On July, 1956 the largest magnitude earthquake in Europe took place. It had a magnitude of 7.7 on the moment magnitude scale, and a maximum intensity of 9 (IX) on the mercalli intensity scale (1). The epicenter (The point on the earth’s surface where an earthquake originates from) was located to the south of the island of Amorgos, which is the easternmost island of the Cyclades in the Aegean Sea.
The 1956 Earthquake was the largest earthquake in Greece in the 20th century, and has not been matched since. The Earthquake left the island of Santorini completely devastated, and left the neighboring island of Amorgos with significant damage as well.
In Figure 1 the 1st epicenter (purple point) is the main shock and it had a surface magintude of 7.7. 13 mins later it was followed by an aftershock (blue point) earthquake with a magnitude of 7.2 (1). As you can see both epicenters were a good distance away from the island of Santorini, but it was the island that suffered the most damage. The first shock covered an area of 270,000 km and the second shock covered an area of 180,00 km.
The Earthquake also triggered a tsunami. The tsunami affected most of the Aegean Sea. Because of the distribution of observed run ups, combined with the inconsistent timings of the wave arrivals at different locations, it was concluded that the tsunami was actually triggered by multiple underwater landslides due to the earthquake (1). The tsunami, with a maximum wave height of 30 m at the south coast of Amorgos caused damages within a region of 100 km. Amorgos is exactly 92.6 km away from Santorini (1). In Figure 2, you can see that the tsunami appproached Santorini from the east. A family of 7 was out on a boat that day when the wave hit Santorini, and completely capsizing the boat, killing both the parents (1).
The topography of Santorini plays a specific role in why the earthquake was able to cause so much damage. The cliff walls and soft sediment from the pumice and ash amplifies seismic waves at the surface.
The damage was severe, especially in Santorini. Oia was one of the cities mostly damaged by the earthquake, and that was because Oia was built on unconsolidated, fragmented pieces of scoria. The earthquake caused the stutters built on the scoria to fail and collapse. The earthquake completely demolished 529 houses and left many other houses damaged as well. 53 people were killed as a result of the earthquake, and two other people were killed as a result of the tsunami (1).
Many people were left homeless and traumatized because of the 1956 earthquake. The cost of repairing the buildings that were damaged were to great and so many people lot there homes and businesses. Thousands of people left the island of Santorini due to the earthquake.
It has been 62 years since the 1956 Amorgos Eartquake that changed the lives of many Santorinians. The Earthquake left many of the buildings in ruins, especially Oia. But as you can see in Figure 3, Oia has not changed much. Most of Oia’s structures are built in exactly the same hazardess places that were completely demolished in the earthquake 62 years ago. If another earthquake of the same magnitude as the 1956 earthquake occurs, Oia would fall under the same devastating events. Many of the building would collapse and some will even be subjected to major landslides. Santorini is a catastrophe waiting to happen.
1. “1956 Amorgos Earthquake” Wikipedia. Wikimedia Foundation, 08 June 2018. Web 27 December 2017.