An application for removing cultural noise from aeromagnetic data (short note)

INTRODUCTION A high-resolution aeromagnetic survey collected over the North Slope of Alaska by World Geoscience was acquired in response to a need for highly detailed data in an areawhere traditional geophysical techniques are expensive and prohibitive (McConnell, 1995) (Figure 1). These data were recently released to the University of Texas’ Institute for Geophysics and provide a unique opportunity to investigate the problem of cultural noise suppression in aeromagnetic data. The data contain isolated magnetic anomalies that are presumably from the many drill platforms and their accompanying cultural objects such as buildings and pipe repositories (Figure 2). We present a new, automatedmethod to reduce the amplitude of these cultural anomalies without affecting the magnetic signal from the surrounding geology. The importance of removing cultural noise is important to both processing and interpreting magnetic data. The location and subsequent removal of cultural noise can improve the calculated differences between survey and tie lines, for example, resulting in a more accurately leveled data set. Furthermore, many data sets can be more rigorously interpreted with the absence of cultural noise. A difficulty arises, however, because the cultural objects are randomly located and oriented as well as oddly shaped. Ravat (1996) cites the example of a chemical waste site where steel drums are buried at various depths and have various shapes. In situations such as these, linear inverse modeling only works approximately (Ravat, 1996) and band-pass filtering will not succeed because it will remove naturally occurring magnetic anomalies that happen to have wavelengths comparable to the magnetic anomalies from the cultural objects. In our data, filtering out wavelengths<3500m (500 fiducials; 1 fiducial is equal to the nominal sample rate, or∼7m) reduces the amplitudes of the cultural noise but also affects the mag-