Survivors and victims' relatives will this week mark the 20th anniversary of the 2004 Indian Ocean earthquake and tsunami, which killed more than 220,000 people across more than a dozen countries ...

One of modern history's worst natural disasters, the tsunami left about 230,000 dead across a dozen countries.

Remembering the 2004 tsunami: A look back at the tragedy, global response, and ongoing efforts for resilience and preparedness.

One of modern history's worst natural disasters, the tsunami left about 230,000 dead across a dozen countries.

At the time of the earthquake, there was no warning system in place in the Indian Ocean. But now, 1,400 stations globally cut warning times to just minutes after a tsunami wave forms.

2004 Indian Ocean Tsunami: What To Know 20 Years On A 9.1-magnitude earthquake triggered huge waves that swept into coastal areas of Indonesia, Sri Lanka, India, Thailand and nine other nations.

Survivors and victims' relatives will this week mark the 20th anniversary of the 2004 Indian Ocean earthquake and tsunami, which killed more than 220,000 people across more than a dozen countries.