20 years later: A look at the deadliest disaster to strike Earth in modern history

Twenty years have now passed since a massive earthquake and subsequent tsunami devastated communities in Southeast Asia, resulting in more than 220,000 confirmed deaths and millions displaced following the historic event. 

On the morning of Dec. 26, 2004, an estimated 9.2-magnitude earthquake violently shook the seafloor off Indonesia, sending a 100-foot wall of water towards communities around the Indian Ocean. 

Countries such as Indonesia, Sri Lanka, India and Thailand were the hardest hit, with entire villages collapsing and being washed away. 

Survivors faced isolation and disease as initial rescue and relief efforts were stretched thin due to the overwhelming scope of the disaster.

At the time, U.S. President George W. Bush remarked that the scale of the losses was beyond comprehension, as some governments were accused of delaying the emergency response.

In the years following the disaster, the international community raised more than $13 billion in donations, making it the largest humanitarian response to any natural disaster.

Researchers who have studied the region and visited the areas impacted by the Boxing Day Tsunami say signs of the disaster are still visible decades later. 

Experts have noted that the affected regions continue to lag behind economically compared to areas not impacted by the waves, and many survivors still live with post-traumatic stress.

FAULT THAT TRIGGERED 7.0 EARTHQUAKE OFF CALIFORNIA NOT KNOWN TO PRODUCE SIZABLE TSUNAMIS

What triggered the earthquake and could it happen again?

According to the U.S. Geological Survey, the historic earthquake was caused by the subduction of the Indo-Australian tectonic plate beneath the Eurasian plate. 

The region, known as the Sunda Trench, is highly seismic and has produced several earthquakes with magnitudes exceeding 7.0 since 2004.

Statistically, the occurrence of a magnitude 9.0 earthquake along the fault does not happen but once every several hundred years to over 1,000 years; however, seismologists caution that the interval between such events can be highly irregular.

The National Earthquake Information Center estimates that around 12,000–14,000 earthquakes occur each year around the world, but only a small minority are felt by humans on the surface.

Earthquakes with a magnitude of 8.0 or greater are considered to be "great quakes" and only occur once every two years along the thousands of fault lines around the world.

WHAT IS A TSUNAMI?

Is the region more prepared for a tsunami?

In the wake of the 2004 disaster, millions of dollars were spent on the upgrade and establishment of tsunami warning systems that were not widely available before the event.

Buoys have been deployed to detect sea level changes, sirens have been installed in some coastal areas for evacuations and education is now part of the preparedness curriculum.

One of the many systems that has been deployed is known as the Indian Ocean Tsunami Warning System (IOTWS), which became fully operational in 2011.

Despite the investments, the United Nations admits there are still large stretches of the world’s coastline that may not be prepared for a similar devastating event.

The organization’s Decade of Ocean Science for Sustainable Development is aiming to make 100% of at-risk communities tsunami ready by 2030.

"Disasters can strike at any time. Always stay alert by being aware of your surroundings, understanding potential hazards, recognizing natural warning signs, and knowing the evacuation routes to a safe place. You must stay strong," Syarifah Nargis, a survivor of the 2004 tsunami, recently shared with UNESCO.