Tournier, Nicolas (2024). Lake-based paleoseismology in central Sulawesi, Indonesia. (Thesis). Universität Bern, Bern

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Abstract

Earthquakes are the main cause of considerable human losses and damage on Earth. The most active seismic areas are now widely studied. However, the hazard potential and recurrence rate of major earthquake events remains poorly understood for some seismic faults. This is the case of the island of Sulawesi, in eastern Indonesia. Although the magnitude 7.5 Palu earthquake in 2018 focused seismological research on the section that ruptured, the Palu-Koro fault runs for hundreds of kilometers across the island of Sulawesi. The entire fault is considered to be a potential source of earthquakes, yet it is understudied. Seismic risk evaluation is crucial to prepare populations for major earthquakes, and thus limit fatalities and damage. Analysing the seismic hazard is an essential part of this evaluation. It consists of identifying past earthquakes and their recurrences and then estimating the probability of return of these types of events, based on the principle that if an earthquake of a given magnitude has occurred in a region in the past, a similar event could occur in the same region in the future. Instrumental and historical records of earthquakes on the island of Sulawesi only cover the last 100 years. This time range prevents the identification of major earthquakes with magnitudes greater than 6, as their return periods exceed the seismological records. While it is difficult to study seismic evidence in a tropical setting, due to the enhanced erosion and the dense vegetation, paleoseismology is here essential in evaluating the island's seismic hazard. Lake Towuti and Lake Poso are two ancient tectonic lakes located in central Sulawesi. The sediments act as natural seismographs and cover several hundreds thousands years. Core samples and sediment boreholes taken at Lake Towuti, in complement of seismic reflection data, have enabled to understand how the lake reacted to climatic and tectonic fluctuations. On the other hand, bathymetric and seismic data from Lake Poso have made it possible to identify and correlate slope collapse deposits triggered by seismic events, and also to observe fault structures directly beneath the sediment surface, revealing tectonic activity.

Item Type:	Thesis
Dissertation Type:	Cumulative
Date of Defense:	19 September 2024
Subjects:	500 Science > 550 Earth sciences & geology
Institute / Center:	08 Faculty of Science > Institute of Geological Sciences
Depositing User:	Sarah Stalder
Date Deposited:	25 Sep 2025 13:24
Last Modified:	29 Sep 2025 22:25
URI:	https://boristheses.unibe.ch/id/eprint/6737

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