Deskripsi Kepakaran
I have worked as researcher at the Research Centre of Geotechnology, Indonesian Institute of Sciences (LIPI) since 2006. My research focuses on earthquake geology and paleoseismology. The title of my PhD dissertation was “Paleoseismology of tropical Indonesia (Cases study in Sumatran fault, Palukoro – Matano fault and Lembang fault”. Indonesia is located at the junction of three plates, the Indo-Australian plate subducting at a rate of 7 cm/yr beneath the Eurasian plate and the Pacific plate subducting at a rate of 12 cm/yr beneath the Eurasian plate. The interactions between the three plates produce active faults, sources of large onshore earthquakes. One of the most fundamental practices to mitigate earthquake disasters is studying the geological characteristics of the earthquake sources. Paleoseismology is an appropriate geological method to characterize past movements of active faults. This method is relatively new, rapidly growing, and has been applied to active faults mainly in dry and subtropical regions. I applied this method to three active faults on three major islands in Indonesia which is under typical tropical climate (three black rectangle on figure below). Through these studies, I was able to collect paleoseismic data that are fundamental to seismic hazard mitigation in seismically active islands of Indonesia. The first study location is the Sianok-Sumani-Suliti segment, part of the Sumatran fault. The Sumatran fault is an arc-parallel right-lateral strike-slip fault related to the oblique subduction of the Indo-Australian plate beneath the Eurasian plate along the Sunda trench. The Mw 6 doublets earthquake in 2007 produced 22.5-km-long surface ruptures. We conducted post-earthquake fieldwork to map the location and amount of offset of the surface ruptures. The 2007 doublets earthquake ruptured only part of the entire length of the Sianok-Sumani-Suliti segment. The ruptured part of the Sianok segment is 22.5 km long compared to the total length of 90 km while the surface rupture along the 60-km-long Suliti segment was 22.5 km in length. All historical earthquakes similar doublet earthquakes with similar magnitudes. The first earthquake always occurred in the south and triggered subsequent event in the north with time lags of several hours. The average recurrence interval of such earthquake doublets is around 80 years. The second study site is the Palukoro-Matano fault in Sulawesi Island. We studied 20 faults in central Sulawesi area, five segments of the Palukoro fault, and seven segments of the Matano faults. The study shows that the movement of the Matano transform fault. In Saluki segment (part of the Palukoro fault), there are systematic left-lateral river offsets which indicate a slip rate less than 58 mm/yr. The 2012 earthquake (M6.2) is similar to the 1907 earthquake. Paleoseismic trenching showed evidence for three earthquake events that are correlated to the 1909, 1468 and 1338 earthquakes. Since 2014, we have communication about repeating of 1909 earthquake to National Hazard meeting, government and National media. In September 2018, Mw7.4 big earthquake really hit Palu City. The third site is the Lembang fault in West Java. Our study shows that the fault has a left-lateral component of movement. This 29-km-long fault is divided into six sections. The river offsets and fault activity analyses show that the fault has a slip rate of 3-5.5 mm/yr. Paleoseismic trenching shows the evidence of an earthquake event that occurred in the 15th century (1450-1460) and 60 BC. These paleoseismic studies have successfully filled the information gap of fault parameters for the three important active faults. Our results from the three locations demonstrated that paleoseismology can be successfully done in the tropics (especially in Indonesia). Mapping the surface ruptures after an earthquake event is the fastest and most precise method to delineate the active fault lines.