A5074200441- Geophysical and Geoelectrical Methods
- Geomagnetism and Paleomagnetism Studies
- Planetary Science and Exploration
- Geophysical Methods and Applications
- Geology and Paleoclimatology Research
- Astro and Planetary Science
- Geochemistry and Geologic Mapping
- Geophysics and Gravity Measurements
- Seismic Waves and Analysis
- Geological and Geochemical Analysis
- Seismic Imaging and Inversion Techniques
- Earthquake Detection and Analysis
- Methane Hydrates and Related Phenomena
- Geological and Geophysical Studies
- earthquake and tectonic studies
- Geological Studies and Exploration
- High-pressure geophysics and materials
- Geological Modeling and Analysis
- Underwater Acoustics Research
- Geological formations and processes
- Space Exploration and Technology
- Hydrocarbon exploration and reservoir analysis
- Reservoir Engineering and Simulation Methods
- NMR spectroscopy and applications
- Computational Physics and Python Applications
Geological Survey of Canada
2008-2018
Natural Resources Canada
2002-2018
University of Naples Federico II
2012
United States Naval Research Laboratory
2005
University of Alaska System
2005
Geophysical Center
2005
United States Navy
2005
McGill University
1986-1987
A new method for magnetic interpretation has been developed based on the generalization of analytic signal concept to three dimensions. The absolute value is defined as square root squared sum vertical and two horizontal derivatives field. This exhibits maxima over magnetization contrasts, independent ambient field source directions. Locations these thus determine outlines sources. Under assumption that anomalies are caused by contacts, used estimate depth using a simple amplitude half‐width...
Research Article| September 01, 1991 Chicxulub Crater: A possible Cretaceous/Tertiary boundary impact crater on the Yucatán Peninsula, Mexico Alan R. Hildebrand; Hildebrand 1Department of Planetary Sciences, University Arizona, Tucson, Arizona 85721 Search for other works by this author on: GSW Google Scholar Glen T. Penfield; Penfield 2Aerogravity Division, Carson Services Inc., 32A Blooming Road, Perkasie, Pennsylvania 18944 David A. Kring; Kring Mark Pilkington; Pilkington 3Geophysics...
A global Earth Magnetic Anomaly Grid (EMAG2) has been compiled from satellite, ship, and airborne magnetic measurements. EMAG2 is a significant update of our previous candidate grid for the World Digital Map. The resolution improved 3 arc min to 2 min, altitude reduced 5 km 4 above geoid. Additional track line data have included, both over land oceans. Wherever available, original shipborne were used instead precompiled oceanic grids. Interpolation between sparse lines in oceans was by...
A major tool in the initial recognition and study of terrestrial impact craters, ∼20% which are buried beneath postimpact sediments, is geophysics. The general geophysical character craters compiled outlined with emphasis on its relation to process as an aid additional craters. most common conspicuous signature a circular gravity low. For simple bowl‐shaped models indicate that anomaly largely due presence interior allochthonous breccia lens. In complex modeling indicates main contribution...
The North American gravity database as well data-bases from Canada, Mexico, and the United States are being revised to improve their coverage, versatility, accuracy. An important part of this effort is revising procedures for calculating anomalies, taking into account our enhanced computational power, improved terrain databases datums, increased interest in more accurately defining long-wavelength anomaly components. Users may note minor differences between previous values a result these...
PreviousNext No AccessSEG Technical Program Expanded Abstracts 19963‐D magnetic imaging using conjugate gradientsAuthors: Mark PilkingtonMark PilkingtonGeological Survey of Canadahttps://doi.org/10.1190/1.1826377 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Permalink: https://doi.org/10.1190/1.1826377FiguresReferencesRelatedDetailsCited ByComprehensive approaches the inversion data with strong remanent...
Remanent magnetization can have a significant influence on the shape of magnetic anomalies in areas that are generally characterized by induced magnetization. Since modeling is nonunique, additional constraints direction useful. A method proposed here to study possible contribution remanent particular anomaly, comparing two functions calculated directly from observations: (1) amplitude analytic signal, and (2) horizontal gradient pseudogravity. From relative position maxima these derived...
I have developed an inversion approach that determines a 3D susceptibility distribution produces given magnetic anomaly. The subsurface model consists of 3D, equally spaced array dipoles. incorporates norm enforces sparseness and depth weighting the solution. Sparseness is imposed by using Cauchy on parameters. inverse problem posed in data space, leading to linear system equations with dimensions based number data, [Formula: see text]. This contrasts standard least-squares solution, derived...
Many geophysical variables exhibit fractal or at least scaling behaviour, notably in having power spectra proportional to some of frequency. Power magnetic susceptibility logs from boreholes are spatial frequency f −2 for wavelengths 0.1 100 m. If the spectrum magnetization crust is known then field surface can be calculated. We show that if with a single exponent observed −3 aeromagnetic data implies three‐dimensional −4 distribution length scales 1 1000 km. One way reconcile two results...
With the availability of large digital datasets magnetic data (e.g. Committee for Magnetic Anomaly Map North America, 1988) need automated techniques analysis anomalies is growing. Several methods have been developed that successful in predicting source characteristics, using certain assumptions.
