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Improved Understanding of The 2018 Mw7.5 Palu Earthquake Using Local Earthquake Tomography and Numerical Ground Motion Simulation

Identification

Clé publique

doi:10.25911/8pep-j161

Auteurs

Sakti, Artadi Pria

Année déclarée

2026

Langue déclarée

und

Type source

Thesis (PhD)

Première détection

2026-11-09T19:08:45.211378+00:00

Dernière observation des métadonnées

2026-11-09T19:08:45.211378+00:00

Dernière vérification HTTP

Non effectuée

Résumé documentaire — langue originale

The Palu Koro Fault (PKF) in Central Sulawesi is a highly active fault posing significant seismic risk. It runs through Palu, a city of 500,000 population, forming a sediment-filled graben. On September 28, 2018, a Mw7.5 earthquake at 12 km depth caused widespread destruction, including fatalities, building collapse, liquefaction, and a tsunami. This thesis investigates the regional velocity structure of Central Sulawesi, its correlation with geological features and its relationship to the rupture of 2018 Palu earthquake. The study incorporates local earthquake tomography (LET) and long-period ground motion simulations using three-dimensional (3-D) and basin models to analyze basin effects during the earthquake. For LET we have utilized P-wave arrival times recorded by both permanent and temporary seismograph networks covering the period from October 2018 to December 2021, following the 2018 Palu earthquake. Additionally, we incorporated data from a regional seismograph network operational in 2015. In total, the dataset comprises 434 local earthquakes and 3,121 P-wave phases collected from 30 seismic stations, which were used in the tomographic inversion. Hypocenter locations were simultaneously refined during the P-wave velocity inversion process. My improved aftershock locations in the 3-D model show that aftershocks in the northern part of the 2018 earthquake’s rupture area concentrate on a secondary fault, where rupture is widely thought to have initiated. For the first time, this research depicts some detailed geological features and velocity structure around PKF: 1) A very pronounce lateral velocity variation at depth 10 km along Sulawesi’s Neck area which coincides with the Palu 2018 earthquake rupture zone, 2) high velocities along the PKF in the upper crust associated with plutonic formations resulting from magmatic activity as recent as the mid-Pliocene, and 3) Low velocity areas in the south of Palu Valley coincident with identified strong geothermal signatures in the uppermost crust. The results show that these structures correlate with the fault rupture of the 2018 earthquake and suggest that the Pliocene plutonism may have affected the rupture pattern of the 2018 earthquake. According to several geophysical studies, the Palu Basin consists of thick sedimentary layers, which can contribute to basin effects during the 2018 Palu event. By combining the basin structure from previous studies with the regional structural data from this study, a simulation of the 2018 Palu earthquake was successfully conducted, capturing the basin effects. The results reveal significant amplification, ranging from 2 to 4 times, with PGV at 0.5 Hz reaching 200 cm/s and a shaking duration extended by 30 seconds within the Palu Basin, Bay, and Valley. Simulated MMI values, derived from 3-second PSA, indicate very high intensities (MMI VIII–X) in these regions. Amplification was most pronounced at the center of the basin, where spectral periods shifted from approximately 2.5 to 3–4 seconds, correlating with the collapse and severe damage of mid-rise buildings. The mismatch between the natural periods of these buildings (0.4–0.8 s) and the simulated long-period ground motions, highlights both model limitations and structural vulnerabilities, particularly in soft-story designs, which may have extended the natural period closer to 3 seconds, contributing to the damage. Although the simulation could not capture short-period motions, it underscores the significant influence of basin effects and construction quality. The prolonged shaking and extensive ground motion in the basin suggest substantial basin effects, which likely contributed to the observed structural damage, oceanic landslides triggering the tsunami, and widespread liquefaction in several areas.

Identifiants

DOI

10.25911/8pep-j161

HANDLE

1885/733806540

OAI

oai:openresearch-repository.anu.edu.au:1885/733806540

Repères documentaires

Famille documentaire

Thèse

Types déclarés par les sources

Thesis (PhD)

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Sources

Repository · Document 1 · Document 2

• DOI · https://doi.org/10.25911/8pep-j161
• Document · https://hdl.handle.net/1885/733806540

Statut documentaire

Pertinence à examiner

Bibliothèque

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