Field Insights and Analysis of the 2018 Mw 7.5 Palu, Indonesia Earthquake, Tsunami and Landslides

Abstract

A devastating Mw 7.5 earthquake and tsunami struck northwestern Sulawesi, Indonesia on 28 September 2018, causing over 4000 fatalities and severe damage to several areas in and around Palu City. Severe earthquake-induced soil liquefaction and landslides claimed hundreds of lives in three villages within Palu. The mainshock occurred at 18:03 local time at a depth of 10 km on a left-lateral strike-slip fault. The hypocenter was located 70 km north of Palu City and the rupture propagated south, under Palu Bay, passing on land on the west side of Palu City. The surface rupture of the earthquake has been mapped onshore along a 30 km stretch of the Palu-Koro fault. We present results of field surveys on the effects of the earthquake, tsunami and liquefaction conducted between 1–3 and 12–19 of October 2018. Seismic intensities on the Modified Mercalli Intensity (MMI) scale are reported for 375 sites and reach a maximum value of 10. We consolidate published tsunami runup heights from several field studies and discuss three possible interrelated tsunami sources to explain the variation in observed tsunami runup heights. Due to limited instrumentation, PGA and PGV values were recorded at only one of our field sites. To compensate, we use our seismic intensities and Ground Motion to Intensity Conversion Equations (GMICEs) and Ground Motion Prediction Equations (GMPEs) developed for similar tectonic regions. Our results indicate that the maximum predicted PGAs for Palu range from 1.1 g for GMICEs to 0.6 g for GMPEs.

Susceptibility Assessment of Earthquake-Induced Landslides: The 2018 Palu, Sulawesi Mw 7.5 Earthquake, Indonesia

“…However, a small number of landslides (≈ 2%) occurred in flat to moderate sloping areas (< 8°). In this case, a massive flow slide was developed during the earthquake-induced liquefaction in an alluvial fan deposit on a denudational slope near Palu Bay (Cilia, et al, 2021;Jalil, et al, 2021;Tohari, A. et al, 2022). Aside from that, the slope along the riverbanks in the plain geomorphic conditions is also prone to seismically triggered landslides (Hu et al, 2021;Wubalem, 2021).…”

Study of Damage to Residential Buildings, Soil Geophysics and The Relationship Between the Epicentrum Distance and the Level of Damage Caused by Earthquake

“…The research was carried out in the villages of Liang, Tulehu and Waai village, Salahutu District, Central Maluku Regency, which are villages with a high number of damaged dwellings (Cilia et al, 2021). Collecting data on damage to residential buildings using the stratified purposive sampling method, namely observing and measuring damage to residential buildings at all levels of damage (light, moderate and severe) at the location of the earthquake disaster that has been determined through the Decree of the Central Maluku Regent.…”

“…Earthquake-prone areas in Maluku include the southeastern regions, Ambon Island , Spooky and Hurry (Naik et al, 2019). Meanwhile, the center of the fault is in the Ambon Sea and West Seram (Cilia et al, 2021;Mezősi, 2022).…”

Introduction to “Sixty Years of Modern Tsunami Science, Volume 1: Lessons and Progress”

“…The next paper, by Cilia et al (2021), addresses the devastating earthquake (M w = 7.5) and tsunami of 28 September 2018 in the Gulf of Palu, Northwestern Sulawesi, Indonesia, which caused over 4,000 casualties and considerable damage around Palu City. The authors gather the results of many field studies (including their own), compiling detailed measurements of seismic intensities, tsunami runup and liquefaction.…”