Commemoration of the great Earthquake in Constantinople.

Commemorated October 26 in the Orthodox Christian Menaion

From the Prologue

In the time of the Emperor Leo the Isaurian, in 740, there was a terrifying and long-lasting earthquake in Constantinople. The people realised that this was God's punishment for their sins, and entreated the most holy Mother of God and St Dimitrios with great penitence, until God had mercy and the earthquake ended.