[S-TT53] 空中からの地球計測とモニタリング

[STT53-P03] Three Dimensional Geophysical Inversion of Airborne Magnetic Data from the Yellowstone National Park (YNP), Western North America

*Mohammad Shehata^1,2、Hideki Mizunaga² (1.Department of Geology, Faculty of Science, Port Said University, Egypt、2.Department of Earth Resources Engineering, Faculty of Engineering, Kyushu University, Japan)

キーワード：Yellowstone National Park YNP, magnetic inversion, hydrothermal alteration

Yellowstone National Park (YNP) displays numerous and extensive hydrothermal features. Airborne Total Magnetic Intensity (TMI) data of the area was acquired from the USGS. TMI data was processed and Reduce-to-Pole (RTP) map was produced. Analytic Signal (ASA) and Theta map filters were applied to the magnetic data to delineate the structural Lineaments of the magnetic sources. Three dimensional geophysical inversion was applied to the magnetic data using the algorithms of Li and Oldenburg (1996), the inversion reveals the 3-D distribution of the magnetic susceptibility for a depth of few kilometers which delineate the alteration zones of the geothermal system in the area. The inversion parameters were selected to fit both the resolution of subsurface model and calculation capacity of the running computer. The boundary of Yellowstone caldera was delineated efficiently from the ASA and Theta maps. Inversion results show that the hydrothermal zones coincide with magnetic lows observed in aeromagnetic surveys, which suggests a strong demagnetization of both the shallow and deep substratum within these areas associated with the removal of magnetic minerals by hydrothermal alteration processes over a thickness of a few hundred meters in hydrothermal areas at YNP, and that the maximum degree or maximum thickness of demagnetization correlates closely with the location of hydrothermal activity and mapped alteration.
References
Li, Y., and Oldenburg, D. W. (1996). 3-D inversion of magnetic data. Geophysics, 61(2), 394-408