Source Characteristics of the 28 September 2018 Mw 7.5 Palu-Sulawesi, Indonesia (SE Asia) Earthquake Based on Inversion of Teleseismic Bodywaves

Yolsal‐Çevikbilen, Seda; Taymaz, Tuncay

doi:10.1007/s00024-019-02294-1

Cited by 18 publications

(7 citation statements)

References 46 publications

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“…In addition, whereas many published models simulate some, or even most, recorded runups around the Bay, the mechanisms are often ad hoc and do not reproduce the timing of tsunami waves from eyewitness accounts or the video evidence. Most coseismic tsunami sources (e.g., USGS, 2018;Socquet et al, 2019;Jamelot et al, 2019;Yolsal-Çevikbilen and Taymaz, 2019), are based on a primarily horizontal strike-slip earthquake mechanism, with limited vertical seabed motion (1-2 m). Theoretically, this should not be strongly tsunamigenic and should not, therefore, generate the elevated tsunami runups recorded from the south of the bay.…”

Section: Introductionmentioning

confidence: 99%

New High-Resolution Modeling of the 2018 Palu Tsunami, Based on Supershear Earthquake Mechanisms and Mapped Coastal Landslides, Supports a Dual Source

2021

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The Mw 7.5 earthquake that struck Central Sulawesi, Indonesia, on September 28, 2018, was rapidly followed by coastal landslides and destructive tsunami waves within Palu Bay. Here, we present new tsunami modeling that supports a dual source mechanism from the supershear strike-slip earthquake and coastal landslides. Up until now the tsunami mechanism: earthquake, coastal landslides, or a combination of both, has remained controversial, because published research has been inconclusive; with some studies explaining most observations from the earthquake and others the landslides. Major challenges are the numerous different earthquake source models used in tsunami modeling, and that landslide mechanisms have been hypothetical. Here, we simulate tsunami generation using three published earthquake models, alone and in combination with seven coastal landslides identified in earlier work and confirmed by field and bathymetric evidence which, from video evidence, produced significant waves. To generate and propagate the tsunamis, we use a combination of two wave models, the 3D non-hydrostatic model NHWAVE and the 2D Boussinesq model FUNWAVE-TVD. Both models are nonlinear and address the physics of wave frequency dispersion critical in modeling tsunamis from landslides, which here, in NHWAVE are modeled as granular material. Our combined, earthquake and coastal landslide, simulations recreate all observed tsunami runups, except those in the southeast of Palu Bay where they were most elevated (10.5 m), as well as observations made in video recordings and at the Pantoloan Port tide gauge located within Palu Bay. With regard to the timing of tsunami impact on the coast, results from the dual landslide/earthquake sources, particularly those using the supershear earthquake models are in good agreement with reconstructed time series at most locations. Our new work shows that an additional tsunami mechanism is also necessary to explain the elevated tsunami observations in the southeast of Palu Bay. Using partial information from bathymetric surveys in this area we show that an additional, submarine landslide here, when simulated with the other coastal slides, and the supershear earthquake mechanism better explains the observations. This supports the need for future marine geology work in this area.

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Section: Introductionmentioning

confidence: 99%

New High-Resolution Modeling of the 2018 Palu Tsunami, Based on Supershear Earthquake Mechanisms and Mapped Coastal Landslides, Supports a Dual Source

2021

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“…On September 28 2018, a 7.5 Mw left-lateral strike-slip earthquake occurred 75 km north of Palu City (Hui et al 2018;Socquet et al 2019;Zhang, Chen, and Feng 2019). Following the main shock, the earthquake resulted in liquefaction and building collapse (Bradley et al 2019;Sassa and Takagawa 2018;Syifa, Kadavi, andLee 2019, Maidiawati et al, 2020;Paulik et al 2019;Yolsal-Cevikbilen et al, 2019), as well as a destructive tsunami that impacted the coastal areas of the Palu Bay (Omira et al 2019;Mikami et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Consideration of submarine landslide induced by 2018 Sulawesi earthquake and tsunami within Palu Bay

