Sanding Wells on The Island of Lombok due to Earthquake Vibrations

Abstract

The Lombok earthquake in 2018 was unique, the shocks occurred sequentially. Several major earthquakes were followed by thousands of aftershocks. The earthquake caused a devastating disaster which destroyed many homes, buildings including wells as the main fresh water supply in the Lombok Island. The focal mechanism of main earthquake shows a thrust fault mechanism. Lombok Island is originally a volcano Island which is still growing actively. Therefore surface of Island is dominated by volcanic materials, such as: volcanic rock, volcanic ash, pumice. This paper describes the phenomenon of sanding wells in Lombok, including the physical mechanisms among rock’s grains when vibrating earthquake waves. These earthquake waves can eliminate static friction between grains and reduce cohesion between grains of rock. Some subsurface images shows a strong correlation between damage grade and the existence of loose sand and hard rock.

Near-surface resistivity imaging using resistivity Tomography in some most impacted areas due to the 2018 Earthquake in North Lombok Island

“…This sanding or liquefaction process occurs because sediment from the bottom of the well rises to the top when an earthquake occurs(B. E. B. Nurhandoko et al 2021). Figure 4 shows the condition of several residents' wells that were damaged where the bottom of the well became shallowing and even total loss of water column.…”