Abstract
The 7.4 Mw earthquake on 28th September 2018 in Palu City triggered a flow liquefaction phenomenon in the Balaroa and Petobo areas, contributing to significant casualties and building damage. This paper presents the results of a liquefaction study to map subsurface conditions in these areas using the multi-electrode resistivity method with the dipole-dipole configuration. The objective of this study is to understand factors controlling the flow liquefaction phenomenon. Based on the interpretation of 2-D resistivity images, the liquefied soil layers are characterized by lower resistivity values than the non-liquified layers. These contrasts of resistivity values form a gently sloping boundary between the liquefied and non-liquefied soil layers. The resistivity image perpendicular to the flow direction indicates the presence of a subsurface basinal morphology in the Balaroa area, suggesting that a shallow groundwater zone is present within the liquefiable soil layer. Thus, the subsurface topographical condition is the main governing factor of flow liquefaction phenomena during the 2018 Palu earthquake.
Highlights
The earthquake (7.4 Mw) that occurred in Palu City, Sigi, and Donggala Regencies on 28 September 2018 caused a tsunami and a flow liquefaction phenomenon in several areas in Palu City and Sigi Regency
This paper presents the results of a liquefaction study to evaluate subsurface conditions controlling flow liquefaction phenomenon in Balaroa and Petobo areas using the multi-electrode resistivity method
The resistivity profiles show that the soil layers near the surface have low resistivity values of less than 50 m, which is likely to be associated with alluvial deposits
Summary
The earthquake (7.4 Mw) that occurred in Palu City, Sigi, and Donggala Regencies on 28 September 2018 caused a tsunami and a flow liquefaction phenomenon in several areas in Palu City and Sigi Regency. The phenomenon of flow liquefaction in Palu City and Sigi Regency only occurred in some areas (see Fig. 1). This difference in liquefaction vulnerability is likely influenced by geological, hydrological, and subsurface soil structure conditions that vary from one region to another. It is essential to have good knowledge and understanding of the factors of geological conditions and subsurface structures that control flow liquefaction in Palu City and Sigi. Such knowledge is required to establish an effective strategical plan to mitigate this earthquake-collateral hazard in this region
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