Edge detection, depth estimation and 3D-inverse modelling of the Red Sea and Zagros gravity anomalies using the gravity data extracted from EGM2008 Geo-potential Model

Using geophysical methods and measuring physical properties of subsurface rocks are good solutions for investigating the subsurface structures and exploring underground buried resources (such as oil, gas, water, minerals, etc.). This research investigates the anomaly sources of Zagros and the Red Sea by using the derivative filters, regularized filters, analytic signal, local-phase filter, 3D-inverse modelling with the Li-Oldenburg method. For this purpose, these filters are first applied to artificial models to determine the capability of each of these filters, a comparisons is also will be made between edge detection filters and finally applied to the real gravity of Zagros and Red Sea regions (taken from the EGM2008 Global Model). The overall result is that the effective depth of the sources of gravity anomalies of the Red Sea is approximately 200 km, and incoherently, up to a depth of 300 km. The effective depth of the Zagros anomalies sources is also about 180 km and since then it has continued inconsistently up to 400 km.

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Joint Gravity and Seismic Reflection Methods to Characterize the Deep Aquifers in Arid Ain El Beidha Plain (Central Tunisia, North Africa)

Water ◽

10.3390/w13091310 ◽

2021 ◽

Vol 13 (9) ◽

pp. 1310

Author(s):

Hajer Azaiez ◽

Hakim Gabtni ◽

Mourad Bédir

Keyword(s):

Seismic Reflection ◽

Large Scale ◽

Seismic Analysis ◽

Gravity Data ◽

Geophysical Methods ◽

Gravity Anomalies ◽

Integrated Approach ◽

Central Tunisia ◽

Deep Aquifers ◽

Advanced Analysis

Electric resistivity sounding and tomography, as well as electromagnetic sounding, are the classical methods frequently used for hydrogeological studies. In this work, we propose the development and implementation of an original integrated approach using the unconventional hydro–geophysical methods of gravity and seismic reflection for the fast, large–scale characterization of hydrogeological potential using the Ain El Beidha plain (central Tunisia) as an analogue. Extending the values of vintage petroleum seismic reflection profiles and gravity data, in conjunction with available geological and hydrogeological information, we performed an advanced analysis to characterize the geometry of deep tertiary (Oligocene and Eocene) aquifers in this arid area. Residual and tilt angle gravity maps revealed that most gravity anomalies have a short wavelength. The study area was mainly composed of three major areas: the Oued Ben Zitoun and Ain El Beidha basins, which are both related to negative gravity trends corresponding to low–density subsiding depocenters. These basins are separated by an important NE–SW trend called “El Gonna–J. El Mguataa–Kroumet Zemla” gravity high. Evaluation of the superposition of detected lineaments and Euler deconvolution solutions’ maps showed several NE–SW and N–S relay system faults. The 3D density inversion model using a lateral and vertical cutting plane suggested the presence of two different tectonic styles (thin VS thick). Results from the gravity analysis were in concordance with the seismic analysis. The deep Oligocene and Eocene seismic horizons were calibrated to the hydraulic wells and surrounding outcrops. Oligocene and Eocene geological reservoirs appear very fractured and compartmented. The faulting network also plays an important role in enhancing groundwater recharge process of the Oligocene and Eocene aquifers. Finally, generated isochron maps provided an excellent opportunity to develop future comprehensive exploration surveys over smaller and more favorable areas’ sub–basins.

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Shallow vs. Deep Subsurface Structures of Central Luconia Province, Offshore Malaysia Reveal by Aeromagnetic, Airborne Gravity and Seismic Data

Applied Sciences ◽

10.3390/app11115095 ◽

2021 ◽

Vol 11 (11) ◽

pp. 5095

Author(s):

Siti Nur Fathiyah Jamaludin ◽

Manuel Pubellier ◽

Benjamin Sautter

Keyword(s):

