Salt and Diapiric Anomalies in the Southeast Bonaparte Gulf Basin

1974 ◽  
Vol 14 (1) ◽  
pp. 85 ◽  
Author(s):  
D. W. Edgerley ◽  
R. P. Crist

The Southeast Bonaparte Gulf Basin comprises a Phanerozoic sedimentary sequence bordered by Precambrian rocks of the Kimberley, Sturt and Darwin Blocks. This portion of the basin developed as a subsiding graben, in which the flanks are separated from the central collapsed area by terraces that foundered to intermediate depths. Geophysical data acquired in the area since 1965 suggest the existence of large quantities of evaporites in the basin. Wells drilled in the area have confirmed the seismic evaluation. These evaporites were initially deposited across existing terraces and basinal areas prior to the later Devonian. Salt and diapiric structures of various types are widely distributed within the basin. The origin and growth of most of these structures is associated with epeirogenic movements along faults that demarcate the major structural elements of the basin.

1968 ◽  
Vol 5 (3) ◽  
pp. 621-628 ◽  
Author(s):  
J. R. Vail ◽  
N. J. Snelling ◽  
D. C. Rex

The significance of new age determinations on pre-Katangan (Late Precambrian) rocks and minerals from Zambia and adjacent parts of Tanzania and Rhodesia is discussed. In northwestern Rhodesia, the Lomagundi-Piriwiri sediments were deposited between 2500 and 2000 m.y. ago and were folded along meridional trends at circa 1940 m.y. A later episode of folding and metamorphism along similar trends occurred about 1700 m.y. ago, but only affected the western part of the sedimentary sequence (the Piriwiri Series). This latter date is comparable to that which appears to characterize the Tumbide trend, a N- to NE-trending fold system, in Zambia.In Zambia the Tumbide trend is the oldest tectonic episode preserved in the basement and is found only in isolated blocks and cores into which later tectonisms have not penetrated. The dominant pre-Katangan tectonism is represented by the NE to ENE Irumide trend. Such tectonic trends are particularly well developed in the Irumide Orogenic Belt of northern Zambia and adjacent Tanzania. Age determinations set a younger limit of circa 900 m.y. to this trend and the existence of an Irumide Cycle between about 1600 and 900 m.y. is suggested. The possibility that the relatively unmetamorphosed sediments of the Upper Plateau Series and Abercorn Sandstones at the southern end of Lake Tanganyika, the Mafingi Series of northern Malawi, and the Konse Series of Tanzania, represent near-contemporaneous platform deposition associated with the Irumide belt is considered.From this and other recent studies the distribution of orogenic belts in central and eastern Africa can be revised and a number of features of their pattern and inter-relationships noted.


2021 ◽  
Vol 4 (3) ◽  
pp. 140-150
Author(s):  
Sadık Can Girgin ◽  
Cem Göksoy ◽  
Emine Daş ◽  
İbrahim Serkan Mısır

In precast reinforced concrete buildings, which constitute an important part of the industrial buildings in Turkey, the force flow between the structural elements is provided by beam-column connections with or without transferring moments. In general, moment resisting beam-column connections with mechanical or emulative components are applied at the mezzanine level. For precast concrete structures, strength-based design is the most common design approach in engineering practice. In recent years, performance based seismic design and evaluation approach also gained attention which provides numerical estimation of the damage in structural elements subjected to earthquake loading. This study presents the performance based seismic assessment of a two-story precast building based on the seismic evaluation requirements of Turkish Building Earthquake Code 2018. For this purpose, numerical simulation model has been established by using lumped plasticity models for connections and distributed plasticity models for columns. Strong ground motion records are scaled based on TBEC-2018 acceleration spectrum for a specific location, and nonlinear time history analyses are performed in x and y directions simultaneously. The performance evaluation results using average deformations show that there is a significant difference between plastic rotation and reinforcing bar strain performance limits.


2020 ◽  
Vol 6 (2) ◽  
pp. 141-154
Author(s):  
Rinda Fitri Nabhilla ◽  
Gati Annisa Hayu

A research about structural analysis of eight-story office building due to earthquake load and to identify the performance level of the structure referring to ATC-40. Performance Based Seismic Evaluation (PBSE) concept is used for earthquake engineering by using one of the method which is Pushover Analysis to evaluate the structure. This method is to purposely apply escalating static lateral load to the structure until failure occurs to the structural elements and targeted structural displacement was obtained. Determining the targeted displacement is referring to ATC-40, FEMA 365, and FEMA 440. Results show that targeted displacement value is 0,015 m for X direction and Y direction as well as the total drift was obtained as much as 0,0066 m for X direction and 0,00273 m for Y direction. According to the structural deformation and criteria from ATC-40 the performance level of the structure is at Immediately Occupancy (IO).


2021 ◽  
Vol 61 (2) ◽  
pp. 679
Author(s):  
Jelena Markov ◽  
Claudio Delle Piane ◽  
Ernest Swierczek ◽  
Clive Foss ◽  
Mohinudeen Faiz

The Beetaloo Sub-basin is known for its vast unconventional hydrocarbon resources even though it is relatively underexplored. There is reasonably good coverage of 2D seismic within the sub-basin which is used as the basis for most structural interpretations. However, seismic quality varies, and it is occasionally deteriorated by the presence of basalts from the Kalkarindji suite and the karstic nature of the Gum Ridge formation. Aeromagnetic data, constrained by petrophysical logs are used, to map faults in the basalts of the Kalkarindji suite and their lateral extent to the South and the East of the sub-basin. The same structural elements are identified in the full tensor gravity gradiometry data. The top of this unit is observed in the electrical conductivity profiles, derived from Tempest data, in the NW part of the eastern sub-basin.


