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Estimation of depth to magnetic source using maximum entropy power spectra, with application to the Peru-Chile Trench

By
Richard J. Blakely
Richard J. Blakely
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Slamak Hassanzadeh
Slamak Hassanzadeh
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Published:
January 01, 1981

Estimations of the depth to magnetic sources using the power spectrum of magnetic anomalies generally require long magnetic profiles. The method developed here uses the maximum entropy power spectrum (MEPS) to calculate depth to source on short windows of magnetic data; resolution is thereby improved. The method operates by dividing a profile into overlapping windows, calculating a maximum entropy power spectrum for each window, linearizing the spectra, and calculating with least squares the various depth estimates. The assumptions of the method are that the source is two dimensional and that the intensity of magnetization includes random noise; knowledge of the direction of magnetization is not required. The method is applied to synthetic data and to observed marine anomalies over the Peru-Chile Trench. The analyses indicate a continuous magnetic basement extending from the eastern margin of the Nazca plate and into the subduction zone. The computed basement depths agree with acoustic basement seaward of the trench axis, but deepen as the plate approaches the inner trench wall. This apparent increase in the computed depths may result from the deterioration of magnetization in the upper part of the ocean crust, possibly caused by compressional disruption of the basaltic layer. Landward of the trench axis, the depth estimates indicate possible thrusting of the oceanic material into the lower slope of the continental margin.

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Contents

GSA Memoirs

Nazca Plate: Crustal Formation and Andean Convergence

La Verne D. Kulm
La Verne D. Kulm
Editor
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Jack Dymond
Jack Dymond
Editor
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E. Julius Dasch
E. Julius Dasch
Editor
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Donald M. Hussong
Donald M. Hussong
Editor
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Roxanne Roderick
Roxanne Roderick
Associate Editor
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Geological Society of America
Volume
154
ISBN print:
9780813711546
Publication date:
January 01, 1981

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