The massive Dec. 26, 2004,
tsunami was triggered by a magnitude 9.1
earthquake off Sumatra island.
![Indonesia, Thailand mark 15th anniversary of massive tsunami](https://media.zenfs.com/en/ap.org/e1d1fc7b5b58312d873aa4efcfc68898)
Indonesia's Aceh province, which was closest to the earthquake, was hit first and hardest.
More than 170,000 people died in
Indonesia alone, about three-quarters of the overall death toll.