Seismic activity along the Periadriatic and Sava Faults in the past two millennia – an archaeoseismological assessment

Most of the Periadriatic Fault System have been active during Oligocene and Miocene times. Its western part seems to be inactive ever since, while the Lavanttal and Sava faults in the east show limited seismic activity. We conducted a systematic archaeoseismological survey along the Periadriatic-Sava fault system, assessing buildings and archaeological sites for earthquake damage. Eight sites, four Roman and four Medieval, display evidence for destructive earthquakes during the past 2000 years. These are San Candido (Medieval) and Lienz (Medieval) on the Pustertal fault, Teurnia (Roman) and Millstatt (Medieval) on the Mölltal fault, Arnoldstein (Medieval) and Magdalensberg (Roman) just north of the Karavanka fault, Roman Celeia (Celje) at the Savinja / Sava faults, and Roman Siscia (Sisak) nearby the Sava fault. Damaged upright walls of Medieval buildings and deformed floors of Roman settlements testify to local intensity up to IX. Ongoing studies of archaeological stratigraphy and construction history allow dating of one or more seismic events at each site, ranging from the 1^st century AD to the 17^th century. We would be cautious about pointing out epicentres at this moment. However, it is remarkable that sites, 70 km apart in average, along a a 380 km long segment of an ‘inactive’ fault zone carry evidence for so many high-intensity destructive events.