Geophysics Report Ashegoda

May 2012

Geophysical Investigation for

Wind Turbine Foundation Sites at Ashegoda

Wind Farm Project

Client: Ethiopian Electric Power Corporation

Consultant: Terrasol

Contractor: Vergnet

By

Dr. Berhanu Gebregziabher

(Assist. Professor of Geophysics, Mekelle University)

Mr. Shishay Tadios

(Lecturer of Engineering Geology, Mekelle University)

(Mekelle University)

Contents

1. Introduction ................................................................................................................................ 1

2. Data Acquisition ........................................................................................................................ 4

3. Data Processing and Results ...................................................................................................... 6

4. Interpretations and Discussions ................................................................................................ 11

4.1 Site-42 ................................................................................................................................. 12

4.2 Site-44 ................................................................................................................................. 16

4.3 Site-44B ............................................................................................................................... 20

5. Conclusion and Recommendations .......................................................................................... 24

5.1 Conclusions ......................................................................................................................... 24

5.2 Recommendations ............................................................................................................... 25

References ..................................................................................................................................... 27

Ashegoda Wind Turbine Foundation Sites Geophysical Investigation

Dr. Berhanu Gebregziabher (Assist. Professor of Geophysics, P.O.Box 231, Mekelle University) Tel., +251-914-004361 E-Mail: [email protected] Page 1

1. Introduction

Geophysics is the only branch of the earth sciences that can truly ``look`` into the solid earth

(Musset and Khan, 2000). Geophysics ``sees`` the Earth in terms of its physical properties,

which complement the usual types of geological information. A geophysical survey can

provide detailed information about the subsurface in very little time. Compare the cost of

obtaining similar information purely through manual excavation or drilling, a geophysical

survey is cost effective and enabling us to cover several hectares per day for site

characterization or detailed cross-sectional investigations. Most of the geophysical

techniques are environmentally friendly and there are no risks of exposing harmful waste or

aggravating ground conditions which are a frequent limitation of conventional ground

exploration methods.

A geophysical survey was carried out in May 2012 at Ashegoda area for wind turbine

foundation site investigation. The aim was in general to identify and characterize the

subsurface geology down to a depth of 30 meters and to investigate the cause and extent of

the anomalous ground conditions such as:

Identifying the different lithological units and geological structures existing in the

site

Identifying the nature and distribution of underground karstic features (cavities)

existing in the site (as the area is mainly dominated by carbonate rocks, presence of

solution cavities is expected), and

Investigating other geological features of geotechnical significance, for example,

determining the depth to the bed rock, determining overburden sediment thickness,

and weathered zones.

This report presents the findings of the geophysical surveys and the ground investigations,

discusses the interpretive ground conditions revealed by the investigations and any potential

impacts on the proposed development, presents a risk assessment and makes recommendations

for remedial measures and any additional fieldworks.



To achieve the above objectives, 2D electrical resistivity imagings have been conducted at three

wind turbine foundation sites (Site-42, Site-44, and Site-44B).

The interpretations carried out in this report and the opinions and comments expressed are based

on a 2D Electrical Resistivity surveys. There may, however, be conditions pertaining at the site

which have not been disclosed by the investigation and which therefore could not be taken into

account. Using these techniques we can be able to confirm the presence of anomalous features in

the subsurface of the three proposed sites.

Resistivity of the subsurface may vary both vertically and horizontally in two dimensional (2D).

To investigate such electrical structures, the electrode arrays need to be both expanded and

moved laterally. At present, field techniques and modern instruments to carry out 2D and 3D

resistivity surveys are well developed. 2D electrical resistivity imaging/tomography surveys are

usually carried out using a large number of electrodes connected to a multi-core cable along a

single survey line or profile (e.g., Gebregziabher et al., 2010 and Gebregziabher, 2011). Relative

to the 1D (VES or Profiling), a more accurate model of the subsurface is a 2D model where the

resistivity changes in the vertical direction as well as in the horizontal direction along the survey

line can be observed.

