Potential field migration for rapid 3D imaging of entire gravity gradiometry surveys

Introduction Gravity gradiometry has come to be routinely integrated into exploration workflows, since it can provide an independent measure of the subsurface density distribution. 3D density models derived from gravity gradiometry data are used to improve velocity models used in seismic imaging of complex salt and basalt structures. The advantage of gravity gradiometry over other gravity methods is that the data are extremely sensitive to localized density contrasts within regional geological settings. High quality data can be acquired from either airborne or shipborne platforms over very large areas for relatively low cost. A number of publications have discussed the use of 3D regularized inversion with both smooth (e.g., Li, 2001) and focusing (e.g., Zhdanov et al., 2004) stabilizers for the interpretation of gravity gradiometry data. A variety of fast imaging techniques related to Euler decomposition have also been developed. Most of these are based on the superposition of analytical responses from specific sources (e.g., Fedi, 2007). These imaging methods typically estimate the positions and some parameters of the sources based on field attenuation characteristics. In this paper, we present a different approach to imaging based on the idea of potential field migration as originally introduced by Zhdanov (2002). The new approach provides a rapid method for direct transformation of the observed gravity gradiometry data into a 3D density distribution. Migration can be mathematically described as the action of the adjoint operator on the observed data. This concept has been