When an earthquake threatens to turn part of an ocean into fast-moving walls of water, tsunami warning scientists can do nothing for the first five minutes except wait for information. But within the next five minutes, they have to decide whether to issue a warning of danger.
A strong earthquake has rattled the Indonesian capital of Jakarta, just days after a major quake triggered a deadly tsunami in the region.
A major earthquake off the coast of Java and a tsunami that followed has killed at least 155 people, according to Red Cross officials.