The principle of electrical resistivity imaging is based on the injection of a direct current (DC) to

the earth’s subsurface and measurement of the induced potential difference or voltage (Fig. 1.1).

Electric current (the flow of electric charges) is pumped to the ground by a driving force called

voltage (potential difference) from a battery or generator. When both the positive and negative

terminals of the DC source voltage are attached to the ground using conductive wires (called

electrodes), electrons start to flow through the earth’s subsurface from the negative terminal to

the positive terminal of the DC source (conventionally the current direction is the reverse). A

measure of the material (earth) to oppose the passage of the electric current is called electrical

resistance and like any other semi conductor materials, the earth is acting as a resistor.



Figure 1.1 Current flow (solid lines) radiating out from a source electrode (C1) and converging on a sink

electrode (C2) and equipotential surfaces (dashed lines) at P1 and P2. Modified after Knödel et al. (2007).

The resistivity measurements are normally made by injecting current into the ground through

two current electrodes C1 and C2, and measuring the resulting voltage difference ( V ) at two

potential electrodes P1 and P2 as shown in Fig 1.1. The potential difference is then given by

22122111

21

1111

2 pcpcpcpc

pprrrr

IVVV

Rearranging the above equation for the resistivity, it becomes

I

VKa

where

22122111

1111

2

pcpcpcpc rrrr

K is called the geometric factor which depends on the

arrangement of the four electrodes. After arranging the distances (r) between the current and

potential electrodes according to some well-known configurations one can determine the

resistivity of the ground.



2. Data Acquisition

2D electrical resistivity surveys using Wenner array have been conducted at three wind turbine

foundation sites (Site-42, Site-44, and Site-44B) of the Ashegoda wind farm project east of

Mekelle in May, 2012. Each site has covered using three parallel survey lines (profiles) of 2D

Electrical Resistivity Imaging with 10 meters spacing between the lines (Fig. 2.1).

Figure 2.1 Location of the geophysical survey lines and topography of the study area (GPS readings are

in Adindan).

Field techniques and equipment to carry out 2D and 3D resistivity surveys are fairly well

developed. 2D electrical imaging/tomography surveys are usually carried out using a large

number of electrodes connected to a multi-core cable along a single survey line. The instruments



used for these surveys include a multi-electrode and multi-channel measuring device with

decoders (switching boxes), 64 stainless steel electrodes which are durable and have fairly low

self-potentials, two multi-core cables for connecting the 64 electrodes, and a power supply

battery. The measuring device was SAS4000 terrameter manufactured by ABEM-Sweden with a

power supply 12V external battery. It measures both the transmitted current and voltage and

stores these quantities together with the resistivity data. The switching box called lund imaging

system decodes measurements and sent to the terrameter by activating and deactivating a set of

four electrodes step by step. The electrodes location and elevation were measured by GPS.

During our data acquisition, we select the Wenner-alpha array technique for all the nine lines

because it has a good vertical resolution and it is an attractive choice for surveys in a noisy area

due to its high signal strength.

Sites Profiles Starting Point End Point Remarks

Longitude Latitude Longitude Latitude

Site-42

Line-1 567033 1489863 566896 1489994 Across the excavated center

Line-2 567027 1489856 566890 1489987 10 m south of line-1

Line-3 567039 1489870 566902 1490001 10 m north of line-1

Site-44

Line-1 566770 1490535 566959 1490535 Across the excavated center



Site-44B

Line-1 566860 1490510 567032 1490430 Across the proposed site



Table 2.1 GPS location of the survey lines at sites-42, -44, and -44B (GPS readings are in Adindan).



Each profile(line) was 189m long across the excavated sites using the Wenner-alpha array of

minimum electrode spacing 3m and a maximum of 63 m so that to attain a maximum depth of

investigation down to 30 meters. The starting and last positions of the survey lines are shown in

table 2.1. The topography is a little bit rugged due to nature and manmade excavations and it

varies from 2482 m to 2502m above sea level (Fig. 2.1).

