Indonesia earthquake: Soil liquefaction blamed for building collapses

By Nicola Davis

Dramatic footage has emerged from the city of Palu on the Indonesian island of Sulawesi, with buildings collapsing as the ground slides beneath them.

The phenomenon, known as soil liquefaction, is thought to have occurred as a result of the recent 7.5 magnitude earthquake, which also triggered a devastating tsunami. The death toll has already passed 1,200 and is expected to rise further.

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“When soil is saturated, the space between individual particles is completely filled with water,” said Dr Stavroula Kontoe of Imperial College London. “Seismic shaking increases the water pressure between the soil particles; the particles can lose contact with each other which in turn leads to an overall loss of soil strength and stiffness.”

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But Kontoe says disasters are not inevitable. “There are several mitigation techniques which can limit or even eliminate [soil liquefaction’s] consequences. These techniques usually involve strengthening the soil deposits in areas where liquefaction has been identified as a major hazard and/or adopting drainage measures to prevent the increase of the water pressure during the strong shaking.”

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