Electronic Theses and Dissertation

Aktivitas tektonik pada Segmen Aceh di sepanjang Sesar Sumatra telah membentuk zona pengangkatan (uplift) dan zona cekungan (basin) yang menyebabkan perbedaan kondisi geologi di kedua zona. Perbedaan tersebut memengaruhi sedimen dan karakter litologi bawah permukaan, sehingga penting untuk dikaji guna memahami kondisi geologi, potensi geoteknik, kebencanaan dan kepentingan lainnya di wilayah penelitian. Penelitian ini bertujuan untuk memperoleh variasi nilai resistivitas bawah permukaan, mengidentifikasi litologi, serta melihat komparasi karakteristik litologi di kedua zona. Penelitian ini menggunakan metode geolistrik resistivitas 2D konfigurasi Wenner-Schlumberger, dengan delapan lintasan yang masing-masing sepanjang 162 meter dan spasi elektroda 6 meter. Lintasan tersebut terdiri dari tiga pada zona uplift dan lima pada zona basin. Pengolahan data diproses menggunakan perangkat lunak Res2DInv dengan model inversi smoothnest-constrained least-square inversion. Hasil penelitian didapatkan nilai resistivitas sekitar 1 - 250 Ωm, yang diinterpretasikan terdiri dari lanau (1 -10 Ωm), Lempung (11 - 50 Ωm), pasir lempungan ( 51 -100 Ωm), pasir ( 101 - 200 Ωm), dan batugamping (> 200 Ωm).Keberadaan sedimen tersebut, pada zona uplift didominasi oleh batugamping dan sebagian lempung dan lanau. Sedangkan pada zona basin terdistribusi secara merata oleh lanau, lempung, pasir, dan sebagian kecil pasir lempungan dan kerikil pasiran. Hasil komparasi di kedua zona menunjukkan perubahan distribusi material bawah permukaan dari daerah yang dipengaruhi batugamping pada zona uplift menuju daerah yang didominasi sedimen alluvial pada zona basin. Hasil dan temuan ini menunjukkan adanya perbedaan yang sangat signifikan pada variasi nilai resistivitas, litologi, ketebalan dan distribusi kedalaman lapisan batuan dan sedimen.
Kata kunci: Metode resistivitas, Segmen Aceh, Uplift, Basin, Banda Aceh

ABSTRACT Tectonic activity along the Aceh Segment of the Sumatran Fault has formed uplift and basin zones, resulting in distinct geological conditions between the two areas. These differences influence sedimentation and subsurface lithological characteristics, making them important to investigate for understanding the geological conditions, geotechnical potential, natural hazards, and other relevant aspects of the study area. This study aims to determine the variation of subsurface resistivity values, identify subsurface lithology, and compare the lithological characteristics between the uplift and basin zones. The study employed the two-dimensional (2D) electrical resistivity method using the Wenner–Schlumberger array, with eight survey lines, each 162 m long and an electrode spacing of 6 m. The survey consisted of three lines in the uplift zone and five lines in the basin zone. The resistivity data were processed using RES2DINV software with the smoothnest-constrained least-square inversion model. The results indicate resistivity values ranging from approximately 1 to 250 Ω·m, which were interpreted as silt (1 -10 Ω·m), clay (11 - 50 Ω·m), clayey sand (51 - 100 Ω·m), sand (101 - 200 Ω·m), and limestone (>200 Ω·m). The uplift zone is predominantly composed of limestone with minor occurrences of clay and silt, whereas the basin zone is characterized by a more uniform distribution of silt, clay, sand, and minor clayey sand and sandy gravel. The lithological comparison between the two zones reveals a transition in subsurface material distribution from limestone-dominated deposits in the uplift zone to alluvial sediment-dominated deposits in the basin zone. These findings demonstrate significant differences between the two zones in terms of resistivity variation, lithology, layer thickness, and the depth distribution of subsurface rock and sediment units. Keywords: Resistivity method, Aceh Segment, Uplift, Basin, Banda Aceh