Twenty years to the day later, the number remains hard to comprehend. A tsunami that emerged off the coast of Indonesia killed 230,000 people, not only in Indonesia but in several other countries. In a New York Times essay, USC engineering professor Costas Synolakis explores the warning and communication failures that contributed to the death toll. India, for example, "failed to warn people on its eastern coast even after the tsunami wreaked havoc in the Andaman Islands, hours before striking the mainland." Since then, the world has made decent strides. Only six tsunamographs—devices on the seafloor that emit warnings—existed before the 2004 tsunami. "Now there are about 60 in the Pacific and the Caribbean and about 10 in the Indian Ocean."
But there's still a long way to go, warns Synolakis. "More tsunamographs and seafloor seismometers are essential"—as is machine learning for smarter warnings. Earlier this month, for example, millions of people received warnings of a potential tsunami off the coast of Northern California, prompting some to evacuate. But that "tsunami was only about two inches high by the time it reached the coast," he notes. "A lot of the confusion would have been avoided if there had been more specific information for different locales, and this is entirely possible to provide." Read the full essay for more details on what steps Synolakis advocates. (More tsunami stories.)