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Dear Label_Name,

Greetings! I hope you are well.

I am writing on behalf of an international publishing house, Science and Education Publishing, USA (http://www.sciepub.com).

Science and Education Publishing (SciEP) is a multidisciplinary open access publisher of Journals covering the fields of Science, Technology and Medicine. All SciEP publications are subject to high-quality peer review, editorial and production processes and are freely available online.

Welcome to the April, 2013 edition of SciEP newsletter, providing monthly summaries of articles on science & education related topics of interest to scientist and professionals. The mission of our journals is to provide an open access forum for publishing new findings on issues pertinent to scientific and academic field. We also invite you to submit original research papers, review articles, short reports, or case studies are considered for publication in our Multidisciplinary Journals.

American Journal of Public Health Research
DOI: 10.12691/ajphr-1-1-3

The Implementation of a Tele-Homecare System with Service Oriented Architecture and HL7 Message Transmission Standard
Ching-Sung Wang

American Journal of Medical and Biological Research
DOI: 10.12691/ajmbr-1-1-2

The Influence of Ethanol on Pyruvate Kinases Activity in Vivo, in Vitro, in Silico
Lelevich Sergey Vladimirovich, Khrustalev Vladislav Victorovich, Barkovsky Eugene Victorovich, Shedogubova Tatyana Aleksandrovna

American Journal of Medical Sciences and Medicine
DOI: 10.12691/ajmsm-1-1-1

Clinical and Histological Features in Wegener Granulomatosis
Li Cavoli Gioacchino, Passantino Rita, Bono Luisa, Tortorici Calogera, Ferrantelli Angelo, Giammarresi Carlo, Rotolo Ugo

American Journal of Infectious Diseases and Microbiology
DOI: 10.12691/ajidm-1-1-2

The Curse of Lymphatic Filariasis: Would the Continual Use of Diethylcarbamazine Eliminate this Scourge in Papua New Guinea?
Anne Lanham, Lillian Mwanri

We have released issues of some journals on February 2013.
American Journal of Public Health Research
American Journal of Medical Sciences and Medicine
American Journal of Medical and Biological Research
American Journal of Pharmacological Sciences
American Journal of Clinical Medicine Research
American Journal of Nursing Research
American Journal of Cancer Prevention
American Journal of Medicine Studies
American Journal of Infectious Diseases and Microbiology
American Journal of Cardiovascular Disease Research
American Journal of Biomedical Research
American Journal of Mechanical Engineering
American Journal of Microbiological Research
Journal of Preventive Medicine
American Journal of Food and Nutrition
American Journal of Hypertension Research
American Journal of Sports Science and Medicine
Journal of Cancer Research and Treatment
American Journal of Zoological Research
Journal of Biomedical Engineering and Technology
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Euler Deconvolution of Gravity Data for Structural Mapping and Heat Source Targeting In the Silali Geothermal Field, Kenya

Daniel N. Nyakundi*, Erick R. Nyakundi, Solomon Namaswa

Department of Physics, Kisii University, Nairobi, Kenya

Abstract: Gravity data analysis is a widely applied technique for imaging the Earth’s subsurface. This study interprets satellite-derived gravity data over Silali geothermal field to delineate subsurface structures and identify zones favourable for geothermal resource development. Standard reduction procedures were applied to raw gravity data to obtain a complete Bouguer Anomaly (CBA) map. Residual gravity anomalies were extracted using Butterworth and bandpass filters in Oasis Montaj. The anomalies predominantly trend in North-South, Northwest –Southeast directions, forming grabens and horsts that localize magmatic intrusions and geothermal up flow zones. Further enhancement using upward continuation, analytic signal, Power spectrum analysis, and located Euler deconvolution revealed intermediate and deep seated structures. Spectral analysis indicates sediment thickness between 1500 and 5300 metres sufficient to sustain geothermal energy systems. The analytic signal delineates potential intrusions and faults, particularly in the central, South-East, and Western zones. Euler deconvolution solutions (structural index = 0.5, 1.0, 2.0) cluster mainly North and West of the caldera, outlining dense magmatic bodies and fault-controlled features influencing geothermal fluid flow. These findings provide valuable insights for targeting drilling locations in the Silali geothermal system.