Gravity Data ◽

Gravity Anomalies ◽

Airborne Gravity ◽

Deep Subsurface ◽

Southern Boundary ◽

Shallow Subsurface ◽

Subsurface Structures ◽

Crustal Block ◽

Central Luconia ◽

Seismic Lines

Across the Luconia continental shelf, the nature and structures of the crust are lacking geological understanding and precise characterization. Newly acquired, aeromagnetic, and airborne gravity data were used to assess deep and shallow sub-surface signals within the Central Luconia Province, off the coast of Sarawak, offshore Malaysia. Regional aeromagnetic anomalies appear to primarily reflect deep crustal features while depth (Z) tensors of airborne gravity anomalies evidence shallow subsurface structures. Strike directions of the interpreted structural trend on aeromagnetic and airborne gravity anomalies maps are measured and plotted into rose diagrams to distinguish the structural orientations for all datasets. Signature patterns extracted from the depth profiles were correlated with parallel seismic lines and nearest exploration wells and coincide well with the top of carbonate for Cycle IV/V and structures seen within the Cycle I and II sediments. The orientation of faults/lineaments at shallower depth is dominated by a NW-SE orientation, similar with the faults extracted from two recently published structural maps. Deeper subsurface sections yielded E-W to NWW-SEE dominant directions which were never presented in the published literature. The E-W oriented anomalies are postulated to represent the remnants of the accretion between the Luconia crustal block and southern boundary of the Palawan block. The NW-SE trend follows the same direction as prominent faults in the region. The insight into shallow and deep subsurface structures in Central Luconia Province imaged through airborne gravity and aeromagnetic data should provide guidelines and complementary information for regional structural studies for this area, particularly in combination with detailed seismic interpretation. Further evaluation on the response of Air-FTG® gravity and aeromagnetic could lead to the zonation of potential basement highs and hydrocarbon prospects in this area.

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Study of salt structures from gravity and seismic data in Santos Basin, Brazil

Geofísica Internacional ◽

10.22201/igeof.00167169p.2016.55.3.1722 ◽

2016 ◽

Vol 55 (3) ◽

Author(s):

Renata Regina Constantino Regina Constantino ◽

Eder Cassola Molina ◽

Iata Anderson de Souza

Keyword(s):

Gravity Anomaly ◽

Crustal Structure ◽

Gravity Data ◽

Geophysical Methods ◽

Gravity Anomalies ◽

Sedimentary Basins ◽

Final Conclusion ◽

Additional Information ◽

Salt Layer ◽

Modelling Studies

Seismic is one of the main methods used for the identification of structures and stratigraphic studies in sedimentary basins. In the Santos Basin, numerous 2D and 3D seismic surveys are being conducted in order to get a better ima-ge of the geological section to depths beyond the base of salt layer. Crustal modelling studies that make joint interpretation of seismic and gravity data are found in the literature, however there are few studies that relate gravity anomalies directly to salt structures. This work aims to associate gravity anomalies with salt structures from seismic and gravimetric interpretation. For studies aimed to model the crustal structure from gravity field data, the knowledge of two major discontinuities is required, the basement and the Moho. Such interfaces are often not easily seen by seismic and so, during this study, they were found by different methods involving analysis of gravity anomalies. The other interfaces involving density contrasts were analyzed based on seismic interpretation. The results showed that the obtained seismic geological interpretations may provide additional information when compared to gravity anomaly data. In all the modelled profiles, some geological information of the Santos Basin that are not visible in the seismic, could be interpreted according to the geological model and the adjustment of gravity anomaly curves. As a final conclusion of this work, it is suggested that the combined analysis of the two cited geophysical methods, can provide important information about the crustal structure and to assist in modelling the salt layer.

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A discussion on the structure and evolution of the Red Sea and the nature of the Red Sea, Gulf of Aden and Ethiopia rift junction - Seismic and gravity data from afar in relation to surrounding areas

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1970.0040 ◽

1970 ◽

Vol 267 (1181) ◽

pp. 339-358 ◽

Cited By ~ 25

Keyword(s):

Red Sea ◽

Gravity Data ◽

Gravity Anomalies ◽

Seismic Energy ◽

Free Air ◽

Seismic Surface Waves ◽

Free Air Gravity ◽

Surrounding Areas ◽

Tectonic Features ◽

Afar Triangle

The Afar triangle is bordered, to the west, by a seismic belt running along and on top of the escarpment. Seventy-five percent of the seismic energy of the area is released along this belt. The epicentre distribution along the western escarpment coincides either with major north-south marginal tectonic features or with cross-rift faulting. A second epicentre lineation runs at N 15° E through central Afar. To the south-east, in the region of the Gulf of Tadjura, epicentre locations offer no distinct lineation. The sum of the free-air gravity anomalies over Afar is almost zero; Bouguer values are generally negative and strictly proportional to elevation. Absolute Bouguer positive values are found only over volcanic centres and along the northeastern coast; their maximum does not compare with the positive values found over the nearby Red Sea trough. Evidence based on attenuation and dispersion of seismic surface waves and on gravity profiles suggests a continental crustal structure of relatively ‘standard’ thickness under the Afar triangle.

