The Indonesian island devastated by a magnitude 7.5 earthquake and tsunami in 2018 was Sulawesi. The disaster struck on 28 September 2018 in Central Sulawesi, with the epicenter in mountainous Donggala Regency. The shallow earthquake ruptured the Palu-Koro Fault and heavily affected Palu, Donggala, and Sigi.
The earthquake was followed by a tsunami that swept into Palu Bay, where waves reached several metres in some locations. Severe soil liquefaction also caused neighborhoods such as Petobo and Balaroa to collapse or move dramatically. The combined earthquake, tsunami, and landslides killed about 4,340 people and displaced hundreds of thousands.
The event is sometimes called the Palu earthquake or the Sulawesi earthquake and tsunami. Its unusually destructive tsunami was linked to several contributing factors, including underwater landslides, the shape of Palu Bay, and the earthquake’s shallow depth. Lombok had suffered another deadly Indonesian earthquake earlier in 2018, while Sumatra and Java are also earthquake-prone islands, but Sulawesi is the canonical answer.