Unique geologic insights from “non-unique” gravity and magnetic interpretation

GSA Today ◽  
2011 ◽  
Vol 21 (12) ◽  
pp. 4-10 ◽  
Author(s):  
Richard W. Saltus ◽  
Richard J. Blakely
Keyword(s):  
Magnetic Interpretation ◽  
Gravity And Magnetic ◽  
Gravity And Magnetic Interpretation

Gravity and magnetic interpretation of the Deer Lake basin, Newfoundland

1984 ◽  
Vol 21 (1) ◽  
pp. 10-18 ◽  
Author(s):  
H. G. Miller ◽  
J. A. Wright
Keyword(s):  
Magnetic Data ◽  
Lake Basin ◽  
Magnetic Interpretation ◽  
Seismic Surveys ◽  
Reflection And Refraction ◽  
Gravity And Magnetic ◽  
Refraction Seismic ◽  
Gravity And Magnetic Data ◽  
Gravity And Magnetic Interpretation ◽  
Total Sediment

Detailed reconnaissance gravity surveys in the Deer Lake Carboniferous basin have been conducted using a station spacing of 2.5 km. The digitized aeromagnetic data for the basin were reduced to a 1:253 440 scale composite map. These two data bases were used to determine the configuration of major features and the total sediment thickness at various locations in the basin. Preliminary seismic results from reflection and refraction seismic surveys planned on the basis of these results are discussed. Modelling of gravity and magnetic data indicates that the Humber syncline contains approximately 1.2 km of sediments underlain on the west by rocks similar to the Long Range Complex. The eastern limb of the syncline is underlain by rocks similar to the Gull Pond Igneous Suite. The Howley Formation is deduced to be approximately 1.5 km thick and floored by rocks similar to the Topsails Igneous Suite.

FREQUENCY ANALYSIS FOR GRAVITY AND MAGNETIC INTERPRETATION

Geophysics ◽  
1958 ◽  
Vol 23 (1) ◽  
pp. 97-127 ◽  
Author(s):  
William C. Dean
Keyword(s):  
Frequency Response ◽  
Downward Continuation ◽  
Linear Filter ◽  
Second Derivative ◽  
Magnetic Interpretation ◽  
Electric Circuits ◽  
Frequency Responses ◽  
Upward Continuation ◽  
Gravity And Magnetic ◽  
Gravity And Magnetic Interpretation

The operations of second derivative, analytic continuation, smoothing, the removing of residuals or regionals, and others in gravity and magnetic interpretation are analogous mathematically to the filtering action of electric circuits. The main difference between the two is that electrical filters act on functions of one variable (time), whereas the geophysical filters must act on functions of the two space variables (x and y). This paper develops linear filter theory for gravity and magnetic interpretation. As an application of the theory, downward continuation is discussed in some detail. The frequency response of upward continuation is an exponential function decreasing with increasing frequency. The inverse process of downward continuation has a frequency response which is the reciprocal of the upward continuation response. This paper discusses a method of matching frequency responses by coefficient sets and shows by examples some of the inherent difficulties in downward continuation. A final example calculated analytically shows how good a downward continuation can be expected from a finite coefficient set.

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