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A least‐squares minimization approach to depth determination from numerical horizontal gravity gradients

Geophysics ◽

10.1190/1.1443857 ◽

1995 ◽

Vol 60 (4) ◽

pp. 1259-1260 ◽

Cited By ~ 14

Author(s):

El‐Sayed Mohamed Abdelrahman ◽

Sharafeldin Mahmoud Sharafeldin

Keyword(s):

Least Squares ◽

Least Squares Method ◽

Gravity Data ◽

Gravity Anomalies ◽

Depth Estimation ◽

Horizontal Cylinder ◽

Theory And Practice ◽

Gravity Gradient ◽

Quantitative Interpretation ◽

Gravity Gradients

The sphere and the horizontal cylinder models can be very useful in quantitative interpretation of gravity data measured in a small area over buried structures. Several graphical and numerical methods have been developed by many workers for interpreting the residual gravity anomalies caused by these models to find the depth of most geologic structures. Excellent reviews are given in Saxov and Nygaard (1953) and Bowin et al. (1986). The numerical approaches (Odegard and Berg, 1965; Gupta, 1983; Sharma and Geldart, 1968; Lines and Treitel, 1984; and Shaw and Agarwal, 1990) may have advantages in theory and practice over graphical depth estimation techniques (Pick et al., 1973: Nettleton, 1976; Telford et al., 1976). However, effective quantitative interpretation procedures using the least‐squares method based on the analytical expression of simple numerical horizontal gravity gradient anomalies are yet to be developed.

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Identifying Subsurface Structures beneath the Sumani and Sianok Segments of the Great Sumatran Fault using Combined Geophysical Methods

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/873/1/012004 ◽

2021 ◽

Vol 873 (1) ◽

pp. 012004

Author(s):

Harman Amir ◽

Satria Bijaksana ◽

Darharta Dahrin ◽

Andri Dian Nugraha ◽

Ilham Arisbaya

Keyword(s):

Magnetic Measurements ◽

Gravity Data ◽

Bouguer Anomaly ◽

Geophysical Methods ◽

Fault System ◽

Subsurface Structures ◽

Gravity And Magnetic ◽

Geophysical Study ◽

Anomaly Map ◽

Sumatran Fault

Abstract The 1900 km long Great Sumatran Fault is a complex active fault system that is divided into segments that include the Sumani and Sianok segments in a rather densely populated area of the West Sumatra Province. Major earthquakes have occurred in these two segments that include the March 2007 Sumatra earthquake. Mitigating future risks requires a better understanding of these complex segments. To identify the subsurface structures beneath the Sumani and Sianok segments, we are conducting combined geophysical study that include gravity and magnetic. Gravity data were obtained from the published regional Bouguer anomaly map of the area around these two segments. The measurements from which the map was derived were rather sparse. Thus, more detailed magnetic measurements were carried out in this study. Magnetic measurements were also expected to be more sensitive as the predominant rocks in the study area are volcanic as well as other type of intrusive rocks. These gravity and magnetic analyses were complemented by seismicity data that include relocated seismicity data that will enhance the modelling of subsurface structures. Progress of this study will be reported. Challenges and obstacles will also be presented.

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Gravity Analysis for Subsurface Characterization and Depth Estimation of Muda River Basin, Kedah, Peninsular Malaysia

Applied Sciences ◽

10.3390/app11146363 ◽

2021 ◽

Vol 11 (14) ◽

pp. 6363

Author(s):

Muhammad Noor Amin Zakariah ◽

Norsyafina Roslan ◽

Norasiah Sulaiman ◽

Sean Cheong Heng Lee ◽

Umar Hamzah ◽

...

Keyword(s):

River Basin ◽

Rock Type ◽

Gravity Data ◽

Power Spectral Analysis ◽

Depth Estimation ◽

Structural Features ◽

Peninsular Malaysia ◽

Gravity Survey ◽

Basement Rock ◽

Geophysical Techniques

Gravity survey is one of the passive geophysical techniques commonly used to delineate geological formations, especially in determining basement rock and the overlying deposit. Geologically, the study area is made up of thick quaternary alluvium deposited on top of the older basement rock. The Muda River basin constitutes, approximately, of more than 300 m of thick quaternary alluvium overlying the unknown basement rock type. Previous studies, including drilling and geo-electrical resistivity surveys, were conducted in the area but none of them managed to conclusively determine the basement rock type and depth precisely. Hence, a regional gravity survey was conducted to determine the thickness of the quaternary sediments prior to assessing the sustainability of the Muda River basin. Gravity readings were made at 347 gravity stations spaced at 3–5 km intervals using Scintrex CG-3 covering an area and a perimeter of 9000 km2 and 730 km, respectively. The gravity data were then conventionally reduced for drift, free air, latitude, Bouguer, and terrain corrections. These data were then consequently analyzed to generate Bouguer, regional and total horizontal derivative (THD) anomaly maps for qualitative and quantitative interpretations. The Bouguer gravity anomaly map shows low gravity values in the north-eastern part of the study area interpreted as representing the Main Range granitic body, while relatively higher gravity values observed in the south-western part are interpreted as representing sedimentary rocks of Semanggol and Mahang formations. Patterns observed in the THD anomaly and Euler deconvolution maps closely resembled the presence of structural features such as fault lineaments dominantly trending along NW-SE and NE-SW like the trends of topographic lineaments in the study area. Based on power spectral analysis of the gravity data, the average depth of shallow body, representing alluvium, and deep body, representing underlying rock formations, are 0.5 km and 1.2 km, respectively. The thickness of Quaternary sediment and the depth of sedimentary formation can be more precisely estimated by other geophysical techniques such as the seismic reflection survey.

