CIGONDONG: As Indonesia reels from the carnage of yet another natural disaster, authorities around the globe are working on how they can prepare for the kind of freak tsunami that battered coasts west of Jakarta this month. The Dec 23 tsunami in the Sunda Strait killed around 430 people, capping a year of earthquakes and tsunamis in the vast archipelago, which straddles the seismically active Pacific Ring of Fire.
Seismologists and authorities say a perfect storm of factors caused the tsunami and made early detection near impossible given the equipment in place. But the disaster should be a wake-up call to step up research on tsunami triggers and preparedness, said several of the experts, some of whom have travelled to the country to investigate what happened.
“Indonesia has demonstrated to the rest of the world the huge variety of sources that have the potential to cause tsunamis. More research is needed to understand those less-expected events,” said Stephen Hicks, a seismologist at the University of Southampton. Most tsunamis on record have been triggered by earthquakes. But this time it was an eruption of Anak Krakatau volcano that caused its crater to partially collapse into the sea at high tide, sending waves up to 16 feet high smashing into densely populated coastal areas on Java and Sumatra islands.
But the eruption didn’t rattle seismic monitors significantly, and the absence of seismic signals normally associated with tsunamis led Indonesia’s geophysics agency (BMKG) initially to tweet there was no tsunami. Muhammad Sadli, head of geophysics at BMKG, later said its tidal monitors were not set up to trigger tsunami warnings from non-seismic events.
The head of Japan’s International Research Institute of Disaster, Fumihiko Imamura, said he did not believe Japan’s current warning system would have detected a tsunami like the one in the Sunda Strait. “We still have some risks of this in Japan ... because there’s 111 active volcanoes and low capacity to monitor eruptions generating a tsunami.”
Scientists have long flagged the collapse of Anak Krakatau, around 155 km west of the capital, as a concern. A 2012 study published by the Geological Society of London deemed it a “tsunami hazard”.
Anak Krakatau has emerged from the Krakatoa volcano, which in 1883 erupted in one of the biggest explosions in recorded history, killing more than 36,000 people in a series of tsunamis and lowering the global surface temperature by one degree Celsius with its ash.
Some experts believe there was enough time for at least a partial detection of last week’s tsunami in the 24 minutes it took waves to hit land after the landslide on Anak Krakatau. But a country-wide tsunami warning system of buoys connected to seabed sensors has been out of order since 2012 due to vandalism, neglect and a lack of public funds, authorities say.
“The lack of an early warning system is why Saturday’s tsunami was not detected,” said disaster agency spokesman Sutopo Nugroho, adding that of 1,000 tsunami sirens needed across Indonesia, only 56 are in place. “Signs that a tsunami was coming weren’t detected and so people did not have time to evacuate.”
But other experts say even if this network had been working, averting disaster would have been difficult. “The tsunami was very much a worst-case scenario for any hope of a clear tsunami warning: a lack of an obvious earthquake to trigger a warning, shallow water, rough seabed, and the close proximity to nearby coastlines,” said seismologist Hicks.
In the Philippines, Renato Solidum, undersecretary for disaster risk reduction, said eruptions from the country’s Taal volcano had caused tsunami waves before in the surrounding Taal Lake. He said that what happened in Indonesia showed the need to “re-emphasise awareness and preparedness” regarding volcanic activity and its potential to trigger tsunamis in the Philippines.
Published in Dawn, December 31st, 2018