Delineating hydrothermal stockwork copper deposits using controlled-source and radio-magnetotelluric methods: A case study from northeast Iran

Geophysics ◽  
2009 ◽  
Vol 74 (5) ◽  
pp. B167-B181 ◽  
Author(s):  
Mehrdad Bastani ◽  
Alireza Malehmir ◽  
Nazli Ismail ◽  
Laust B. Pedersen ◽  
Farhang Hedjazi
Keyword(s):  
Signal To Noise Ratio ◽  
Three Dimensional ◽  
Near Surface ◽  
2D Inversion ◽  
Controlled Source ◽  
Copper Mineralization ◽  
Radio Transmitters ◽  
Ground Magnetic ◽  
2D Resistivity

Radio- and controlled-source-tensor magnetotelluric (RMT and CSTMT) methods are used to target hydrothermal veins of copper mineralization. The data were acquired along six east-west- and three north-south-trending profiles, covering an area of about [Formula: see text]. The tensor RMT data were collected in the [Formula: see text] frequency band. A double horizontal magnetic dipole transmitter in the [Formula: see text] frequency range allowed us to constrain the deeper parts of the resistivity models better. To obtain optimum field parameters, ground magnetic profiling was conducted prior to the RMT and CSTMT surveys. Although the study area (in Iran) is remote, a number of radio transmitters with acceptable signal-to-noise ratio were utilized. The 2D inversion of RMT data led to unstable resistivity models with large datamisfits. Thus, the RMT data were used to complement and analyze the near-surface resistivity anomalies observed in the 2D CSTMT models. Analyses of strike and dimensionality from the CSTMT data suggests that the low-resistivity structures are mainly three dimensional; therefore, 2D inversion of determinant data is chosen. Independent 2D inversion models of the determinant CSTMT data along crossing profiles are in good agreement. Known copper mineralization is imaged well in the CSTMT models. The thinning of the conductive overburden correlates very well with magnetic highs, indicating the bedrock is resistive and magnetic. In this sense, the magnetic and electromagnetic fields complement each other. Analysis of the 2D resistivity models indicates the volcanic rock deepens at the center of the study area. This zone is associated with a magnetic low and therefore is recommended for detailed exploration work.

Northwestern Williston Basin case histories with 3-D seismic data

Geophysics ◽  
1991 ◽  
Vol 56 (11) ◽  
pp. 1849-1874
Author(s):  
D. L. Connelly ◽  
B. J. Ferris ◽  
L. D. Trembly
Keyword(s):  
Signal To Noise Ratio ◽  
Three Dimensional ◽  
Cost Effective ◽  
Field Studies ◽  
Careful Analysis ◽  
Williston Basin ◽  
Event Correlation ◽  
Near Surface ◽  
Single Fold ◽  
Exploration Area

Two Northwestern Williston Basin field studies illustrate the cost‐effective geological and three‐dimensional seismic methods used to explore for structurally controlled oil reservoirs in the Tule Creek area of northeast Montana. These examples present the geologic and seismic characteristics of a Mississippian Charles C zone pool at Northwest Poplar field and a Devonian Nisku accumulation at Long Creek West field. A classic, upward‐shoaling, nearshore marine carbonate sequence characterizes the reservoir and associated strata in both fields. The Charles C zone pool of Northwest Poplar field is a subtle, tectonically‐controlled accumulation which remained undiscovered and downdip from the large, nearby, well‐known East Poplar field until 1983. Long Creek West field exhibits the subtle character of small closed structures produced by multistage evaporite solution. Three‐dimensional (3-D) seismic techniques best detect such fields of low vertical relief and small areal extent. The significant acquisition costs of multifold, 3-D seismic surveys led us to design, acquire, process, and interpret single‐fold 3-D surveys to disclose these subtle, small structures. Augmented conventional 48-channel vibroseis crews collected the 3-D data. Near‐surface glacial till deposits in the area created residual statics and normal‐moveout problems on the single‐fold data. These processing problems were handled by constraining the statics and normal‐moveout velocity solutions with plausible geologic conditions: the near‐flat attitude of the reflecting beds, and the inferred horizontal simplicity of the earth velocity field. Our geologically constrained processing methods included: single‐event correlation picking, single‐fold, surface‐consistent statics, and velocity interpolation on flattened events. In addition, spatially oriented six‐fold stacking increases the signal‐to‐noise ratio in areas where poor signal quality exists. In the case of Northwest Poplar field, geologic studies and subsequent interpretations involving isochron mapping techniques showed that the absence of Mississippian evaporites and paleostructural thinning produce disruption of evaporite events and interval thinning near the evaporites, respectively. Long Creek West field exhibited the interval thickening below, and the interval thinning above the trap formed by two‐stage evaporite solution. Careful analysis of geologic conditions coupled with single‐fold 3-D methods makes it possible to economically explore for small undiscovered structural traps in a mature exploration area.

