Evaluation of the efficiency of shortened low-pass filters computed by inverse fourier transform for potential fields of spherical bodies and planar regionals

Abstract EN

The purpose of a se pa ra tio n filler may be defined as suppressing deep-rooted anomalies a nd faithfully reproducing shall ow-rooted ones.

Such se para tio n could be performed by th e transformation of gridded data using a set of coefficients computed by numerical evaluation o f the Inver se Fourier Transform of the filler matrix .

A residual field du e to an arbitrar y spherical structure is ch osen for testing and ev alu ating this method for obtaining a shortened mat rix.

The sphe rical mod el and plan ar regional a re used mer ely due to th e simplicity of calcula t ions .

Th e ef ficien cy o f the low pass filler is st ati sti cally computed and me asured by the normalized residual root mean sq uare (nrrrns) between the theoretical a nd filtered field s .

Th e e fficie ncy o f filtering, du e to different low pass filler parameters and matrix sizes .

has been stu die d .

Vari ou s inter-r el ati on sh ip curves , concerning th e regional ization param et er (0 ).

matrix length (M), and depth to the cau sativ e bod y (Z), have be en co nstructed for ch oosing a matrix which ap proximates th e the oreti cal filler respon se best.

It was found that the choi ce o f a low pass filler (smoo thing) parameter of 0 = 60 and a matrix length of M = 21 is a compromi se between the practical matrix size and the required eff iciency o f th e low pass filler at different depth units (Z) .

It is also co nclu ded that filter parameters and matrix len gth s suitable for se para tion of deep sphe rical local bodies are effi ciently used for sha llower o nes .