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INTERNATIONAL JOURNAL OF GEOMATICS AND GEOSCIENCES

Volume 4, No 3, 2014

© Copyright by the authors - Licensee IPA- Under Creative Commons license 3.0

Research article ISSN 0976 – 4380

Submitted on December 2013 published on March 2014 447

Detection of possible causes of earthquakes in central Sudan: An integrated

GIS approach Khalid A. Elsayed Zeinelabdein1, Eiman A. Mohamed2, Elsheikh M. Abdelrahman3

Department of Geology, Faculty of Petroleum and Minerals, Al Neelain University, Sudan

National Centre for Research, Remote Sensing and Seismological Science Authority, Sudan

Geological Research Authority of Sudan, Ministry of Mining

[email protected]

ABSTRACT

Several big earthquakes have been recorded in the recent years. Nevertheless, there are no

sufficient and reliable studies on earthquakes in Sudan. The main subjective of this study is to

integrate the geophysical methods for the surface interpretations in addition to, Landsat

images supported with gravity data and digital elevation model (DEM) to investigate the

possible causes of earthquake that took place in the study area. Remote sensing is useful in

mapping and analysing structural elements, especially in remote regions. Subsurface

geophysical methods are among the best supplement to surface interpretations made from

satellite images. In this paper, Landsat images supported by gravity data, geology and DEM

were used to investigate the relationship between the lineaments and the earthquake events

occurred in central Sudan. The integrated analysis has shown that the area is traversed by

several systems of fractures and fault zones which are liable to rejuvenation from time to time.

The earthquakes that occurred in low areas may be attributed to subsidence that occurred in

the sedimentary basins while the few events that occurred out of the sedimentary basins may

be attributed to movements along pre-existing faults due to reactivation. The events that are

located at or near prominent lineaments are probably related to shear zones such as Keraf or

CASZ or may be related to subsidence in rift basins or basin structures associated with pull a

part process of tectonic activity. Strike-slip faults are difficult to detect from gravity data

since there is no considerable down throw associated with such type of faults.

Key words: Remote sensing, GIS, earthquakes, DEM, gravity, Landsat images, central

Sudan.

1. Introduction

Sudan is located within the stable African plate, which is characterized by low seismic

activity. Despite this fact, the central intra-plate region witnessed scattered earthquakes

capable of producing damages. In Sudan, several big earthquakes have been recorded in the

recent years. Nevertheless, there are no sufficient and reliable studies on earthquakes in

Sudan (Mohmmed and Elsayed Zeinelabdein, 2012; Mohamed 2013). Such studies that deal

with forecasting and predicating earthquakes are, so far, absent. Therefore, the main

subjective of this study is to integrate the geophysical methods for the surface interpretations

in addition to, Landsat images supported with gravity data and digital elevation model (DEM)

to investigate the possible causes of earthquake that took place in the study area.

Although the interpretation of land morphology applied to tectonic deformation has been

broadly studied, there are few examples of integration of digital methods for tectonic

geomorphology with the classical approach (Burbank and Anderson, 2001; Keller and Pinter,

Detection of possible causes of earthquakes in central sudan: An integrated GIS approach

Khalid A. Elsayed Zeinelabdein et al

International Journal of Geomatics and Geosciences

Volume 4 Issue 3, 2014 448

2002; Jordan et al., 2005; Nappi et al., 2009). Quantitative analysis of the topographic

features contributes to study the interaction between tectonics and surface processes,

providing a basis for modelling landscape evolution. Particularly, analysis of DEMs

represents a methodology for studying the morphotectonics of an area quantitatively,

recognizing the main tectonic structures (e.g., Jordan et al., op. cit.). Geologic structures may

produce linearly aligned features not typically common in nature, therefore, recognizing,

measuring, and interpreting all the linear and areal surface features is of great importance in

geodynamics. Intersection of bedding with the topographic surface can appear as linear

features or planar features in DEMs. Linear morphological expressions of fractures include:

linear valleys, linear ridgelines, and linear slope breaks.

