The BMKG issued a tsunami warning based on seismographic data . An alert was broadcast from radios and mosque loudspeakers on the mainland , prompting thousands to flee to higher ground . It was later cancelled , but officials said that a tsunami warning system installed following the 2004 Indian Ocean earthquake and tsunami had failed to function properly . According to Indonesian officials , two of the system 's buoys out at sea had been vandalized and were inoperative . The claim of a breakdown was disputed by German officials who were working with the Indonesians to maintain and develop the system . Jörn Lauterjung , the head of the German-Indonesia Tsunami Early Warning Project , said that it had " worked very well " , only one sensor had not been working and its failure had not harmed the system 's operation . However , the epicentre of the earthquake was so close to the islands that a warning would probably have been too late in any case , as the tsunami only took about five to ten minutes to reach Pagai
2004 Indian Ocean earthquake and tsunami
2004 Indian Ocean earthquake and tsunami
2010 Mentawai earthquake and tsunami