[SunkenCiv]

Thanks VR. It’s no accident that Poseidon Earthshaker (as Homer put it) was the Greek god of earthquakes as well as the seas. If memory serves, Thucydides relates a specific quake to a specific tsunami, one that destroyed an Athenian fort and its garrison.

[Verginius Rufus]

Of course Poseidon would have been the patron deity--Poteidaia was a Corinthian colony and therefore spoke the Doric dialect, in which Poseidon was "Poteidan." Poteidaia was supposedly founded by Euagoras, son of Periander, tyrant of Corinth. In 479 men from Poteidaia fought on the Greek side in the battle of Plataia.

Afterwards the city was a member of the Athenian Empire but maintained ties with Corinth. It revolted from Athens in 432 and was eventually reduced by siege--that is one of the incidents which Thucydides singles out as complaints which led to the outbreak of the Peloponnesian War in 431 (Corinth being one of the cities which pushed Sparta into going to war).