Åknes is an unstable mountainside on the western side of the Sunnylvsfjorden in Stranda Municipality, Møre og Romsdal. It is closely monitored by NVE due to the risk of a rockslide-generated tsunami that could affect larger areas, including settlements around the Geirangerfjord. A robust monitoring system is important for providing warnings and initiating necessary measures. 

NORSAR has contributed to this monitoring since 2005. The system, which continuously transmits data, includes a microseismic network of geophones installed in 2005 around the top scarp of Åknes. In 2009, a broadband seismometer was installed in a more stable part of the slope. Finally, in 2017, a string of eight geophones was installed in a borehole down to a depth of 50 meters. The seismic monitoring system complements the direct measuring systems operated by NVE. 

The purpose of the seismic monitoring is twofold: 

1. Contribute to an early warning system. A significant increase in microseismic activity can indicate movement in the slope. 
2. Improve understanding of the dynamics of the mountainside. This involves identifying different types of signals and their origins. 

You can follow the seismic measurements here: Åknes Rock Slide - NORSAR.

The illustration below illustrates the diversity of seismic signals that we record at Åkenes (From: Langet & Silverberg 2023).