The measured apparent resistivity values can be shown as a pseudo-section, which involves an

arbitrary allocation of the position of the apparent resistivity data points. The pseudo-section

does not reflect the actual resistivity distribution in the subsurface, because the potential fields

are deformed due to heterogeneity and topographical effects. Therefore, 2D and 3D inversion

algorithms are used to calculate a true resistivity model from the apparent resistivity data.

3. Data Processing and Results

In 2D electrical resistivity imaging, the aim of inversion is to reconstruct a true resistivity

distribution in the subsurface by creating a 2D resistivity model, which has a model response that

is similar to the measured apparent resistivity data.

The collected data are plotted in the form of pseudo-sections which can provide an initial picture

of the subsurface geology (e.g., Fig. 3.1a top). However, a 2D inversion of the measured data is

necessary for the final interpretation by transforming the apparent resistivities and pseudo-depths

into a 2D true resistivity model. In recent years, several computer programs have been developed

to carry out such inversions (e.g., Loke and Barker, 1996 and Günther, 2004). Our data is

processed by applying a smoothness-constrained inversion using a Finite-element based software

RES2DINV ver.3.54.44 (Geotomo software, Malaysia) in order to create 2D subsurface

resistivity models.



The final model is calculated in an iteration process which includes step-by-step forward

modeling and inversion. After an initial resistivity model is chosen and parameterized, the model

responses (apparent resistivities) are calculated using the forward modeling in order to compare

them with the measured apparent resistivities. The program compares the forward modeling

results with the measured data, the quality of the fit is determined and the parameter values for

the next iteration step are specified. Then, the initial model is modified in each iteration using

different algorithms (for example, using Gauss-Newton) to minimize the misfits between the

calculated and measured apparent resistivities. This process is continued until a selected

minimum error (misfit) is reached for the maximum number of iterations. When the misfit is

minimized with a lower RMS error, the inversion stops and outputs the final resistivity model.

After the inversion stops, the model response (calculated data) and the misfits between the

measured and calculated data are analyzed. The calculated data can be displayed in the same way

like the measured data, for example, as shown in Fig. 3.1a (middle). The data misfit, which is the

difference between the measured and calculated data divided by the measured data in percent,

helps to see how the observed data are fitted by the model. The final inverted model result with

true resistivity and depth is displayed, for example, as shown in Fig. 3.1a (bottom).

Site-42

a

b

c

Figure 3.1 Site-42: Comparison of measured data (top), calculated or

model response (middle), and the 2D electrical resistivity inverted models

(bottom) for line-1(a), line-2(b), line-3(c).



Site-44

a

b

c

Figure 3.2 Site-44: Comparison of measured data (top), calculated or





Site-44B

a

b

c

Figure 3.3 Site-44B: Comparison of measured data (top), calculated or



4. Interpretations and Discussions

The purpose of the geophysical surveys is interpretation in terms of geology. The values of

resistivity provide only a rough indication of what the lithologies are. Even within a single

formation the resistivity often varies because there may be a water table or due to abrupt changes

in salinity or clay content. Conversely, a geological boundary may not be detectable if it

separates layers with small resistivity contrast. Geological interpretation must therefore be based

on a sound knowledge of the geology as revealed by borehole data.

The final result of a 2D resistivity survey is cross-sections of the calculated rock resistivity

model along the profile line as shown in Figs. 4.1- 4.9. These cross-sections should be assessed

in terms of the lithological and structural interpretation of the resistivity data. The assessment of

inversion results is ambiguous due to the limited number of values and precision of the data. This

ambiguity is influenced by the data coverage (density), the errors in the data, sensitivity of the

electrode configuration, and the degree of misfits between the observed and predicted data. To

reduce the ambiguity, knowledge of the geology and borehole logs are necessary.

