Greece Publishes First Complete Seismic Map of Active Faults

Scientists from the National Observatory of Athens (NOA), working with colleagues in New Zealand, have produced a new seismic map outlining Greece’s active fault lines, identifying 892 in total. They explain that Greece is “squeezed” between the African plate to the south and the Asian plate to the east — a geological pressure that drives the seismic activity capable of triggering earthquakes.

Using high-resolution Digital Elevation Models (DEMs) provided by the Hellenic Land Registry, the team uncovered hundreds of previously unrecorded faults and refined the mapping of those already known. Their work resulted in AFG (Active Faults Greece), the country’s first comprehensive database of active seismic faults.

The international scientific team, which includes Dr. John Begg, Dr. Vasiliki Mouslopoulou, Dr. Dave Heron and Professor Andy Nicol, wrote that beneath the Greek landscape lies a perpetual geological machine.

“The country, wedged between two continents, is deformed by the persistent movement of Africa to the north and Eurasia to the south. The relief of Greece continues to change today, mainly through the action of active seismic faults. Many of these faults remain, however, well hidden under vegetation, within the growing urban landscapes, or the complexity of the relief itself.

The researchers argue that, “With (Greece’s) economy increasingly based on tourism and with the ambition to become an energy hub in the Eastern Mediterranean, Greece urgently needs to better understand the dispersion of seismic sources across the country. This requires the detailed mapping of active faults throughout the land and underwater area of ​​Greece.”

AFG delivers to the scientific community the first pan-Hellenic map of active faults based on the morphology of the relief, at a consistent scale of 1:25,000.

‘Active Faults Greece’

The AFG seismic map records 3,815 fault traces, grouped into 892 faults, with more than half mapped for the first time, while it also contains 35 surface ruptures associated with historical earthquakes.

Each fault, according to the research, is classified as:

* Active, when the relief appears to have been deformed recently

* Possibly active, when the fault is visible in the relief but the evidence regarding its activity is less clear

* Uncertain, when more observations are needed to confirm the existence of the fault

As the scientific team emphasizes, further classification includes how strongly the faults have left their mark on the relief: “Traces like ‘stabs’ indicate recent activity (probably within the Holocene, that is, the last 10,000 years), while more rounded traces indicate progressively older earthquakes,” it notes.

In total, more than 2,000 fault traces in the AFG are characterized as active, while about 1,600 as possibly active. The analysis also showed that more than half of Greece’s active faults control river flow, sediment deposition and shape the boundaries between mountains and valleys. These relationships, as the researchers report, indicate that, inevitably, some active faults still remain invisible, “buried” under newer sediments.

Advanced methodology

Speaking to the Athens-Macedonian News Agency about the active faults in Greece, the researchers said, that “In recent years, technology has come to radically change the way we ‘see’ the Earth.”

Analyzing the methodology they applied, they emphasize that digital elevation models (DEMs) allow scientists to “read” the terrain and its movements, with an accuracy that was previously not possible.

In particular, they explain that a DEM is not just a map; it is a three-dimensional representation of the Earth’s surface. Each point in the model has a height, allowing scientists to visualize in exquisite detail the complexity of the terrain and identify structures that are invisible to the naked eye.

For the geomorphologist, the surface of the earth is a book that narrates the movements of the plates and the vibrations of time, and they add that “in digital models, scientists study the landscape, as it appears stripped of cities or vegetation, looking for systematic signs of active faults.”

However, mapping active faults is not only about ‘science’, as the Principal Researcher of the Geodynamic Institute of the National Observatory of Athens, Dr. Vasiliki Mouslopoulou and member of the scientific team, told AMNA: “It has practical implications for the safety and sustainability of the country’s infrastructure. Roads, bridges, dams and power plants must be designed knowing the distribution of active seismic sources that can move the ground. The information provided by AFG, when merged with instrumental recordings of earthquakes and ground deformations, can improve Greek seismic hazard models.”

‘Tehnology is not enough, human experience is needed

For his part, Dr John Begg, a key contributor to AFG, noted to ΑMNΑ that, “Technology alone is not enough. The interpretation of DEMs requires the experienced eye of a geologist, one who can distinguish a tectonic front from an erosion surface. The digital indications are validated when they are cross-referenced with a series of fault activity criteria, with on-site observations and comparison with existing studies. The strength of AFG lies in combining technological tools with decades of geological knowledge.”

As the researchers note, such an approach is particularly revealing for a country with a pronounced relief, such as Greece. “Careful observation, combined with the experience of the observer, is capable of separating the traces created by earthquakes from those carved by natural erosion or man. Derived images with special lighting (hillshades) and slope maps show that the inversion of a valley, the diversion of a river or the triangular front of a mountain are unmistakable “geomorphological fingerprints” of past earthquakes along active faults,” the searchers report.

The AFG database is freely accessible to everyone. In addition, through an interactive map of Greece, every engineer, researcher or citizen can know where the active faults around them are located and what their main characteristics are. AFG – Active Faults Greece hopes to contribute to national efforts to record active seismic sources in Greece and to become a model for other seismically active countries to use digital landscapes to identify active faults.