1993 ◽  
Vol 9 (4) ◽  
pp. 803-816 ◽  
Author(s):  
S. Pezeshk ◽  
T. S. Chang ◽  
K. C. Yiak ◽  
H. T. Kung

The focus of this paper is to develop a screening procedure to obtain information and assess vulnerability of bridges located in the New Madrid seismic zone (NMSZ). This screening methodology includes structural elements, site, foundation, and importance of the bridge. An inventory of the river-crossing bridges in Memphis and Shelby County is made using the developed screening procedure; potentially hazardous bridges that require further detailed seismic evaluation and/or immediate seismic retrofitting are identified. The results of this study are important for future maintenance and improvement, earthquake loss estimates, seismic hazard/risk reduction, and earthquake preparedness/rescue plans for river-crossing bridges in the NMSZ.


Author(s):  
M. J. Russell ◽  
R. E. Spears ◽  
R. G. Kobbe

The structure of a building undergoing a seismic reevaluation at the Idaho National Laboratory includes a number of steel plate walls and a roof liner which will act as shear diaphragms during an earthquake. Since the facility was designed and built long before such criteria were formulated, it is not surprising that these walls are not configured to meet all of the recently formulated requirements for such structures. To take advantage of these unusual structural elements, nonlinear analysis was used to ensure accurate modeling of the plate walls in a linear elastic seismic analysis of the full superstructure. The modeling was also used to establish the capacity of the plate.


2021 ◽  
Author(s):  
P Wozniakowska ◽  
D W Eaton ◽  
C Deblonde ◽  
A Mort ◽  
O H Ardakani

The Western Canada Sedimentary Basin (WCSB) is a mature oil and gas basin with an extraordinary endowment of publicly accessible data. It contains structural elements of varying age, expressed as folding, faulting, and fracturing, which provide a record of tectonic activity during basin evolution. Knowledge of the structural architecture of the basin is crucial to understand its tectonic evolution; it also provides essential input for a range of geoscientific studies, including hydrogeology, geomechanics, and seismic risk analysis. This study focuses on an area defined by the subsurface extent of the Triassic Montney Formation, a region of the WCSB straddling the border between Alberta and British Columbia, and covering an area of approximately 130,000 km2. In terms of regional structural elements, this area is roughly bisected by the east-west trending Dawson Creek Graben Complex (DCGC), which initially formed in the Late Carboniferous, and is bordered to the southwest by the Late Cretaceous - Paleocene Rocky Mountain thrust and fold belt (TFB). The structural geology of this region has been extensively studied, but structural elements compiled from previous studies exhibit inconsistencies arising from distinct subregions of investigation in previous studies, differences in the interpreted locations of faults, and inconsistent terminology. Moreover, in cases where faults are mapped based on unpublished proprietary data, many existing interpretations suffer from a lack of reproducibility. In this study, publicly accessible data - formation tops derived from well logs, LITHOPROBE seismic profiles and regional potential-field grids, are used to delineate regional structural elements. Where seismic profiles cross key structural features, these features are generally expressed as multi-stranded or en echelon faults and structurally-linked folds, rather than discrete faults. Furthermore, even in areas of relatively tight well control, individual fault structures cannot be discerned in a robust manner, because the spatial sampling is insufficient to resolve fault strands. We have therefore adopted a structural-corridor approach, where structural corridors are defined as laterally continuous trends, identified using geological trend surface analysis supported by geophysical data, that contain co-genetic faults and folds. Such structural trends have been documented in laboratory models of basement-involved faults and some types of structural corridors have been described as flower structures. The distinction between discrete faults and structural corridors is particularly important for induced seismicity risk analysis, as the hazard posed by a single large structure differs from the hazard presented by a corridor of smaller pre-existing faults. We have implemented a workflow that uses trend surface analysis based on formation tops, with extensive quality control, combined with validation using available geophysical data. Seven formations are considered, from the Late Cretaceous Basal Fish Scale Zone (BFSZ) to the Wabamun Group. This approach helped to resolve the problem of limited spatial extent of available seismic data and provided a broader spatial coverage, enabling the investigation of structural trends throughout the entirety of the Montney play. In total, we identified 34 major structural corridors and number of smaller-scale structures, for which a GIS shapefile is included as a digital supplement to facilitate use of these features in other studies. Our study also outlines two buried regional foreland lobes of the Rocky Mountain TFB, both north and south of the DCGC.


Author(s):  
Jun Jiao

HREM studies of the carbonaceous material deposited on the cathode of a Huffman-Krätschmer arc reactor have shown a rich variety of multiple-walled nano-clusters of different shapes and forms. The preparation of the samples, as well as the variety of cluster shapes, including triangular, rhombohedral and pentagonal projections, are described elsewhere.The close registry imposed on the nanotubes, focuses attention on the cluster growth mechanism. The strict parallelism in the graphitic separation of the tube walls is maintained through changes of form and size, often leading to 180° turns, and accommodating neighboring clusters and defects. Iijima et. al. have proposed a growth scheme in terms of pentagonal and heptagonal defects and their combinations in a hexagonal graphitic matrix, the first bending the surface inward, and the second outward. We report here HREM observations that support Iijima’s suggestions, and add some new features that refine the interpretation of the growth mechanism. The structural elements of our observations are briefly summarized in the following four micrographs, taken in a Hitachi H-8100 TEM operating at an accelerating voltage of 200 kV and with a point-to-point resolution of 0.20 nm.


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