Nagai

Muhari²,

Pakoksung

et al. 2021

Coastal Engineering Journal

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On September 28 2018, an Mw 7.5 strike-slip earthquake occurred to the north of Palu Bay on the Sulawesi Island, Indonesia. This triggered a destructive tsunami within the bay, which reached Palu city. Simulation have been conducted to investigate the landslide source. However, the tsunami should be investigated considering a physical model in the area where detailed bathymetric survey had not been conducted. In this study, we investigated the impact of coastal landslides on the southern part of the bay using a two-layer model. Owing to the increasing collapse volume, the southern west coastal landslide could approximately explain the observations in Palu city. However, the calculated mass volume of the source largely overestimated the bathymetric survey data. Hence, we considered the possibility of submarine landslide in the southern part of the bay and the simulation results could approximately explain the maximum tsunami heights in the southern part of the bay. These results suggest that more detailed multibeam data will be required to investigate the possible submarine landslide in the southern area which could induce a destructive tsunami reaching Palu city within a few minutes after the collapse.

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“…More complex coseismic deformation models have been developed in an effort to reproduce the specific details of the tsunami (e.g., Ulrich et al, ; Yolsal‐Çevikbilen & Taymaz, ) and to combine landslide and coseismic sources (e.g., Gusman et al, ). However, the tide gauge at Pantoloan port and the post‐tsunami surveys measuring the runup heights (e.g., Fritz et al, ; Omira et al, ) which are used to characterize the tsunami do not uniquely constrain the source.…”

Section: Introductionmentioning

confidence: 99%

Modeling the Sources of the 2018 Palu, Indonesia, Tsunami Using Videos From Social Media

et al. 2020

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The 2018 Palu tsunami contributed significantly to the devastation caused by the associated MW 7.5 earthquake. This began a debate about how the moderate size earthquake triggered such a large tsunami within Palu Bay, with runups of more than 10 m. The possibility of a large component of vertical coseismic deformation and submarine landslides have been considered as potential explanations. However, scarce instrumental data have made it difficult to resolve the potential contributions from either type of source. We use tsunami waveforms derived from social media videos in Palu Bay to model the possible sources of the tsunami. We invert InSAR data with different fault geometries and use the resulting seafloor displacements to simulate tsunamis. The coseismic sources alone cannot match both the video‐derived time histories and surveyed runups. Then we conduct a tsunami source inversion using the video‐derived time histories and a tide gauge record as inputs. We specify hypothetical landslide locations and solve for initial tsunami elevation. Our results, validated with surveyed runups, show that a limited number of landslides in southern Palu Bay are sufficient to explain the tsunami data. The Palu tsunami highlights the difficulty in accurately capturing with tide gauges the amplitude and timing of short period waves that can have large impacts at the coast. The proximity of landslides to locations of high fault slip also suggests that tsunami hazard assessment in strike‐slip environments should include triggered landslides, especially for locations where the coastline morphology is strongly linked to fault geometry.

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Source Characteristics of the 28 September 2018 Mw 7.5 Palu-Sulawesi, Indonesia (SE Asia) Earthquake Based on Inversion of Teleseismic Bodywaves

Cited by 18 publications

References 46 publications

New High-Resolution Modeling of the 2018 Palu Tsunami, Based on Supershear Earthquake Mechanisms and Mapped Coastal Landslides, Supports a Dual Source

New High-Resolution Modeling of the 2018 Palu Tsunami, Based on Supershear Earthquake Mechanisms and Mapped Coastal Landslides, Supports a Dual Source

Consideration of submarine landslide induced by 2018 Sulawesi earthquake and tsunami within Palu Bay

Modeling the Sources of the 2018 Palu, Indonesia, Tsunami Using Videos From Social Media

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