Client

Municipality of Stalden

Geological Office

Rovina + Partner AG

Services Provided

• Seismic campaign with 47 passive seismic point measurements.
• Passive seismic mapping (Vibrometry) for lateral delineation and internal compartmentalization of the active landslide.

Project Description

In April 2025, a debris flow from the Roorbach-Riedji area deposited large amounts of sediment at the bottom of the valley. As part of a hazard assessment, the question arose as to the extent of the active landslide Roorbach-Riedji. Further, it was necessary to determine whether other previously unknown active landslides exist in the area. In this context, Spektrum Geophysik AG was commissioned to conduct a passive seismic mapping.

To this end, the seismic ground motion at numerous measurement locations was recorded overnight using portable geophones. The subsequent analysis of the seismic amplification reveals several potentially unstable areas that can be clearly delineated from the presumably stable areas. Modal analysis was used to calculate the resonance frequency of the sliding bodies and the associated vibration behavior, which further allows for the determination of internal sliding compartments. The results of the seismic mapping, which were available within a very short time, facilitate a data-based planning of further investigations (e.g., drilling) and measures as well as the creation of hazard scenarios.