Sunda Strait tsunami calls into question warning mechanisms

Written by Putt Punyagupta

On December 22, a tumultuous series of waves pummelled coastal settlements on the Indonesian islands of Sumatra and Java, killing nearly 300 and injury upwards of 1,000.

It was spurred by the eruption of the volcano Anak Krakatau — “child of Krakatoa” in Bahasa Indonesia — a subsidiary volcano formed from a caldera following the cataclysmic eruption of 1883. The volcano hadbecome increasingly active over the past few months.

Sutopo Purwo Nugroho, the spokesman of the National Disaster Management Agency of Indonesia,, warned of a possible additional tsunami due to the continued eruptions of Anak Krakatau, urging people in coastal settlements not to carry out activities on the beach and to stay away from the coast until further notice is given.

The unconventional nature of this tsunami contributed to its surprise factor. It struck at 21:30 local time, and prior to the arrival waves, very few warning signs could be discerned. The sea water did not drastically recede as it would with an earthquake tsunami. Moreover, the activity of Anak Krakatau has often been described by locals as continuous but low-scale; thus, few designated the volcano as a potential cause for a tsunami.

The disaster called into question the efficacy of Indonesia’s tsunami warning systems. It was revealed by Nugroho that Indonesia’s early warning system is set to monitor earthquakes rather than undersea landslides and volcanic eruptions, both of which can cause deadly waves of the same magnitude. However, the institution of such a system was recognized as necessary due to thirteen percent of the world’s volcanoes being situated in Indonesia. A lack of funds and degradation of mechanisms involved also meant that any warning system had been defunct since 2012.

The tsunami that struck of the coast of Sulawesi earlier this year in September, as well as the calamitous boxing day tsunami of December 2004 that killed over 228,000 in 13 different countries were both spurred by earthquakes. Waves precipitated by volcanic debris as was the case in this recent tsunami are not as frequent.

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