Sub Surface Active Fault Identification on Quaternary and Tertiary Rocks using Geoelectric Method in Cilaki Drainage Basin, Southern Part of West Java, Indonesia

Abstract

The geophysical surveys are needed to obtain information on subsurface geology for infrastructure development, mitigation of landslide and geothermal. Cilaki drainage basin is an area Garut Regency at southern part of West Java. The area has complex geological and the main target in development plan of Southern part of West Java. The electrical resistivity method of the Schlumberger configuration was used to identify the geological subsurface and the active fault of the study area. The measurement of the electrical resistivity was made on 7 lanes (GL 1 until GL 7). The location has a height of 195 to 925 meters above sea level with depth reaching more than 120 meters and electrical resistivity value of 6-450 Ω meters. Generally, the electrical resistivity value of Quaternary rock units have value between 80 and 450 Ω meters and Tertiary rock unit have value of 6-40 Ω meters. Based on the results of data analysis can be interpreted that the area has been deformed. This is reflected also in the geomorphology as an indication of tectonic phenomenon in the form of active faults. Quantitatively, this is reflected in the value of the mountain-front sinuosity (Smf) index which ranges 1.036 to 2.173. This phenomenon occurs in geomorphology which is composed of Tertiary and Quaternary rocks.

Development of Active Fault Mapping Method Using Geoelectric and Geographical Information System

“…The brightness value of the same surface material caused by topographic conditions, shadows, and sunlight intensity is seen using this band combination method to more clearly observe the distribution of land cover [11]. Field validation exercises are then conducted on the ground using near-surface geoelectric tools using a Naniura model NRD 22S resistivity-meter and then plotting the field measurement results on the study area's geological map allows for additional interpretation regarding the active fault to get a better geomorphological analysis [12]. Institute for Aerospace Survey and Earth Sciences) system, which comprises analytical, synthetic, and pragmatic surveys, provides the foundation for the interpretation [13].…”

Gravity Modeling to Understand the Subsurface Geology of the Central Part of West Bandung Regency (Citatah Karst Area, Cipatat-Padalarang)

“…The geophysical method is used to identify the exact location of active subterranean faults. Ground penetrating radar [23], geoelectric method [24], gravity method [25], and HVSR inversion method [26], are several geophysical methods commonly used to detect subsurface structures.…”

Clay Mineral Variations in an Active Fault Zone and Their Impact on Landslides

“…Another definition of active faults is that they have moved within the most recent 10,000 years [21]. By using the regional tectonic study of southern West Java, Cisewu is included in the areas which are affected by tectonic activity with main compressive stress direction oriented South to North [1,24]. Also, the lithology is dominated by Quaternary volcanic deposits.…”

“…Therefore, the vary of the active fault classes can be determined by smf and Vf formulas as a morphotectonic approach [1,25]. The presence of active faults as part of active tectonics is also indicated by the results of geophysical surveys [24] and the presence of the epicenter of earthquakes on land [26] The 33 sites of mountain-front sinuosity (Smf) index measurement of Cisewu area have calculated to determine the tectonic activity class. Commonly, Smf values of Cisewu area and surrounding classify into Class 1 as active tectonism with value close to 1.…”