A New Method for the Collection of Marine Geomagnetic Information: Survey Application in the Colombian Caribbean
23 Dec 2020-Journal of Marine Science and Engineering (Multidisciplinary Digital Publishing Institute)-Vol. 9, Iss: 1, pp 10
TL;DR: In this paper, a grid of geomagnetic data was surveyed in an area close to the Island of San Andres in the north-west of the Colombian maritime territory, and the results showed negligible differences between the magnetic data obtained for the years 1970 and 2018 for all the variables measured, such as the inclination, declination, and total magnetic field.
Abstract: In recent years, the Oceanographic and Hydrographic Research Center (part of the General Maritime Directorate of Colombia (DIMAR) has made important efforts to advance research in the field of marine geophysics, in particular, the techniques of geomagnetism, sub-bottom profiling, and side-scan sonar, the first being the most developed at the present time. A method is presented for the acquisition of geomagnetic data in marine environments, as used by DIMAR in the Colombian maritime territory. The development of the geomagnetic method not only offers the opportunity to advance basic scientific knowledge, but it is also of great importance in support of national sovereignty issues. Among other applications, the most representative uses of the geomagnetic method are the location of pipelines and metal plates, detection of buried ordnance, identification of sites of archaeological interest, and the identification and characterization of geological structures. As a result of testing the method, a grid of geomagnetic data was surveyed in an area close to the Island of San Andres in the north-west of the Colombian maritime territory. The survey was prepared with a regional geometric arrangement, the result of which was compared with survey data obtained from the National Oceanic and Atmospheric Administration (NOAA) magnetic data repository and carried out in the same study area. Despite the long time interval between the two surveys, almost 50 years, no significant differences were observed in terms of the analyzed variables. Finally, results show negligible differences between the magnetic data obtained for the years 1970 and 2018 for all the variables measured, such as the inclination, declination, and total magnetic field. These differences may be attributable to a geological component or also to the acquisition and processing methods used in the 1970s.
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TL;DR: In this article , the authors present and discuss alternative scenarios for the nature of the underlying crust below the sedimentary sequences in the Cayos Basin, and characterize the basin through the interpretation of magnetic and gravity anomaly grids, and 2D forward modeling, constructed based on three sections, by considering restriction seismic data from previous works.
2 citations
TL;DR: Long-term erosion is experienced by most of the coastlines worldwide, and it is usually attributed not only to sea level rise but also to the retention of sand in dams, the occupation of dry beaches by urbanized areas, the disturbance of the natural patterns of longshore drift, the mining of sand as building material for construction, and so on.
Abstract: Long-term erosion is experienced by most of the coastlines worldwide, and it is usually attributed not only to sea level rise but also to the retention of sand in dams, the occupation of dry beaches by urbanized areas, the disturbance of the natural patterns of longshore drift, the mining of sand as building material for construction, and so on [...]
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Book•
22 Apr 2013TL;DR: In this paper, a combination of textbook and reference manual provides a comprehensive account of gravity and magnetic methods for exploring the subsurface using surface, marine, airborne and satellite measurements.
Abstract: This combination of textbook and reference manual provides a comprehensive account of gravity and magnetic methods for exploring the subsurface using surface, marine, airborne and satellite measurements It describes key current topics and techniques, physical properties of rocks and other Earth materials, and digital data analysis methods used to process and interpret anomalies for subsurface information Each chapter starts with an overview and concludes by listing key concepts to consolidate new learning An accompanying website presents problem sets and interactive computer-based exercises, providing hands-on experience of processing, modeling and interpreting data A comprehensive online suite of full-color case histories illustrates the practical utility of modern gravity and magnetic surveys This is an ideal text for advanced undergraduate and graduate courses and reference text for research academics and professional geophysicists It is a valuable resource for all those interested in petroleum, engineering, mineral, environmental, geological and archeological exploration of the lithosphere
271 citations
TL;DR: The igneous forearc basement along the Pacific coast of northern Central America (between southern Mexico and Costa Rica) comprises a highly tectonized accretionary assemblage of igneous and ultramafic rocks as discussed by the authors.
Abstract: The igneous forearc basement along the Pacific coast of northern Central America (between southern Mexico and Costa Rica) comprises a highly tectonized accretionary assemblage of igneous and ultramafic rocks. Volcanic and gabbroic rocks with primitive arc geochemical signatures formed between ∼100 and ≥180 Ma and are interpreted to have originated by arc magmatism resulting from subduction of the Pacific–Farallon plate. Geochemically enriched ocean island basalt (OIB)-like units are interpreted as accreted seamounts and islands of a hotspot track, which was active between ≥220 and 100 Ma and originated from a hotspot located in the central Pacific. Based on their combined Pb, Nd and Hf isotopic compositions an affiliation of these rocks with the Caribbean Large Igneous Province or the present-day Galapagos hotspot appears unlikely. Rocks of similar age and geochemistry are exposed on the Santa Elena Peninsula in Costa Rica, suggesting that a similar forearc basement is accreted to the continental Chortis Block from southern Mexico to Costa Rica.
