dave Hale’s superior fault-oriented semblance algorithm. The methodology is applied on a complex faulted reservoir interval under gas chimneys in a Malaysian basin, yet the results were promising. Despite the poor data quality, the methodology led to detailed discontinuity information with several major and minor faults extracted automatically. This hybrid approach not only improved the fault tracking accuracy but also significantly reduced the fault interpretation time and associated uncertainty. It is equally helpful in detecting any seismic objects like fracture, chimneys, and stratigraphic features. Full article

(This article belongs to the Special Issue Integration of Methods in Applied Geophysics)

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18 pages, 11078 KiB

Open AccessArticle

Theoretical and Experimental Investigation of Vehicle-Mounted Transient Electromagnetic Method Detection for Internal Defects of Operational Tunnels

by Wangping Qian, Honghui Li, Jun Yu and Zhenyuan Gu

Appl. Sci. 2021, 11(15), 6906; https://doi.org/10.3390/app11156906 - 27 Jul 2021

Cited by 3 | Viewed by 1662

Abstract

With the durable operation of high-speed railway tunnels in China, many tunnel defects successively appeared in the tunnel lining structure and gradually threatened the safe operation of the tunnels. In the limited maintenance time of high-speed railways, it is urgent to find out [...] Read more.

With the durable operation of high-speed railway tunnels in China, many tunnel defects successively appeared in the tunnel lining structure and gradually threatened the safe operation of the tunnels. In the limited maintenance time of high-speed railways, it is urgent to find out and maintain tunnel defects, especially internal defects. We propose an applied detection technology called the vehicle-mounted transient electromagnetic method (TEM). The detection technology aims to rapidly detect and locate the internal defects of the lining structure throughout the entire tunnel. Firstly, we investigate tunnel defects in detail and introduce the rapid detection method. Secondly, we analyze the principle and process of vehicle-mounted TEM. Thirdly, the rationality and applicability of vehicle-mounted TEM are verified by three different methods, including theoretical analysis, numerical simulation, and laboratory experiment. Finally, we compare the inversion results of experimental data under the two conditions. The results illustrate that tunnel surface defects are the external manifestations and characteristics of tunnel defects, while the forms of surface defects are directly related to internal defects. This detection method is suitable for the significant resistivity difference between tunnel defects and surrounding rocks, and its rationality is effectively validated. Furthermore, the apparent resistivity results reveal that there is a low resistivity region in front of the transmitter coil, and that the relative position can be preliminarily judged. The research results can provide a potential and significant application technology for the rapid detection of tunnel defects. Full article

(This article belongs to the Special Issue Integration of Methods in Applied Geophysics)

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35 pages, 113921 KiB

Open AccessArticle

Spatiotemporal Properties of Seismicity and Variations of Shear-Wave Splitting Parameters in the Western Gulf of Corinth (Greece)

by Vasilis Kapetanidis, Georgios Michas, George Kaviris and Filippos Vallianatos

Appl. Sci. 2021, 11(14), 6573; https://doi.org/10.3390/app11146573 - 16 Jul 2021

Cited by 10 | Viewed by 2115

Abstract

The Western Gulf of Corinth (WGoC) exhibits significant seismicity patterns, combining intense microseismic background activity with both seismic swarms and short-lived aftershock sequences. Herein, we present a catalogue of ~9000 events, derived by manual analysis and double-difference relocation, for the seismicity of the [...] Read more.

The Western Gulf of Corinth (WGoC) exhibits significant seismicity patterns, combining intense microseismic background activity with both seismic swarms and short-lived aftershock sequences. Herein, we present a catalogue of ~9000 events, derived by manual analysis and double-difference relocation, for the seismicity of the WGoC during 2013–2014. The high spatial resolution of the hypocentral distribution permitted the delineation of the activated structures and their relation to major mapped faults on the surface. The spatiotemporal analysis of seismicity revealed a 32-km-long earthquake migration pattern, related to pore-pressure diffusion, triggering moderate mainshock-aftershock sequences, as fluids propagated eastwards in the course of ~15 months. The anisotropic properties of the upper crust were examined through automatic shear-wave splitting (SWS) analysis, with over 2000 SWS measurements at local stations. An average fast shear-wave polarization direction of N98.8°E ± 2.8° was determined, consistent with the direction of the maximum horizontal regional stress. Temporal variations of normalized time-delays between fast and slow shear-waves imply alterations in the level of stress or microcrack fluid saturation during the long-lasting pore-pressure diffusion episode, particularly before major events. The present study provides novel insights regarding seismicity patterns, active fault structures, anisotropic properties of the upper crust and triggering mechanisms of seismicity in the WGoC. Full article

(This article belongs to the Special Issue Integration of Methods in Applied Geophysics)

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14 pages, 4915 KiB

Open AccessArticle

Traffic Monitoring System Based on Deep Learning and Seismometer Data

by Ahmad Bahaa Ahmad and Takeshi Tsuji

Appl. Sci. 2021, 11(10), 4590; https://doi.org/10.3390/app11104590 - 18 May 2021

Cited by 14 | Viewed by 5332

Abstract

Currently, vehicle classification in roadway-based techniques depends mainly on photos/videos collected by an over-roadway camera or on the magnetic characteristics of vehicles. However, camera-based techniques are criticized for potentially violating the privacy of vehicle occupants and exposing their identity, and vehicles can evade [...] Read more.

Currently, vehicle classification in roadway-based techniques depends mainly on photos/videos collected by an over-roadway camera or on the magnetic characteristics of vehicles. However, camera-based techniques are criticized for potentially violating the privacy of vehicle occupants and exposing their identity, and vehicles can evade detection when they are obscured by larger vehicles. Here, we evaluate methods of identifying and classifying vehicles on the basis of seismic data. Vehicle identification from seismic signals is considered a difficult task because of interference by various noise. By analogy with techniques used in speech recognition, we used different artificial intelligence techniques to extract features of three, different-sized vehicles (buses, cars, motorcycles) and seismic noise. We investigated the application of a deep neural network (DNN), a convolutional neural network (CNN), and a recurrent neural network (RNN) to classify vehicles on the basis of vertical-component seismic data recorded by geophones. The neural networks were trained on 5580 unprocessed seismic records and achieved excellent training accuracy (99%). They were also tested on large datasets representing periods as long as 1 month to check their stability. We found that CNN was the most satisfactory approach, reaching 96% accuracy and detecting multiple vehicle classes at the same time at a low computational cost. Our findings show that seismic methods can be used for traffic monitoring and security purposes without violating the privacy of vehicle occupants, offering greater efficiency and lower costs than current methods. A similar approach may be useful for other types of transportation, such as vessels and airplanes. Full article

(This article belongs to the Special Issue Integration of Methods in Applied Geophysics)

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