The study area is located in central Sudan. It is bounded by longitudes: 30o00' - 35o30' E and

latitudes: 12o00' - 16o30' N (Figure 1). This area consists mostly of flat or undulating plains

and low lying plateaux; throughout the central parts small rocky hills protrude from the

superficial deposits that form the plains. This region is characterized by arid – semi arid

climatic conditions, where the temperature ranges from 42°C in the summer to 32°C in the

winter. Rain falls between July and September, resulting in an average of 175 mm annually.

The major drainage system in study area is the River Nile and its tributaries in addition to

ephemeral streams which flow during a short period after the rainy season. The area is

sparsely vegetated with grasses and herbs with widely scattered shrubs covering the plains

during the rainy season and the few succeeding months.

Figure 1: Location map of the study area





Geologically, the study area is composed of high-grade gneisses, structurally overlain by low-

grade metasedimentary-metavolcanic sequences. Ophiolite fragments structurally overlie the

layered sequences. Syn-orogenic and Younger granites intrude the above-mentioned

sequences, usually forming conspicuous, hilly dissected massifs. Sandstones of Cretaceous

age overlie unconformably the older sequences followed by the Gezira and Umm Ruwaba

formations. Superficial deposits usually blanket the sequence.

2. Data types

The following data types were made available for the current study: Shuttle Radar

Topographic Mission (SRTM) Digital Elevation Model (DEM) data with 90m and 20

Landsat 5 TM scenes obtained from the Global Land Cover Facility (GLCF) at the University

of Maryland, USA. Gravity point data with 5km separation. Geological map of Sudan (GRAS,

2004) at the scale of 1:2000000 obtained from the Geological Research Authority of Sudan

(GRAS).

3. Methodology

The present study adopted an integrated methodology of remote sensing, GIS, gravity and

DEM analysis to infer the possible causes of earthquakes in central Sudan. 20 Landsat 5 TM

scenes were stitched together to produce image mosaic, which was resized to portray only the

study area. Diversity of digital image processing procedures with special emphasis on spatial

enhancements was applied to this image. Lineaments were manually on-screen delineated at

the scale of 1:250 000 in the GIS environment. 90m-resolution DEM was used as a

supplement for delineating the lineament features in areas where Landsat image failed to

draw them.

Since we are interested only in deep structures, the gravity data was first processed to

separate the regional component of the gravity field using aerial averaging method (Serkerov,

1999). Both Bouguer anomaly and the regional gravity point data were interpolated using

kriging resampling method. Contour lines were generated with 5 mGal contour interval.

Qualitative interpretation was conducted, whereby structural faults were delineated.

A digital version of the geological map of Sudan was imported into the GIS software. This

map was cropped using the shape file of the study area to be further manipulated with other

data types. Earthquake events of known epicentres coordinates were enter to the GIS database

and overlay analysis was performed in order to decipher interrelationship between these

events and the other data types.

4. Results and discussion

4.1 The Digital Elevation Model (DEM)

DEM presented in Figure (2) shows that the area is divided into regions with different

geomorphological characteristics. The central part of the area is characterized by low flat

topography, while the peripheries are relatively elevated. Overlying the earthquake events

over the DEM, it can be noticed that the earthquake events are clustered in some parts of the

area. Considering the timing of occurrence, it is apparent that the pre-2000 events are located

in the southern part of the area, while the post-2000 events are located in the northern part.

From the topographical point of view, most of the earthquake events are located in areas

characterized by low topography occupied by sedimentary basins and a few are located in





high areas underlain by basement rocks. This may give clue on the different nature of the

earthquake causing mechanisms. Accordingly, the earthquakes occurred in low areas may be

attributed to subsidence occurred in the sedimentary basins, while the few events occurred

out of the sedimentary basins may be attributed to movements along pre-existing faults (most

probably strike-slip faults or shear zones) as a result of reactivation.

Figure 2: Digital Elevation Model of the study area overlain by the earthquake events.

