Tuesday, December 25, 2018

As Death Toll From Krakatoa Tsunami Climbs, Warnings From 6 Years Ago Came True

From UPI (also on blogroll at right):

Dec. 25, 2018 at 11:46 AM
Death toll from Indonesia tsunami soars to 429, expected to climb
The death toll from a tsunami that hit Indonesia rose to 429 Tuesday, but the toll could be even higher once rescue workers get into areas that are currently inaccessible due to road and bridge damage.
The tsunami hit beaches full of people on Saturday, sweeping them out to sea without warning. More than 1,500 have been injured and officials hiked the official toll Tuesday. The tsunami damaged more than 600 houses and displaced 12,000 people.

"There are six villages that we haven't been able to enter yet because the roads, bridges are badly damaged,'' Sutopo Purwo Nugroho, spokesman for the Southeast Asian country's disaster mitigation agency, told reporters. "The road was actually in bad condition even before the tsunami.''

Volcanic activity at Mount Anak Krakatau could trigger additional mudslides and more deadly tsunamis, officials said. The volcano is part of the Ring of Fire, a volcanic hot zone that stretches 25,000 miles from New Zealand to Japan. It's believed that the eruption forced rock beneath the water to shift, displacing the water above it....MORE

And from Volcano Discovery:
Tuesday Dec 25, 2018 11:58 AM | BY: T
Krakatoa volcano (Sunda Strait, Indonesia): scientists had explained and warned about the tsunami risk 6 years earlier - prediction came true

Exaggerated cross section and bathymetry of the Krakatau caldera, showing the flank collapse modeled in 2012 (image: Giachetti et al, 2012)

Sometimes, science has already answers for tragic events, but their voice is not heard or underestimated at the time. The Indonesia tsunami disaster two days ago is such an example: What happened on 22 Dec 2018 had actually already been described and warned about for years in amazing detail:

In January 2012, scientist around volcanologist Dr Thomas Giachetti from the University of Oregon published results of numerical modelling simulating a flank collapse and associated tsunami at Anak Krakatau island and warned about the devastating effects it would have on nearby coasts:
In their paper adequately called "Tsunami hazard related to a flank collapse of Anak Krakatau Volcano, Sunda Strait, Indonesia", they "numerically simulate a sudden southwestwards destabilization of a large part of the Anak Krakatau Volcano, and the subsequent tsunami formation and propagation."

Anak Krakatau island - the intra-caldera complex called "Child of Krakatau" - has been growing rapidly growing since it first breached the surface of the sea in 1928. Since then, in less than 100 years, it built an overlapping cone during several eruptions, the latest being the one that started May 2018 and still continues. What makes the island particularly prone to gravitational flank failure is that it has been constructed close and above a steep submarine slope, the NE margin of the caldera basin left by the massive 1883 eruption.

As a consequence of this underwater topography, combined with strong sea currents, the western slope of Anak Krakatau has developed to be much steeper than the eastern. Giachetti et al. observed that as the volcano continues to grow towards the SW (which it had done particularly well visible during the recent eruption, s. attached image comparing 2007 and 2018), "landslides along its southwestern flank cannot be excluded. Such a landslide would be directed southwestwards into the 1883 caldera and would trigger waves that would propagate into the Sunda Strait, possibly affecting the Indonesian coasts".

The modeled waive heights in various location correspond amazingly well with what had been observed. At Anyer, for example, waves of up to 1.5 meters would arrive in 38 minutes. Inside the caldera, neighboring islands such as Rakata or Sertung would be hit by waves 15-30 meters in height in less than a minute after the event....MUCH MORE