Edge Detection and Depth Estimates – Application to Pseudogravity and Reduced to Pole Results: Part I Edge detection on an oversampled synthetic anomaly with no additional noise Comparing Horizontal Gradient, Total Gradient (Analytic Signal), and Local Wavenumber

Magnetic anomaly calculated for 1.5 meters above the ground surface. Dimensions are kilometers, sampling interval is 400 meters, contour interval is 10 nT, inclination = 68 o. Subsurface model: Minimum depth is 250 meters, maximum is 3.35 kilometers Magnetic susceptibility is constant and positive with no remanent magnetization

The Model from Different Perspectives East-west faults get deeper and have less throw along strike from the center as they traverse from edge to edge of the model area The north-south fault gets deeper to the south but the throw is constant The long wavelength shape is that of a truncated dome.

Total field anomaly; inclination = 68 o Reduced to pole anomaly

Reduced to pole anomaly (RTP)Horizontal Gradient of the RTP anomaly

Maxima of the Horizontal Gradient of the RTP anomaly Maxima of the Horizontal Gradient of the RTP anomaly overlain on the source model

Total Gradient (Analytic Signal) of the RTP anomaly Reduced to pole anomaly (RTP)

Maxima of the Total Gradient of the RTP anomaly Maxima of the Total Gradient of the RTP anomaly overlain on the source model

Reduced to pole anomaly (RTP)Local Wavenumber of the RTP anomaly

Maxima of the Local Wavenumber of the RTP anomaly Maxima of the Local Wavenumber of the RTP anomaly overlain on the source model

Total field anomaly (inc = 68 o )Pseudogravity (Vertical Integral of RTP)

Pseudogravity Horizontal Gradient of the Pseudogravity

Maxima of the Horizontal Gradient of the Pseudogravity Maxima of the Horizontal Gradient of the Pseudogravity overlain on the source model

Pseudogravity Total Gradient (Analytic Signal) of the Pseudogravity

Maxima of the Total Gradient of the Pseudogravity Maxima of the Total Gradient of the Pseudogravity overlain on the source model

Pseudogravity Local Wavenumber of the Pseudogravity

Maxima of the Local Wavenumber of the Pseudogravity Maxima of the Local Wavenumber of the Pseudogravity overlain on the source model

The Model from Different Perspectives East-west faults get deeper and have less throw along strike from the center but go from edge to edge of the model area The north-south fault gets deeper to the south but the throw is constant The long wavelength shape is that of a truncated dome.

All Maxima; Analysis on PseudogravityAll Maxima; Analysis on RTP Maxima from the methods: Blue = HGM; Green = AS; Magenta = LWN For each case, operating on the pseudogravity (vertical integration of RTP) results in fewer spurious results; vertical integration is a low-pass operator. East-west faults run edge to edge and get deeper away from the center; only the LWN maxima trace faults continuously to the edges on both PSG and RTP. Only HGM on PSG gives insight into the curved nature of the main dome.

Top Four Quintiles of Gradient Maxima From the Pseudogravity Classed post map of the four upper quintiles of the combined results of HGM, AS, and LWN analysis of the pseudogravity (purple, blue, green, and red in order of increasing significance).