Reading Greece’s restless landscape
Greece is a land of dramatic contrasts — from snow capped mountains to deep blue gulfs, from ancient city walls perched on rocky ridges to plains that have nurtured civilizations for millennia. But beneath this timeless landscape lies a restless geological engine. The Greek mainland, cradled between the converging African and Eurasian tectonic plates, is one of the most earthquake-prone regions in Europe.
The same tectonic forces that have created Greece’s beauty over millions of years, continue to shape it today. Understanding where and how the Earth moves is essential for a developing country and the ambitions of its people. Yet, many of Greece’s active faultlines remain poorly mapped - hidden by vegetation, urban growth, or the complexity of its rugged terrain. Over the past two decades, however, a quiet revolution has been transforming our ability to see the ground beneath our feet — not with hammers and compasses alone, but through the digital landscapes revealed by Digital Elevation Models (DEMs). It is this digital perspective that underpins the Active Faults Greece (AFG) : a national-scale effort to catalogue and characterize the country’s active fault systems.
From Maps to Models: Seeing the Unseen
A Digital Elevation Model is, in essence, a three-dimensional representation of the Earth’s surface (Fig. 1). Each point has a measured elevation, allowing scientists to visualize the shape of the land in extraordinary detail. Derived from radar, aerial photography, or laser scanning (LiDAR), DEMs can reveal subtle topographic variations invisible to the naked eye (Fig. 1).
For a tectonically active country like Greece — with steep relief, dissected valleys, and rapidly deforming crust — this technology is transformative. Shaded-relief images generated from DEMs highlight faint linear features, scarps, and ridges that betray the presence of (previously hidden) active faults. Features just a few metres high but kilometres long, can now be mapped across entire regions.
The AFG team used 2- and 5-metre-resolution DEMs from the Greek Cadastre Agency, processed into multiple hillshade, slope, and elevation maps using GIS software (Fig. 1). By varying illumination angles and overlaying drainage networks, they identified fault scarps, offset valleys, and triangular facets — the geomorphic fingerprints of past earthquakes. Once digitized and verified against field observations and existing studies, these features form the backbone of Greece’s first consistent, geomorphology-based active fault database.
Figure 1: Enhanced fault mapping through digital elevation raster images. Here, an area in south Peloponnese is (a) lit from 315° at 40°; (b) illustrated with slightly transparent hillshade underlain by the colour-ramped DEM; (c) shown as colour ramped DEM and hillshade overlain by slightly transparent slopemap; and (d) populated by fault traces mapped using collectively the above data.
Perhaps the greatest contribution of DEMs is that they allow us to see beyond the obvious — to perceive the slow, relentless movements shaping Greece over millennia. The ridges, basins, and valleys that define the Greek landscape are not static. They are part of a living landscape shaped by forces below the Earth’s surface.
The Language of the Landscape
To a geomorphologist, the Earth’s surface is a manuscript written by tectonic forces. Faults that slip during large earthquakes leave indelible scars recorded in this manuscript.
Figure 2: An illustration showing some of the landforms geomorphologists use to reveal the presence of active faults and past large-magnitude earthquakes at the ground surface.
Fault scarps form step-like slopes where the ground has been vertically displaced by past large-magnitude earthquakes. Repeated ruptures tilt valleys and basins, offset rivers, and carve triangular mountain facets (Fig. 2). In places, such as the southeast Peloponnese, sharp scarps up to 50 metres high slice across stream networks, ponding drainage and redirecting flow — unmistakable evidence for past large-magnitude earthquakes (Fig. 3).
By analyzing hillshades under different lighting settings, geoscientists can identify these signatures systematically (Figs 1-3). Drainage deflections, slope breaks and asymmetries point to ongoing crustal motion and help distinguish tectonic features from those carved by erosion. When combined with field data and an understanding of surface age, these digital clues reveal which faults are active and how they continue to shape the Greek landscape.
Figure 3: Sharp active normal fault scarps, formed during past large-magnitude earthquakes, traverse the landscape of southeast Peloponnese. Faults here back-tilt stream gradients, ponding drainage and re-routing streams.
A digital map of a restless nation
The AFG project represents a landmark achievement: the first nationwide, geomorphology-based active fault map of Greece compiled at a consistent scale of 1:25,000. It illuminates hundreds of hidden faults bringing us one step closer to understanding the dynamic Earth beneath our feet.
The database contains 3,815 individual fault traces, grouped into 892 faults and 236 fault systems. Over half of these traces are mapped here for the first time, revealing previously unrecognized fault strands in both mountainous and low-relief regions.
Each fault trace is categorized by activity and morphology:
- Active (clearly displacing Quaternary deposits or young landforms)
- Probably active (geomorphically expressed but with lesser certainty)
- Uncertain (possible tectonic features lacking definitive evidence)
Further descriptors — sharp, moderate, rounded, poor — capture the “freshness” of fault scarps and inform geoscientists on when they last moved. “Sharp” scarps typically indicate Holocene (≤10,000 years) ruptures, while “rounded” features may record older activity.
The AFG mapping shows that about 57% of active faults control local sediment deposition, forming the boundaries of mountain ranges and basins. This tectonic control over topography and sedimentation is key to understanding how Greece’s landforms evolve — and where buried faults may lie beneath younger deposits.
In total, over 2,000 fault traces are classified as active, with another 1,600 probably active. The vast majority — more than 99% — are normal faults, reflecting the extensional regime that dominates the Greek mainland.
From Pixels to preparedness
Mapping active faults is more than a scientific exercise. Greece’s infrastructure, from motorways and bridges to dams and power stations, must all contend with the possibility of ground rupture and strong shaking. Knowing where faults are and how they behave feeds directly into seismic hazard models and land-use planning. Understanding what magnitudes these faults can generate and how frequently they rupture, helps engineers and planners design safer infrastructure.
Freely available through GFZ Data Services, the AFG dataset provides an open-access foundation that informs onshore seismic hazard models, land-use planning, and future field studies. It also offers a reproducible framework for other tectonically active nations seeking to integrate topographic data with seismic risk analysis.
Without a Trained Eye, Pixels are Only Pretty
The growing availability of high-resolution topographic data — from Copernicus, TanDEM-X, and national LiDAR programs — is driving a renaissance in Greek geomorphology and tectonic research.
Yet, technology alone does not tell the whole story.
Interpreting DEMs still requires the trained eye of the geologist — one that can tell a tectonic scarp from an erosional slope. The strength of AFG lies in combining these digital tools with decades of geological insight.
AFG offers an important step toward a comprehensive, open-access understanding of Greece’s active faults, informed by science. AFG data underpin potential seismic hazard assessment for industrial and infrastructural development that might otherwise go ahead, blind to the economic risk and ignoring the need for economic resilience.
- AFG may be viewed via cellphone, tablet or PC on a publicly available Web Map Server (WMS)
- GIS Users may access the Active Faults Greece dataset as a hosted service from here
- Layerfiles for use in ArcGIS Pro and QGIS may be accessed from here