4.2 Lineament analysis

The lineament analysis is important in studying earthquakes since most of lineaments may

represent the surface expression of deep fractures, shear zones or faults (Elsayed

Zeinelabdein and Albiely, 2006). The integration of lineaments with earthquake events within

the framework of the present study is aimed at finding a relationship between the linear

features and the earthquake events that took place in central Sudan. Generally, detection of

lineaments strongly depends on a number of factors, such as current level of stress in the

crust. The accumulation of stress deep in the crust improves all processes and changes the

density and orientation of lineaments, prior to a strong earthquake. Therefore, the density of

lineaments indicates that the crust is more permeable and the elevation of fluids and gases is

allowed to the surface (Sharifi, 2004).

The different orientation of lineaments can be observed in Figure (3). This map shows that

some lineaments extend for several tens of kilometres to more than 100 km. The majority of

this class has the NW general trend. The other lineaments appeared to be shorter with no

predominant directions. The central part of the area reveals little or no lineaments because it

is mostly covered by recent deposit consisting of black cotton soil or sand dunes. On the

other hand, the north-eastern, north-western and south-western parts of the area are

characterized by high frequency lineaments (high number of lineament per unit area).





Figure 3: Lineament map of the study area overlain by the earthquake events.

In the north-eastern part of the study area, most of the lineaments have the NE trend. These

lineaments may represent deep structures associated with Central African Shear Zone

(CASZ). In the same area some lineaments were found to have the N-S direction near and

around Abu Deleig. This type of lineaments may be related to the Keraf Shear Zone (KSZ),

which extends from northern Sudan and expected to continue in this area (Elsheikh et al.,

2013). The north-western part of the study area is characterized by lineaments oriented

almost in all directions. The bulk of these lineaments are short in length with the general

trend to NW with subordinate long lineaments trending NE. In the south-western part of the

area, the lineaments are not so intensive, with two main trends: the NE, which may to be

related to CASZ, and the NW, may represent the release fractures of the CASZ. The

simultaneous analysis of lineaments and the earthquake events allowed us to state the

following comments.

1. The epicentre of the 1966 Dumbeir earthquake is situated near a prominent lineament

with the trend to NE-SW. This permitted to connect this event to reactivation of deep

faulting related to CASZ.

2. The epicentre of the 1993 Khartoum earthquake is located in the north-western part of

the study area. This part is characterized a big number of earthquake events. The

events are most probably related to subsidence occurring in rift basins or basin

structures associated with pull a part process of tectonic activity.

3. The epicentres of the 2003 Abu Deleig and the 2009 Gala En Nahal earthquakes are

located in the north-eastern part of the study area. Both events are caused by

movements along shear zones. The 2003 event is related to the Keraf Shear Zone,

while the 2009 event is related to Central African Shear Zone.





4.3 Gravity data

Structural faults (Figure 4) were generated from gravity point data so as to be integrated with

earthquake events. From Figure (4) it is clear that large number of faults has the NW trend. A

similar number has the NE trend and a lesser number has the N-S trend, with subordinate

number with the E-W trend. It can be noticed that most of the epicentres are not directly

located on faults. Instead Dumbeir epicenter is located near an ENE trending fault and Abu

Deleig is located near a NE trending fault, while the two others are located away from any of

the faults. This result can be understood from the standpoint of view that strike-slip faults are

difficult to detect from gravity data since there is no considerable down throw associated with

such type of faults. From another point of view, epicentres of some events such as those of

1974, 2004 and 2007 are located directly on faults.

Figure 4: Faults delineated from interpretation of regional gravity data overlain by

earthquake events.

4.4 Geology

Integration of Geology and earthquake events (Figure 5) revealed that most of the events

occurred in areas occupied by sedimentary rocks in rift basins as mentioned earlier. Most of

earthquake events in Sudan are shallow with low magnitude.

The simultaneous analysis of the geology lineaments, faults and earthquake events gives an

opportunity to widen the view and link all the factors that may cause the earthquake together.

The 1966 J. Dumbeir earthquake occurred in an area characterized by moderate lineament

density and a few number of faults. This area is occupied by basement rocks.





