Observation and Measurement Techniques

Turner, Gillian; Rasson, Jean L.; Reeves, C.V.

doi:10.1016/b978-0-444-53802-4.00098-1

Cited by 16 publications

(8 citation statements)

References 72 publications

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“…10b). These disturbances in magnetic field are attributed to differences in the nature of the rocks composing the basement (Turner, Rasson & Reeves, 2007). We do not attempt to identify the exact nature of these rocks here; rather, we use these contrasted anomalies to characterize differences of rock types that compose the basement (Purucker & Whaler, 2007; Lund et al 2015).…”

Section: Resultsmentioning

confidence: 99%

Controlling factors for differential subsidence in the Sonoma Foreland Basin (Early Triassic, western USA)

et al. 2017

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Sediments deposited from the Permian–Triassic boundary (~252 Ma) until the end-Smithian (Early Triassic;c.250.7 Ma) in the Sonoma Foreland Basin show marked thickness variations between its southern (up toc.250 m thick) and northern (up toc.550 m thick) parts. This basin formed as a flexural response to the emplacement of the Golconda Allochthon during the Sonoma orogeny. Using a high-resolution backstripping approach, a numerical model and sediment thickness to obtain a quantitative subsidence analysis, we discuss the controlling factor(s) responsible for spatial variations in thickness. We show that sedimentary overload is not sufficient to explain the significant discrepancy observed in the sedimentary record of the basin. We argue that the inherited rheological properties of the basement terranes and spatial heterogeneity of the allochthon are of paramount importance in controlling the subsidence and thickness spatial distribution across the Sonoma Foreland Basin.

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Section: Resultsmentioning

confidence: 99%

Controlling factors for differential subsidence in the Sonoma Foreland Basin (Early Triassic, western USA)

et al. 2017

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“…Magnetic surveying has been extensively used in the search for mineral deposits, oil and gas reservoirs, geothermal resources, as well as for a variety of other purposes such as natural hazards assessment, basement structural studies, mapping subsurface archaeology and unexploded ordnance (UXO) (Nabighian et al, 2005;Eppelbaum, 2011;Fairhead, 2012;Hinze et al, 2013;Eppelbaum, 2015;Kruse, 2013;Haldar, 2018;Turner et al, 2015;Zhou, 2018). In general, magnetic measurements can provide information on and insight into the physical, chemical, and even biological processes that have affected the iron phases within.…”

Section: Introductionmentioning

confidence: 99%

“…Traditionally, aeromagnetic surveys are often conducted using fixed-winged aircraft with sensors mounted on both the wings (horizontal sensor configuration) or a tail-boom behind the aircraft. Thanks to decades of development and noise reduction techniques coupled with new advances in sensor technologies, such modern aeromagnetic surveys can achieve a sensitivity of 0.1 nanoTesla (nT) (Eppelbaum, 2015;Aminzadeh and Dasgupta, 2013;Turner et al, 2015). However, geophysicists have realized that aeromagnetometry using light-weight and compact platforms such as unmanned aerial vehicles (UAV) can even further reduce the surveying cost and make it more convenient in terms of logistics (Eppelbaum and Mishne, 2011;Tuck et al, 2018;Mu et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Experiments on magnetic interference for a portable airborne magnetometry system using a hybrid unmanned aerial vehicle (UAV)