58 citations
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08 Nov 2007
TL;DR: Elements of vector analysis can be found in this article, where Green's Theorem in potential theory is used to explain the inversion of potential field data in geophysics.
Abstract: Elements of Vector Analysis- Introductory Remarks- Gravitational Potential and Field- Electrostatics- Magnetostatics- Direct Current Flow Field- Solution of Laplace Equation- Direct Current Field Related Potential Problems- Complex Variables and Conformal Transformation in Potential Theory- Green's Theorem in Potential Theory- Electrical Images in Potential Theory- Electromagnetic Theory (Vector Potentials)- Electromagnetic Wave Propagation Problems Related to Geophysics- Green's Function- Numerical Methods in Potential Theory- Analytical Continuation of Potential Field- Inversion of Potential Field Data
46 citations
TL;DR: In this article, field tests were conducted to determine representative total-intensity magnetic anomalies due to the presence of underground storage tanks and 55-gallon steel drums at drum-to-sensor separations of 11 feet.
Abstract: Field tests were conducted to determine representative total-intensity magnetic anomalies due to the presence of underground storage tanks and 55-gallon steel drums. Three different drums were suspended from a non-magnetic tripod and the underlying field surveyed with each drum in an upright and a flipped plus rotated orientation. At drum-to-sensor separations of 11 feet, the anomalies had peak values of around 50 gammas and half-widths about equal to the drum-to-sensor separation. Remanent and induced magnetizations were comparable; crushing one of the drums significantly reduced both. A profile over a single underground storage tank had a 1000-gamma anomaly, which was similar to the modeled anomaly due to an infinitely long cylinder horizontally magnetized perpendicular to its axis. A profile over two adjacent tanks had a smooth 350-gamma single-peak anomaly even though models of two tanks produced dual-peaked anomalies. Demagnetization could explain why crushing a drum reduced its induced magnetization and why two adjacent tanks produced a single-peak anomaly.
A 40-acre abandoned landfill was surveyed on a 50- by 100-foot rectangular grid and along several detailed profiles. The observed field had broad positive and negative anomalies that were similar to modeled anomalies due to thickness variations in a layer of uniformly magnetized material. It was not comparable to the anomalies due to induced magnetization in multiple, randomly located, randomly sized, independent spheres, suggesting that demagnetization may have limited the effective susceptibility of the landfill material. A different 6-acre site survey conducted on a 10- by 10-foot grid was analyzed to determine the maximum station spacing and line separation that could have been used. Essentially, all of the anomalies at this site would have been resolved by a survey conducted on a 20- by 20-foot grid and the larger anomalies would have been detected by a 50- by 50-foot grid.
33 citations
TL;DR: The Third International Conference on Metrology for Archaeology and Cultural Heritage (Lecce, Italy, 23-25 October 2017) as mentioned in this paper presented a selection of papers related to the new perspectives on geophysics for archaeology.
Abstract: This Special Issue hosts a selection of papers presented at the Third International Conference on Metrology for Archaeology and Cultural Heritage (Lecce, Italy, 23–25 October 2017), related to the new perspectives on geophysics for archaeology. In recent years, archaeological prospecting has seen major advances through a variety of remote sensing and computing technologies. Geophysical instrumentation continues to improve in sensitivity and acquisition speed, and new multi-sensor arrays, e.g., drawn by carts over land, now permit vast areas to be rapidly covered. On the other hand, the availability of highresolution remote sensing techniques provides multiscale and multi-temporal approaches to the study of ancient settlements and landscapes, and proves fundamental in the reconstruction of their development over centuries. Nowadays, research in landscape archaeology needs the integration of different high-resolution remote sensing techniques such as satellite (optical and radar data), aerial (photographic, infrared and lidar data from aircraft and unmanned aerial vehicles), but also land acquisitions (integration of different geophysical techniques, field walking, and differential GPS topographical surveys). All these investigations are based on a geoarchaeological approach, with several aims ranging from historical reconstruction to preventive archaeology and from the preservation of archaeological and monumental heritage to noninvasive diagnosis through micro-geophysical techniques. Several geophysical methods have often been applied successfully for archaeological purposes. Among them, the most frequently used are certainly ground penetrating radar (GPR) (Leucci et al. 2016), magnetic (Eppelbaum et al. 2001), electrical resistivity
30 citations