Scenario‑based tsunami hazard assessment in the Tolo Thrust, Southeast Sulawesi (Indonesia)

Abstract

The Tolo Thrust, located in eastern Indonesia, is a potentially tsunamigenic structure capable of generating destructive tsunamis that threaten coastal communities surrounding Tolo Bay. This study presents a scenario‑based tsunami hazard assessment using the Cornell Multi‑grid Coupled Tsunami Model (COMCOT) to evaluate the effects of earthquake magnitude and rupture configuration on tsunami generation and propagation. Sixteen earthquake scenarios were considered, including a Mw 8.0 worst‑case scenario and fifteen alternative Mw 7.5‑7.8 scenarios representing variations in rupture geometry and slip distribution. The Mw 8.0 scenario produced the largest tsunami amplitudes and the broadest distribution of coastal impacts, with maximum wave heights reaching 2.76 m at Menui Island, 2.20 m at North Konawe, 2.12 m at Wawonii Island, and 2.05 m at Kendari City. Tsunami travel‑time contours calculated at 5‑min propagation period indicate that near‑field locations such as Menui and Wawonii Islands may experience tsunami arrival within approximately 1‑3 min after earthquake occurrence, whereas more distant coastlines, including South Buru and Sula Islands, may receive the first waves after 30‑55 min. Although the Mw 7.5‑7.8 scenarios generally generated lower tsunami amplitudes, several rupture configurations produced localized wave amplification comparable to larger events, highlighting the importance of rupture directivity, fault geometry, and regional bathymetry in controlling tsunami hazards. The results indicate that tsunami impacts are concentrated along the eastern coast of Southeast Sulawesi and around Menui and Wawonii Islands, while the semi‑enclosed geometry of Tolo Bay plays a major role in focusing tsunami energy. These findings provide a scientific basis for tsunami early‑warning systems, evacuation planning, and coastal risk mitigation strategies for Southeast Sulawesi and adjacent island communities.