The historical record suggests that the south-central coast is more vulnerable to earthquakes than it actually is.
Geological research has shown that a wall of water struck land in 1737. There was no such wave in written documents from the time.
There are records of an earthquake in the area in 1737, but there is no evidence that it generated a wave.
It suggests that our future predictions are based on a mistake. If earthquakes have the potential to produce a tsunami, they may arrive as frequently as once every 130 years.
The discovery is based on the layers of silt found in a tidal marsh near Valdivia, a historic city on the south coast of Chile that was hit by a massive earthquake in 1960.
The event triggered a deadly wave that hit the coast of the country at a height of 25 meters, as well as battering the coast of Japan, the Philippines, New Zealand and Hawaii.
The earthquake in 1737 did not have a wave, but it was followed by two other earthquakes.
Researchers have suggested that the 1737 earthquake was caused by a deep fissure between two plates underneath the land, rather than under the sea.
The researchers found evidence of land flooding when they analyzed the algae found in Chaihun.
The Chaihun tidal marsh has an aerial view. The University of Northumbria.
The authors say that the evidence of coastal subsidence and tsunami inundation at Chaihun is better explained by offshore, shallow megathrust slip than by deeper slip below land.
The most likely depth of the earthquake that caused the tsunami is around 20 kilometers. A shallow earthquake that hits offshore is more likely to cause a wave.
Three distinct sand sheet layers were found at Chaihun.
The deposits of layer A coincide with the 1960 earthquake and the sands of B and C are from the 1737 and 1575 earthquakes.
The closest earthquake to this salt marsh was the 1737 one, which happened when layer B was deposited. The 1737 earthquake may have caused a smaller wave than the 1960 one, according to other geological research.
We need to be aware that the same fault lines can produce slightly different natural disasters in the future.
Historic records of flooding along particular coastlines are used to predict the potential future risk of a future tsunami.
Sometimes the records are incomplete because of the impact of societal unrest or other crises. It is believed that uprisings that drove settlers from most of the colonial outposts in the area may be the reason for the lack of chronicles of a tsunami.
Researchers are calling for caution when it comes to using historical records to predict earthquakes.
We need to compare historical records to direct geological evidence to better understand what could happen in the future.
The new findings only come from one region of the coast, so more research is needed in other areas to understand the scope and timing of the 1737 tsunami.
The study was published in a journal.