Keywords: Gravity anomalies, geothermal, delineate, power spectrum analysis, Euler Deconvolution

Received July 04, 2025; Revised August 06, 2025; Accepted August 13, 2025

Citation: Daniel N. Nyakundi, Erick R. Nyakundi, Solomon Namaswa, Euler Deconvolution of Gravity Data for Structural Mapping and Heat Source Targeting In the Silali Geothermal Field, Kenya. Journal of Geosciences and Geomatics, 13 (2). 43-51. January 2025. doi:10.12691/jgg-13-2-2

1. Introduction

Gravity data and edge detection techniques have become vital tools in mapping subsurface geology and delineating structural lineaments originating from shallow, intermediate, and deep [1,2,3,4,5]. The application of advanced filtering techniques to potential filed data has significantly improved the resolution and accuracy of geological interpretations [3,5,6,7].

The gravity method is particularly useful in identifying spatial variations in rock density (𝞺) which lead to changes in the Earth’s gravitational field strength [8,9,10,11,12,13] for imaging the subsurface structures [11,14] to delineate geothermal heat source. This method is noninvasive and cost-effective as it does not require injecting of energy into the subsurface. It is ideal for geothermal exploration due to its sensitivity to density contrasts associated with magmatic intrusions, fractured zones, and hydrothermally altered rocks.

Gravity data helps locate geological features such as faults, igneous intrusions, and sedimentary basins based on density differences. Positive gravity anomalies typically indicate denser subsurface bodies like mafic intrusions or crystalline basement rocks, while negative anomalies often correspond to porous, altered, or fractured formations [15]. These variations provide insights into subsurface conditions relevant to geothermal heat sources.

In geothermal settings, the gravity method assists in determining the depth, geometry, and location of magmatic bodies that may serve as heat sources. It also identifies structural controls such as faults that act as conduits for geothermal fluids.

To isolate the gravity signal associated with geothermal structures, standard corrections-such as for elevation, topography, latitude, and tides- must be applied to raw gravity data [8,11,16,17,18]. This yields a complete Bouguer Anomaly (CBA), which better reflects subsurface density variations [11,17,19]. Residual gravity anomalies, extracted through bandpass and Butterworth filters, help identify shallow and deep geological features.

Euler deconvolution is used to estimate the depth and geometry of subsurface sources by analyzing potential field gradients. This method does not require prior assumptions about the source orientation and is widely used for automatic structural interpretation model [20,21]. In this study, located Euler was applied due to its improved accuracy and reduced sensitivity to noise. The structural indices of 0.5, 1.0 and 2.0 were used to characterize different source types, such as contacts, faults, and cylindrical bodies [22].

The objective of this study was to use gravity data to image subsurface structures and estimate the depth of potential geothermal heat sources in the Silali geothermal field.

1.1. The Study Area

Silali geothermal field is located to the East of Kapedo Town between Baringo and Turkana counties, 50km North of Lake Baringo and about 120km south of Lake Turkana at 1⁰10’N, 36⁰12’E [23]. The study area is indicated by the blue square in Figure 1. Most of the geothermal prospects and fields associated with Quaternary volcanic center and fissure, of the recent tectonic activity of the rift floor [24,25] that overly the products of Miocene and Pliocene volcanism are found within the rift valley. The shield volcanoes are built generally of intermediate lavas and the interrelated pyroclastic, thus indicating the presence of near surface hot bodies [26].

1.2. Geology of Silali Area

The volcano is a broad shield which rises 760m from the rift floor reaching to an altitude of 1528 meters above sea level on the summit. The shield is elongated in North-South direction, having basal dimensions of 36 km by 25 km and is occupied by a spectacular summit caldera that measures 8 km by 5 km, bounded by 300 m cliffs. The collapse of the caldera was related to magma withdrawal at depth [27,28]. The caldera aligned in Northwest-Southeast direction and fissures and faults trending in Northeast- Southwest [23,29].