A multi-scale ground and drone-borne magnetic survey approach for the detection and investigation of archaeological structures

2021 ◽  
Author(s):  
Bruno Gavazzi ◽  
Hugo Reiller ◽  
Marc Munschy ◽  
Gilles Pierrevelcin ◽  
Florian Basoge ◽  
...  
Keyword(s):  
Vertical Component ◽  
High Amplitude ◽  
Magnetic Survey ◽  
Rhine River ◽  
Near Surface ◽  
Multi Scale ◽  
Electric Power Line ◽  
Frequency Magnetic Field ◽  
Ground Magnetic

<p><span>Ground magnetic surveys are commonly used for imaging near-surface structures in archaeological studies. Usually, surveys are conducted using vertical component gradiometers or scalar gradiometers to produce a vertical pseudo-gradient map. Scalar magnetometers can also be used, albeit less frequently, to produce maps of the total magnetic anomaly. In all these cases, the equipment is pushed or pulled by an operator or carried behind a vehicle. Here we present a third approach made available by the use of three-component fluxgate magnetometers: fast surveys over large areas using a compact lightweight drone flying automatically 1 to 2 m above the ground and high precision surveys acquired by an operator 0,2 to 1 m above the ground. A case study on the gallo-roman site of Oedenburg, </span><span>located</span><span> along the Rhine River in its upper valley, illustrates the results that can be obtained with the approach. A comparison with previously acquired pseudo-gradient surveys show</span><span>s</span><span> that the presented method allows a faster coverage, a greater resolution for the imaging of short wavelength structures (such as walls) and a better capacity of imaging large wavelength structures (such as pathways, palaeochannels or soil composition variations). As the site is crossed by a high voltage electric power line, a method to suppress the high-amplitude 50 Hz frequency magnetic field is presented.</span></p>

Three-dimensional supervirtual seismic refraction interferometry: a case study in western Saudi Arabia

Geophysics ◽  
2021 ◽  
pp. 1-53
Author(s):  
Paul Edigbue ◽  
Abdullatif Al-Shuhail ◽  
Sherif M. Hanafy
Keyword(s):  
Signal To Noise Ratio ◽  
Seismic Refraction ◽  
Three Dimensional ◽  
Data Set ◽  
Arrival Times ◽  
3D Geometry ◽  
Weight Drop ◽  
First Arrival ◽  
3D Seismic Data

The semiautomatic seismic refraction supervirtual interferometry (SVI) algorithm was developed to improve the conventional SVI method. The conventional SVI method utilizes convolution techniques and involves the raw trace, which reintroduces noise back into the enhanced trace. However, the semiautomatic method uses a first arrival reference picked from a raw trace to compute the arrival times of all enhanced virtual traces. The semiautomatic SVI method has been extended recently from 2D to 3D geometry and applied on a synthetic 3D seismic data set utilizing the raw traces of only one inline. We present a case study of the semiautomatic 3D SVI method by applying the algorithm on an active seismic refraction dataset that consists of 82,944 raw traces from 288 shot gathers that use an accelerated weight drop source. Due to possible differences in the source wavelet among shots, the semiautomatic 3D SVI method was applied on the 288 raw traces from each shot gather separately. The SVI technique generated 41,328 distinct correlograms from one shot, which resulted in producing a trace with a much better signal-to-noise ratio.

