Aceh Besar (Indonesia) The Identification of Seulimeum Fault System in Iejue, by Using Magnetic Technique

Muhammad Taqiuddin Zakaria

Postgraduate Student, Geophysics Section, School of Physics, 11800 Universiti Sains Malaysia, Penang, Malaysia; e-mail: taquddinzakaria92@gmail.com

Dr. M.M. Nordiana

Lecturer, Geophysics Section, School of Physics, 11800 Universiti Sains Malaysia, Penang, Malaysia; e-mail: mmnordiana@usm.my

Dr. Rosli Saad

Associate Professor

Senior Lecturer Geophysics Section, School of Physics, 11800 Universiti Sains Malaysia Penang, Malaysia; e-mail: rosli@usm.my

Dr. I. N. Azwin

Lecturer, Geophysics Section, School of Physics, 11800 Universiti Sains Malaysia,

Penang, Malaysia e-mail: nurazwinismail@yahoo.com

Nur Khairunnisa Aqilah Yunos

Postgraduate Student, Geophysics Section, School of Physics, 11800 Universiti Sains Malaysia, Penang, Malaysia; e-mail: nisaaqilahyunos@yahoo.com.my

ABSTRACT

Magnetic is a non-destructive geophysical technique that live the Earth's force field at specific location. It has numerous application in engineering and environmental field like locating a fault zone. Fault ar delineated as two-dimensional or gently arced fracture in a rock mass wherever there are important relative displacement on the fracture as a result from the world movement. The purpose of this study is to spot the Seulimeum fault system in Iejue, Aceh Besar (Indonesia) by using a magnetic technique and correlate the result with geologic map and conjointly to grasp a trend pattern of fault system. Magnetic survey was conducted with the proton meter with fifty m interval of every magnetic station (rover). This survey consist of three distinction survey lines with length of one kilometer of every line. The magnetic data was processed by utilizing Microsoft excels and Surfer10 code that was displayed in a variety of contouring and disclosed fault zones. The local magnetic price covers from -150 to 600 nongovernmental organization. The result showed a low residual magnetic value at a north half compared to south a part of study space that indicated a pattern of fault zone. Magnetic residual was successfully correlate with the geologic map that show the existence of the Seulimeum fault in this study space.

INTRODUCTION

The Aceh province in Indonesia, located around the Sumatran geologic process zone. The Great Sumatran Fault (GSF) is recorded as dextral break zone that contain a result from the oblique convergence of the geologic process between the Indo-Australian and Eurasian plates (Bellier et al., 1997). Strike-slip faulting occurs hundred kilometers to the east of the ditch and involves slip directed parallel to the trench that is submit to the island Island. This fault is classified into three major sections that ar southern, central, and northern (Aydan, 2009). The Sumatran Fault with 1900 km long structure of the right lateral strike slip is very divided and consists concerning twenty major segments. Most segment ar vary in length concerning sixty to two hundred kilometer, (Natawidjaja and Wahyu, 2007).

From the history of earthquake along Sumatran Fault that has been documented in 1980 shows the correlation of the segmentation of the fault and the location of the earthquake within the past ruptures (Natawidjaja et al., 2006). The sumatran fault runs length of the Barisan Mountains, a range elated basements blocks, granitic intrusions and Tertiary sediments, topped by Tertiary-Recent geological phenomenon. The Sumatran Fault System in Aceh can be classified into 2 major segments that ar Seulimeum and Aceh fault. Geomorphic features shows the Seulimeum Fault still active compare to Aceh Fault. This fault cut through Plio-Pleistone sediments and volcanic product of the active Seulawah Agam volcano and displaces the axial traces of east-west trending folds. This process cause the epoch deposits moved from the southwest facet of the fault to northwestwards (Bennett et al., 1981).

GENERAL GEOLOGY

Aceh is located at northern a part of the island island. There are four major volcano-sedimentary sequences, separated by unconformities ar known that is 3 are pre-Tertiary in age and others is Tertiary to Recent (Cameron et al., 1980). Sumatran Fault system occurs from the Middle epoch and also the gap of the Andaman Sea. Pre-Tertiary basements rocks outcrop mainly on the central spine of the Barisan Mountains, which extend the length of the island parallel to the southwest value. Figure 1 shows the regional tectonic setting of island island.

The area from northeast and southwest is overlain by Tertiary substance and volcanic rocks. Rock unit of all ages are transacted by Sumatran Fault that follow the NW-SE trend (Barber and Crow, 2003). The geology of Banda Aceh Quadrangle has been mapped (figure 2) by airman et al., 1981. The lithology of the study area, Ieju is dominated by Lam Tuba volcanic that is composed of andesitic to volcanic rock volcanic, pumiceous breccia, tuffs, agglomerate and ash flows with composition of tuffaceous and calcareous sandstones, conglomerates and mudstones(Bennett et al., 1981). The geological formation shaped a geographics depression, occupied with alluvial flat and low flat-top hills among Barisan vary (Katili and Hehuwat, 1967; Page et al., 1979). Figure 3 shows the location of Iejue within the google earth.

Aceh Besar (Indonesia) The Identification of Seulimeum Fault System in Iejue, by Using Magnetic Technique

METHODOLOGY

The ground magnetic survey is distributed with proton precession meter device and international Positioning System (GPS) navigation for real -time measurements. Three distinction survey line that is L1, L2, and L3 with length of 1 kilometer and fifty m interval of every magnetic station (rover) is setup so as to distinctive the submerged characteristics. A base station with magnetic homogeneity is carefully chosen to record magnetic reading at time interval sixty seconds for diurnal correction plagued by the Earth's field. Figure 4 and five shows the magnetic line and magnetic station in a survey space. The magnetic data is measured freelance grid was later combined to made single master grid. This single master grid is processed using Surfer10 code to made full magnetic map (figure 6). All the magnetic information were corrected for diurnal variation and IGRF correction to get a corrected magnetic anomaly data for mapping the residual magnetic relief map.

RESULTS AND DISCUSSION

Magnetic results show lateral view of the faulting system in the study space (Figure 7). The local magnetic price covers from -150 to 600 nongovernmental organization. The total intensity mangnetic anomaly study space shows low magnetic price from -150 nongovernmental organization to -50 nongovernmental organization at northwest half whereas extremely magnetic anomalies from vary two hundred nongovernmental organization to 450 nongovernmental organization at southeast of study area. The long dislocation from northwest part to southeast direction of study space is taken as geologic fault.

CONCLUSION

The magnetic result from this survey shows that a Seulimeum fault trend is from NW-SE direction and also supported by geologic map that recommended there ar many little fault exist in this survey space. From this survey it shows that magnetic method is appropriate in determination and mapping the fault zone beside establish the submerged characteristic.

ACKNOWLEDGEMENTS

The authors wish to convey to lecturers, technical staffs and all member of Geophysics cluster, Universiti Sains Malaysia (USM), Penang, Malaysia, all students and staffs of Faculty of Science, Universitas Syiah Kuala(UNISYIAH), Banda Aceh (Indonesia) for their assistance throughout the geology field information acquisition.

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