A preliminary, full spectrum, magnetic anomaly grid of the United States with improved long wavelengths for studying continental dynamics:  A website for distribution of data

Ravat, D.; Finn, C.; Hill, Patricia L.; Kucks, R.P.; Phillips, Jeffrey D.; Blakely, Robert F.; Bouligand, C.; Sabaka, Terence J.; Elshayat, A.; Aref, A.; Elawadi, Eslam

doi:10.3133/ofr20091258

Cited by 23 publications

(17 citation statements)

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“…Magnetic anomaly grids covering the United States are publicly available [ Ravat et al ., ], but the grid spacing is 1.25 km. To resolve features at a finer scale, we reprocessed flight line data covering north central Oklahoma.…”

Section: Methodsmentioning

confidence: 99%

“…Magnetic anomaly grids covering the United States are publicly available [Ravat et al, 2008], but the grid spacing is 1.25 km. flight lines were spaced 5-10 km apart in the study area ( Figure S2).…”

Section: Methodsmentioning

confidence: 99%

“…To gain improved imagery, we despiked and then gridded the flight line data at 500 m spacing. Individual surveys were combined using standard grid-knitting methods with the regional grid by Ravat et al [2008] as a reference ( Figure S3). Decorrugation [Urquhart, 1988] and low-pass matched filters [Phillips, 2001] were applied to effectively remove aliasing artifacts between flight lines and signals corresponding to source depths of 500 m or less (resembling noise), respectively.…”

Section: Methodsmentioning

confidence: 99%

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Geologic influence on induced seismicity: Constraints from potential field data in Oklahoma

Shah

Keller

2017

Geophysical Research Letters

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Recent Oklahoma seismicity shows a regional correlation with increased wastewater injection activity, but local variations suggest that some areas are more likely to exhibit induced seismicity than others. We combine geophysical and drill hole data to map subsurface geologic features in the crystalline basement, where most earthquakes are occurring, and examine probable contributing factors. We find that most earthquakes are located where the crystalline basement is likely composed of fractured intrusive or metamorphic rock. Areas with extrusive rock or thick (>4 km) sedimentary cover exhibit little seismicity, even in high injection rate areas, similar to deep sedimentary basins in Michigan and western North Dakota. These differences in seismicity may be due to variations in permeability structure: within intrusive rocks, fluids can become narrowly focused in fractures and faults, causing an increase in local pore fluid pressure, whereas more distributed pore space in sedimentary and extrusive rocks may relax pore fluid pressure.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Geologic influence on induced seismicity: Constraints from potential field data in Oklahoma

Shah

Keller

2017

Geophysical Research Letters

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“…This introduces residual trends in the data and discontinuities along the survey boundaries. This merging requires accurate main field models for all corresponding epochs (e.g., Ravat et al 2003;Ravat et al 2009). The typical spatial resolution of aeromagnetic surveys ranges between a few hundreds meters to hundreds of kilometres.…”

Section: Aeromagnetic Datamentioning

confidence: 99%

The Magnetic Field of the Earth’s Lithosphere

et al. 2010

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The lithospheric contribution to the Earth's magnetic field is concealed in magnetic field data that have now been measured over several decades from ground to satellite altitudes. The lithospheric field results from the superposition of induced and remanent magnetisations. It therefore brings an essential constraint on the magnetic properties of rocks of the Earth's sub-surface that would otherwise be difficult to characterize. Measuring, extracting, interpreting and even defining the magnetic field of the Earth's lithosphere is however challenging. In this paper, we review the difficulties encountered. We briefly summarize the various contributions to the Earth's magnetic field that hamper the correct identification of the lithospheric component. Such difficulties could be partially alleviated with the joint analysis of multi-level magnetic field observations, even though one cannot avoid making compromises in building models and maps of the magnetic field of the Earth's lithosphere E. Thébault ( ) 96 E. Thébault et al.at various altitudes. Keeping in mind these compromises is crucial when lithospheric field models are interpreted and correlated with other geophysical information. We illustrate this discussion with recent advances and results that were exploited to infer statistical properties of the Earth's lithosphere. The lessons learned in measuring and processing Earth's magnetic field data may prove fruitful in planetary exploration, where magnetism is one of the few remotely accessible internal properties.

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“…To address this issue, Geoscience Australia flew a mesh of long-range aeromagnetic profiles which were used to correct the long wavelengths for the 5 th edition of the Australian magnetic anomaly map (Milligan et al, 2010). A similar correction of long wavelengths by long-range aeromagnetic profiles was carried out for North America (Ravat, 2009). For NGDC's global magnetic reference field models, the continental scale compilations, together with some isolated smaller surveys, were merged into a common global grid, displayed in Fig.…”

Section: Aeromagnetic Compilationsmentioning

confidence: 99%

High Definition Geomagnetic Models: A New Perspective for Improved Wellbore Positioning

et al. 2012

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Earth's gravity and magnetic fields are used as natural reference frames in directional drilling. The azimuth of the bottomhole assembly is inferred by comparing the magnetic field measured-while-drilling (MWD) with a geomagnetic reference model.To provide a reference of sufficient quality for accurate well placement, the US National Geophysical Data Center (NGDC), in partnership with industry, has developed high-definition geomagnetic models (HDGM), updated regularly using the latest satellite, airborne and marine measurements of the Earth's magnetic field. Standard geomagnetic reference models represent the main magnetic field originating in the Earth's liquid core, but the new models additionally account for crustal magnetic anomalies, which constitute a significant source of error in directional drilling. NGDC maintains a public archive of global ship and airborne magnetic field measurements. These are compiled into a global magnetic anomaly grid and expanded into ellipsoidal harmonics. The harmonic expansion coefficients are then included in the high-definition models to accurately represent the direction and strength of the local geomagnetic field. The latest global model to degree and order 720 resolves magnetic anomalies down to 28 km half-wavelength, achieving more than an order-of-magnitude improvement over previous models.A side-by-side comparison of different on-and off-shore regions shows the high level of local detail represented in the new model. Accounting for a larger waveband of the geomagnetic spectrum significantly improves the accuracy of the reference field. This directly benefits the reliability of the well azimuth determination. We further demonstrate that model accuracy is a prerequisite for applying drill string interference corrections. Finally, an accurate reference model facilitates the validation of MWD surveys by keeping the field acceptance criteria centered on the true downhole magnetic field. Together, these factors improve well placement, prevent and mitigate the danger of collision with existing wellbores and enable real-time steering to save rig-time and reduce drilling costs.

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A preliminary, full spectrum, magnetic anomaly grid of the United States with improved long wavelengths for studying continental dynamics: A website for distribution of data

Cited by 23 publications

References 0 publications

Geologic influence on induced seismicity: Constraints from potential field data in Oklahoma

Geologic influence on induced seismicity: Constraints from potential field data in Oklahoma

The Magnetic Field of the Earth’s Lithosphere

High Definition Geomagnetic Models: A New Perspective for Improved Wellbore Positioning

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