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Von Frese, R.
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Von Frese, R.
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- PublicationOpen AccessSatellite magnetic anomalies of the Antarctic crust(1999-04)
; ; ; ; ; ; ; ; ;von Frese, R. R. B.; Byrd Polar Research Center and Department of Geological Sciences, The Ohio State University, Columbus, OH 43210, U.S.A. ;Kim, H.R.; Byrd Polar Research Center and Department of Geological Sciences, The Ohio State University, Columbus, OH 43210, U.S.A. ;Tan, L.; Byrd Polar Research Center and Department of Geological Sciences, The Ohio State University, Columbus, OH 43210, U.S.A. ;Kim, J. W.; Department of Earth Sciences, Sejong University, Republic of Korea ;Taylor, P. T.; NASA Geodynamics Branch, Code 921, Goddard Space Flight Center, Greenbelt, MD 20771, U.S.A. ;Purucker, M. E.; RSTX at NASA Geodynamics Branch, Code 921, Goddard Space Flight Center, Greenbelt, MD 20771, U.S.A. ;Alsdorf, D. E.; Department of Geological Sciences, Cornell University, Ithaca, NY 14853, U.S.A ;Raymond, C. A.; et Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099, U.S.A.; ; ; ; ; ; ; Spatially and temporally static crustal magnetic anomalies are contaminated by static core field effects above spherical harmonic degree 12 and dynamic, large-amplitude external fields. To extract crustal magnetic anomalies from the measurements of NASA's Magsat mission, we separate crustal signals from both core and external field effects. In particular, we define Magsat anomalies relative to the degree 11 field and use spectral correlation theory to reduce them for external field effects. We obtain a model of Antarctic crustal thickness by comparing the region's terrain gravity effects to free-air gravity anomalies derived from the Earth Gravity Model 1996 (EGM96). To separate core and crustal magnetic effects, we obtain the pseudo-magnetic effect of the crustal thickness variations from their gravity effect via Poisson's theorem for correlative potentials. We compare the pseudo-magnetic effect of the crustal thickness variations to field differences between degrees 11 and 13 by spectral correlation analysis. We thus identify and remove possible residual core field effects in the Magsat anomalies relative to the degree 11 core field. The resultant anomalies reflect possible Antarctic contrasts due both to crustal thickness and intracrustal variations of magnetization. In addition, they provide important constraints on the geologic interpretation of aeromagnetic survey data, such as are available for the Weddell Province. These crustal anomalies also may be used to correct for long wavelength errors in regional compilations of near-surface magnetic survey data. However, the validity of these applications is limited by the poor quality of the Antarctic Magsat data that were obtained during austral Summer and Fall when south polar external field activity was maximum. Hence an important test and supplement for the Antarctic crustal Magsat anomaly map will be provided by the data from the recently launched Ørsted mission, which will yield coverage over austral Winter and Spring periods when external field activity is minimal.239 1006 - PublicationRestrictedGraphical interactive generation of gravity and magnetic fields(2011-04)
; ; ; ; ; ;Pignatelli, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Nicolosi, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Carluccio, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Chiappini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;von Frese, R.; School ofEarthSciences,TheOhioStateUniversity,Columbus,43210OH,USA; ; ; ; This paper presents a MATLAB®- based geopotential field generator called GamField that constructs and visualizes subsurface sources in 3-D space and computes their gravity and magnetic effects. GamField also computes anomaly gradients and remanent magnetization effects. The user inputs Cartesian prisms along with their physical properties to fabricate subsurface sources. Examples illustrating the utility of GamField for synthetic anomaly generation of gravity and magnetic fields are shown. ftp://ftp.ingv.it/pub/alessandro.pignatelli/Pignatelli646 86 - PublicationRestrictedA model of the secular change of the geomagnetic field for Antarctica(2002)