Figure 1. Map showing the location of study area

There is a 30 km wide trachyte shield volcano initiated during the early Quaternary times with the eruption of largely basaltic lavas. The eruptions are predominantly composed of basalts, trachytes with minor hawaiites, mugearites, benmoreites and phonolites [23,28,30], Figure 2. The main structures in the area surrounding Silali include the faults trending in Northeast-Southwest and the caldera. In the North, orientation is parallel to the rift margin and trends Northeast-Southwest while in the South, individual deformation belts are narrower trending more in North-South. These faults and fractures in the rift are curvilinear which stretch up to 5 km, and are often composed of a series of echelon segments linked by short up-faulted horsts or transfer faults [30].

Figure 2. Geology map of the study area

Post caldera is indicated by numerous faults which cut the caldera walls and the lavas on the caldera floor [30]. The continued eruptions (post, intra caldera) indicate that the magma body at Silali is still active [13].

The major geothermal manifestations occur within the caldera floor and on the Eastern faulted slopes of the volcano. Some manifestations also occur along river Suguta to the West and along fractures in the far North of the volcano. Manifestations are in form of altered grounds, steaming grounds, hot springs and fumaroles. The highest temperature and most extensive activities occur in the Eastern half of the caldera floor; most hot altered grounds are aligned along the North-South fissure zone [31]. Around Kapedo along the Suguta river is a fault zone directly below the Discoid Trachyte, it could be the source of a series of hot springs [28]. The Lorusio hot springs, North of Kapedo flow Eastwards away from the West ranges of hills hosting dyke swarms and volcanic cones [32].

Extraction and utilization of heat from the core, requires a medium to transport the heat to shallow depths. Conduction and convection are the common modes of heat transfer. Meteoric water is essentially the carrier [33], once penetrated into the Earth’s crust and has been heated on contact by the hot rocks. The generally North-East and some East-West, North-South trending fault structures, the master rift faults and the fractured Plio-Pleistocene lavas within the rift floor acting as conduits for recharging the system. Fault network and dykes, and abundant meteoric fluids [31] are very essential in the sustenance of a geothermal system. The height of the plateaus compared to the rift floor allows for sufficient hydraulic gradient to enable deep hydrogeological recharge to the hot magma and normal faults conducting hot fluids from deep to geothermal reservoirs at shallower depth [32]. The Northwest-Southeast lineament and the North-East fissure swarm may be such important conduits of deep fluids thus significant for the geothermal prospect.

2. Methodology

Gravity data used was obtained from satellite at https://topex.ucsd.edu/cgi-bin/get_data.cgi (Topex data; Scripps Institution of Oceanography, University of California San Diego), with 1 arc-minute resolution (1'= 1.85 km). The gravity data set used consists of 456 gravity station in total. For the calculation of the Complete Bouguer Anomaly (CBA), it was necessary to use the elevation where the CBA was calculated. The elevation was provided by a digital elevation model obtained from OpenTopography at https://doi.org/10.5069/G93T9FD9, (NASA JPL (2021). <i>NASADEM Merged DEM Global 1 arc second V001</i>).

The Gravity Absolute Base Station for base station at 184518.14E, 102930.23N (longitude 36.1665, Latitude 0.9274), and Elevation 1028.00 was 977671.181mGal, had a gravity reading of 0.8mGal. This was used to generate absolute gravity for other stations.

The datum adopted in 1971 by the international Gravity Standardization Network (IGSN 71) [34] was used in reducing the gravity observations. The latitude correction g∅ (Equation (1)) (theoretical sea-level gravity) at latitude Ø, was computed from the (1903) gravity formula as modified by the international union of geodesy and geophysics (Geodetic Reference System, 1967) (I.A.G. 1967).

[picture] | (1)

Where ∅ is the Latitude measured in radians.

Free Air Correction (FAC) was done using (Equation (2)) for a point with a height h above the geoid. The negative sign shows the reduction of gravity due to height [19,35].

