Patterns and Controls of Earthquake-Triggered Landslides in Greece: Evidence from a Long-Term National Inventory

Earthquake-triggered landslides (ETLs) constitute one of the most hazardous secondary earthquake environmental effects, causing severe impacts on the natural and built environment as well as on human life. Greece is particularly prone to the occurrence of such phenomena due to its complex geotectonic framework and high seismicity. Despite their significance, a comprehensive national-scale assessment of earthquake-triggered landslides in Greece, spanning from antiquity to the present, has been lacking.

This study presents the first extensive temporal, spatial, and statistical analysis of ETLs in Greece, covering an exceptionally long time period from 279 BC to 2023. Through a systematic review and reevaluation of Greek and international scientific literature, historical sources, earthquake catalogues, technical reports, and field survey data, a total of 673 ETLs associated with 144 earthquakes with Mw ranging from 4.0 to 8.3 were identified and documented. The analysis was supported by Geographic Information Systems (GIS), enabling the integration and correlation of ETLs with geological, geomorphological, tectonic, seismological, and environmental parameters.

The results indicate that the highest concentration of ETLs occurs in western Greece, particularly in the Ionian Islands and the Peloponnese, regions characterized by active tectonic structures and intense seismic activity. Most ETLs are associated with geotectonic units belonging to the External Hellenides, while limestone-dominated lithologies and post-alpine deposits were identified as particularly susceptible to landslide occurrence. The majority of documented ETLs were triggered by earthquakes of moderate to strong magnitude (Mw=5.5-7.0), highlighting the importance of such events in generating widespread slope failures. Rockfalls represent the most frequent type of ETLs in Greece, accounting for nearly half of the recorded cases, reflecting the steep topography and widespread exposure of fractured rock masses.

Spatial analysis further revealed that the distribution of the ETLs is not random but predominantly occur within areas classified as high and very high susceptible. Although less frequent, coastal and offshore landslides were also documented and constitute a significant hazard, as they may be associated with secondary effects such as local tsunami and coastal instability. The impact of ETLs on the built environment of Greece is substantial, including damage to buildings, transportation networks, and critical infrastructure, which in turn exacerbates the socio-economic consequences of earthquakes and poses additional public health risks.

The findings of this study emphasize the critical importance of systematically recording and analyzing ETLs as an integral component of seismic risk assessment. The compiled dataset and the derived spatial and statistical insights provide a valuable foundation for improving landslide susceptibility assessment, land-use planning, Civil Protection strategies, and disaster risk reduction policies. In a seismogenic country such as Greece, understanding the patterns and controlling factors of ETLs is essential for enhancing resilience and mitigating the compound and cascading impacts of future seismic events.