Geoscience: Previously unrecorded Chilean tsunami identified

A large earthquake off the coast of south-central Chile in 1737 may have caused a substantial tsunami that was previously absent from historical records, according to an article published online in Communications Earth & Environment. Recognition of this event suggests tsunamis along the Chilean coast may have been more frequent than previously suggested by historical records alone.

Tsunami hazard assessment is often based on records of flooding along particular coastlines. The frequency of past tsunami occurrence is used to predict the potential future risk. However, such records are sometimes incomplete because reporting of tsunamis can be greatly affected by societal unrest, other crises or errors in reporting.

Emma Hocking and colleagues investigated sediments within tidal marshes close to the area where the 1737 earthquake struck. They found widespread sandy layers, dating to the same time as the earthquake, that may have been formed by a tsunami wave. The authors also found a mixture of marine and freshwater algae species and evidence of land subsidence, allowing them to rule out river flooding or a distantly generated tsunami as the cause of the sand deposits.

The authors suggest that geological evidence should also be considered when predicting future tsunami risk, as historical records alone may not provide a complete documentation of their occurrence and characteristics.