"In April 2012, Indonesia's Banda Aceh, the city worst hit by the tsunami that killed at least 226,000 people on Boxing Day ten years ago, received a terrifying reminder of how unprepared it was for the next disaster. As an 8.6-magnitude quake struck at sea, thousands of residents shunned purpose-built shelters and fled by car and motorcycle, clogging streets with traffic. A network of powerful warning sirens stayed silent.
No wave came. But if it had, the damage would have been "worse than 2004, if it was the same magnitude of tsunami", said Harkunti Rahayu, from Indonesia's Bandung Institute of Technology.
As the 10th anniversary of the disaster approaches, experts and officials say weaknesses remain across the region in a system designed to warn people and get them to safety."