The 2018 Sulawesi earthquake had a magnitude of 7.5. It struck Central Sulawesi, Indonesia, on 28 September 2018, with its epicentre in Donggala Regency, roughly 70 kilometres from the city of Palu.
The earthquake occurred on the Palu-Koro Fault, a major strike-slip fault where blocks of crust move sideways past one another. Despite that motion, the disaster generated a tsunami, probably through a combination of seafloor movement, underwater landslides and coastal ground deformation.
Some reports give the earthquake as magnitude 7.6 because Indonesian authorities and international agencies used different measurement and reporting conventions. A value of 7.5 is the widely cited USGS estimate and is the canonical answer expected for this quiz question.