ALBERT

Description: Indonesia is one of the most earthquake-prone countries in the world. Its highly complex tectonics setting is the result of collision between the Australian and Sunda blocks, and the interaction of the Pacific and Philippine Sea plates. Prior to 2017, the National Center for Earthquake Studies of Indonesia database recognised 295 active faults throughout Indonesia. The additional seismic stations operated by the Agency for Meteorology, Climatology, and Geophysics over the past 5 years has greatly improved the detection of small earthquakes from previously unidentified faults. In this study, we investigate recent destructive earthquake sequences in Indonesia along with their associated foreshock and aftershocks. We find, using a variety of techniques including relative relocation of hypocenters, focal mechanism determination, and Coulomb stress modelling, that the main shocks occurred on previously unknown faults, including the Majene Fault in West Sulawesi, the Kalaotoa Fault in the Flores Sea, a small graben system in Semangko Bay (Southern Sumatra), the Kajai Fault in Pasaman (West Sumatra), and a conjugate fault in Cianjur (West Java). Mapping these active faults is very important for updating seismic hazard maps and understanding their implications. The Turkey earthquake on February 6, 2023, serves as a reminder that shallow crustal earthquakes caused by active terrestrial faults located near large population centers pose a major natural hazard.