Since there are two borehole data in the study area (at Site-42 and Site-44) and by including the

geological history and information from the stratigraphy of the local geology, we interpret easily

the geo-electrical layers of the nine profiles at the three sites. From the geological observation

the area is covered with old horizontally stratified sedimentary rocks of limestone, marl and

shale intercalations which are later disturbed or uplifted by the younger age dolerite igneous

intrusions. Accordingly, the interpretations of the geo-electrical layers of the three sites are

discussed as follows.



4.1 Site-42

This site has been investigated using three parallel lines (lines-1, -2, and -3) from southeast to the

northwest directions of spacing about 10 meters between the lines. The 2D electrical resistivity

tomography of each line has been discussed as follows.

From the geo-electrical results of the three lines, four lithological layers are interpreted as highly

fractured limestone, slightly weathered limestone, marl-shale intercalation, and dolerite

intrusions (Fig. 4.1).

The top part of this site is covered by a highly fractured limestone with the highest resistivities

which reaches from 600 ohm.m to 20,000 ohm.m. Such very high resistivities could be due to the

air filled fracture zones and karsts near to the surface. The maximum thickness is at the center

and northwest direction of the site that goes down to 8 meters depth. This layer is underlain by a

limestone with less degree of fracturing as it is also revealed from borehole information, which is

less than 4 meters thick. As shown from the interpreted results of the three lines (Fig. 4.1), the

marl-shale intercalation layer is below the limestone layer and it is not continuous laterally

because of dolerite dykes of igneous intrusions at two places. Normally, the marl-shale

intercalation rock unit shows the lowest resistivities (less than 80 ohm.m) that are due to the

conductivity nature of the clay minerals inside the shale rocks. The dolerite dykes are intruded

near to the surface at the left and right sides of the excavated foundation site (WEC-42) and

show intermediate resistivities from 100 ohm.m to 400 ohm.m (Fig. 4.1, middle). This is

relatively lower resistivity for dolerites and that might be due to high degree of weathering.

To see geological structures such as fractures and weak zones near to the floor of the excavated

site (WEC-42), a different processing technique is applied only for data between x=57 meter and

x=159 meter (Fig. 4.2). The aim of this processing technique is to amplify the vertical structures

so that to improve our understanding of weak zones such as fractures and vertical contacts at

shallow depths but with better resolution and scale near to the foundation site.



Figure 4.1 Site-42: Interpreted 2D electrical resistivity models for; line-2(top), line-1(middle), and line-

3(bottom).

karsts

karst

karsts



Figure 4.2 Site-42: Shallow interpretations of 2D electrical resistivity models for; line-2(top), line-

1(middle), and line-3(bottom).



Figure 4.3 Site-42: Horizontal resistivity sections at different depths derived from the 2D inversion

results. Dot lines indicate the survey lines.



Therefore, based on the interpreted geo-electrical layers in Fig. 4.2(middle), the fractures are

clearly observed at the floor of the excavated foundation site (WEC-42) that go down to 3 meters

depth. The top of the dolerite could be found at about 7 meters depth below the floor of WEC-42

or 11 meters below the platform which is also approved by the borehole information.

Horizontal resistivity sections for different depths can also be derived from the data of the 2D

profiles (Fig. 4.3). Accordingly, the lithologies interpreted from the resistivity values are mapped

at depths of 1 m, 5 m, and 18 m. At shallow depths the study area is mainly covered by the high

resistive fractured limestone. At 5 meters depth, the limestone covers most of the area but

pinches out towards southeast of the site. At 18 meters depth two dolerite dykes are mapped and

both of them are elongated almost in the north-south directions.

4.2 Site-44

At site-44 five lithological layers are interpreted from the 2D-electrical resistivity images of the

three lines (Fig. 4.4). At the surface most of the area is covered with a thin layer of limestone

about 1.5 m thick. This is underlain by a thin marl-shale intercalation unit which is about 4 m

thick. A limestone layer is again repeated at 6 meters depth below the platforms at the center and

eastern part of the site with a maximum thickness of about 12 m (e.g., east of line-1). This layer

is again underlain by marl-shale intercalation layers at the western and eastern part of the survey

lines.

