Just about everything that could go wrong, did go wrong in quake
PA LU, INDONE S I A » The sun was starting to dip, turning the sky a brilliant orange hue. Then the ground shook.
It felt more powerful than those in recent memory.
In Palu, they thought they knew all the risks. Indonesians live along one of the world’s most active fault lines — and Palu, in particular, sits atop a gradually slipping plate.
But a tsunami surge through the narrow bay and mud flows burying villages and residents were never among their fears until last week.
Indonesia has spent millions on disaster preparedness since a massive earthquake and tsunami in December 2004.
But this time, everything that was meant to work did not.
A warning system based on computer simulations failed to gauge the chances of a huge tsunami, estimating waves far smaller. Tsunami detection buoys were not functioning or in the wrong location.
Even the sensors that did work fooled scientists to think the worst was over — even while a third deadly tsunami surge was bearing down on Palu.
Now, the devastation on the western coast of Sulawesi island will now add a new chapter to the understandings of how shifts on the ocean floor can spawn deadly walls of water, and can turn firm soil into muddy rivers that entombed hundreds of people.
Scientists say the backtoback disasters — which have killed nearly 1,600 people — were among the most complicated they had seen. It began Sept. 28 just after 6 p.m. with a magnitude 7.5 slipstrike quake, where the earth moves side by side.
Usually, quakes that thrust up the seabed prompt a tsunami watch — such as the giant dome of seawater that crashed across Asia’s Indian Ocean region in 2004, killing almost 230,000 people, including tens of thousands in Indonesia.
The Sept. 28 slipstrike, located about 48 miles from Palu, was not something that experts usually predict would prompt a powerful tsunami.
“It was not a straightforward event,” said Adam Switzer, principal investigator at the Singaporebased Earth Observatory. “This earthquake was beyond the bounds of the warning systems” available.
The immediate analysis also was compromised by problems with Indonesia’s network of tsunamidetection buoys, which detect changes in the sea even deep below the surface.
Dozens of buoys in the Java Sea were broken, damaged or stolen. Others that functioned were not at the right spot and estimated the tsunami risk inaccurately — predicting the waves would be 2 feet high, 9 feet in a worstcase scenario. Instead, the tsunami sent water as high as 20 feet.