On Saturday, National Disaster Mitigation Agency (BNBP) spokesperson Sutopo Purwo Nugroho shared a time-lapse of satellite imagery on his Instagram account, showing how liquefaction devastated neighborhoods on Sept. 28 in Palu, Central Sulawesi .
"Process of soil liquefaction in Petobo Housing Complex, Palu, using WordView satellite imaging at 0.5 meter [per] pixel resolution. Houses and buildings were swept away and sunk [into] mud that appeared due to the earthquake," he posted in Indonesian on @sutopopurwo.
"The search and rescue team is working to recover bodies in this area. Victims continue to be found ," he added.
A tsunami and soil liquefaction followed the 7.4-magnitude earthquake that shook Palu.
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Proses likuifaksi tanah di Komplek Perumahan Petobo, Kota Palu hasil rekaman citra Satelit WorldView resolusi pixel 0.5 meter. Rumah dan bangunan terseret oleh lumpur yang muncul akibat gempa dan menenggelamkannya. Tim SAR terus bekerja melakukan evakuasi di daerah ini. Korban terus ditemukan.
A post shared by Sutopo Purwo Nugroho (@sutopopurwo) on
Soil liquefaction, a geological process by which the soil structure collapses, is relatively unknown among the Indonesian public, including survivors and witnesses of the disaster.
The Jakarta Post correspondent Ruslan Sangadji reported that on the morning after the quake, survivors referred to the phenomenon as "land tsunami".
Witnesses said the "mud" rolled like ocean waves.
Houses in Petobo shifted as much as 700 meters from their original locations.
Yahdi Basma, a Central Sulawesi councilor, whose two-story house moved 700 meters and was partially submerged in the liquefied soil, said the "mud" also dragged coconut trees a few hundred meters. However, he said, the trees were still alive.