Seulimeum segment characteristic indicated by 2-D resistivity imaging method

NRIAG Journal of Astronomy and Geophysics xxx (2017) xxx–xxx

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Seulimeum segment characteristic indicated by 2-D resistivity imaging method M. Syukri a, R. Saad b,⇑ a b

Geophysics Section, Department of Physics, Faculty of Sciences, Syiah Kuala University, Banda Aceh, Indonesia School of Physics, Universiti Sains Malaysia, 11800 Penang, Malaysia

a r t i c l e

i n f o

Article history: Received 28 November 2016 Revised 12 March 2017 Accepted 2 April 2017 Available online xxxx Keywords: Sumatran fault Seulimeum segment Horst and graben 2-D resistivity

a b s t r a c t The study conducted at Aceh (Indonesia) within Krueng Raya and Ie Seu Um vicinity with the same geology setting (Lam Teuba volcanic), to study Seulimeum Segment characteristic using 2-D resistivity imaging method. The 2-D resistivity survey applied Pole-dipole array with minimum electrode spacing of 2 and 5 m for Ie Seu Um study area, while 10 m for Krueng Raya area. Resistivity value of Ie Seu Um study area has been correlated and validated with existing outcrops and hot springs which the value used to identify overburden, saturated area and bedrock of Krueng Raya area. The resistivity value of overburden in Krueng Raya area was identify as <30 Ohm.m, bedrock is >30 Ohm.m and saturated zone is <9 Ohm.m. The imaging results used to identify the Seulimeum segment system, where the depth is increasing from southern part (20–50 m) to northern part (50–200 m) when approaching the Andaman Sea and breaks into two sections to produce horst and graben system which indicate that it produced from the moving plat. Ó 2017 Production and hosting by Elsevier B.V. on behalf of National Research Institute of Astronomy and Geophysics. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

1. Introduction A major fault running entire length of Sumatra Island from south-east to north-west was named as Sumatran fault. The Sumatran fault accommodates mostly by strike-slip fault system which located between Indo-Australia and Eurasian plates (Sieh and Natawidjaja, 2000) and the active fault ends at the north part of Sumatera Island, just below Banda Aceh (Muztaza et al., 2014; Doust and Noble, 2008). Seulimeum Segments is an extension from Sumatran fault which is located in Aceh and it also accommodate by strike-slip

fault system (Nurhasan et al., 2011). Studies have been conducted at the segments with multidisciplinary techniques/methods, but no deep crustal studies have been investigated. After-shock event at the two segments has been identified, even though with small magnitude. Assumption can be made in the future that there is still have high possibility to rupture. Therefore detail and rapid investigation on the two segments is very important in order to understand the system and processes. 2-D resistivity survey conducted crossing predicted Seulimeum Segment starting from Krueng Raya until Ie Seu Um to identify the system.

2. Geology of study area

⇑ Corresponding author. E-mail addresses: [email protected], [email protected] (M. Syukri), [email protected], [email protected] (R. Saad). Peer review under responsibility of National Research Institute of Astronomy and Geophysics.

Production and hosting by Elsevier

The study conducted including Krueng Raya and Ie Seu Um areas which covered about 9.2 km2 (Fig. 1). On the northern part of the study area was gently flat and nearby Andaman Sea. Moving towards the southern part of the study area, the ground topography is very rough with mixture of primary/secondary jungle, villages and farms. Hot spring was identified at Ie Seu Um area which located on the south-east part of Krueng Raya. Aceh is located at the northern part of Sumatera Island, consisting four major volcano-sedimentary sequences, separated by unconformities which are pre-Tertiary in age and the others are

http://dx.doi.org/10.1016/j.nrjag.2017.04.001 2090-9977/Ó 2017 Production and hosting by Elsevier B.V. on behalf of National Research Institute of Astronomy and Geophysics. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Please cite this article in press as: Syukri, M., Saad, R. Seulimeum segment characteristic indicated by 2-D resistivity imaging method. NRIAG Journal of Astronomy and Geophysics (2017), http://dx.doi.org/10.1016/j.nrjag.2017.04.001

