In 365 AD, the Mediterranean region was shaken by one of the greatest earthquakes ever seen by mankind. The earthquake and subsequent tsunami had an estimated magnitude of 8.0 or more in the Richter scale and killed tens of thousands of people, destroying the city of Alexandria in the Egypt, and several others around.

However, new research shows that the events were somewhat different than previously imagined. Its seismic legacy, in fact, may not be correct, which can mean drastic changes for the modeling of earthquakes and Tsunami that happen today in the region.

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Current rock formations in the city of Crete. Credit: Richard Ott / AGU

The consensus within the scientific community was that the sinking zone of a tectonic plate under the city of Crete it had caused a giant earthquake. However, new evidence has shown that, in fact, a series of minor faults along the coast of Crete may have been the real cause of the tremors, which may be behind the rocky elevations found in that region today.

"Our findings collectively support the interpretation that damaging earthquakes and tsunamis in the Eastern Mediterranean could originate from normal failures, highlighting the potential risk of normal failure earthquakes," said the researchers in their article published in the journal AGU Advances.

Research lines

To reach these conclusions, scientists looked at the fossil shorelines exposed by seismic surveys and applying radiocarbon dating techniques. With that, the researchers were able to “go back in time” to find out more precisely how the soil really changed to produce the broken landscape.

Graphs show the evolution of rock formations in the Crete region. Credit: AGU

The elevation of the soil around the beaches, which is about 9 meters, exposed and killed many large marine animals. The skeletons and shells found in this area reveal important clues about the region's biodiversity and how it was affected by the earthquake. Fossils of small snails, worms and corals have been found in eight locations around Crete.

This gave researchers 32 new data points in terms of geological ages. Then, they used computer models to adjust dates and locations with possible seismic activity. Some historical reports of earthquakes in the area were also taken into account in the research.

Guilty came before

These results suggest that other earthquakes in the first centuries of the millennium are some of the likely culprits for modeling the region's rocky chains. That is, they arose before the legendary earthquake of 356 AD, which was considered the culprit until now.

This new hypothesis is supported by other evidence, including an apparent abandonment of the old port of Falasarna, which occurred in the middle of AD 66. But the team warns that these data are not conclusive at this stage. This means that the normal failures in the region's tectonic plates have the potential to cause more destruction than previously thought.

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"Based on these findings and the best consistency with the long-term record of the extent of the earth's crust in the region, we favor a normal source of failure for the 365 AD earthquake and previous earthquakes," said the researchers. "However, we note that more research, and especially geophysical images, are needed to properly understand the risks in the area," they added.

According to Science Alert, this is not just a simple curious fact of history, as the modern earthquake predictions and models in the area need to be adjusted. Now, the researchers want to see more seismic measurements and recordings in the Mediterranean region, particularly far from the coastlines, which is where most of the data was collected.

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