[picture] | (2)

Bouguer correction (BC) was computed to take into account the pulling effect of the rock mass of the station and datum plane with elevation. It was done using (Equation (3)). It approximates the rock layer beneath the observation point to an infinite horizontal slab with thickness equal to the elevation of the observation above the datum [8,11].

[picture] | (3)

Terrain correction was calculated to account for topographic relief in the vicinity of the gravity station [17] and large elevation differences. The net effect of hills and valleys reduce the observed gravity value of the station. Terrain correction each gravity station was calculated using Gravity.omn extension in Oasis Montaj using (Equation (4)):

[picture] | (4)

TC is terrain correction (gu), 𝞺 is Bouguer correction density, r₁ is inner radius (m), r₂ is outer radius (m) θ is the angle subtended by radius r₁ and radius r₂ enclosing the said section. n is the average elevation of the section under consideration.

Free air anomaly (FAA) was calculated by subtracting latitude correction from absolute gravity then adding correction for station elevation [3] using (Equation (5)):

[picture] | (5)

The complete Bouguer anomaly (BA) was calculated after the processes of gravity reduction have been eliminated. (Equation (6)) was used to calculate BA.

[picture] | (6)

gϕ is latitude correction; h is station elevation in meters; gobs is absolute gravity.

For gravity reduction and terrain correction, a Bouguer reduction density of 2.67 g/cm³ was applied [8,11,36]. This value is widely accepted in gravity studies for crystalline continental crust, especially of granitic composition. Granitic rocks typically exhibit densities ranging from 2.5 to 2.8 g/cm³, with 2.67 g/cm³ often used as a practical average for global studies.

However, studies specific to the Kenya Rift system - such as those by Simiyu and Keller (2001) and Mariita (2003) - have suggested a slightly lower average density of 2.55 g/cm³ for terrain and Bouguer corrections, based on direct measurements in the Southern and Northern segments of the rift. Despite this, they concluded that using the standard value of 2.67 g/cm3 does not significantly alter the gravity anomaly results or interpretations in the regional-scale geothermal studies. Thus, for consistency and broader applicability, the 2.67 g/cm3 value was adopted in this study, while recognizing the localized variation and its minor influence on anomaly amplitudes.

The CBA obtained was projected to WGS 84,UTM 37N (World Gravity Station 84, Universal Transverse Mercator Zone 37 North for generating the Bouguer anomaly map Figure 4, using the Kriging grid method of window size 500 by 500. This study applied power spectrum, upward continuation, bandpass, Butterworth, analytical signal, and Euler tools in Oasis Montaj 6.4.2.

The Magmap extension, a 2D FFT filter was applied on the CBA map to produce the radially Averaged Power Spectrum. The gradients for the tangents drawn to the curves were used to estimate the depth. Upward Continuation at one cell size (500m) was applied to CBA anomaly suppressing the signature of less geological interest. Butterworth filter, cutoff wavelength was set at 10000 m and filter order 8 while, Bandpass parameters were set at 500 m for long wavelength and 10000 m for short wavelength as outlined by Harrison and Dickinson method [37], Figure 5 and Figure 6. Depths to source bodies were estimated using power spectrum analysis and Euler deconvolution. The power spectrum method yielded average depths of ~1500 m for shallow sources and up to ~5340 m for deeper ones, Figure 7. The analytical and Euler deconvolution, using structural indices (SI) of 0.5, 1.0, and 2.0, produced depth estimates ranging from ~1060 m to ~4747 m Figures 8, 9, 10 and 11. The technique relates the potential field to the location of the source of an anomaly with a degree of homogeneity expressed as a structural index [38]. Uncertainty in this depth estimation arises primarily from: window size and sampling resolution used in spectral analysis, assumptions in the structural index selection during Euler deconvolution, and noise and overlapping anomalies, especially in regions of complex geology. In this study, a 12% depth tolerance and a 20% horizontal location tolerance were applied to constrain Euler solutions and reduce scatter [39]. Despite these controls, typical uncertainty margins for such methods are approximately ±10 – 20% of the estimated depth, depending on the data quality and geologic complexity. For example, a source estimated at 3000 m depth may have an error margin of ± 300 – 600 m.

