Interpretation of fault system in the Tana Sag, Kenya, using edge recognition techniques and Euler deconvolution

Abstract

Abstract The recognition of fault structures in gravity anomaly data is the most important step in the interpretation of geological and geophysical data. Edge detection and edge enhancement are commonly used for researching the edge locations of geological bodies. The edge recognition techniques applied in this paper are the tilt angle (TA) and its horizontal derivative (TA-THDR), as well as the normalized vertical derivative of the total horizontal derivative (NVDR-THDR), in which higher order derivative was involved. The results of TA and its total horizontal derivative provide detailed information to reflect the deeper sources boundaries more accurately and effectively. The information outside the geological body edges obtained from the NVDR-THDR results is eliminated by using a threshold value greater than 0, which improves the horizontal resolution to detect the fault structures with smaller scale or deeper depth. However, tilt angle and its horizontal derivative are found to be sensitive to noise, as the higher order derivative is. The noise effect is reduced by using upward continuation during the processing of the measure gravity data. To better recognize the fault system, we have compared the results obtained from the derivative mode of Euler deconvolution technique with those from TA and its total horizontal derivative and NVDR-THDR. Application to the Tana Sag demonstrates that the results correspond well with those inferred from previous work. The faults within Tana Sag can be divided into large-scale NW (NWW) trending and small-scale NE (NEE) trending, with the latter generally cutting off the former. And we also have found that the comparative analysis of edge recognition techniques and the ED method can extract richer information on source body edges and identify more horizontal fault locations than previous methods. These three techniques have agreed closely in detecting the edge boundaries of the deeper sources with clear precision.