*The Principle of Interpretation of Gravity Data Using Second Vertical Derivative Method DOI: http://dx.doi.org/10.5772/intechopen.100443*

shown in **Figure 3**. The second vertical derivative map shows the distribution of the second-order vertical derivative in mGal/m<sup>2</sup> . The value ranges from 320,000,000 mGal/m<sup>2</sup> to 100,000,000 mGal/m<sup>2</sup> . The zero values show the edges of the deeper feature. As defined earlier, the portion with less density is considered to contain more sediment. The map shows that density distribution is decreasing inward between 8°N to 10.5°N and 11°E to 13°E. The same thing happens between 12.5°N to 13°N and 11.2°E to 12°E. The zero contours can be observed throughout the map, which means that there are so many boundaries or edges in the area.

The second vertical derivative map in **Figure 3** shows that the "polarity" of the anomaly can still be recognized, that is, the low density in the Central part relative to its surroundings*.* The second vertical derivative method of gravity anomaly illustrates the amplitude of gravity anomaly that is triggered by fault structure that gives the impression of residual anomaly. The map of the second vertical derivative method in this study shows that the method is useful in enhancing weaker local anomalies, edges of geologically anomalous density distributions were defined, and geologic units are identified. The second vertical derivative is interested in nearsurface anomalous effect at the expense of the effects that are of deep origin. This study embraced the use of the second vertical derivative because of its tendency to emphasize local anomalies and isolate them from the local background, which can be seen in **Figure 3**. When compared to the Bouguer map in **Figure 2**, it can be observed that the calculation of gradients has boosted refined features of gravity data that else cannot be noticed visually from the original data. High gradients observed in the middle of the map can be connected to the high contrast of the subsurface physical properties and vice versa [11].

Gradients, and also their magnitude, are commonly engaged to delineate boundaries of anomalous sources. The map produced extended zero contours,

**Figure 2.** *Bouguer gravity map.*

which corresponds to the edges of local geologically anomalous density distribution structures. The quantity zero mGal/m<sup>2</sup> coincides with most of the lithological boundaries, when compared with the major geologic contacts.
