The July 9, 1956 earthquake is among the main seismic events that occurred in 20th century Greece. The image shows the epicenter of the earthquake (red star) (Okal et al., 2009)
Amorgos, main square
Certainly one of the strongest seismic events occurred in 20th-century Greece was the July 9, 1956 earthquake in the Aegean Sea. The earthquake, recorded at 03:11 GMT (05:11 local time) had epicenter about 5km east/northeast of the island of Santorini and 7.8 magnitude (calculated by Gutenberg and reported by the International Seismological Summary - ISS).
The magnitude and earthquake characteristics caused a tsunami that affected the Aegean Sea coast.
In 2003 Okal et al. (2009) conducted an empirical and interview field survey with some residents of Amorgos island, the main island of the Cyclades archipelago.
Particularly interesting was the testimony of two shepherds, retired at survey time, who assisted from Mouros locality to the event.
Both eyewitnesses, respectively 33 and 18 years old in 1956, interviewed separately, described the phenomenon as characterized by an initial sea withdrawal-very evident-occurred a few minutes after the earthquake.
Mouros is rightly listed among the sites where major run-ups were detected where tsunami exceeded 20m.
In addition, the Northern coasts of the Crete Island were extensively damaged, in Kalymnos (Calimnos) the withdrawal of the sea and the consequent tsunami, invaded the entire town of Pothea (for about 1.5km from the coast) causing extensive damage to housing and port structures due to the strong sea pressure.
It was estimated that tsunami reached 25m of local run-up.
The earthquake caused 53 deaths and more than 100 injuries. Extensive and widespread damage was reported, particularly on the island of Santorini.
References:
- Ambraseys, N.N., The seismic sea wave of July 9, 1956, in the Greek Archipelago. Journal of Geophysical Research, vol. 65, no. 4, p. 1257-1265. DOI:10.1029/JZ065i004p01257
- Papadopoulos, Gerassimos A., and B.J. Chalkis, Tsunamis observed in Greece and the surrounding area from antiquity up to the present times. Marine Geology, vol. 56, issues 1-4, April 1984, p. 309-317
- Maramai, A., Graziani, L., Brizuela Reyes, B. (2019). Euro-Mediterranean Tsunami Catalogue (EMTC) (Version 2.0). Istituto Nazionale di Geofisica e Vulcanologia (INGV). https://doi.org/10.13127/tsunami/emtc.2.0
- Okal, E. A., Synolakis, C. E., Uslu, B., Kalligeris, N., & Voukouvalas, E. (2009). The 1956 earthquake and tsunami in Amorgos, Greece. Geophysical Journal International, 178(3), 1533-1554.