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M. Syukri, R. Saad / NRIAG Journal of Astronomy and Geophysics xxx (2017) xxx–xxx

Andaman Sea

Krueng Raya

Tertiary to Recent. Banda Aceh Quadrangle and Krueng Raya lithology is dominated by Lam Tuba volcanic (Fig. 2). It composed of andesitic to dacitic volcanics, pumiceous breccia, tuffs, agglomerate and ash flows. The intruded ash into the Seulimeum formation composed of tuffaceous and calcareous sandstones, conglomerates and minor mudstones (Bennett et al., 1981). The flat and low alluvial including flat-topped hills, within Barisan range, runs along the entire western edge of the Sumatera Island. A continuous axial valleys system follow closely the Barisan range crest, marks an outcrop of the main fault line (Sumatran fault system) with right lateral fracture system. Two main faults system controlled the area with orientation of NW to SE. The topographic morphology of the Krueng Raya is subdued because the rocks are strongly fractured and altered (Katili and Hehuwet, 1967; Page et al., 1979).

3. Methodology 2-D resistivity imaging method conducted by injecting direct current into the ground through a pair of current electrode and

N

Ie Seu Um

0

C1

P1

P2

C2

2.5 km

Fig. 1. Two study area; Ie Seu Um and Krueng Raya for Seulimeum Segment study. Predicted faults marked as black line (Google Earth, 2016).

Fig. 3. Electrode arrangement for 2-D resistivity imaging.

Andaman Sea

SEDIMENTS and METASEDIMENTS Alluvium (undifferentiated): gravels, sands, mud, etc. Lam Teuba Volcanics: andesitic to dacitic volcanic, pumiceous breccias, tuffs, agglomerates, ashflows: Qvtl = mudflows with DTvt

Study area

Indrapuri formation: older terrace deposite, partly volcanic, volcanic gravels and sands. Seulimeum formation: tuffaceous and calcareous sandstones, conglomerates, minor mudstones.

INTRUSIVE ROCKS

Tangse serpentinite: serpentinite

massive

Indrapuri complex: tectonic melange serpentinite, serpentinised ultramafic, undifferentiated igneous and sedimentary rocks. Faults, uncertain 0

5

N

10 km

B’

B’

B Fig. 2. Geology of the study area (Modified from Bennett et al., 1981).

Please cite this article in press as: Syukri, M., Saad, R. Seulimeum segment characteristic indicated by 2-D resistivity imaging method. NRIAG Journal of Astronomy and Geophysics (2017), http://dx.doi.org/10.1016/j.nrjag.2017.04.001

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M. Syukri, R. Saad / NRIAG Journal of Astronomy and Geophysics xxx (2017) xxx–xxx

measuring potential difference using a different pair of potential electrode planted on the ground surface. The method use to investigate electrical properties of subsurface by calculating apparent resistivity distribution of the materials (qa) from data measuring on ground surface (Fig. 3). The measured apparent resistivity (qa) mostly depends on a combination of resistance and dielectric related to lithology and geology of the subsurface (Edwin and Cahit, 1988). Rock types such as igneous and metamorphic; typically having high resistivity values depending on degree of fractures. Since water table in Malaysia is generally shallow, the fractures are commonly filled with ground water (Muztaza et al., 2014). High fracturing rocks will result a lower resistivity values. Table 1 shows the resistivity values of rocks and soil types (Keller and Frischknecht, 1996).