The epicenter of the 1993 Khartoum earthquake is located in an area characterized by high

lineament density and considerable number of faults. The area is covered predominantly by

sedimentary rocks. The 2003 Abu Deleig earthquake is situated in an area of moderate

lineament density and limited number of major faults. The geology of the area comprised

mainly of basement rocks. However, sedimentary basins are found closely to the north. The

2009 Gala En Nahal earthquake occurred in an area of high lineament density and limited

number of major faults. The basement rocks are the main geological units in the area with

sedimentary formation in the nearby vicinity.

Figure 5: Simplified geological map (modified after GRAS, 2004) overlain by earthquake

events.

5. Conclusions

Integrated analysis of DEM, regional gravity, lineaments, geology and earthquake events of

Central Sudan has shown that the area is traversed by several systems of fractures and fault

zones which are liable to rejuvenation from time to time.

Multispectral remote sensing (Landsat TM) image enhancement and interpretation proved to

be useful in identification, detection, and delineation of linear features and geological

structures in Central Sudan. Bouguer Anomaly data processing and interpretation allowed the

recognition and delineation of the major deep faults in the study area.

The outcome of lineaments, faults, geology and events data integration and analysis in the

GIS environment is that:





(i) The earthquakes that occurred in low areas may be attributed to subsidence that occurred

in the sedimentary basins while the few events that occurred out of the sedimentary basins

may be attributed to movements along pre-existing faults due to reactivation;

(ii) The events are located at or near prominent lineaments which are probably related to

shear zones such as Keraf or CASZ or may be related to subsidence in rift basins or basin

structures associated with pull a part process of tectonic activity;

(iii) strike-slip faults are difficult to detect from gravity data since there is no considerable

down throw associated with such type of faults.

Acknowledgments

The Global Land Cover Facility of Maryland University is acknowledged for providing the

remote sensing data. Thanks are due to the Geological Research Authority of Sudan for

making the geological map available for the present study.

6. References

1. Burbank, D. and Anderson, R., (2001), Tectonic geomorphology. Blackwell science,

Oxford.

2. Elsayed Zeinelabdein, K.A. and Albiely, A.I., (2006), The application of remote sensing

in hydrogeological investigations in arid regions, Red Sea Hills, NE Sudan. XIth

International Congress on Mathematical Geology, Université de Liège – Belgium, Sep.

3-8.

3. Elsheikh, A.E.M., Elsayed Zeinelabdein, K.A., El Khidir, S.O. and Ibrahim, A.E.,

(2013), The geometric configuration of the newly discovered Abu Deleig Sedimentary

Sub-basin, Central Sudan, using remote sensing, structural analysis and geophysical

survey. Arab. J. Geosc. DOI 10.1007/s12517-013-0883-8.

4. GRAS, 2004. Geological map of Sudan.

5. Jordan, G., Mejninger, B.M.L., van Hinsbergen, D.J.J., Meulenkamp, J.E. and van Dijk,

P.M., (2005), Extraction of morphotectonic features from DEMs: Development and

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Observation and Geoinformation, 7, pp 163-182.

6. Keller, E.A. and Pinter, N., (2002), Active Tectonics: Earthquakes, Uplift, and

Landscape, 2nd ed. Prentice Hall, p 359.

7. Mohamed, E.A., (2013), Integration of remote sensing and gravity data interpretation for

the purpose of monitoring and predicting earthquakes, Central Sudan. Ph.D. Thesis,

Sudan Academy of Sciences.

8. Mohamed, E.A. and Elsayed Zeinelabdein, K.A., (2012), Thermal infrared remote

sensing images: a possible precursor for earthquake prediction, Abudeleig Area, Central

Sudan. 5th SAPEG conference and exhibition, Khartoum, Sudan.





9. Nappi, R., Alessio, G., Vilardo, G. and Bellucci Sessa, E., (2009), Analisi Morfometrica

integrata in ambiente GIS applicata adree tettonicamente attive. Memorie della Società

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10. Serkerov, S.A., (1999), Gravity and magnetic exploration. Nedra, Moscow, p 437.

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Coastline of the Caspian Sea. Iranian National Center for Oceanography (INCO), pp16-

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