Assessing tsunami risk along the Aceh coast, Indonesia: a quantitative analysis of fault rupture potential and early warning system efficacy for predicting arrival time and flood extent

The Aceh coast (western Indonesia) is prone to regular tsunamis, as evidenced by historical records and paleo-tsunami studies. Effective community preparedness and response plans are essential in this context. Critical to these efforts is understanding the Estimated Times of Arrival (ETAs) of tsunamis, which dictate the vital window for post-earthquake actions and the likelihood of survival during an approaching tsunami. Our study aimed to assess the time available for communities in Aceh and nearby islands (Weh, Nasi, Breuh, Simeulue, Banyak) to respond and evacuate following an earthquake. We investigated ETA influenced by faults like Aceh-Andaman, Nias-Simeulue, and Batu segments, considering earthquake scenarios: 9.15 Mw (2004 tsunami reconstruction), 9.2 Mw, 8.9 Mw, and 8.6 Mw for Nias-Simeulue and Batu segments. Using the nonlinear shallow water equation (NSWE) model and numerical discretization with the finite difference method, we simulated tsunamis and projected arrival times. Our findings highlighted critical ETA ranges: 8–25 min on northern coasts, 19–37 min on western shores, 17–27 min on southwestern coasts, and 11–67 min on southern coasts. These results are essential for enhancing early warning systems and optimizing evacuation plans, and bolstering coastal community preparedness and resilience to tsunamis. Further studies are needed to conduct a comprehensive investigation of ETA, which includes potential rupture scenarios and a wider observation area, including expanding the modeling of tsunami generation mechanisms, which includes tsunamis generated by underwater landslides due to earthquakes or volcanic activity. Assessing ETA is pivotal for tsunami preparedness, contributing to more effective early warning systems and evacuation strategies. Integrating our ETA findings into policies will significantly enhance the preparedness and resilience of coastal communities in the face of ongoing tsunami risks. This study represents a valuable contribution to disaster risk reduction, offering actionable insights for safeguarding vulnerable coastal regions.