Below the center of the three lines, a huge dolerite dyke is intruded. The top of the dolerite dyke

is found at a minimum depth of 6 meters from the platform, for example, at the centers of line-2,

line-3, and at x=78 m of line-1 (Fig. 4.4). The maximum depth for the top of the dolerite is found

at about 18 meters from the platform of line-1 exactly 14 meters below the excavated floor of the

foundation site WEC-44. Under the floor of WEC-44, a 3 m thick limestone layer is underlain by

about 9 m thick marl-shale intercalations that might be underlain by a 2 m thick limestone on top

of the dolerite intrusion as shown in Fig. 4.4(middle). The highest resistivities of the dolerite

indicate that the dolerite is massive especially towards southern part of the site.



Figure 4.4 Site-44: Interpreted 2D electrical resistivity models for; line-3(top), line-1(middle), and line-

2(bottom).



Figure 4.5 Site-44: Shallow interpretations of 2D electrical resistivity models for; line-3(top), line-




Similar to site-42, a special processing technique is also applied using only the data near to the

platforms by giving more weight to the vertical structures so that to see the extent of fractures

and vertical weak zones within the lithologic units (Fig. 4.5). Accordingly, the open or air filled

fractures can be observed with higher resistivity as shown, for example, at the floor of WEC-44

of Fig. 4.5(middle). One of the fractures (at x-102 of line-1) could go down to 4 meters depth but

the rest fractures go not more than 2 meters depth. At line-3 two fracture zones are also detected

at x=102 m and x=112 m that are filled with marl and shale.

As shown in Fig. 4.6 horizontal resistivity sections are prepared at 1m, 5m, 10m, and 18m depths

from the data of the 2D profiles. At shallow depths around WEC-44, it is mainly covered by the

low resistivity shale and marl intercalations. At 5 meters depth, half of the floor of the excavated

site lies over a thick marl-shale intercalation at the eastern part. But its western half floor is

underlain by dolerite. At 18 meters depth the whole floor will be over dolerite dykes.

Figure 4.6 Site-44: Horizontal resistivity sections at different depths derived from the 2D inversion




4.3 Site-44B

From the three parallel 2D-electrical resistivity images, five lithological layers are interpreted at

this site (Fig. 4.7). A thin limestone layer, which is about 2 m thick, is detected at the surface of

the three lines towards the northwest directions. This thin limestone layer is underlain by a marl-

shale intercalation layer with a relatively lower resistivities. The maximum thickness of this

lithologic layer is about 5 meters and found exposed at the surface between x=60 m and x=165 m

at line-2 as shown in Fig. 4.7(top). By comparing its relative thicknesses from the three lines, the

marl-shale layer is getting thicker and thicker toward the northern part of the site. The third layer

is interpreted as a very thick limestone with a maximum thickness of 20 meters towards the

southeast. This is with a relatively higher resistivity and it is found exposed to the surface at the

southern and southeastern part of the site. The fourth geo-electrical layer is interpreted as the

marl-shale intercalation with a relatively lower resistivity below 20 meters from the platform

whereas; at line-3 this layer is detected at about 15 meters depth. This might be pushed upwards

by a dolerite intrusion as clearly seen from line-3 in Fig. 4.7(bottom). The top to the dolerite

dyke is also detected from lines-1 and -2 but at about 30 meters depth from the platform as

shown in Figs. 4.7(top and middle).

To see the degree of fracturing a vertical structure enhancing processing technique is applied for

data sets between x = 66 m and x = 126 m of the three lines as shown in Fig. 4.8. Based on the

results, high degree of fracturing is observed at the top part of the limestone especially at lines-1

and -3 where it is exposed to the surface. But at line-2, the limestone is overlain or covered by 3

to 5 meter thick marl-shale intercalation layer and no fractures are clearly observed. This might

be due to low degree of weathering relative to the limestone exposed at the surface as shown in

lines-1 and -3. Therefore, based on the interpreted results, the fractures detected at lines-1 and -3

could go down to 3 meters depth.