Euler deconvolution is based on the Euler equation of homogeneity [22,40] (Equation (7)):

[picture] | (7)

N is a constant, defined as the structural index (SI), characterizing the source type, shape (geological contacts, faults, horizontal cylinder/faults, or sphere and the rate at which field amplitude decreases with distance from the source [22].

3. Results and Discussions

3.1. Elevation Map

The elevation topography map Figure 3 shows high density (gravity) is corresponding to elevation, the higher the elevation the higher is the gravity. This observation was attributed to denser intrusion were pushed very close to the surface during vulcanization. At low altitude below 630 meters above sea level corresponds to low gravity of between (-290 and -267mGal) likely to suggest that the less sedimentary rocks settled in the North- East region of the study area after the formation of the volcano. More lava and porous material flowed northward. Also the rocks may have been highly fragmented resulting in low gravity. The Western part of the caldera is the highest and is home to two peaks while the Eastern part one peak relatively lower than those in the Western part. The Bouguer anomaly map revealed similar features as the elevation topography map.

3.2. Bouguer Anomaly

The Bouguer anomaly map, Figure 4, revealed a strong contrast in gravity values (-290 to -81mGal), indicating significant variation in subsurface rock densities. High anomalies in the Northwestern and central parts correlate with intrusive mafic bodies or uplifted basement, while low anomalies in the Northeast suggest sediment-filled basins or caldera collapse zones. These variations help define geothermal target zones, particularly where steep anomaly gradients imply fault boundaries or magmatic contacts. A sharp contrast in the gravity anomalies implies presence of adjacent or nearby geological features with very different densities. This could be due to different rock types, magma chambers and sedimentary basins. The magnitude of the gravity difference is proportional to the density contrast and the volume (size or depth) of the anomalous body.

There are two high densities (gravity), one to the North-West trending in the North-South direction while the other is circular located at the caldera. The high gravity ranges between -184 to -81mGal. The two high gravity regions are separated by a low gravity ranging from -258 to -226mGal. The lowest gravity is located to North-East ranging from -290 to -273mGal, taken to be low-density blocks or sedimentary basins. The low gravity anomaly is trending in the Northeast – Southwest. The decrease in Bouguer anomaly indicates an increase in sedimentary thickness cover or basement depth. A gradual decrease in Bouguer values indicates a gradual increase in the crustal thickness [41,42]. The non-complexity of the gravity anomaly indicates crustal stability. North-East region shows that the sedimentary terrain is widening moving northwards from the caldera. The terrain basin is high around the caldera and on the North-West part. The Bouguer anomaly map suggests a continuation of gravity effects of various litho -stratigraphic units composing the sedimentary cover and basement complex [43]. The high gravity anomalies indicate the presence of high density materials in the subsurface than the surrounding rocks e.g. basalt and mafic igneous rocks. Low gravity anomalies suggest less dense materials e.g. sedimentary basins and granitic intrusions.

Such contrasts in the gravity anomalies often mark boundaries between distinct geological unit e.g. crustal faults, igneous intrusions into sedimentary strata. Hence it is used in mapping subsurface structures. A large difference in gravity anomalies directly correlates with significant subsurface density variations, often highlighting critical geological features or resources.

3.3. The Residual Anomaly Map

3.3.1. Bandpass

The residual anomaly map, Figure 6 enhanced shallow structures. It emphasized small-scale faults and intrusive features trending North-South, Northeast-Southwest, and Northwest-Southeast. These alignments match known rift structures and suggest interconnected fault and fracture systems that facilitate geothermal fluid flow. The distribution of the anomalies depicts a lateral variation in the basement related to geological structures.

The transitions from high to low gravity indicate the presence of faults through which metrological water can infiltrate to recharge the reservoir. The linear elongation of the high density rocks indicates the presence of faults or shear zones and the contacts/ boundary between sedimentary and igneous or metamorphic rocks. Also it could be representing igneous intrusions like dykes or sills.

