Earthquake hazard describes how often earthquakes trigger certain levels of ground shaking at a specific location. Earthquake hazard assessment considers the history of earthquakes in earthquake catalogues (databases), ground shaking models as well as geological and tectonic conditions. Robust earthquake hazard assessments are therefore a prerequisite of defining earthquake risk. Europe’s first earthquake risk model includes the data of the 2020 European Seismic Hazard Model, which is the updated version of the European earthquake hazard model.

The type of subsoil at a specific location or beneath a building has, in addition to the distance from the epicentre and the depth and magnitude of an earthquake, a significant influence on the expected ground shaking. The softer the ground, the more likely it is that ground shaking will be amplified, and damage will occur.

The impact of the local soil conditions on the ground shaking is included in the earthquake risk calculations through a so-called regional site response model. This regional model uses slope (topography) and surficial geology as proxies for local site conditions, given that it would be far too complex and time-consuming to map in detail the properties of the soil across the whole of Europe.

Earthquake risk can only occur where there are buildings and people (referred to as ‘exposure’). An area with a high level of earthquake hazard but with no exposure will not have any earthquake risk. In general, high-density, greatly developed areas like cities and urban areas have a higher concentration of exposure than rural regions and are thus subject to higher levels of earthquake risk.

The exposure model used for the European earthquake risk model describes the spatial distribution and characteristics of around 145 million buildings and their occupants in 44 European countries. The model does not capture the details of every individual building, but instead provides an estimate of the buildings of different types (referred to as building classes) within the many administrative regions in each country.  

The characteristics of the buildings we spend our time in for leisure or work are important in defining earthquake risk. The better a house resists an earthquake, because, for example, it has been designed and reinforced accordingly, the less damage will occur if an earthquake occurs. Well-constructed buildings made from reinforced concrete and wood are generally able to withstand stronger earthquakes and are less vulnerable than brick buildings.