On 28 May 2025, an ice–rock avalanche with a volume of ca. 9 million cubic meters buried parts of the Swiss village of Blatten. The event claimed the life of a local herder and caused widespread destruction and infrastructure damage in the valley. Given the dense broadband network of the Swiss Seismological Service, the seismic record of the Blatten event was of exceptional quality with several dozen stations located within a 100–200 km radius.

At frequencies below 0.1 Hz (or periods longer than 10 seconds), seismic wave propagation can be accurately modeled, allowing for the inversion of landslide seismic records for the forces exerted on the Earth’s surface. In this presentation we will focus on the centroid single force inversion of the lower frequencies of the Blatten seismic record. We will discuss how the resulting force history constrains the trajectory and motion of the avalanche’s centroid and how it can be used to tune granular flow models to provide insights into flow dynamics and frictional losses. The latter point is particularly critical, since the presence of significant ice volumes in granular masses reduces friction, leading to uncertain runout predictions.