Table 2 ABEM SAS4000 Terrameter data acquisition setting. Function

Setting

Value

Current

Maximum Minimum Auto – – – Maximum Minimum –

50 mA 1 mA – 0.3 s 0.3 s 3s 3 1 50 Hz

Mode Acquisition delay Acquisition time Total cycle time Stack Power line frequency

Forward measurement C1

P2

P1 na

a

Table 1 Resistivity value of rocks and soil (Keller and Frischknecht, 1996). Material

Resistivity (Om)

Alluvium Sand Clay Groundwater (fresh) Sandstone Shale Limestone Granite

10–800 60–1000 1–100 10–100 8 - 4x103 20 - 2x103 50 - 4x103 5x103 - 1x106

Reverse measurement P2

P1 a

C1 na

Fig. 5. Forward and reverse measurement of pole-dipole array (Loke, 1999).

Fig. 4. 2-D resistivity imaging electrode array and their geometric factor, k (Loke, 2011).

Please cite this article in press as: Syukri, M., Saad, R. Seulimeum segment characteristic indicated by 2-D resistivity imaging method. NRIAG Journal of Astronomy and Geophysics (2017), http://dx.doi.org/10.1016/j.nrjag.2017.04.001

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M. Syukri, R. Saad / NRIAG Journal of Astronomy and Geophysics xxx (2017) xxx–xxx

Selector

Terrameter

Selector

Terrameter

Smart cable E1

E2 . . .

E20

E21 E1

E22

E23. . .

E2 . . .

E40

E41

E20

E21

E22

E23. . .

E40

E41

Smart cable ROLL-UP

Fig. 6. Roll-up techniques.

L3,0m

Outcrop

Outcrop

L2,0m L1,0m

L4,0m

Hot Spring and outcrop

L1,80m

N

80m

0

L2,80m

L3,200m L4,200m

Fig. 7. 2-D resistivity survey lines at Ie Seu Um (Google Earth, 2016).

The apparent resistivity (qa) is calculated based on Eq. (1.1).

qa ¼ k

V I

ð1:1Þ

where V = voltage I = current k = geometric factor

shows ABEM SAS4000 Terrameter data acquisition setting used for all survey lines. Pole-dipole array was used based on the deepest depth penetration beside provide a good resolution. Pole-dipole array is an asymmetrical arrangement which influence the anomalies by giving asymmetrical apparent resistivity. To eliminate the asymmetry affect, reverse measurement also taken (Fig. 5). Roll-along techniques was applied to complete the total length of each survey line if the total length of the survey line exceeding more then one spread. The overlapped applied was at the centre of the previous spread (Fig. 6). Ie Seu Um is a hot spring area with outcrop identified at the western and eastern part of the area. Four resistivity survey lines; L1–L4 were conducted at the area (Fig. 7). L1 and L2 conducted using two smart cables with 2 m minimum electrode spacing, while L3 and L4 using two smart cables with 5 m minimum electrode spacing. The 2-D resistivity data was processed to identify resistivity value of overburden and bedrock, and the values will be use for correlation and validation of Krueng Raya study area. Fig. 8 shows Krueng Raya study area with six resistivity survey lines; L5–L10. The survey lines were conducted using four smart cables with 10 m minimum electrode spacing. Roll-up techniques was applied for survey line L5, L6, L8 and L10. The 2-D resistivity data was processed, correlated and validated with the value identified from Ie Seu Um result for Seulimeum Segment identification. The 2-D resistivity data were processed using Res2Dinv (ver.3.56.70) to produce inverse model resistivity section. The inversion model converted to surfer8 format for validation, correlation and interpretation. The overburden and bedrock resistivity value of Ie Seu Um area are used as a bench mark to delineate Seulimeum Segment of Krueng Raya.