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Deep Learning-Based Object Detection, Localisation and Tracking for Smart Wheelchair Healthcare Mobility

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph18010091 ◽

2020 ◽

Vol 18 (1) ◽

pp. 91

Author(s):

Louis Lecrosnier ◽

Redouane Khemmar ◽

Nicolas Ragot ◽

Benoit Decoux ◽

Romain Rossi ◽

...

Keyword(s):

Object Detection ◽

Object Tracking ◽

Indoor Environment ◽

Distance Estimation ◽

Depth Estimation ◽

Detection Algorithm ◽

Use Case ◽

Detection Distance ◽

Detection Depth ◽

Sort Algorithm

This paper deals with the development of an Advanced Driver Assistance System (ADAS) for a smart electric wheelchair in order to improve the autonomy of disabled people. Our use case, built from a formal clinical study, is based on the detection, depth estimation, localization and tracking of objects in wheelchair’s indoor environment, namely: door and door handles. The aim of this work is to provide a perception layer to the wheelchair, enabling this way the detection of these keypoints in its immediate surrounding, and constructing of a short lifespan semantic map. Firstly, we present an adaptation of the YOLOv3 object detection algorithm to our use case. Then, we present our depth estimation approach using an Intel RealSense camera. Finally, as a third and last step of our approach, we present our 3D object tracking approach based on the SORT algorithm. In order to validate all the developments, we have carried out different experiments in a controlled indoor environment. Detection, distance estimation and object tracking are experimented using our own dataset, which includes doors and door handles.

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The utility of the enhancement techniques for mapping subsurface structures from gravity data

Frontiers in Scientific Research and Technology ◽

10.21608/fsrt.2021.94294.1047 ◽

2021 ◽

Vol 0 (0) ◽

pp. 0-0

Author(s):

Luan Pham ◽

TUYEN NGUYEN XUAN ◽

Ahmed Eldosouky ◽

Thanh Do ◽

Toan Nguyen

Keyword(s):

Gravity Data ◽

Subsurface Structures

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Basin Depth Mapping Beneath Wellington City Based on Residual Gravity Anomalies

10.26686/wgtn.15176061 ◽

2021 ◽

Author(s):

◽

Alistair Stronach

Keyword(s):

Gravity Anomaly ◽

Sedimentary Basin ◽

Gravity Data ◽

Three Dimensional ◽

Maximum Amplitude ◽

Central Business District ◽

Gravity Anomalies ◽

Depth Map ◽

Capital City ◽

Detailed Knowledge

New Zealand’s capital city of Wellington lies in an area of high seismic risk, which is further increased by the sedimentary basin beneath the Central Business District (CBD). Ground motion data and damage patterns from the 2013 Cook Strait and 2016 Kaikōura earthquakes indicate that two- and three-dimensional amplification effects due to the Wellington sedimentary basin may be significant. These effects are not currently accounted for in the New Zealand Building Code. In order for this to be done, three-dimensional simulations of earthquake shaking need to be undertaken, which requires detailed knowledge of basin geometry. This is currently lacking, primarily because of a dearth of deep boreholes in the CBD area, particularly in Thorndon and Pipitea where sediment depths are estimated to be greatest. A new basin depth map for the Wellington CBD has been created by conducting a gravity survey using a modern Scintrex CG-6 gravity meter. Across the study area, 519 new high precision gravity measurements were made and a residual anomaly map created, showing a maximum amplitude anomaly of -6.2 mGal with uncertainties better than ±0.1 mGal. Thirteen two-dimensional geological profiles were modelled to fit the anomalies, then combined with existing borehole constraints to construct the basin depth map. Results indicate on average greater depths than in existing models, particularly in Pipitea where depths are interpreted to be as great as 450 m, a difference of 250 m. Within 1 km of shore depths are interpreted to increase further, to 600 m. The recently discovered basin bounding Aotea Fault is resolved in the gravity data, where the basement is offset by up to 13 m, gravity anomaly gradients up to 8 mGal/km are observed, and possible multiple fault strands identified. A secondary strand of the Wellington Fault is also identified in the north of Pipitea, where gravity anomaly gradients up to 18 mGal/km are observed.

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