Per the Artscroll Siddur after an earthquake we make a Bracha "Oseh Maaseh Breishis". Up to how long after the earthquake can you make this Bracha? (sources please)
Piskei Teshuvos (227:2) cites Bircas HaBayis who says that the blessing can only be recited during the quake or within 2-3 seconds (תוך כדי דיבור) after it's over.
He also says (from Teshuvos Shevet HaKehasi) that even mild quakes warrant this blessing, and (from Shaarei Teshuvah in the name of Maharam Chaviv) that if another quake occurs even that same day, the blessing is repeated, as long as some time has passed and the person is no longer thinking about it.