New earthquake assessments available to strengthen preparedness in Europe

During the 20th century, earthquakes in Europe accounted for more than 200,000 deaths and over 250 billion Euros in losses. Comprehensive earthquake hazard and risk assessments are crucial to reducing the effects of catastrophic earthquakes. The newly released update of the earthquake hazard model and the first earthquake risk model for Europe are the basis for establishing mitigation measures and making communities more resilient. They significantly improve the understanding of where strong shaking is most likely to occur and what effects future earthquakes in Europe will have. The development of these models was a joint effort of seismologists, geologists, and engineers across Europe with the contribution of members from the GFZ German Research Centre for Geosciences (GFZ). The research has been funded by the European Union’s Horizon 2020 research and innovation programme.

Background earthquake hazard and risk

Earthquakes cannot be prevented nor precisely predicted, but efficient mitigation measures informed by earthquake hazard and risk models can significantly reduce their impacts. The 2020 European Seismic Hazard and Risk Models offer comparable information on the spatial distribution of expected levels of ground shaking due to earthquakes, their frequency of occurrence as well as their potential impact on the built environment and on people’s wellbeing. To this aim, all underlying datasets have been updated and harmonised – a complex undertaking given the vast amount of data and highly diverse tectonic settings in Europe. Such an approach is crucial to establish effective transnational disaster mitigation strategies that support the definition of insurance policies or up-to-date building codes at a European level (e.g., Eurocode 8) and at national levels. In Europe, Eurocode 8 defines the standards recommended for earthquake-resistant construction and retrofitting buildings and structures to limit the impact due to earthquakes. Open access is provided to both, the European Seismic Hazard and Risk Models, including various initial components such as input datasets.

The updated earthquake hazard model benefits from advanced datasets

Earthquake hazard describes potential ground shaking due to future earthquakes and is based on knowledge about past earthquakes, geology, tectonics, and local site conditions at any given location across Europe. The 2020 European Seismic Hazard Model (ESHM20) replaces the previous model of 2013.

The advanced datasets incorporated into the new version of the model have led to a more comprehensive assessment. Consequently, ground shaking estimates have been adjusted in comparison to the previous 2013 European model. In some regions, such as Germany, lower estimates are found, which is consistent with the most recent German seismic hazard model developed by GFZ (Grünthal et al., 2018). In other regions like western Turkey, Greece, Albania, Romania, southern Spain, and southern Portugal, however, higher ground shaking estimates have increased. The updated model also confirms that Turkey, Greece, Albania, Italy, and Romania are the countries with the highest earthquake hazard in Europe, followed by the other Balkan countries. But even in regions with low or moderate ground shaking estimates, damaging earthquakes can occur at any time.

European Earthquake Hazard Map
European Earthquake Hazard Map. Earthquake hazard measures the seismic shaking expected with a 10% probability within the next 50 years. (CC BY: Danciu L., Nandan S., Reyes C., Basili R., Weatherill G., Beauval C., Rovida A., Vilanova S., Sesetyan K., Bard P-Y., Cotton F., Wiemer S., Giardini D. (2021) – The 2020 update of the European Seismic Hazard Model: Model Overview. EFEHR Technical Report 001, v1.0.0, https://doi.org/10.12686/a15)

Furthermore, specific hazard maps from Europe’s updated earthquake hazard model will serve for the first time as an informative annex for the second generation of the Eurocode 8. Eurocode 8 standards are an important reference to which national models may refer. Such models, when available, provide authoritative information to inform national, regional, and local decisions related to developing seismic design codes and risk mitigation strategies. Integrating earthquake hazard models in specific seismic design codes helps ensure that buildings respond appropriately to earthquakes. These efforts thus contribute to better protect European citizens from earthquakes.

Main drivers of the earthquake risk are older buildings, high earthquake hazard, and urban areas

Earthquake risk describes the estimated economic and humanitarian consequences of potential earthquakes. In order to determine the earthquake risk, information on local soil conditions, the density of buildings and people (exposure), the vulnerability of the built environment, and robust earthquake hazard assessments are needed. According to the 2020 European Seismic Risk Model (ESRM20), buildings constructed before the 1980s, urban areas, and high earthquake hazard estimates mainly drive the earthquake risk.

Although most European countries have recent design codes and standards that ensure adequate protection from earthquakes, many older unreinforced or insufficiently reinforced buildings still exist, posing a high risk for their inhabitants. The highest earthquake risk accumulates in urban areas, many of which have a history of damaging earthquakes, such as the cities of Istanbul and Izmir in Turkey, Catania and Naples in Italy, Bucharest in Romania, and Athens in Greece. In fact, these four countries alone experience almost 80% of the modelled average annual economic loss of 7 billion Euros due to earthquakes in Europe.

European Earthquake Risk Map
European Earthquake Risk Map. Earthquake risk is a probabilistic measure of future economic loss and casualties due to seismic shaking. (CC BY: H. Crowley, J. Dabbeek, V. Despotaki, D. Rodrigues, L. Martins, V. Silva, X. Romão, N. Pereira, G. Weatherill, L. Danciu (2021) European Seismic Risk Model (ESRM20). EFEHR Technical Report 002 V1.0.0, https://doi.org/10.7414/EUC-EFEHR-TR002-ESRM20).

The potential impact of earthquakes in a moderate seismicity area like Germany can also be significant because of the high exposure, i.e. regions with a large number of buildings, particularly those of high economic value. The German average annual economic loss is estimated to 260 million euros, but losses from individual events may be significantly higher. If the Roermond (1992) earthquake were to occur today the ESRM20 model predicts an average of 400M EUR of economic loss for the German territory.

Developing the models

A core team of researchers from different institutions across Europe, including GFZ worked collaboratively to develop the first openly available Seismic Risk Model for Europe and to update Europe’s Seismic Hazard Model. They have been part of an effort that started more than 30 years ago and involved thousands of people from all over Europe. These efforts have been funded by several European projects and supported by national groups over all these years.

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