; ; ; ; ;Torta, J. M.; Observatori de l’Ebre, CSIC, 43520 Roquetes, Tarragona, Spain ;De Santis, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Chiappini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;von Frese, R. R. B.; Department of Geological Sciences, and Byrd Polar Research Center, The Ohio State University, Columbus, OH 43210, USA; ; ; An improved model of geomagnetic secular change for the Antarctic was developed using observatory annual mean values measured in Antarctica during the last 40 years. Spherical cap harmonic analysis (SCHA) with a power series time dependence was used to model spatial and temporal variations of main field differences at spatial wavelengths from 3000 to 13,000 km. The model was designed to facilitate merging satellite, airborne, marine and terrestrial magnetic data sets recorded at very different epochs in the Antarctic where significant annual geomagnetic changes have occurred. It improves the fit to observatory data by up to about 50% relative to the International Geomagnetic Reference Field.198 28 - PublicationOpen AccessDevelopment of an improved geomagnetic reference field of Antarctica(1999-04)
; ; ; ; ;De Santis, A.; Istituto Nazionale di Geofisica, Roma, Italy ;Chiappini, M.; Istituto Nazionale di Geofisica, Roma, Italy ;Torta, J. M.; Museo Nacional de Ciencias Naturales, CSIC, Madrid, Spain ;von Frese, R. R. B.; Department of Geological Sciences and Byrd Polar Research Center, The Ohio State University, Columbus, OH 43210, U.S.A.; ; ; The properties of the Earth's core magnetic field and its secular variation are poorly known for the Antarctic. The increasing availability of magnetic observations from airborne and satellite surveys, as well as the existence of several magnetic observatories and repeat stations in this region, offer the promise of greatly improving our understanding of the Antarctic core field. We investigate the possible development of a Laplacian reference model of the core field from these observations using spherical cap harmonic analysis. Possible uses and advantages of this approach relative to the implementations of the standard global reference field are also considered.211 201 - PublicationOpen AccessMapping and interpretation of satellite magnetic anomalies from POGO data over the Antarctic region(1999-04)
; ; ; ;Purucker, M. E.; Raytheon ITSS at Geodynamics Branch, Goddard Space Flight Center, Greenbelt, MD, U.S.A. ;von Frese, R. R. B.; Byrd Polar Research Center and Department of Geological Sciences, The Ohio State University, Ohio, U.S.A. ;Taylor, P. T.; NASA, Geodynamics Branch, Goddard Space Flight Center, Greenbelt, MD, U.S.A.; ; A satellite magnetic anomaly map made using the POGO magnetic field data is compared to three maps made using Magsat data. A total of 14 anomalies with magnitudes greater than 3 nT can be identified in all four of the maps poleward of 60°S latitude. Forward models of the Antarctic continental and oceanic lithosphere are produced which use magnetic crustal thickness based on seismic and heat flow data, and which also use the distribution of the Cretaceous Quiet Zone from marine geophysics. These simple models can explain significant parts of eight of the 14 identified anomalies. The remaining anomalies may be caused by lateral variations of magnetization, inadequate models of the magnetic crustal thickness, or remanent magnetizations in directions other than the present field. In addition, contamination of the magnetic anomaly maps by fields of time-varying external origin (and their corresponding internal parts) is still a significant problem in the Antarctic region.167 772 - PublicationOpen AccessSatellite mapping of the Antarctic gravity field(1999-04)
; ; ; ; ; ;von Frese, R. R. B.; Byrd Polar Research Center and Department of Geological Sciences, The Ohio State University, Columbus, OH 43210, U.S.A. ;Roman, D. R.; Byrd Polar Research Center and Department of Geological Sciences, The Ohio State University, Columbus, OH 43210, U.S.A. ;Kim, J. H.; Department of Civil Engineering, Kyongnam National University, Republic of Korea ;Kim, J. W.; Department of Earth Sciences, Sejong University, Republic of Korea ;Anderson, A. J.; Department of Physics, University of California-Santa Barbara, CA 93106, U.S.A.; ; ; ; The production and analysis of the Antarctic digital magnetic anomaly map will be greatly aided by complementary gravity data. They help to constrain thickness variations of the crust and related magnetic effects that may be used for correcting long-wavelength errors in near-surface magnetic survey compilations. They also limit ambiguities in geological interpretations of magnetic anomalies. Antarctic free-air gravity anomalies are available from the 1° Earth Gravity Model 1996 (EGM96). These coefficients satisfy gravity estimates from satellite radar altimetry, as well as surface or near-surface measurements in roughly 75% of the 30 arc-minute blocks south of 60°S. For the remaining blocks, the EGM96 predictions are limited in resolution to degree 70 based on satellite orbital analyses. Anomaly predictions over the unsurveyed regions of the Antarctic will be greatly improved by additional orbital measurements from the pending low-altitude (i.e., 150-500 km) CHAMP and GRACE satellite missions of ESA and NASA, respectively. Shorter wavelength anomalies are available from Geosat and ERS-1 & 2 radar altimetry data for marine regions away from the shoreline that compare very well with modern, good-quality shipborne data. Over the Gunnerus Ridge region, for example, satellite altimetry-derived free-air gravity predictions at a 3-5 km grid interval have an accuracy of about 3 mgals or less.196 198 - PublicationRestrictedPreface to Tectonophysics, 347, 1-3 (2002)(2002-03-19)