ABSTRACT Euler deconvolution and the analytic signal are both used for semi‐automatic interpretation of magnetic data. They mostly to delineate contacts obtain rapid source depth estimates. For deconvolution, quality estimation depends mainly on choice proper structural index, which is a function geometry causative bodies. applies only functions that homogeneous. This case field due contacts, thin dikes poles. Fortunately, many complex geological structures can be approximated by these...
A digital magnetic anomaly database and map for the North American continent is result of a joint effort by Geological Survey Canada (GSC), U. S. (USGS), Consejo de Recursos Minerales Mexico (CRM). The represent substantial upgrade from previous compilation data America, now over decade old.
Abstract Aside from its significance in establishing the impact-mass extinction paradigm, Chicxulub crater will probably come to exemplify structure of large complex craters. Much Chicxulub’s may be ‘mapped’ by tying gravity expression seismic-reflection profiles revealing an ∼180 km diameter for now-buried crater. The distribution karst topography aids outlining peripheral as also revealed horizontal gradient anomaly. fracturing inferred control groundwater flow is apparently related...
Abstract— The structural, topographic and other characteristics of the Vredefort, Sudbury, Chicxulub impact structures are described. Assuming that originally had same morphology, observations/interpretations for each structure compared extended to structures. This does not result in any major inconsistencies but requires observations be scaled spatially. In case Vredefort this is accomplished by scaling outer limit particular shock metamorphic features. Chicxulub, a reasoned assumption as...
We have developed an approach for the interpretation of magnetic field data that can be used when measured anomalies are affected by significant remanent magnetization components. The method deals with effects using normalized source strength (NSS), a quantity calculated from eigenvectors gradient tensor. NSS is minimally direction present and compares well other transformations same purpose. It therefore offers way inverting containing magnetizations, particularly these unknown possibly...
Locating the edges of magnetized sources provides a fundamental tool in geologic interpretation magnetic field data. Much recent effort has been expended on developing improvements to existing edge-detection methods, resulting purported increases accuracy and continuity along edges, reduction noise effects, limiting influences variable depth source, magnetization direction, source dip. These endeavors are valuable provide interpreters with wider range tools carry out interpretations...
The Chicxulub crater is an ∼180‐km‐diameter peak‐ring based on drill hole logs and samples, potential fields, seismic reflection profiles, surface fracture patterns. A structural cross section produced these constraints has the features expected for a large complex impact crater. Bouguer‐gravity anomaly consists of broad ∼90‐km radius, ∼30‐mGal low with central ∼20‐km ∼20‐mGal high two <5‐mGal concentric lows at ∼35‐ ∼60‐km radius. gravity disrupted by large‐scale basement anomalies...
Abstract Evidence from borehole susceptibility logs and the spectral analysis of aeromagnetic data suggests that three‐dimensional distribution magnetization within crust can be described as fractal. This property exploited in magnetic interpretation methods which explicitly require statistical information on spatial variation magnetization. Specifically, we address problem source depth estimation through downward continuation gridding survey using method kriging. When are continued...
Delineating the edges of magnetized bodies is a fundamental application magnetic data to geological mapping in areas limited exposure. Especially Pre-Cambrian shield-like regions, locating lateral changes magnetization outcropping crystalline rocks provides spatial information that crucial extending mapped geology into sparsely exposed or completely covered areas. Although not all contacts correspond lithological contacts, former provide key on structural regimes, deformation styles and...
We present a method for determination of the topography an interface separating two uniformly but differently magnetized media. The technique is developed within framework discrete linear inverse theory and exploits quasi‐linearity problem to derive simple, efficient algorithm suitable use on large gridded data sets. Variation auxiliary parameters allows suite acceptable models be produced rapidly; these can appraised in light available geologic geophysical evidence. Because very matrices...
SUMMARY We have examined acoustic, density resistivity, gamma-ray and neutron logs from a number of boreholes in both sedimentary igneous sequences. We show that the power spectra these geophysical variables obey scaling law, is, are proportional to some frequency. In general, approximately inversely This suggests frequency-dependent noise models more appropriate for modelling spatial variation parameters than widely assumed white (frequency-independent) model should be incorporated into...
PreviousNext No AccessSEG Technical Program Expanded Abstracts 2011Understanding imaging methods for potential field dataAuthors: Maurizio FediMark PilkingtonMaurizio FediDepartment of Earth Sciences, University Naples Federico II, Italy.Search more papers by this author and Mark PilkingtonGeological Survey Canada, 615 Booth Street, Ottawa, Ontario, Canada K1A 0E9Search authorhttps://doi.org/10.1190/1.3628194 SectionsSupplemental MaterialAboutPDF/ePub ToolsAdd to favoritesDownload...
AbstractPotential field (gravity and magnetic) data are fundamental to geologic mapping approaches based on geophysical interpretations. Lithologic structural information can be extracted from amplitudes trends of the gravity magnetic anomalies. To assist in interpretation, enhancements commonly used transform original into new quantities that emphasize or suppress some specified component, resulting a more easily interpreted representation. The number available is rapidly increasing begs...