Liquidation or liquefaction of land events for many earth experts and researchers is common. However, what happened in Sigi and Palu District shortly after an earthquake measuring 7.4 on the Richter scale shook East of the Donggala Sea on Friday (28/9), considered creepy.
"That is the most sinister example of liquefaction I have ever seen. Many strange noises are heard," said Geologist from the University of Saint Louis in the US, John Encarnacion responding to videos of liquefaction events that occurred in Sigi Regency and Palu City to Antara via message briefly received in Jakarta, Wednesday (3/10).
In the beginning, he had even thought the event in one of the videos that had been viral on social media was a tsunami. He suspects that the entire area in the video is actually above the silt and sand deposits from the coast or river that are not consolidated and saturated in water. When the material is shaken by an earthquake, the soil melts.
The age of the sand and mud deposits, according to his estimation, the freezing process can reach thousands to tens of thousands of years. "(Age) is very young and not enough time to turn into stone. (Liquidation) This is actually the same situation happening in many coastal areas," he said.
When asked about the link between liquefaction and the tsunami, he said they were two different phenomena. Tsunamis begin because sea levels are disturbed, either by fault movements or underwater landslides. Meanwhile, liquefaction occurs because water-rich sediments are shaken violently by the earthquake.
Previously it was reported that a number of locations in the City of Palu and Sigi experienced a phenomenon of liquefaction after the earthquake 7.4 on the Richter Scale (SR). Not only the house that was 'swallowed' when the land was disbursed, it happened but also some of the residents who lived on it.
Petobo village is one of the most affected locations of the earthquake, in addition to the Balaroa National Housing area. Thousands of victims are estimated to still be buried in the ground with buildings in the two locations.
"We have not identified it at the Balaroa National Park and Petobo Village because the location is very severe," said Palu City Regional Disaster Management Agency Head Fresly Tampubolon in Palu, Monday (1/10).
The two regions, namely Balaroa and Petobo, are the most devastating centers of damage because houses and public facilities at that point are buried in the ground like they were swallowed up by the earth. According to a number of witnesses, a few seconds after the 7.4 SR earthquake shook Palu, the village area was seen with a fairly high burst of water, then suddenly the land surface dropped so that it dragged all the objects above it.
In fact, some buildings like mosques shifted about 50 meters away from their original position. "My wife and children cannot be saved. I expect them to be trapped in the house and then rolled up in the ground," said Husnan, one of the victims' families.