Figure 3. Elevation topography map

Figure 4. Complete Bouguer anomaly map

3.3.2. Butterworth

The Butterworth residuals, Figure 5, presented broader, smoother anomalies representing deeper crustal features. Major ring structures and central uplift zones typical of Silali caldera complex are visible on the map as fault-controlled features.

Figure 5. Butterworth residual map

Figure 6. Bandpass residual map

High gravity anomalies likely indicate dense substance bodies such as mafic or ultramafic intrusions near the caldera and along major faults, solidified magma chambers, uplifted basement rocks. These zones may correlate with heat source or structural highs in the geothermal system. While low gravity anomalies suggest sedimentary basins, fractured or altered zones affected by hydrothermal alteration process, often associated with fluid accumulation and geothermal reservoirs.

The central caldera appears as a low anomaly due to infill of less dense pyroclastic and sedimentary material. Fault zones and fracture systems align with linear low anomalies, acting as fluid conduits. Peripheral high anomalies mark intrusions or structural boundaries of the geothermal system. Dominant North-South, Northwest-Southeast trending lineament reflects the regional tectonic stress regime and rift related faulting, matching kwon rift structures at Silali. These are the major fault-fracture zones and subsurface intrusions. Which are critical for geothermal exploration as they control fluid flow, heat transport and reservoir permeability.

The bandpass gives a stronger delineation of silali caldera ring fractures and intra-caldera faulting. It reveals a clear separation of near-surface magmatic bodies from regional basement. The Butterworth is linked to deeper crustal structures, offering context for the location of magma reservoirs feeding the geothermal system. Highlights broad zones of crustal thinning or uplift tied to the rift setting. Together, they provide complementary insights into shallow and deep geothermal controls.

Figure 7. Radially averaged power spectrum

3.4. Radial Averaged Power Spectrum

Spectral analysis of the radial power spectrum, Figure 7, identified two dominant depth intervals ~1500 m (shallow sources like dykes, sills, and geothermal reservoirs) and ~5340 m (intermediate intrusions or solidified magma bodies). The slope of tangent drawn for each component segment was used as a proxy for mean depth [44].

3.5. Analytical Signal

It enhances the edges and boundaries of geological bodies, accurate at discriminating geo-bodies [45,46]. Areas of high analytical signal values often correspond to edges of dense or less dense bodies like faults, contacts, dykes, intrusive bodies or sedimentary basins. The analytical signal map Figure 8, highlighted areas with strong contrasts – central, Southeast and Western zones – indicating likely fault zones, intrusions, or lithological boundaries.

The high gravity anomalies indicate denser subsurface materials possibly mafic or ultramafic intrusions beneath the volcano, volcanic plugs or solidified lava flow and uplifted basement rocks associated with rifting. Low analytical signals are seen mainly at the North-East, South and West zones. These Low anomalies are likely due to sediment-filled grabens, caldera infill, fault zones or caldera collapse structures.

Figure 8. Analytical signal Map

Figure 9. Located Euler solutions map (SI 0.5)

The high analytical signal amplitude is a proof of the presence of faults or shear zones, contacts between different rock types, intrusive bodies like dykes or plutons, with linear gravity gradients indicating major fault lines. While low analytical signal amplitude suggests the presence of homogeneous rock units like granitic, plutons and sedimentary layers or basins. The faults trend in Northwest-Southeast and Northeast-Southwest consistent with known regional stress orientations typical of the East Africa Rift System.

3.6. Euler Deconvolution

Euler deconvolution solutions (SI 0.5, 1.0, 2.0) showed clustered solutions in regions of structural complexity. Structural Index 0.5 identified ribbon-like features interpreted as faults or sills; SI 1.0 captured pipe-like structures like vertical dykes; and SI 2.0 detected cylindrical intrusions, plugs or major fault intersections. Solution depths ranged from ~1060 m to ~4747 m consistent with the spectral depth estimates.