Jirigalatu¹,

Krishna²,

Silva³

et al. 2020

Preprint

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Abstract. Airborne magnetic surveys are an important and efficient tool for mapping the subsurface, providing insights e.g. into mineral deposits. Compared to traditional ground methods, airborne magnetic surveys offer great advantages with improved access and rapid sampling. But the cost and hassle of transporting and operating a conventional manned airborne magnetic survey system are strong impediments for its wider use. In addition, the conventional airborne systems are challenged by the need for low-altitude (&leq; 80 m) surveying to detect small-scale subsurface features evident in ground surveys. Portable and compact airborne magnetic survey systems using unmanned aerial vehicles (UAVs) can not only bridge the gap between conventional airborne magnetic surveys and ground magnetic surveys but also complement magnetic surveys to fit broader geophysical applications. Therefore, developing high-quality, stable, and portable UAV-borne survey systems is of high interest to the geophysical exploration community. However, developing such a system is challenging owing to strong magnetic interference introduced by onboard electric engines and other onboard electronic devices. As a result, tests concerning the static and dynamic magnetic interference of a UAV are critical to assess the severity of the interference and can help to improve the design of the system at the early stage of development. A static experiment and two dynamic experiments were conducted to understand the characterization of the magnetic interference of our hybrid vertical take-off and landing (VTOL) UAV. The results of the static experiment show that the wing area is highly magnetic due to the proximity to servomotors and motors, but the area along the longitudinal axis of the UAV is relatively magnetically quiet. To reduce the magnetic signature, the highly-magnetic servomotors on the wings were replaced with less magnetic servomotors of a brush-less type. Assisted by aerodynamic simulations, we further designed a front-mounting solution for two compact magnetometers. Two dynamic experiments were conducted with this setup to understand the dynamic interference of the UAV in operation. The results of the dynamic experiments reveal that the strongest source of in-flight magnetic interference is mainly due to the cables connecting the battery to the flight controller and that this effect is most influential during pitch maneuvers of the aircraft.

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“…Since its beginning in the 1950s, paleomagnetism has seen at least three generation of rock magnetometers [Turner et al, 2015]: astatic systems, spinner magnetometers, and superconducting magnetometers. Astatic system was used during the earliest paleomagnetic studies, such as Blackett [1952] and Pozzi and Thellier [1963], and it was quickly replaced by spinner magnetometers [Nagata, 1961].…”

Section: Introductionmentioning

confidence: 99%

Estimating the magnetization distribution within rectangular rock samples

Reis

Oliveira

Yokoyama

et al. 2016

Geochem Geophys Geosyst

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Over the last decades, scanning magnetic microscopy techniques have been increasingly used in paleomagnetism and rock magnetism. Different from standard paleomagnetic magnetometers, scanning magnetic microscopes produce high‐resolution maps of the vertical component of the magnetic induction field (flux density) on a plane located over the sample. These high‐resolution magnetic maps can be used for estimating the magnetization distribution within a rock sample by inversion. Previous studies have estimated the magnetization distribution within rock samples by inverting the magnetic data measured on a single plane above the sample. Here we present a new spatial domain method for inverting the magnetic induction measured on four planes around the sample in order to retrieve its internal magnetization distribution. We have presumed that the internal magnetization distribution of the sample varies along one of its axes. Our method approximates the sample geometry by an interpretation model composed of a one‐dimensional array of juxtaposed rectangular prisms with uniform magnetization. The Cartesian components of the magnetization vector within each rectangular prism are the parameters to be estimated by solving a linear inverse problem. Our method automatically deals with the averaging of the measured magnetic data due to the finite size of the magnetic sensor, preventing the application of a deconvolution before the inversion. Tests with synthetic data show the performance of our method in retrieving complex magnetization distributions even in the presence of magnetization heterogeneities. Moreover, they show the advantage of inverting the magnetic data on four planes around the sample and how this new acquisition scheme improves the estimated magnetization distribution within the rock sample. We have also applied our method to invert experimentally measured magnetic data produced by a highly magnetized synthetic sample that was manufactured in the laboratory. The results show that even in the presence of apparent position noise, our method was able to retrieve the magnetization distribution consistent with the isothermal remanent magnetization induced in the sample.

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Observation and Measurement Techniques

Cited by 16 publications

References 72 publications

Controlling factors for differential subsidence in the Sonoma Foreland Basin (Early Triassic, western USA)

Controlling factors for differential subsidence in the Sonoma Foreland Basin (Early Triassic, western USA)

Experiments on magnetic interference for a portable airborne magnetometry system using a hybrid unmanned aerial vehicle (UAV)

Estimating the magnetization distribution within rectangular rock samples

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