Presentation_Amplitude of the magnetic anomaly vector in low latitudes via equivalent layer.pdf (5.6 MB)

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posted on 2019-09-25, 13:18 authored by Shayane GonzalezShayane Gonzalez, Valeria C. F. BarbosaValeria C. F. Barbosa, Felipe F. MeloFelipe F. Melo, Vanderlei C. Oliveira Jr.Vanderlei C. Oliveira Jr.Slides for the oral presentation given at the Sixteenth International Congress of the Brazilian Geophysical Society.

"The interpretation of total-field anomalies data presents

complexities due to dipolar characteristics of the

anomalies. Usually, the geophysicists apply some

transformations to the measured total-field anomaly to

assist the magnetic interpretation and inversion. However,

it can lead to an unstable transformed data at low latitude

regions. To transform the total-field anomaly into the

amplitude of the magnetic anomaly vector, we can use

the equivalent layer technique and the Fourier filtering.

These two methods are applied to synthetic magnetic

data simulated at high- and low-magnetic latitudes. At

high latitude, the computed amplitude of the magnetic

anomaly vector either by applying the Fourier filtering or

by employing the equivalent layer technique is equal to

the true one. However, at low latitudes, the computed

amplitude of the magnetic anomaly vector differs from the

true one either by applying the Fourier filtering or by

employing the equivalent layer technique. Both computed

amplitudes of the magnetic anomaly vector exhibit

striations in the direction of declination at low latitudes.

However, at low latitudes, the magnitudes of the

differences between the true and the computed amplitude

of the magnetic anomaly vector produced by employing

the equivalent layer technique are substantially smaller

than the ones produced by applying the Fourier filtering.

The better result produced by the equivalent layer

technique is because the stabilization imposed by the

Tikhonov regularization. We also applied the equivalent

layer technique and the Fourier filtering to real total-field

anomaly at a low latitude region encompassing the

Central Amazonian Province and the Carajás Mineral

Province, Brazil, aiming at computing the amplitude of the

magnetic anomaly vector. Likewise, both transformations

exhibit undesirable striations; however the one obtained

via the equivalent layer technique yields better result in

comparison with those obtained via the Fourier filtering.

complexities due to dipolar characteristics of the

anomalies. Usually, the geophysicists apply some

transformations to the measured total-field anomaly to

assist the magnetic interpretation and inversion. However,

it can lead to an unstable transformed data at low latitude

regions. To transform the total-field anomaly into the

amplitude of the magnetic anomaly vector, we can use

the equivalent layer technique and the Fourier filtering.

These two methods are applied to synthetic magnetic

data simulated at high- and low-magnetic latitudes. At

high latitude, the computed amplitude of the magnetic

anomaly vector either by applying the Fourier filtering or

by employing the equivalent layer technique is equal to

the true one. However, at low latitudes, the computed

amplitude of the magnetic anomaly vector differs from the

true one either by applying the Fourier filtering or by

employing the equivalent layer technique. Both computed

amplitudes of the magnetic anomaly vector exhibit

striations in the direction of declination at low latitudes.

However, at low latitudes, the magnitudes of the

differences between the true and the computed amplitude

of the magnetic anomaly vector produced by employing

the equivalent layer technique are substantially smaller

than the ones produced by applying the Fourier filtering.

The better result produced by the equivalent layer

technique is because the stabilization imposed by the

Tikhonov regularization. We also applied the equivalent

layer technique and the Fourier filtering to real total-field

anomaly at a low latitude region encompassing the

Central Amazonian Province and the Carajás Mineral

Province, Brazil, aiming at computing the amplitude of the

magnetic anomaly vector. Likewise, both transformations

exhibit undesirable striations; however the one obtained

via the equivalent layer technique yields better result in

comparison with those obtained via the Fourier filtering.

*"*