; ; ; ;von Frese, R. R. B.; Department of Geological Sciences, The Ohio State University, Columbus, OH 43210, USA ;Taylor, P. T.; Geodynamics Branch, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA ;Chiappini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; ; Antarctica is the most poorly understood region of our planet. It, however, maintains an important geologic record of the Gondwana and Rodinia evolution and therefore is a center of extensive scientific inquiry. Magnetic data provide a critical window for geological studies due to the nearly ubiquitous snow and ice cover of this forbidding region. Consequently, numerous magnetic surveys have been carried out for site-specific geologic objectives since the International Geophysical Year 1957/1958. Plans for an international project to process and combine these disparate data sets into a single magnetic anomaly map were formulated at the 1993 meeting of the International Association of Geomagnetism and Aeronomy (IAGA) in Buenos Aires, Argentina. Both IAGA and the Scientific Committee on Antarctic Research (SCAR) passed resolutions of encouragement (Johnson et al., 1996; Chiappini et al., 1999). At a 1995 workshop at the British Antarctic Survey in Cambridge, UK, it became clear that these individual magnetic surveys could indeed be combined into a regional synthesis to further enhance their utility for geological studies (Johnson et al., 1996, 1997; Chiappini et al., 1998, 1999). Accordingly, the Antarctic Digital Magnetic Anomaly Project (ADMAP) was launched at this first workshop (ADMAP I) to compile and integrate into a digital database existing near-surface and satellite magnetic anomaly data of Antarctica and the surrounding oceans south of 60jS. An international working group of 32 scientists from eight countries that operate magnetic programs in the Antarctic was established. The working group adopted protocols for making existing and future magnetic data sets available to this international effort. In particular, existing Antarctic magnetic data holdings will be deposited in the world data centers by the end of this first phase of the project in 2002.153 23 - PublicationRestrictedRegional magnetic and gravity anomaly correlations of the Southern Tyrrhenian Sea(2010-07)
; ; ; ; ; ;De Ritis, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Ventura, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Chiappini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Carluccio, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Von Frese, R.; School of Earth Science, Ohio State University, Columbus, OH 43210, USA; ; ; ; The complex magnetic and gravity anomaly fields of the Southern Tyrrhenian Sea provide a record of the complicated properties and evolution of the underlying crust. Geologic interpretation of these anomalies is hindered by the effects of anomaly superposition and source ambiguity inherent to potential field analysis. A common approach to minimizing interpretational ambiguities is to consider analyses of anomaly correlations. Spectral correlation filters are used to separate positively and negatively correlated anomaly features based on the correlation coefficient given by the cosine of the phase difference between common wavenumber components. This procedure is applied to reduced-to-pole magnetic and first vertical derivative gravity anomalies for mapping correlative crustal magnetization and density contrasts. Adding and subtracting the standardized outputs of the filters yield summed (SLFI) and differenced (DLFI) local favorability indices that, respectively highlight positive and negative feature correlations in the anomaly data sets. Correlative maxima mainly reflect volcanic structures, and secondarily intrusive bodies and pre- Tortonian carbonates of the Maghrebian chain and the basement rocks of the Sardinia eastern margin. Correlative minima mostly mark sediment-filled peri-Tyrrhenian structural basins related to the Pliocene extensional tectonics, and intra-slope marine depressions related to post-Pliocene and still-active compressional tectonics off Northern Sicily. Prominent inverse anomaly correlations mainly reflect crustal features around the southern margin of the Tyrrhenian Sea that include higher density, lower magnetization pelagic-to-terrigenous and flysch-type nappes of the Sicilian-Maghrebian chain, as well as lower density, higher magnetization sediments filling depressions of the chain, and syn-rift sediments of Southeastern Sardinia.485 45