Numerical modelling of the potential for landslide-induced tsunamis, Mount Gamalama, Indonesia

Mount Gamalama is a stratovolcano forming Ternate Island in Indonesia. Collapse of the volcanoes flank has the potential to generate large tsunamis, potentially mega-tsunamis. This active volcanic island has a history of tsunami generation in 1608, 1840, and 1871. However, the generation mechanism of these tsunamis is unknown. Numerical simulation was used to understand the level of instability of the volcano flanks and the travel time and velocity of of the potential landslides and ensuing tsunamis on nearby coastlines. We also determined the factors that affect the size of the tsunami generated. An open-source finite-element code, Fluidity, was used to simulate the tsunami generation and propagation. A three-material model is considered: a viscous subaerial slide material, water, and air to capture the complex physics and interaction of the landslide and water. The results show that the subaerial mass failure takes around 2 to 6 minutes to enter the sea and can generate an initial wave of heights ranging from 35 m to 110 m. A volcanic flank collapse on Mount Gamalama would therefore have serious implications for the coastal population in neighbouring islands and submarine infrastructures like underwater cables.