The Horror of Watching the Ground Liquify and Swallow Homes In an Earthquake

Santi was getting ready for Friday evening prayers in Palu, a coastal city of more than 330,000, when the ground, solid earth only moments ago, suddenly turned to liquid and swallowed her concrete home. The city was shaking with a magnitude 7.4 earthquake and, all around her, the ground was turning into something like quicksand. Her neighbors homes started to sink into the earth. Her own house split in half, the bedrooms torn off the structure and moved some 300 meters away.

“It was a complete mess," Santi told me. "I was lucky that I could save myself."

At the same time, a short distance from Santi's home, Fadilah was in a panic. Before the earthquake hit, she was in her home with her two children and their families as the call to prayer, or adzan, rang out across the city. Then, suddenly, it stopped.

The next thing Fadilah remembers hearing was screaming. The ground was violently shaking. Fadilah and her family tried to run, but she didn't get far.

“I tried running but within three seconds the ground started collapsing,” Fadilah said.

She stopped running and started to pray. The ground liquified and began to heave wildly up and down, she said. She stayed there, terrified as the once solid ground gave way.

"It went up to my chest,” Fadilah told me. "I could only pray."

Then, as fast as it began, it stopped. Her children and grandchildren were fine, but her 7-year-old grandson fell into the moving liquified soil.

“It’s a miracle that he’s alive," she told me. "He fell in, but he managed to escape."

What happened here was a little-known geological phenomenon called "earthquake liquefaction," that can sometimes occur during an earthquake on "saturated soil," or soil that's heavy with water. Basically, as the ground shakes, the pressure can force the water between the soil particles, which reduces friction and makes the ground act less like soil and more like water.

And the results can be terrifying to watch.

There was little Fadilah could do but watch her home get swept away. In Balaroa, on the western edge of Palu district, at least 744 homes were destroyed by earthquake liquefaction, according to Indonesia's disaster mitigation agency (BNPB). That makes it one of the worst-hit parts of Palu.

The earthquake and subsequent tsunami killed nearly 1,350, according to the most-recent death tolls. That number will likely continue to rise as search and rescue crews search more collapsed buildings. Santi and Fadilah, who I met at a relief camp in Balaroa, survived alongside their families. All of them were lucky. Santi told me she saw buildings all around her collapsing as she fled her home with her husband and son. But while, physically, all of them are fine, psychologically, the quake has left a deep wound on the family.

“My son is still traumatized," Santi said. "He asked me, ‘Can I sleep with my eyes open? I’m afraid there will be another earthquake.’"