M7.7 Flores Earthquake Triggers Massive Landslides Along Trans-Flores Route
A magnitude 7.7 earthquake that struck Flores on 15 August 2026 triggered massive landslides along the strategic Ende, Nagekeo, Bajawa, and Maumere route. The landslides resulted from a combination of local geological vulnerability and the large amount of seismic energy released. Daryono, a member of the Indonesian Association of Disaster Experts (IABI), said Flores’ geological conditions make several areas prone to landslides when shaken by strong earthquakes.
According to Daryono, Flores Island is dominated by young volcanic rocks and pyroclastic deposits such as tuff and agglomerate that have undergone advanced weathering. “The weathered soil and rock material has a fragile structure and low shear strength, making it highly unstable when subjected to sudden dynamic shaking,” he said.
This vulnerability is exacerbated by Flores’ morphology, which is dominated by mountains and steep slopes with extreme gradients. In addition, slope cutting for the construction of the Trans-Flores national road has reduced support at the base of cliffs and increased gravitational driving forces.
When the M7.7 earthquake occurred, the strong ground acceleration and long shaking duration damaged the cohesive bonds between soil particles. This condition triggered slope failures at various points. Daryono also explained that seismic waves can be amplified due to local site effects on soft soil layers and topographic amplification phenomena.
“Earthquake waves reflect and concentrate in hilltop and cliff areas, making shaking at the top of slopes much stronger than in valley areas,” he said. The cyclic shaking can then eliminate the bearing capacity of soil and rock material, triggering large-scale collapses that buried main road access under thousands of tonnes of soil and rock.
These conditions show that the impact of earthquakes on landslides is influenced not only by earthquake strength but also by geological characteristics, slope gradient, soil conditions, and morphological changes due to infrastructure development.