Figure 4.7 Site-44B: Interpreted 2D electrical resistivity models for; line-2(top), line-1(middle), and line-

3(bottom).



Figure 4.8 Site-44B: Shallow interpretations of 2D electrical resistivity models for; line-2(top), line-




Figure 4.9 Site-44B: Horizontal resistivity sections at different depths derived from the 2D inversion


To see the lateral continuity of the different lithologies, contacts, and structures four slices are

mapped from the 2D geo-electrical layers (Fig. 4.9). At the surface (about 1m depth), the

lithologic contacts are mapped between limestone and marl-shale intercalations. At about 4 m



depth the marl-shale intercalation layer increases its coverage from the northwest towards the

center. At the center and southeast part the marl-shale intercalation layer disappear and it is only

covered by a limestone layer especially towards the southern part of the site. But at 10 meters

depth the limestone is more dominant towards the northern part. At 18 m depth the only

dominant layer is the marl-shale intercalations.

5. Conclusion and Recommendations

5.1 Conclusions

The application of different geophysical methods can reveal features or anomalies in the

subsurface depending on their physical properties. In this work, the aim of the 2D electrical

resistivity surveys were primarily to investigate dissolution zones such as fractures and karsts

and secondary to differentiate the different lithologies of the subsurface by interpreting in terms

of their resistivity distributions, geometry and depth of the anomalies. Therefore, the lithologies,

fractures and dissolution zones are investigated using 2D electrical resistivity imaging surveys by

incorporating information also from boreholes and regional geology.

The 2D electrical resistivity investigation has improved our understanding of the relationships

between the different rock types and the geological structures. All the inversion results show a

resistivity contrast between the high resistive fractured limestone and dolerite intrusions, and the

low resistive marl-shale intercalations (Figs. 4.1-4.9). Therefore, based on the 2D electrical

resistivity results three lithologic types are interpreted as limestone, marl-shale intercalations,

and dolerite igneous intrusions.

The geology of the area includes horizontally stratified sedimentary rocks such as limestone-

marl-shale intercalations that are older in age. These layers are later disturbed by a relatively

younger age igneous intrusions called dolerite dykes. The effects of the dolerite dykes are both in

large scale and small scales. A large area could be uplifted and forms hills that can be covered

with thick limestone-marl-shale intercalations at the top. But within such thick sedimentary

successions at the top of huge dolerite intrusions, secondary dolerite dykes and sills can be

intruded in smaller scales. These can cause fracturing and weakzones in the sedimentary rocks



when they are uplifted by the dolerite intrusions. Therefore, limestones near to dolerite intrusions

are highly affected by fracturing than those limestones far away from the igneous intrusions.

Based on the objectives and the interpreted results from the geophysical investigations, the

following conclusions are drawn about the three foundation sites in the study area.

1. The high degree of limestone fractures observed at the floor of WEC-42 and -44 are due

to the intrusion of small scale dolerite dykes at shallower depths. The detected dolerite

dykes are trending along N-S directions at both sites and found near to the surface at

about 8 meters depth in site-42 and 6 meters depth in site-44. From the three sites, Site-

44B will have fewer disturbances since the top of the dolerite dykes are found at about 30

meters depth.

2. No caves or karsts are detected below the proposed foundation sites. But at site-42, the

upper limestone has more karstifications as shown in Fig. 4.1. This is common if a thick

limestone layer is found at the surface due to dissolution of chemical weathering when it

is in contact with acidic rain.

3. Most of the fractures observed at the floors of WEC-42 and WEC-44 extends down to 3

meters depth. But a fracture at the right side of WEC-44 (at x=102m), is the largest

detected fracture that can go down to 5 meters depth from the floor of the excavated site.

The alignments of the main fractures are similar to the dolerite dykes that trend almost in

the N-S directions. This could imply that the intrusions of the dolerite dykes are the

causes for these fractures. At site-44B, the limestone will have less degree of fracturing

below the surfaces. But near to the surface there are some fractures which might be due

to high degree of weathering.