Distributed acoustic sensing for near-surface imaging using submarine telecommunication cable: a case study in the Trondheimsfjord, Norway

Geophysics ◽  
2021 ◽  
pp. 1-69
Author(s):  
Kittinat Taweesintananon ◽  
Martin Landrø ◽  
Jan Kristoffer Brenne ◽  
Aksel Haukanes
Keyword(s):  
Signal To Noise Ratio ◽  
Seismic Source ◽  
Near Surface ◽  
Acoustic Sensing ◽  
Optical Cable ◽  
Distributed Acoustic Sensing ◽  
Hydrophone Array ◽  
Seismic Images ◽  
Data Processing Methods

Distributed acoustic sensing (DAS) transforms submarine telecommunication cables into densely sampled seismic receivers. To demonstrate DAS applications for seismic imaging, we use an optical cable on the seafloor in the Trondheimsfjord, Norway, to record seismic data generated by a controlled seismic source. The data are simultaneously recorded by a towed hydrophone array and the fiber optic cable. Following our data processing methods, we can produce seismic images of the seafloor and underlying geological structures from both hydrophone array and DAS data. We find that the hydrophone and DAS data have a comparable signal-to-noise ratio. Moreover, DAS images can be improved by using a seismic source that has sufficiently large energy within the frequency range matching the spatial resolution of DAS. The temporal resolution of the DAS images can be improved by minimizing the crossline offset between seismic sources and the DAS cable. The seismic images from DAS can be used to support geohazard analysis and various subsurface exploration activities.

Construction of plastic contact deformation maps on ceramics: a case study on aluminum nitride

1996 ◽  
Vol 54 ◽  
pp. 636-637
Author(s):  
D. L. Callahan
Keyword(s):  
Plastic Deformation ◽  
Aluminum Nitride ◽  
Mechanical Response ◽  
Three Dimensional ◽  
Bright Field Image ◽  
Perfectly Plastic ◽  
Contrast Analysis ◽  
Deformation Patterns

Modern polishing, precision machining and microindentation techniques allow the processing and mechanical characterization of ceramics at nanometric scales and within entirely plastic deformation regimes. The mechanical response of most ceramics to such highly constrained contact is not predictable from macroscopic properties and the microstructural deformation patterns have proven difficult to characterize by the application of any individual technique. In this study, TEM techniques of contrast analysis and CBED are combined with stereographic analysis to construct a three-dimensional microstructure deformation map of the surface of a perfectly plastic microindentation on macroscopically brittle aluminum nitride.The bright field image in Figure 1 shows a lg Vickers microindentation contained within a single AlN grain far from any boundaries. High densities of dislocations are evident, particularly near facet edges but are not individually resolvable. The prominent bend contours also indicate the severity of plastic deformation. Figure 2 is a selected area diffraction pattern covering the entire indentation area.

Cryomicroscopy of crotoxin complex crystals at 400 KV

1989 ◽  
Vol 47 ◽  
pp. 826-827
Author(s):  
Jaap Brink ◽  
Wah Chiu
Keyword(s):  
Signal To Noise Ratio ◽  
3D Structure ◽  
Three Dimensional ◽  
Carbon Films ◽  
Depth Of Field ◽  
Basic Subunit ◽  
Ewald Sphere ◽  
Diffraction Patterns ◽  
Complex Crystals ◽  
Acidic Subunit

