Evaluating earthquake impacts in Oslo, Norway: a multi-method approach

This study conducts a comprehensive seismic risk assessment for Oslo (capital of Norway), integrating both deterministic and probabilistic approaches to capture a holistic view of potential earthquake impacts. The deterministic analysis was based on field data on exposed major faults in the Oslo rift margin and historical earthquakes in this region. Three earthquake scenarios were investigated:

1. An Mw 5.4 earthquake that occurred in 1904 in the Oslo rift zone
2. A hypothetical Mw 6.0 event on the east side of the rift zone
3. A hypothetical Mw 6.0 event along an exposed fault zone in the central rift zone

In the results, among the three scenarios, the second scenario resulted in the highest losses, and the first showed negligible impact. In both the second scenario and the 475-year return period probabilistic scenarios, the Sentrum and Frogner neighbourhoods continually emerged as the most affected areas. The study determined that this is due to a combination of local soil conditions and the prevalence of unreinforced masonry buildings. Ultimately, the combination of deterministic and probabilistic approaches in this study offers a detailed and nuanced understanding of seismic risks in Oslo.