Soil Liquefaction Poses Threat to Quake-torn Lombok Island

TEMPO.CO, Jakarta - The series of earthquakes that recently struck Lombok, West Nusa Tenggara, has triggered trigger soil liquefaction that can reduce the soil density and strength on the resort island.

According to Sri Hidayati, the head of earthquake and tsunami mitigation at the Volcanology and Geological Disaster Mitigation Center (PVMBG), liquefaction has happened in several areas in the Lombok Island. 

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“There are many [liquefaction] spots in the Gangga and Kayangan districts,” she said.

The signs of the natural phenomenon are evident and have been corroborated by local residents during the magnitude 7.0 earthquake on Sunday, August 5. Sri explained locals had reported bursts of water from underneath the cracked earth with some resembling fountains. 

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“It manifests into muddy water mixed with fine sands once it bursts to the earth’s surface. Some cases show that water in wells would disappear and was switched with just sand,” said Sri.

Soil liquefaction causes the overly saturated soil to rapidly lose its strength due to a strong quake. This phenomenon is generally evident in earthquakes over magnitude 6.5. 

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Sri Hidayati advised residents to avoid rebuilding their homes or any building structure over an area affected by soil liquefaction. However, constructing a building structure can still be established over affected soil but must be built with a quake-proof design that has a deeper foundation that goes far under the liquefied soil.

The Lombok Island’s east and north regions were struck by a magnitude 7 earthquake on Sunday, August 5. The area was also shaken by a magnitude 6.4 quake on July 29 that originated from the Flores back arc thrust.

ANWAR SISWADI (CONTRIBUTOR)