## 2 Geological Setting  
Sumatra, one of the large islands in the Indonesian archipelago and the fifth largest in the world, covers an area of 473,606 km\({}^{2}\). It extends 1760 km from northwest (NW) to southeast (SW) and is 400 km wide. Sumatra includes the Mentawai Islands from Simeulue to the Pagai Islands, Enggano Island, and Tin Island, which comprises the Bangka, Belitung, and Riau Islands to the east. The Bukit Barisan Mountain range runs parallel along Sumatra's southwest coast, serving as the backbone of the main island [28]. Sumatra is situated at a plate boundary where the Indian and Australian plates are pushed underneath the Sundaland plate. This oblique subduction has caused the formation of a trench-parallel strike-slip fault near the southwestern coast of Sumatra Island, known as the Sumatran Fault [2]. The fault accommodates most of the lateral motion of the 7 mm/year oblique convergence between the Indo-Australia and Eurasian plates at the Sunda subduction system [5; 29]. The total length of the right-lateral strike-slip Sumatran Fault is 1900 km long, divided into 19 major segments based on second-order geometric irregularities. These segments include Sunda, Semangko, Kumering, Manna, Musi, Ketanu, Dikit, Sulak, Suliiti, Sumami, Sianok, Sumpur, Barumun, Angkola, Toru, Renun, Tripa, Aceh, and Seulimeum [7]. Furthermore, based on the geometry and detailed structure of the Sumatran Fault, the forearc basin, outer-arc ridge, and volcanic arc, Sumatra is divided into northern, central, and southern domains [7]. Based on paleontological evidence surveys regarding the age of stratigraphic units in Sumatra, it has been shown that the fossil rock units in the subsurface pre-tertiary layers of Sumatra range in age from early Carboniferous to mid-Cretaceous [28; 30]. The basement rocks of Sumatra are categorized into northern, central, and southern parts according to their stratigraphic ages: Pre-Carboniferous basement, Carboniferous-Early Permian, Mid-Late Permian, Mid-Late Triassic, and Jurassic-Mid-Cretaceous. In the northern domain, there are three segments of the Sumatran fault: the Aceh and Seulimeum faults in the north section and the Tripa Fault in the southern section [8]. These map quadrangles cover the fault of the Aceh Segment, Banda Aceh [13], and Takengon or Meulaboh [31], which is documented by the Geological Survey Agency of Indonesia and is published in several regional geology maps at 1:250,000 scale. They provide information about the geology of the Aceh Segment Fault, which is given in Figure 1. The Aceh Fault Zone is western Indonesia's northernmost segment of the Sumatran Fault System. It spans 250 km and passes through three districts: West Aceh, Pidie Jaya, and Aceh Besar. The fault segment is divided into seven sub-segments: Beutong, Kuala Tripa, Geumpang, Mane Jantho, Indrapuri, and Pulo Aceh. Each sub-segment varies in length from 15.7 to 50 km and shows right-lateral strike-slip fault kinematics [32]. The Aceh Segment Fault continues offshore of the Andaman Sea and has a dip angle of 12\({}^{\circ}\)-17\({}^{\circ}\)[33]. The northwestern section of the Aceh Segment Fault passes through the low relief region of Banda Aceh. It continues offshore and merges with the Andaman Nicobar Fault [29; 34]. The northern section of Aceh Segment Fault separates high- and low-relief areas, while its southern section crosses the mountainous zone [7]. The high-relief areas are dominated by basement rocks composed of Trias-Cretaceous age metamorphic rocks and igneous rocks with partially Mesozoic sedimentary and Miocene and Quaternary volcanic rocks [6; 32]. The low relief areas are filled with young alluvium deposits composed of silt (gravel sediment) [35]. In the low relief area, the Indrapuri Formation comprises older terrace deposits, partly volcanic gravels, sands, and marine/continental sedimentary, as shown in Figure 1. The stratigraphic of those rocks is shown in Figure 2.  
The fault of the Seulimeum Segment stretches from the Seulawah Agam volcano.