On the 26th of October, the Holy Eastern Church keeps the memory of the Great Earthquake, which struck Constantinople in 740. It must have been a terrible tremblor, as the Synaxarion of that day relates:
In the twenty fourth year of the reign of Leo the Isaurian, in the ninth Indiction, on the 26th of October, there was a great and terrible earthquake in Constantinople, so that the upper stories [of the palace?] and the more splendid of the other buildings collapsed and many people were buried under the ruins. And so on the day of the Great martyr Demetrius we commemorate that terrible threat of the earthquake, going in procession to the church in Blachernae of our all-pure, holy and glorious Lady, Mother of God and Ever-Virgin Mary, where we celebrate the divine Liturgy. At her prayers may we be delivered from every threat and attain eternal good things, in Christ Jesus our Lord, to whom be glory and might to the ages of ages. Amen.
From the liturgy of the day come the following poetic texts (unfortunately my usually very reliable source does not give the Canon of the Earthquake):
When the earth was troubled in fear of your rage, hills and mountains were shaken, Lord; but having looked upon us with an eye of compassion, in your anger do not be enraged at us; but with compassion for the creation of your hands free us from the dread threat of earthquake, as you are good and love mankind.
Fearful are you, Lord, and who can stand against your just rage? Or who can entreat you, or who can supplicate you, good Lord, on behalf of a people that has sinned and is in despair? The heavenly armies, Angels, Principalities and Powers, Thrones, Dominions, the Cherubim and the Seraphim cry out to you on our behalf: Holy, Holy, Holy are you, O Lord; do not despise the works of your hands; through your compassionate mercy save a city endangered!
The Ninevites by their transgressions heard they would be submerged through the threat of earthquake; but by the mediating sign of the whale, repentance summoned resurrection through Jonas; but as you took pity and accepted them, at the cry of your people with the children and beasts, through your Resurrection on the third day spare us too who are being punished, and have mercy.
Because from your unendurable wrath that threatened us you have delivered us and had mercy on us, showing us, O Christ, an ocean of love for mankind, we now give you thanks, having been chastised so as to turn from our wicked deeds that slay us. But look upon us, have compassion on us, O Saviour, at the entreaties of the one who gave you birth.
Immaculate Virgin-Mother, do not cease to implore the Lord who was incarnate from your pure blood on behalf of us who are your servants, that we, the race of mortals, may find grace and prompt help in time of need, rescuing us from the threat of fearsome earthquake and from dangers by your mother’s prayers.
For the Divine Liturgy itself, the appointed readings seem to be:
The Epistle (Hebrews xii, 6-13 & 25-27)
For whom the Lord loveth, he chastiseth; and he scourgeth every son whom he receiveth. Persevere under discipline. God dealeth with you as with his sons; for what son is there, whom the father doth not correct? But if you be without chastisement, whereof all are made partakers, then are you bastards, and not sons. Moreover we have had fathers of our flesh, for instructors, and we reverenced them: shall we not much more obey the Father of spirits, and live? And they indeed for a few days, according to their own pleasure, instructed us: but he, for our profit, that we might receive his sanctification. Now all chastisement for the present indeed seemeth not to bring with it joy, but sorrow: but afterwards it will yield, to them that are exercised by it, the most peaceable fruit of justice. Wherefore lift up the hands which hang down, and the feeble knees, and make straight steps with your feet: that no one, halting, may go out of the way; but rather be healed. See that you refuse him not that speaketh. For if they escaped not who refused him that spoke upon the earth, much more shall not we, that turn away from him that speaketh to us from heaven. Whose voice then moved the earth; but now he promiseth, saying: Yet once more, and I will move not only the earth, but heaven also. And in that he saith, Yet once more, he signifieth the translation of the moveable things as made, that those things may remain which are immoveable.
The Gospel (St Matthew viii, 23-27)
And they came to him, and awaked him, saying: Lord, save us, we perish. And Jesus saith to them: Why are you fearful, O ye of little faith? Then rising up he commanded the winds, and the sea, and there came a great calm. But the men wondered, saying: What manner of man is this, for the winds and the sea obey him?
These lessons, together with the doctrinally-rich texts from Vespers and Matins, supply much food for contemplation.