Throughout the New Testament the Greek word σεισμος (plural σεισμοι) is consistently translated as earthquake. As this Greek word is also adopted in modern languages in relation to earthquakes (seismology, seismograph, …), there doesn’t seem to be any objection against this consistent earthquake translation.
However, the earthquakes in the New Testament always make their appearance in a warlike atmosphere, first of all in the Synoptic Apocalypse (Mark 13 and parallels in Matthew 24 and Luke 21). Mark 13:8 goes as follows: For one people will rise against the other, and kingdom against kingdom; there will be earthquakes in various places, there will be famines. (Some ancient manuscripts add ‘rebellion’ and/or ‘epidemics’.) At first sight the earthquakes are an anomaly between these warlike phenomena, and this accentuation of the war by a disastrous natural phenomenon diverges the attention from a potential historical war to some kind of cosmic conflict. But we can ask this question: could the description above be the homogenous description of a historical war? In other words: could σεισμοι describe a warlike phenomenon?
Let’s start from the basic meaning of σεισμος, which is a broad one like so many ancient Greek words, meaning ‘heavy shaking or trembling’. Josephus uses the corresponding verb σειω in the description of a heavy thunderstorm: For during the night a devastating storm broke out; a hurricane raged, rain fell in torrents, lightning flashed continuously, accompanied by fearful thunderbolts, and the earth quaked (σειομἐνης) with extraordinary rumbles. (War IV:286). Just like we can conclude here from the context that this ‘earthquake’ is part of the description of the thunderstorm, maybe we should interpret the ‘earthquake’ surrounded by other warlike phenomena as just one more element of the description of a war.
In a context of ancient warfare σεισμος might describe the heavy trembling caused by siege engines, the ballista and the battering ram in particular, or the shaking caused by huge ashlars falling down when defensive walls and towers were demolished after the capture of a city. If we interpret σεισμος as a pars pro toto for ‘siege’ and/or ‘capture’, the verse above becomes a homogenous war sentence, and the addition ‘in various places’ supports this interpretation. At least Jotapata, Tarichaeae, Gamla and Jerusalem have been besieged during the war of the Jews against the Romans (66-70 CE).
Besides the synoptic Apocalypse σεισμοι are mentioned in Matthew 27:54 and 28:2, and the verb σειω is used in Matthew 27:51: And behold, the curtain of the temple was torn in two, from top to bottom; and the earth trembled (ἐσείσθη), and the rocks were split. We can read the trembling and the splitting as cause and event: the impact of the battering ram on the walls of Jerusalem that split its ashlars (or ashlars broke when they fell down at the demolition of the walls and towers). In this reading Mark 13:8 becomes a homogenous war verse, combining the siege of Jerusalem (with famine and epidemics as its disastrous effects) with the destruction of its Temple.
Revelation 6:12 combines a great earthquake with the changing of the aspect of sun and moon: When he opened the sixth seal, I looked, and behold, there was a great earthquake; and the sun became black as sackcloth, the full moon became like blood. Here the siege engines (or the demolition of the walls of the temple enclosure) are combined with the burning of the Temple, which caused a huge pillar of smoke that darkened the sun and the moon. Finally in Revelation 11:13 thousands of people are killed in the great σεισμος and a part of the city is destroyed. We can imagine the several tons heavy blocks falling 15 to 20 meters down from the western wall of the Temple Mount into Tyropoeon valley at the demolition of the Herodian citadel by the Romans in September 70 CE.
Translating ‘seismoi’ as earthquakes is a fine example of how undecoded apocalyptic wording produces a mythological translation.