Earthquake hazard and risk: Explanation of what it means
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Every year, millions of earthquakes hit Europe — although the majority are too small to be felt, let alone pose a danger to life or infrastructure. However, according to the European Facilities for Earthquake Hazard and Risk (EFEHR), the larger earthquakes that struck Europe in the 20th century alone accounted for more than 200,000 deaths and more than €250billion (£210billion) in financial losses. While quakes cannot presently be prevented or precisely predicted, hazard and risk models can help develop mitigation measures to reduce their impact when they do strike.
To this end, researchers from EFEHR have today released new quake assessments for Europe — including both an updated earthquake hazard model and the first risk model.
In this setting, hazard refers to the potential for ground tremors in the future, and is calculated based on knowledge about past earthquakes and the local geological conditions.
Risk, meanwhile, considers the estimated economic and humanitarian consequences of these potential quakes — and includes such factors as population density, local social conditions and the vulnerability of the built environment to seismic activity.
In Europe, buildings in active seismic zones must be built or retrofitted to meet the so-called Eurocode 8 standard, which aims to protect human lives, limit damage and ensure that vital civil infrastructures remain operational.
EFEHR said: “The development of these models was a joint effort of seismologists, geologists, and engineers across Europe.
Leading support, they explained, came from members of the Swiss Seismological Service and the Group of Seismology and Geodynamics at ETH Zurich.
“All underlying datasets have been updated and harmonised — a complex undertaking given the vast amount of data and highly diverse tectonic settings in Europe.”
Together, they added, the models will “significantly improve the understanding of where strong shaking is most likely to occur and what effects future earthquakes in Europe will have”.
In comparison to the 2013 European Seismic Hazard Model, the advanced datasets employed in the revised hazard assessment have led to lower estimates of potential seismic activity across “most parts of Europe”.
The exception, EFEHR said, lies in “some regions in western Turkey, Greece, Albania, Romania, southern Spain and southern Portugal, where higher ground-shaking models are observed.”
The updated model has also confirmed that the European countries with the highest earthquake hazards are Turkey, Greece, Albania, Italy and Romania — followed by the other Balkan nations.
But, the experts warned, “even in regions with low or moderate ground shaking estimates, damaging earthquakes can occur at any time.”
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On the risk front, researchers reported that the drivers were, naturally, areas of high seismic activity but also the presence of older and more vulnerable buildings, and urban areas with high population densities.
The researchers said: “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, such as the cities of Istanbul and Izmir in Turkey, Catania and Naples in Italy, Bucharest in Romania, and Athens in Greece, many of which have a history of damaging earthquakes.
“In fact, these four countries alone experience almost 80 percent of the modelled average annual economic loss of 7 billion Euros due to earthquakes in Europe.”
However, EFEHR noted, cities like Zagreb (Croatia), Tirana (Albania), Sofia (Bulgaria), Lisbon (Portugal), Brussels (Belgium), and Basel (Switzerland) have an above-average level of earthquake risk.
London was among the least seismic risk-exposed cities, along with Berlin and Paris.
The assessments were funded by the European Union’s Horizon 2020 research and innovation programme.
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