A powerful 7.5 magnitude earthquake struck northern Indonesia on Friday, northeast of the town of Donggala on the island of Sulawesi. The strongest quake was followed by a damaging tsunami in Palu, the provincial capital with a population of about 335,000.

The details: The earthquake has been followed by numerous strong aftershocks that are also capable of causing significant damage. Early reports from the region suggest widespread damage to homes, along with tsunami-related damage in Palu. Videos posted to Twitter showed onlookers watching as giant waves crashed ashore.

• According to Reuters, the tsunami reached six meters, or about 18 feet, in height. At least 384 have been reported dead, with hundreds more injured or missing.
• "The situation is chaotic, people are running on the streets and buildings collapsed," Dwikorita Karnawati, who heads Indonesia's meteorology and geophysics agency, told Reuters. "There is a ship washed ashore."
• Tsunamis are caused by the sudden displacement of the sea floor during a powerful quake, which can displace large amounts of water and send it sloshing toward shore, building in height as it approaches shallower depths.

The backdrop: Indonesia sits along the so-called "ring of fire" in the Pacific, making it vulnerable to earthquakes and other geological hazards.

Editor’s note: This article has been updated to include more information on the tsunami height and death toll.