Unearthing the buried Palu–Koro Fault and the pattern of damage caused by the 2018 Sulawesi Earthquake using HVSR inversion

Abstract

A systematic pattern of destruction was observed caused by the Mw 7.5 Central Sulawesi Earthquake. In brief, the quake ruptured 180 km of Palu–Koro Fault and led to massive destruction of residential buildings in Palu city, Donggala and Sigi Regencies. In Palu city, the damage was concentrated only in Balaroa and Petobo neighbourhoods where at least 930 and 1255 houses, respectively, collapsed. Microtremor time series recorded prior to the earthquake were used to analyse the subsurface structure of Balaroa and surroundings. Surprisingly, inversion of horizontal-to-vertical spectral ratio curves was able to locate the subsurface fault crossing the Balaroa and its dipping direction. Furthermore, the velocity profile deduced from this inversion points out the importance of local geology in the massive destruction in Balaroa. The existence of a subsurface pond led to an extremely water-saturated sandy soil underneath Balaroa. A combination of high level of water saturation and high peak ground acceleration (0.5–0.7 g) was strongly suspected to be the cause of the mega-liquefaction. The high degree of ground motion (>1.54 g) of spectral acceleration 0.2 s resulted in severe damage in elevated areas in Donggala, while in the Palu Basin, ground motion as high as 1.30g of spectral acceleration 0.5 s led to the destruction of four-storey or higher buildings.

Understanding of subsurface conditions controlling flow liquefaction occurrence during the 2018 Palu earthquake based on resistivity profiles

“…5 also indicates the thickening of alluvial deposits to the east due to the existence of a basinal structure associated with the normal faulting component of the Palu-Koro Fault. [18] also found this basin geometry from the analysis of microtremor measurement data in this area.…”

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

“…b. Medium-severe damage was found in houses without bones and sloofs, buildings that did not use binding frames and joints between the timbers that were not fastened or walls with unreinforced concrete (only stacked and plastered bricks) so that the buildings were fragile and easily collapsed when there was a shock. Earthquake (Cipta et al, 2021).…”

“…The Maluku earthquake in September 2019 with a magnitude of 6.5 resulted in 41 deaths and caused a lot of damage to buildings (Kusumawardani et al, 2021). According to Sianipar, et al, (2019) the Thursday, September 26, 2019 earthquake (main earthquake) was followed by thousands of aftershocks, and various series of earthquake events after the September 26, 2019 incident in Ambon City, Central Maluku, and West Seram were caused by deformation rocks with a fault movement mechanism due to a complicated tectonic setting and directly related to the activity of the Banda Api volcano, and the topography of the Maluku Province (Mori et al, 2022;Cipta et al, 2021).…”

Seismic Hazard Zonation in Gedebage Future Development in Bandung City Using HVSR Inversion

“…The other regions next to the Bandung basin, the seismic velocity structure and seismic hazard analysis of the Jakarta basin, are already investigated using the HVSR method [22], [23]. The same method is also already applied in Palu to image subsurface structure, including to reveal unearthing the buried fault by the same author [11]. HVSR and SPAC also are already applied to reveal the subsurface characteristic of Palu city [12].…”

“…Sources and potentially affected areas should be considered for risk assessment to evaluate seismic hazards [11]. The nearsurface effect (the site effect) relies on local geology conditions, which affected ground motion.…”