Recent mega-tsunami history of mediterranean
http://news.nationalgeographic.com/news/2006/12/061204-tsunami-israel.html
This team's assumption is that the mega-tsunami evidenced in Israel came from Mt. Etna ca 8,000 BCE. However, we also have discontinuties on Malta ca 2,500 BCE.
Now if no terrestrial source can be found for a mega-tsunami, then impact is the only other mechanism which generates enough energy capable of producing one. Indeed, in some cases, no terrestrial source is capable of producing the energy seen.
Fortunately, the experts in this field can back track from the land evidence to an impact point, which can then be verified.