Wednesday, December 15, 2021
On December 26, 2004, a magnitude 9.1 earthquake sent waves across the Indian Ocean that killed about 228,000 people in fifteen countries, with no warning.
On this day in 2004, a magnitude 9.1 megathrust earthquake ruptured the sea floor off the west coast of northern Sumatra. The fault broke for about eight minutes along more than 800 miles, lifting the ocean above it. Waves reached the Indonesian province of Aceh within twenty minutes and ran up to 167 feet in places, pushing three miles inland. Seven hours later the same waves reached the coast of Somalia.
About 228,000 people died across fifteen countries, and 1.7 million were displaced. The Indian Ocean had no tsunami warning system at the time, and no network existed to tell Sri Lanka or Thailand what had happened in Indonesia. Most of the dead never knew a wave was coming. The exceptions came from local knowledge, including communities on Simeulue Island who ran for high ground on sight of the receding water because a story from 1907 had been kept alive.
The world built the Indian Ocean warning system afterward, along with deep ocean sensors that now detect a wave in open water. Sirens still take minutes that a nearby quake does not give you. The natural warning is the one that always works, and it is simple enough for a child to learn. Strong shaking on the coast, a sudden roar, or water pulling out fast all mean go uphill immediately without waiting for an official message. That reflex is worth practicing anywhere a tsunami is possible, and it starts with knowing what to do during an earthquake.