The crotoxin complex is a potent neurotoxin composed of a basic subunit (Mr = 12,000) and an acidic subunit (M = 10,000). The basic subunit possesses phospholipase activity whereas the acidic subunit shows no enzymatic activity at all. The complex's toxocity is expressed both pre- and post-synaptically. The crotoxin complex forms thin crystals suitable for electron crystallography. The crystals diffract up to 0.16 nm in the microscope, whereas images show reflections out to 0.39 nm2. Ultimate goal in this study is to obtain a three-dimensional (3D-) structure map of the protein around 0.3 nm resolution. Use of 100 keV electrons in this is limited; the unit cell's height c of 25.6 nm causes problems associated with multiple scattering, radiation damage, limited depth of field and a more pronounced Ewald sphere curvature. In general, they lead to projections of the unit cell, which at the desired resolution, cannot be interpreted following the weak-phase approximation. Circumventing this problem is possible through the use of 400 keV electrons. Although the overall contrast is lowered due to a smaller scattering cross-section, the signal-to-noise ratio of especially higher order reflections will improve due to a smaller contribution of inelastic scattering. We report here our preliminary results demonstrating the feasability of the data collection procedure at 400 kV.Crystals of crotoxin complex were prepared on carbon-covered holey-carbon films, quench frozen in liquid ethane, inserted into a Gatan 626 holder, transferred into a JEOL 4000EX electron microscope equipped with a pair of anticontaminators operating at −184°C and examined under low-dose conditions. Selected area electron diffraction patterns (EDP's) and images of the crystals were recorded at 400 kV and −167°C with dose levels of 5 and 9.5 electrons/Å, respectively.

scholarly journals Generative Models for Relief Perspective Architectures

2021 ◽  
Author(s):  
Leonardo Baglioni ◽  
Federico Fallavollita
Keyword(s):  
Research Methodology ◽  
Affine Space ◽  
Three Dimensional ◽  
Generative Models ◽  
Linear Perspective ◽  
Dimensional Structure ◽  
Three Dimensional Structure ◽  
Present Essay ◽  
Santa Maria

AbstractThe present essay investigates the potential of generative representation applied to the study of relief perspective architectures realized in Italy between the sixteenth and seventeenth centuries. In arts, and architecture in particular, relief perspective is a three-dimensional structure able to create the illusion of great depths in small spaces. A method of investigation applied to the case study of the Avila Chapel in Santa Maria in Trastevere in Rome (Antonio Gherardi 1678) is proposed. The research methodology can be extended to other cases and is based on the use of a Relief Perspective Camera, which can create both a linear perspective and a relief perspective. Experimenting mechanically and automatically the perspective transformations from the affine space to the illusory space and vice versa has allowed us to see the case study in a different light.

Decolonising a landscape architecture studio: Spatial modelling of student narratives

2021 ◽  
Vol 1 (1) ◽  
pp. 39-47
Author(s):  
Christine Price
Keyword(s):  
Spatial Model ◽  
Meaning Making ◽  
Three Dimensional ◽  
Spatial Modelling ◽  
First Year ◽  
Spatial Form ◽  
Public Park ◽  
New Meanings ◽  
Global North

This paper problematises the dominance of global north perspectives in landscape architectural education, in South Africa where there are urgent calls to decolonise education and make visible indigenous and vernacular meaning-making practices. In grappling with these concerns, this research finds resonance with a multimodal social semiotic approach that acknowledges the interest, agency and resourcefulness of students as meaning-makers in both accessing and challenging dominant educational discourses. This research involves a case study of a design project in a first-year landscape architectural studio. The project requires students to choose a narrative and to represent it as a spatial model: a scaled, 3D maquette of a spatial experience that could be installed in a public park. This practitioner reflection closely analyses the spatial model of one student, Malibongwe, focusing on his interest in meaning-making; the innovative meaning-making practices and diverse resources he draws on; and his expression of spatial signifiers of the Black experiences portrayed in his narrative. This reflection shows how Malibongwe’s narrative is not only reproduced in the spatial model, it is remade: the transformation of resources into three-dimensional spatial form results in new understandings and the production of new meanings.

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