August 24, 358 Tsunami: Marmara Sea, Turkey

358, August 24. Nicomedia. A destructive earthquake in Bithynia in western Anatolia almost totally destroyed Nicomedia (Izmit) and its district. The shock was felt over a large area and had social repercussions... The flooding by the sea of the lower parts of Nicomedea was probably the result of the tempest, rather than a seismic sea wave. There is no mention of sea waves elsewhere ...

An oration was composed on the occasion, and the event is mentioned by almost all near-contemporary writers. However, it appears that the effects of the earthquake were less catastrophic than individual reports seem to indicate. Far more was rumored to have happened to those at a distance than had actually happened, and both pagan and ecclesiastical writers seem to exaggerate the destruction, attributing it to the wrath of their gods.

Impressively many sources survive for this earthquake: the effects on Nicomedea were of intense interest to near-contemporary ecclesiastical historians, insofar as the earthquake prevented a synod from being held in Nicomedea. This was at the time of the Arian dispute, and the Nicomedea Synod was intended as an orthodox rival to the Arian synod held in Arinium. Predictably the Arian writer Philostorgius sees the earthquake as suppressing an impious synod, and talks about the inundation of Nicomedea by a sea wave, while the orthodox writer Sozomen attemps to show that the accounts of the destruction of Nicomedea were exaggerated. By way of mitigation he points out that Nicaea, Perinthus and Constantinople were also affected, and that the citadel tower of Nicomedea survived.

(above from reference #9116)

358, August 24. A tremendous earthquake in Macedonia, Little Asia, Greece, Syria, Egypt, Tsunami, Nicomedia in Bithynia suffered most. (reference #1149)

Note: Ambraseys (2002) (reference #2955) states "This information implies that most probably the sea waves were due to the storm and that the earthquake, which we are told followed a wet period, triggered landslides which carried housed down the hillsides and into the sea. At least for Izmit [Nicomeda] it appears that the damaging waves were generated by landslides which fell into the sea or by slumping of the coast." However, in a later publication (reference #9116) this possible landslide generated tsunami is not mentioned though statements are made that the shock "probably triggered landslide". Reference #11164 (v.2) and #9275 give a validity of 4 (definite tsunami) to this event, citing reference #2955.