HR: 10:50h
AN: GP21D-03 INVITED     [PDF]
TI: High-Altitude Magnetic Survey Over the United States
AU: * Hildenbrand, T G
EM: tom@usgs.gov
AF: U.S. Geological Survey, MS 989, 345 Middlefield Road, Menlo Park, CA 94025 United States
AU: Keller, G
EM: keller@geo.utep.edu
AF: University of Texas at El Paso, Department of Geological Sciences, El Paso, TX 79968 United States
AU: Pellerin, L
EM: pellerin01@aol.com
AF: Green Engineering, Inc., 2215 Curtis Street, Berkeley, CA 94702 United States
AU: Phillips, J
EM: jeff@usgs.gov
AF: U.S. Geological Survey, MS 964, Denver Federal Center, Denver, CO 80225 United States
AU: Ravat, D
EM: ravat@geo.siu.edu
AF: Southern Illinois University at Carbondale, Department of Geology 4324, Carbondale, IL 62901 United States
AU: Sabaka, T
EM: sabaka@geomag.gsfc.nasa.gov
AF: NASA Goddard Space Flight Center, Geodynamics Branch, Code 921, Greenbelt, MD 20771 United States
AB: The year 2004 offers an exciting and cost-effective opportunity to acquire a high-altitude magnetic data set over the U.S. A national mission is presently being planned to collect IFSAR imagery in addition to total and vector magnetic field data at an altitude of about 15 km. High-altitude magnetic data, needed as a reference field to properly level the U.S. low-altitude magnetic data set (0.3 km altitude), will also provide new insights on fundamental tectonic and thermal processes, thereby enabling a new view of the structural and lithologic framework of continental and offshore regions. A correctly merged, low-altitude magnetic database, using high-altitude magnetic data as a reference field, will be one of the most important legacies of a high-altitude magnetic mission, as it will greatly expand the utility of the invaluable U.S. magnetic data. However, the high-altitude data also have considerable independent scientific value. These unique data will bridge the spectral gap between the spectrums of the low-altitude aeromagnetic and satellite magnetic data. Based on our understanding of the magnetic properties of the lithosphere, the high-altitude data will clearly aid in the solution of a broad range of applied Earth science issues related to: the conundrum of long-wavelength magnetic anomalies; geologic and tectonic processes of crustal accretion and evolution; thermal and mechanical properties of the lithosphere; societal concerns including localization of favorable areas for mineral, energy, and thermal resources; and mitigation of earthquake and volcanic hazards. The wavelength band of a high-altitude survey will be particularly helpful in studying the lower crust--its composition, structure, and thermal regime--and large geologic/tectonic structures, such as basement terranes. In addition, these results will provide significant new constraints for geological interpretation of complementary regional topographic, seismic, electromagnetic, gravity, and heat flow data. The planned mission has led to many challenges. A commonly overlooked parameter in processing aeromagnetic data, namely magnetic effects caused by the electrically conductive Earth, has spawned mission studies related to base-station separation and magnetic induction effects. Induction effects have been observed over significant distances from large conductive structures within the Earth and at coastlines (due to the significant conductivity contrast between the seawater and the landmass). Another problem to overcome is the need to estimate the time-varying ionospheric and magnetospheric magnetic variations in the high-altitude survey data, as they will have wavelengths similar to those of crustal magnetic anomalies. These external fields must be identified and removed from the data to accurately recover the crustal anomaly fields.
DE: 0925 Magnetic and electrical methods
DE: 1594 Instruments and techniques
DE: 5475 Tectonics (8149)
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2003 Fall Meeting