HR: 0800h
AN: T31A-1287    [Abstracts]
TI: Testing the Utilization of Aeromagnetic Data for the Determination of Curie-Isotherm Depth
AU: * Ross, H E
EM: hemiller@pangea.stanford.edu
AF: Department of Geophysics, Stanford University, Stanford, CA 94305-2215 United States
AU: Blakely, R J
EM: blakely@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Road, MS 989, Menlo Park, CA 94025 United States
AU: Zoback, M D
EM: zoback@pangea.stanford.edu
AF: Department of Geophysics, Stanford University, Stanford, CA 94305-2215 United States
AB: We examine the feasibility of using depths to Curie-temperature isotherm in regions with sparse heat-flow measurements, such as intraplate regions of the United States, to detect areas with elevated lower-crustal temperatures. Depth to Curie point is often considered to be a general indicator of temperature at depth. In this study, California was chosen as a test region because of its large number of well-documented surface heat-flow measurements and generally high quality aeromagnetic data. We estimate depths to Curie-temperature isotherm by spectral analysis of aeromagnetic data following the methods of Smith et al. (1974), Shuey et al. (1977), Boler (1978), Connard et al. (1983), and Blakely (1988). However, two modifications are applied to these previous methods as a result of the complex geology of California: We increase the dimensions of sub-regions in a stepwise manner until a peak is observed at the low-wavenumber end of the power spectrum, and we manually fit the observed power spectrum with a theoretical expression that directly yields the depth to the top and bottom of the magnetic layer. In general, we find good agreement between our calculated Curie depths for California and measured heat flow, and we obtain reasonable Curie depths using our modified spectral analysis approach. The Coast Ranges of California are characterized by high heat flow, and our calculated Curie depths are relatively shallow for this province, whereas the Great Valley and Sierra Nevada, characterized by low heat flow, have deeper Curie depths. On the other hand, we also find that the spatial resolution of our method is insufficient to distinguish areas of elevated lower-crustal temperatures in California with lateral dimensions smaller than about 200 km in the absence of heat-flow measurements.
DE: 8110 Continental tectonics--general (0905)
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8122 Dynamics, gravity and tectonics
DE: 8164 Stresses--crust and lithosphere
DE: 7218 Lithosphere and upper mantle
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting