- Greece is moving from 3 to 5 seismic hazard zones to align with the revised Eurocode 8 (EC8).
- Design will shift from simple ground acceleration (PGA) to more complex spectral values to improve safety.
- Implementing these standards nationwide is projected to cost €108 billion for repairs and reinforcement.
- The priority is preventing building collapse, acknowledging that total property damage prevention is financially impossible.
“The issue of seismic protection for existing structures is of great importance for both private and public buildings. The level of seismic safety of a structure built in 1960 is clearly inferior to that of a structure of roughly the same use and type built in 2000, and even more so to a structure that will be built in 2030. At the same time, however, it is a complex problem with many ramifications that are beyond the scope of this discussion,” Professor Kyriazis Pitilakis, AUTH, told the Athenian-Macedonian News Agency.
The Science of Shifting Sands
For twenty years, Greece has relied on the EAK2003 seismic map, a document crafted with the knowledge of a different generation. A dedicated team from Aristotle University of Thessaloniki (AUTH), led by Professor Kyriazis Pitilakis, has spent years processing data from more than 55,000 earthquakes. The result is the ESHM20—a unified European model that ignores political borders to focus on the raw reality of the Earth’s movement.
Key Technical Shifts
- From PGA to Spectra: Engineers will no longer look only at peak ground acceleration. They will now use two spectral acceleration values to predict better how a specific building height and type will respond to a quake.
- The 475-Year Rule: Residential buildings are designed for a “10% probability of exceedance in 50 years”—statistically, the “Big One” that occurs every 475 years.
- Soil Amplification: New factors are being introduced to account for how different soil types (from rock to soft silt) amplify tremor vibrations.
Five Distinctive Seismic Zones
The most striking change is the fragmentation of the country into five distinct seismic zones. The old three-zone system was too broad; the new map uses population density and refined geological data to create a more surgical approach to safety.
- Zone 5 (Deep Red): The highest risk. This now includes the Ionian Islands, the Corinthian Gulf, and Western Peloponnese.
- The Complexity of Athens: Attica proved to be a puzzle. Because it sits at a crossroads of different risk levels, the capital has been split into three zones to ensure that a building in the north and one in the south are engineered for their specific realities.
- The North: Thessaloniki and Halkidiki are now unified in a medium-to-high risk category, while Alexandroupoli has seen its status upgraded due to its growing geopolitical importance.
Series of Earthquakes Shake Lasithi Coastline
Crete in the Orange: The Zone 4 Reality
Under the new classification, the island of Crete is designated as Zone 4, marked by its distinct orange hue on the updated map. This categorization identifies the island as a moderate-to-high earthquake hazard zone, carrying a significant risk for strong shaking. Specifically, it reflects a 10% probability that the island will experience potentially damaging seismic activity within any 50-year window. For residents and developers alike, this means Crete remains in a high seismic design category, requiring rigorous engineering standards to withstand the tectonic pressures of the Mediterranean.
A Legacy of Concrete
The elephant in the room is Greece’s existing infrastructure. Professor Pitilakis points out that between 80% and 90% of Greek buildings were constructed under older, less stringent regulations—or, in the case of pre-1960 structures, no seismic regulations at all. While the new map dictates how we build tomorrow, it also shines a harsh light on the vulnerability of yesterday’s homes. In a hypothetical scenario in which the entire country is subjected to these new design loads, roughly 4% of buildings would still experience “serious to very serious” damage.
Safety has a steep price tag. The AUTH study estimated the cost of repairing and reinforcing Greece’s 3.2 million residential buildings to meet these modern expectations. The figure is staggering: €108 billion—a €20 billion increase over the costs associated with the current 2003 regulations. However, Pitilakis argues that this is a manageable investment when weighed against the alternative. In Thessaloniki alone, while 90% of buildings would fare well under the new standards, the remaining 1% of older structures could still incur €7 billion in damages.