The SI 0.5 solution depth ranged ~1060 m to ~ 2840 m, Figure 9. The deepest Euler solution is solution 18 located in the South of the study area at an estimated depth of 2840 m on gravity high of amplitude of +4.3 mGal, which could be a hot dense materials trapped at depth. Euler solution is solution 3 to the Western part of the study area with estimated depth of ~1060 m on a high gravity of +4.3 mGal, attributed to the caldera wall where dense volcanic rocks were pushed close to the surface. Other materials may have flown out as lava flow hence the shallow Euler solutions. The dense near surface hot bodies could be attributed to the altered ground and the Kappedo hot springs.

Figure 10. Located Euler solutions Map (SI 1.0)

Figure 11. Located Euler solutions Map (SI 2.0)

The solutions depth for SI 1.0 range ~ 1480 m to ~3470 m, and are located both on the gravity high and gravity low, Figure 10. The deep anomalies indicate reduced energies due to large wavelengths having small signal amplitude. The implication could be a pipe like dense hot geological material emanating from the mantle and trapped at this depth within the Earth’s crust.

The Euler solutions of SI 2.0, Figure 11 generated solutions both on the high and low gravity locations. The solution depths are ~2120 m to 4747 m. which indicate the presence of vertical cylinders that could be intrusive plugs, dykes, and vertical sheets associated with igneous intrusions and fault zones. Further it can imply presence of edges of large density contrasts like major faults or steep geological contacts. The solutions located on high gravity Zones, are interpreted to imply hot dense magmatic bodies intruding to near surface, hence responsible for the altered grounds fumaroles, geysers and hot springs.

Euler solutions for the different structural index confirm the presence of the trapped materials and structures elongated both horizontally and vertically which are either connected to the mantle for continual heat transfer from the interior to the crust. Also faults and contact edges and cavities are suspected to be present as the results indicate. The spatial clustering of solutions across all the structural indices reinforces the reliability of the detected structures.

4. Conclusion

This study used gravity data to map subsurface structures and estimate depths of geothermal interest in the Silali geothermal field. The complete Bouguer Anomaly map revealead dense intrutions and sedimentary basins. Bandpass and Butterworth filtering exposed both shallow and deep fault sysytems. Analyitical signal and spectral analysis provided depth estimates and delineated intrusive bodies.

This intergrated analysis supports the presence of fault–dyke–conduit systems that may control geothermal heatflow in the Silali region and provides information for geophysical or drilling investigations.

Euler deconvolution results confirmed vertical and lateral extesion of faults, intrusions , and structural contacts. The solutions’ depth range (1060 – 4747 m) and spatial clustering correspond with known geological features and align with spectral analysis findings.

The high density intruding magmatic materials are responsible for the altered ground, fumaroles, geysers and hot springs as they are the conduits of heat transfer from the mantle. Structural analysis reveals lineaments trending North-South, Northeast-Southwest and North Northwest-Southeast.

These results support the interpretation that Silali’s geothermal sysytem is structurally and magmatically controlled. Fault intersections, dyke intrutions, and ring structures serve as primary conduits for geothermal fluids. Depths of 1500 to 5340 m indicate variable drilling targets, with shallow zones potentially hosting productive reservoirs.

Recommendations

n Conduct intergrated analysis combining gravity, MT, resitivity, and geophysical data to refine drilling targets.

n Focus exploration and drilling in areas with overlapping high analytic signal, clustered Euler solutions, and gravity highs.

n Prioritize zones with N-S, NE-SW, and NW-SE trending lineaments and intersecting structures.

n Deploy high- resolution gravity and seismic surveys in identified target zones for precise reservoir modeling.

These findings can guide geothermal resourse development and support future exploration programs in the Northern Kenya Rift.

ACKNOWLEDGEMENTS

The authors express their sincere appreciation to the Geothermal Development Company (GDC) - Kenya for allowing them carry out research in their geothermal field. In addtion, we extend appreciation to the University of California San Diego and OpenTopography for availing the gravity data and Digital Elevation Model used in this study. We further appreciate the supervisors, members of Pysics department and course mate at Kisii unversity for their positive critique, time and encouragement during the time of the study.

Conflict of Interest

The authors declare that there is no conflict of interst for the publication of this paper..

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