## 5 Results
### Gravity Results  
The CBA map depicted in Figure 10a shows values ranging from 47 to 119 mGal. There were high anomaly values in the north and south, which flanked low anomaly values near Limboto Lake. The distribution of the gravity anomaly showed a W-E striking lineament, which indicated the presence of a depression zone. The high anomaly values in the northern and southern sections correlated with the presence of intrusive rocks and andestile lava, which are volcanic products of old volcanoes. The moderate anomaly values were associated with limestone and sandstone, in accordance with geological studies. The low anomaly values in the center of the study area were associated with low-density materials, reflecting alluvial deposits. These anomalous contrasts indicated that a depression zone was formed by tectonic activity. The separation of CBA anomalies was performed to obtain information related to local geothermal targets from their regional structures. The separation was performed by subtracting the CBA from a polynomial surface, which represented regional surface tendencies. The second-order polynomial was the most suitable regional anomaly representation. This regional anomaly map (Figure 10b) showed an anomaly distribution that extended W-E, and its values increased to the north and south. These features clarified the symmetrical pattern of the anomaly. The high anomaly zones in the northern and southern sections were associated with the presence of andesitic lava and more massive intrusions compared with the central section, which was filled with limestone and alluvial deposits. The residual anomaly map (Figure 10c) showed anomalous contrasts that emphasized the presence of recognized lineaments from the CBA. The high anomaly zones were associated with the presence of intrusive rocks, and andestile lava flanking the limestone and lake sediment in the center of the study area appeared more clearly defined. The locations of geothermal manifestations in the Limboto Lake--Pentadio area were in a transition zone between low and high anomaly zones, which may be attributed to the presence of faults or fracture structures that control the geothermal system in the shallow areas. Figure 10d depicts the horizontal gradient map that indicated the presence of high anomaly values in the southeastern section of the study area, which may be attributed to the existence of intrusive rocks. The NW-SE-trending lineaments flanking the alluvial zone were clearly visible. These lineaments describe a fairly high-to-medium lateral variation that controls the geothermal system, as evidenced by the presence of a geothermal surface manifestation complex. This manifestation complex was located in the transition between the high and low zones, reflecting horizontal discontinuities or faults. The vertical gradient analysis sharpened the anomaly over more regional structures and reduced the anomaly complexity, enabling the visualization of the causative body. The vertical gradient amplitude of the study area is illustrated in Figure 10e. The high gradient values around Limboto Lake indicated the presence of high-density rock close to the filling  
Figure 10: (**a**) Complete Bouguer anomaly (CBA) map from gravity result at Lake Limboto— Pentadio area with an assumed Bouguer density correction of 2.5 g/cm\({}^{3}\); (**b**) regional and (**c**) residual anomaly maps from Bouguer anomaly separation; and (**d**) HD, (**e**) VD, and (**f**) SVD values of the Bouguer anomaly. material of the depression zone. The geothermal manifestation zone was observed in the transition area between the high and medium gradients, as is common in geothermal areas [51]. This transition area was associated with faults that have the potential to act as geothermal fluid pathways to the surface. The SVD map for Limboto Lake, Pentado is shown in Figure 10f. SVD anomalies are related to shallow and local features, which are equivalent to the results of high-frequency filtering.