What a new mapping of active faults reveals for Greece’s seismic hazard map

Scientists from the National Observatory of Athens (NOA) and New Zealand have systematically mapped the entire country using high-resolution Digital Elevation Models (DEMs) from the Hellenic Cadastre, aiming to identify active faults across mainland Greece. Their work uncovered hundreds of previously unknown seismic faults and produced a far more detailed depiction of known ones. The result is AFG (Active Faults Greece), the first nationwide active-fault database compiled based on the geomorphic footprint of faults, published in Scientific Data.

According to the international research team (Dr John Begg, Dr Vasiliki Mouslopoulou, Dr Dave Heron, Prof. Andy Nicol), Greece’s dramatic landscape reflects a continuous geological engine: “the country, squeezed between two continents, is deformed by the northward motion of Africa and the southward motion of Eurasia. Greece’s topography continues to change today largely through the action of active seismic faults. Many of these faults remain hidden beneath vegetation, expanding urban environments, or the complexity of the terrain,” they note.

With Greece’s economy increasingly dependent on tourism and with ambitions to become an energy hub in the Eastern Mediterranean, the researchers stress the urgent need for a better understanding of the distribution of seismic sources across the country—requiring detailed mapping of active faults both on land and offshore.

AFG delivers the first nationwide map of active faults based on landform morphology, using a consistent scale of 1:25,000.

The database includes 3,815 fault traces grouped into 892 faults, over half of which are mapped here for the first time. It also includes 35 surface ruptures linked to historical earthquakes. Each fault is classified as:

• Active, when the landscape shows clear recent deformation
• Probably active, when the fault is visible but evidence of activity is less certain
• Uncertain, when more observations are needed to confirm its existence

Further classification reflects how strongly faults have imprinted themselves on the terrain: sharp, “knife-like” traces indicate recent activity (likely within the Holocene, i.e. the last 10,000 years), while smoother features reflect older earthquakes.

More than 2,000 fault traces are classified as active and about 1,600 as probably active. Analysis shows that over half of Greece’s active faults control river courses, sediment deposition, and the boundaries between mountains and valleys—evidence that some active faults remain hidden beneath younger sediments.

The researchers emphasize that advances in technology have transformed how scientists “see” the Earth. DEMs allow precise analysis of ground deformation. A DEM is not just a map but a full 3D representation of the Earth’s surface. Each point contains elevation data, enabling detailed visualization of terrain complexity and the identification of structures invisible to the naked eye. For geomorphologists, the Earth’s surface acts as a book recording plate movements and past seismic events.

AFG’s methodology involves “reading” the landscape stripped of cities and vegetation, searching for systematic signs of active faults. But mapping faults is not solely an academic exercise.

Dr Vasiliki Mouslopoulou, Lead Researcher at NOA’s Geodynamic Institute, stresses its practical importance: “It has direct implications for the safety and sustainability of national infrastructure. Roads, bridges, dams, and energy facilities must be designed with knowledge of the active seismic sources capable of deforming the ground. When combined with seismic and geodetic data, the AFG database can improve Greece’s seismic-hazard models.”

Dr John Begg adds that technology alone is not enough: “Interpreting DEMs requires the trained eye of a geologist—someone who can distinguish a tectonic scarp from an erosion surface. Digital clues must be validated through fault-activity criteria, field observations, and comparison with existing studies. The strength of AFG lies in combining technological tools with decades of geological expertise.”

This approach is particularly revealing for a country with Greece’s rugged topography. Derived images with specialized lighting (hillshades) and slope visualizations (slopemaps) show that valley inversions, river deflections, or triangular mountain fronts are unmistakable geomorphic signatures of past earthquakes.

The AFG database is publicly accessible. Through an interactive map, engineers, researchers, and citizens can explore active faults near them and view their key characteristics. AFG aims to support national efforts to document Greece’s seismic sources and serve as a model for other earthquake-prone countries seeking to use digital landscapes to identify active faults.