4. Results The geometric factor (k) is identified by electrodes arrangement (Fig. 4) and it is a key factor in identifying depth of penetration. The study conducted at two study area; Ie Seu Um and Krueng Raya (Fig. 1), using 2-D resistivity imaging survey with ABEM SAS4000 Terrameter system including ES10-64C electrode selector, smart cables, 41 stainless steel electrodes and jumpers. The surveys were performed using Pole-dipole array with remote electrode located at distance of 5 times of maximum electrode spacing from each survey line and perpendicular to it. Table 2

Fig. 9 shows 2-D resistivity inversion model of L1-L4 at Ie Seu Um, with resistivity values of 0–2000 Ohm.m. The area divided into two main zones; overburden with resistivity value of < 30 Ohm.m and bedrock with resistivity value of >30 Ohm.m. The hot spring identified onsite flowing from the ground surface was indicate by resistivity value of <9 Ohm.m. Fig. 10 shows 2-D resistivity inversion model of L5–L10 conducted at Krueng Raya. The results were correlated with resistivity

Please cite this article in press as: Syukri, M., Saad, R. Seulimeum segment characteristic indicated by 2-D resistivity imaging method. NRIAG Journal of Astronomy and Geophysics (2017), http://dx.doi.org/10.1016/j.nrjag.2017.04.001

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M. Syukri, R. Saad / NRIAG Journal of Astronomy and Geophysics xxx (2017) xxx–xxx

0

1.6km N

L5, 2120m

L5, 0m L6, 1400m

L6, 0m

L7, 800m L7, 0m

L8, 1200m L8, 0m L9, 800m L9, 0m L10, 1160m L10, 0m Fig. 8. 2-D resistivity survey lines at Krueng Raya (Google Earth, 2016).

Hot spring Distance (m)

60

60

50

50

40

40

L1

Elevation (m)

Elevation (m)

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 76 78

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 79

Distance (m)

70

60

60

50

50

L2 40

40

Distance (m)

80

60

60

40

40

20

L3

9 14 19 24 29 34 39 44 49 54 58 63 68 73 78 83 88 93 98 103 108 113 118 123 128 133 138 143 148 153 158 163 168 173 178 183 188 193 198

4

0

80

Elevation (m)

Elevation (m)

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 79 84 89 94 98 103 108 113 118 123 128 133 138 143 148 153 158 162 167 172 177 182 187 192 196

Distance (m)

20

70

100

100

80

80

60

60

40

40

L4

2000

1000

500

100

200

30

50

15

20

13

5

9

1.5

2

1

0.5

0

Ohm.m

Fig. 9. 2-D resistivity inversion model of line L1-L4 at Ie Seu Um.

Please cite this article in press as: Syukri, M., Saad, R. Seulimeum segment characteristic indicated by 2-D resistivity imaging method. NRIAG Journal of Astronomy and Geophysics (2017), http://dx.doi.org/10.1016/j.nrjag.2017.04.001

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M. Syukri, R. Saad / NRIAG Journal of Astronomy and Geophysics xxx (2017) xxx–xxx

1380

1280

1180

1080

980

880

-100

L6 890

840

790

740

640

590

440

390

340

240

290

190

140

90

40 80

690

-150

-200

-200

Ohm.m

80

2000

30

30

1000

-20

-20

500

-70

-70

L7

200 100

-120

-170

-170

30

-220

20

90

15

40

40

13

-10

-10

9

-60

-60

1090

990

890

790

690

590

490

390

290

190

L8 760

690

480

410

340

270

200

130

60

-160

620

-110 550

-110

90

90

1190

-120

-220

Elevation (m)

N

-50

540

-150

Elevation (m)

780

680

580

480

280

180

0

-50 -100

100 50

0

490

Elevation (m)

50

80

100

380

L5

-160

50

5 2 1.5

30

30

-20

-20

-70

-70

1

-120

-120

L9

Elevation (m)

50 0

1090

990

890

0

Rock head

-270 50 0

-50 -100

790

190

90

-270

690

-220 590

-220

490

-170

390

-170

290

Elevation (m)

0.5

-50

L10

-100

-150

-150

Fig. 10. 2-D resistivity inversion model of line L5-L10 at Krueng Raya.

