Landslides are the most common geological phenomenon in Indonesia.The event is damage to public infrastructure, and fatalities was a big impact. Therefore, mapping the geometry of landslides is a part of the mitigation effort possible by geophysical methods. In this research, we applied seismic refraction tomography (SRT) to study the geometry of the sliding zone from the landslide event.TheNational Disaster Management Authority reported that the area was frequently occurring landslide disaster, i.e. 2018, 2019 and 2020 which caused the public infrastructure and obstructed the road access from the central to the west of Aceh. The SRT was measured in two profileslong the road.Data measurements were conducted on the side of the Babahrot - GayoLues road section that had experienced landslides.Measurements were made using the Seismograph PASI 16S24-P and 24 geophones to obtain a 92-meterlong profile with 2 meter spacing between the geophones. P-wave velocity data modeling is done using ZondST2D software.The results of modeling profiles 1 and 2 describe three different subsurface layers.The SRT profile 1 model consists of slate (0.2 - 0.7 km/s), clay (0.8 - 1.3 km/s), and sandy clay (1.4 - 1.9 km/s).While, the model of profile 2 consists of slate (0.5 - 1.0 km/s), clay (1.1 - 1.6 km/ s), and sandy clay (1.7 - 2.5 km/s).The contrasting wave velocity model shows that the SRT method can be used in landslide studies as a reference in determining the mechanism of the landslide system.

Investigation of geophysical methods describes elements and geological geometry based on the physical properties of the subsurface. In the past decade, the application of resistivity methods has experienced a rapid increase in describing geological structures and settings. The Electrical Resistivity Tomography technique used to describe the geometry of a complex landslide in Blangkejeren, Aceh province, Indonesia. This area is highly influenced by the landscape with slopes, high-rainfall, and tectonic activity of the Sumatran fault which can lead to soil movement. The type of landslides in this area is largely controlled by geo-structural characteristics; rotational and translational slides, as well as the phenomenon of the gravitational slope of high steepness. As a preliminary study, the acquisition of resistivity data was conducted at two locations with a length of each measuring path 330 meters and electrodes spacing 6 meters. The Supersting R8/IP instrument unit with Wenner-Schlumberger array is used to obtain data that has a sensitivity to vertical and lateral changes. The resistivity distribution along the path is obtained from both profiles that are perpendicular to the landslide field. ERT modeling results at both locations showed subsurface structures based on resistivity values such as; slate, clay, and sandy clay. The contrast resistivity between each layer makes it easier to describe the characteristics of the landslide slip plane geometry which is affected by the slope angle. The resistivity method has physical properties that are very sensitive to porosity and groundwater which is the main parameter in a landslide. Finally, it should be noted that the use of the ERT technique as an effective and efficient method in conducting landslide studies as a disaster mitigation effort.

Analisa pola sesar telah dilakukan untuk wilayah sumatera bagian selatan melalui analisis data kegempaan. Data kegempaan yang digunakan adalah data ISC dan dikombinasikan dengan data fokal dari Global CMT dari tahun 1960-2000. Penelitian ini dilakukan dalam tiga tahap, yaitu penentuan persebaran kegempaan, penentuan moment tensor melalui data fokal, dan korelasi data dengan data geologi. Pada posisi geografis 1040-1060 BT terdapat 7 gempa signifikan sepanjang tahun 1960 sampai tahun 2000, diantaranya 3 sesar mendatar (strike slip fault), 1 sesar naik (reverse fault), 1 sesar turun (normal fault) dan 2 sesar oblique. Anomali data terjadi pada seismisitas kegempaan tahun 1960-2000, yaitu teramatinya sesar oblique. Aktifitas kegempaan dipengaruhi oleh aktifitas sesar Sumatera dari Andaman sampai Semangko. Kata kunci: pola sesar, gempa tektonik, fokal, oblique