NSW Geophysics Isostatic Gravity over TMI RTP Tilt

This dataset is part of the Geological Survey NSW Geophysics dataset series.Bouguer gravity that has been isostatically corrected in pseudocolour, superimposed on a greyscale intensity layer showing tilt-filtered total magnetic intensity reduced to the pole. Isostatic correction of the gravity data removes the contribution due to Airy isostasy, the effect in which the depth of the base of the crust is greater in regions of higher topography. Variations in isostatically-corrected gravity should directly reflect differences in the geology of the crust, rather than its thickness. The tilt-filter is a variety of phase filter which, like the more familiar first vertical derivative of TMI (TMI 1VD), traces geological structures. Unlike TMI 1VD however, the tilt-filter is relatively insensitive to the depth of the source geology below the ground, making tilt-filtered TMI a useful tool for tracing geological structure below variable depths of sedimentary cover. Isostatic gravity shares the same units as Bouguer gravity (µms -2). The output of the tilt-filter is an angle, varying between -π/2 and +π/2 radians (i.e. -90° to +90°). This is not related to the strength of the magnetic anomaly, but the spacing between contours of equal tilt angle is related to the depth of the source.