value identified at Ie Seu Um area for geology subsurface information. Generally 2-D resistivity inversion model show the Krueng Raya was divided into two main zones; overburden with resistivity value of <30 Ohm.m and bedrock with resistivity value of >30 Ohm. m with undulating rock head. 5. Discussion and conclusion The overburden and bedrock resistivity value of Krueng Raya area were identified referring to the value identified at Ie Seu Um study area which has been correlated and validated with the existence of outcrops and hot spring. Generally, the resistivity value of

Krueng Raya bedrock was identified with a value of >30 Ohm.m and interpreted as Lam Teuba volcanic. The bedrock was overlaid by overburden with resistivity value of <30 Ohm.m. Fig. 11 shows the depth to bedrock of Krueng Raya area after processing and interpretation. It was identified that the bedrock is undulating shape with depth is increasing from southern part (20–50 m) to northern part (50–200 m) when approaching the Andaman Sea. Line L5–L9 show that the bedrock breaks into two sections to produce horst and graben system. The study shows that Seulimeum Segment consists of horst and graben system and the depth is increasing when approaching Andaman Sea, which indicate that it produced from the moving plat.

Please cite this article in press as: Syukri, M., Saad, R. Seulimeum segment characteristic indicated by 2-D resistivity imaging method. NRIAG Journal of Astronomy and Geophysics (2017), http://dx.doi.org/10.1016/j.nrjag.2017.04.001

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M. Syukri, R. Saad / NRIAG Journal of Astronomy and Geophysics xxx (2017) xxx–xxx

619500

Andaman Sea

2100

Horst 619000

Horst 1050

618500

Northing

L5

100 0 -100 -200 -300

0

Horst 618000

Horst

L6

100 0 -200

617500

1400

-100

700 0

L7

Horst

Horst

100

617000

0

Graben

-100 -200 0

100 200 300 400 500 600 700 800 900

616500 100

L8

N

Graben

-100

616000

0

Fault identified from Geologic map of the Banda Aceh Quadrangle, Sumatra 615500

Fault identified from 2-D resistivity method

615000

0

Horst

100 200 300 400 500

Horst

Graben

800 700

500 400 0 Graben 300 -100 200 100 -200

L9

0

100

0.8 km 779100

1000 1200 1300

600

L10

0 -100 0

778600

Horst

Horst

0

779600

780100

500 600 300 400 100 200

780600

900 700 800

781100

1000 1100

781600

Easting Fig. 11. Bedrock and fault system of study area ‘B’ identified by 2-D resistivity imaging method.

Acknowledgements Thanks to Ministry of Education and Culture, Indonesia for financial support in the scheme of Decentralized Research Competitive Grants Program 2015 (Grand no. 089/UN11.2/LT/

SP3/2015). Special thanks are extended to technical staffs of geophysics laboratory and geophysics postgraduate students, Universiti Sains Malaysia and geophysics students, Faculty of Sciences and Faculty of Engineering, Syiah Kuala University (Aceh).

Please cite this article in press as: Syukri, M., Saad, R. Seulimeum segment characteristic indicated by 2-D resistivity imaging method. NRIAG Journal of Astronomy and Geophysics (2017), http://dx.doi.org/10.1016/j.nrjag.2017.04.001

