Reliability of CHAMP Anomaly Continuations
CHAMP is recording state-of-the-art magnetic and gravity field observations at altitudes raging over roughly 300–550 km. However, the non-uniqueness of the process and satellite anomaly errors severely limit anomaly continuation. Indeed, our numerical anomaly simulations from satellite to airborne altitudes show that effective downward continuations of the CHAMP data are restricted to within approximately 50 km of the observation altitudes while upward continuations can be effective over a somewhat larger altitude range. The great unreliability of downward continuation requires that the satellite geopotential observations must be analyzed at satellite altitudes if the anomaly details are to be exploited most fully. Given current anomaly error levels, multi-field inversion of satellite and near-surface anomalies is the best approach for implementing satellite geopotential observations for subsurface studies. We demonstrate the power of this approach using a crustal model obtained by the inversion of combined near-surface and satellite magnetic anomalies for Maud Rise, Antarctica, in the southwestern Indian Ocean. Our modeling, which also includes regional gravity constraints, suggests that crustal thickness variations and remanent magnetization of the normal polarity Cretaceous Quiet Zone produce the dominant satellite altitude magnehtic anomalies.
Key wordsanomaly continuation Maude Rise Antarctica ADMAP CHAMP Ørsted
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