5.2 Recommendations

Based on the outcomes of the geophysical survey, it is possible to forward the following

recommendations.



1. From the geophysical investigation results the foundation sites of WEC-42 and -44 are

highly fractured. Hence the rock masses in the foundation sites need ground improvement

through grouting or selecting other sites, for example, Site-44B instead of Site-44.

2. Usually limestones near to dykes are highly fractured and weathered due to the igneous

intrusion effects. Moreover, they can also form karsts and caves due to chemical

weathering of dissolution process when they are in contact with acidic water. Therefore,

identifying the location of dykes and karsts is important to select better foundation sites.

3. Borehole site selection and geotechnical investigations become more effective if they are

done based on geophysical investigation results. Hence, we recommend geophysical

investigations such as 2D electrical resistivity tomography prior to geotechnical

investigations.



References

Gebregziabher, B. (2003) Integrated Geophysical methods to investigate geological structures and

hydrostratigraphic unit at Aynalem, SE Mekelle. MSc.Thesis, AAU Libraries-Earth Sciences, Addis

Ababa, Ethiopia.

Gebregziabher, B., Günther, T., and Wiederhold, H. (2010) Joint inversion of seismic refraction and

electrical resistivity tomography to investigate sinkholes. Extended abs., European Association of

Geoscientists & Engineers (EAGE) - Near Surface 2010, Sep. 6 – 8, Zurich, Switzerland.

Gebregziabher, B. (2011) Environmental and Engineering Geophysical Studies for Sinkhole Problems

Using Seismic Reflection, Refraction Tomography, Electrical Resistivity Imaging, and Joint Inversions.

Ph.D. Thesis, TIBUB online at http://edok01.tib.uni-hannover.de/edoks/e01dh11/646420569.

Günther, T. (2004) Inversion methods and resolution analysis for the 2D/3D reconstruction of resistivity

structures from DC measurements. PhD thesis, University of Mining and Technology Freiberg. Available

at http://fridolin.tu-freiberg.de.

Loke, M.H. and Barker, R.D. (1996) Rapid leas-squares inversion of apparent resistivity pseudosections

by a quasi-Newton method. Geophysical prospecting, 44, 131-152.

Mussett, A.E. and Khan, M. A. (2000) Looking into the earth, an introduction to geological geophysics.

Cambridge University press. UK pp. 183-211.

http://edok01.tib.uni-hannover.de/edoks/e01dh11/646420569

http://fridolin.tu-freiberg.de/



Resume

Berhanu Gebregziabher Gared (PhD)

Asst. Professor of Geophysics

Collage of Natural & Computational Sciences

Department of Earth Sciences, Mekelle University

P.O.Box 231, Mekelle, Ethiopia

Tel.: +251914004361 (mobile)

E-mail: [email protected]

Homepage: www.mu.edu.et

Personal Profile

Date of Birth : 19 February 1977

Place of Birth : Tigray, Ethiopia

Sex : Male

Family status : Married and three children

Nationality : Ethiopian

Language : English, Amharic, Tigrigna, German (intermediate), Dutch (intermediate).

Educational Background

Ph.D. in Applied Geophysics from Leibniz University of Hannover, Germany, in February

2011.

M.Sc. in Applied Geophysics from Addis Ababa University Department of Earth Sciences,

Ethiopia, in June 2003.

mailto:[email protected]

http://www.mu.edu.et/



B.Sc. in Geology from Addis Ababa University Department of Earth Sciences, Ethiopia, in

June 2000.

Completed Secondary School with distinction at Atse Yohannes Secondary School, Mekelle,

Ethiopia, in March 1996.

Completed Elementary School at Haik Elementary School, Haik, Ethiopia, in June 1990.

Work/Research Experiences

Aprill 2011 – Recent: Assistant Professor of Geophysics in Mekelle University, College of

Natural and Computational Science Department of Earth Sciences, Mekelle, Ethiopia.