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References Bennett, J.D., McC Jeffrey, D., Bridge, D., Cameron, N.R., Djunuddin, A., Ghazali, S.A., Jeffrey, D.H., Kartawa, W., Keats, W., Rock, N.M.S., Thomson, S.J., Whandoyo, R., 1981, Geologic map of the Banda Aceh Quadrangle, Sumatra. Doust, H., Noble, R.A., 2008. Petroleum systems of Indonesia. Mar. Pet. Geol. 25, 103–129. Edwin, S.R., Cahit, C., 1988. Basic Exploration Geophysics. John Wiley and Sons, New York. Google Earth, 2016. Katili, J., Hehuwet, F., 1967. On the occurrence of large transcurrent faults on Sumatra Indonesia. Osaka City Univ. J. Geosci. 10, 1–17. Keller, G.V., Frischknecht, F.C., 1996. Electrical Methods in Geophysical Prospecting. Pergamon Press, New York. Loke, M.H., 2011. Electrical resistivity surveys and data interpretation. In: Gupta, H (Ed.), Solid Earth Geophysics Encyclopaedia. . second ed., Electrical & Electromagnetic second ed. Springer-Verlag, pp. 276–283. Loke, M.H., 1999, Electrical Imaging Surveys for Environment and Engineering Studies: a practical guide to 2-D and 3-D surveys, 67. Muztaza, M.N., Saad, R., Kamaruddin, N.A., Syukri, M., Ismail, N.A., 2014a. Characterizing features of faults using magnetic method: preliminary results in Seulimeum Fault, Aceh Besar (Indonesia). Int. J. Eng. Innovat. Res. 3 (4), 476–479. Muztaza, M.N., Saad, R., Saidin, M., 2014b. 2-D Resistivity imaging of buried furnace at Sik, Kedah (Malaysia). Electron. J. Geotech. Eng. 19 (Z), 17635–17642. Nurhasan, D., Sutarno, D., Ogawa, Y., Kimata, F., Sugiyanto, D., 2011. Investigation of Sumatran Fault Aceh Segment derived from Magnetotelluric Data. In: The XXV IUGG Conference Melbourne, 27 June–7 July 2011. Page, B.G.N., Bennett, J.D., Cameron, N.R., Bridge, D., McC Jeffery II, D., Keats, W., Thaib, J., 1979. A review of the main structural and magmatic features of northern Sumatra. J. Geolog. Soc. London 1 (36), 569–579. Sieh, K., Natawidjaja, D., 2000. Neotectonics of the Sumatran fault, Indonesia. J. Geophys. Res., Solid Earth (Wiley) 105 (B12), 28295–28326.

Saad, R., was born in Penang (Malaysia) on February, 28th 1960. He is attaching at Geophysics section, School of Physics, Universiti Sains Malaysia (USM) as senior lecturer. He obtained his B.Sc, M.Sc. and Ph.D. from Universiti Sains Malaysia in 1984, 2004 and 2009 respectively. He has served at USM since year 1985. Prior joining USM, he worked as Tutor in Matriculation Centre USM and School of Physics, USM. His current research activities are Engineering and Environment. He expertise is in Electrical method (2D/3D resistivity/IP/ SP), Seismic (Refraction and Reflection), Ground Penetrating Radar, Magnetic and Gravity. He is also a registered member of Institute of Geology Malaysia, Committee member of 2002 One day Geophysics Conference and secretary of 2006 Geophysics conference. He has published several books and more than 80 journals and conference papers.

M. Syukri was born Medan, Indonesia, in 1970. He received the B.Sc. degree in Physics from the Sepuluh Nopember Institute of Technology (ITS), Surabaya, Indonesia, and M.Eng. in Applied Geophysics from Bandung Institute of Technology (ITB) Indonesia, and received Ph.D. degree in Geophysics Section, School of Physics, Universiti Sains Malaysia (USM), Malaysia, in 2006. In 1993, he joined the Department of Physics, Faculty of Sciences, Syiah Kuala University (SKU), as a Lecturer. He is responsible for carrying out teaching and research duties. He lectures Environmental Physics, Thermodynamics, Introductory Geophysics, and Environmental and Engineering Geophysics at the university. He is involved in the administration of degree and postgraduate courses as well as responsible for organizing lectures and supervising final project, seminars and tutorials.

Please cite this article in press as: Syukri, M., Saad, R. Seulimeum segment characteristic indicated by 2-D resistivity imaging method. NRIAG Journal of Astronomy and Geophysics (2017), http://dx.doi.org/10.1016/j.nrjag.2017.04.001