The processes by which tsunamis are generated imply that major destructive events are relatively rare. Thus, during any individual decade it is unlikely that more than a very few major events take place worldwide. However, when considered at the century timescale, the frequency of destructive tsunamis is proportionally increased.

Historical accounts of former tsunamis have particular value as they can provide information on the frequency and magnitude of events for the time period for which historical records are available. For example in Italy the oldest historical record of a tsunami having taken place is for the 79AD eruption of Vesuvius. As numerous tsunamis have taken place along the coastline of Italy since then, historical accounts are a particularly valuable archive that can be used to estimate tsunami (and earthquake) recurrence. In recent years geological investigations have been used to identify tsunamis that took place in prehistory. This has proved possible owing to the recognition that, in many cases, tsunamis deposit sediment in the coastal zone (Dawson, 1994; 1996). Identification of such sediment layers in coastal sediment sequences has led to a different perspective on the past frequency and magnitude of tsunami events in different European coastal regions.

In Europe the coastal areas of the Mediterranean have been particularly susceptible to tsunamis generated by major earthquakes. Four destructive tsunamis have taken place in Europe since the end of the 17th century. Each was associated with considerable loss of life and each area presently coincides with a region that is extremely popular for tourists. Clearly we need to be aware that major tsunami disasters have taken place previously in such areas.

A catalogue of past tsunami events is available by clicking the Past Events link, above left.