April 2007 - December 2010: Researcher in Leibniz Institute for Applied Geophysics

(LIAG), Hannover, Germany in seismic (P- and S-waves) reflection and refraction

tomography data processing and interpretations using ProMAX software.

July 2003 - October 2006 : Lecturer in Mekelle University Department of Earth Sciences,

Ethiopia, and teaching Geophysics, Environmental Science, and Geology courses. Moreover

head of the registrar office for the Faculty of Science and Technology.

July 2000 - September 2001: Graduate Assistant in Mekelle University department of Earth

Sciences, Ethiopia, and teaching Environmental Science and Geomorphology courses and

assisting and coordinating field terrain mapping techniques.

Community Services



Dam site investigation using VES & 2D electrical resistivity imaging at AgulaE-Gerendho

area, in Tigray. The Government of National State of Tigray Bureau of Water Resources.

Dam site investigation using VES and 2D electrical resistivity imaging at Illala-Embanshti

area, in Tigray. The Government of National State of Tigray Bureau of Water Resources.

Dam site investigation using VES & 2D electrical resistivity imaging at Chelekot area, in

Tigray. The Government of National State of Tigray Bureau of Water Resources.

Dam site investigation using Vertical Electrical Sounding (VES) at Hiwane area, in Tigray.

The Government of National State of Tigray Bureau of Water Resources.

Mineral investigation using Magnetic and Induced Polarization (IP) methods at Shire, in

Tigray. Ezana Minning Plc.

Bridge site investigation using 2D electrical resistivity imaging at Illala-Mekelle. Noami-

Consultant.

Publications

Gebregziabher, B. (2011) Environmental and Engineering Geophysical Studies for Sinkhole

Problems Using Seismic Reflection, Refraction Tomography, Electrical Resistivity Imaging, and

Joint Inversions. Ph.D. Thesis, TIBUB online at http://edok01.tib.uni-

hannover.de/edoks/e01dh11/646420569.

Gebregziabher, B., Günther, T., and Wiederhold, H. (2010) Joint inversion of seismic refraction

and electrical resistivity tomography to investigate sinkholes. Extended abs., European

Association of Geoscientists & Engineers (EAGE) - Near Surface 2010, Sep. 6 – 8, Zurich,

Switzerland.





Gebregziabher, B., Günther, T., and Wiederhold, H. (2010) Electrical resistivity and seismic

refraction tomography applied for sinkhole investigations at Münsterdorf, North Germany.

Poster Abs., 70 Jahrestagung der Deutschen Geophysikalischen Gesellschaft (DGG70), 15-18

March 2010, Bochum, Germany.

Gebregziabher, B., Wiederhold, H., and Kirsch, R. (2009) Sinkhole investigations using P- and S-

wave reflection seismic in Schleswig-Holstein, North Germany. Poster Abs., 69 Jahrestagung der

Deutschen Geophysikalischen Gesellschaft (DGG69), 23-26 March 2009, Kiel, Germany.

Wiederhold, H., Gebregziabher, B., and Kirsch, R. (2008) Geophysical investigation of a sinkhole

feature in Schleswig-Holstein. Extended abstract, EAGE Near Surface 2008, 15. – 17.09.2008;

Krakow, Poland.

Gebregziabher, B. (2003) Integrated Geophysical methods to investigate geological structures

and hydrostratigraphic unit at Aynalem, SE Mekelle. MSc.Thesis, AAU Libraries-Earth Sciences,

Addis Ababa, Ethiopia.

References:

1. Prof. Dr. Hans-Joachim Kümpel

Tel: +49 511-643-2101

Email: [email protected]

2. Dr. Helga Wiederhold

Tel: +49 511-643-3520


3. Prof. Dr. Charlotte Krawczyk

Tel: +49 511-643-3518


4. Prof. Dr. Jutta Winsemann

Tel: +49 511-762-2964






Geophysics Report Ashegoda

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