Interesting info that I read notes that in the scriptures, anytime there was (or will be) a resurrection into an immortal body, there was an earthquake there. This is seen in Jesus' resurrection as well as those of the people of God who were resurrected that same day (after Jesus) as recorded in Matthew 27:53. Also, the two witnesses' resurrection in Revelation 11:11-13 precedes an earthquake. It is thought that a nuclear reaction/explosion occurs in the dead body, but this does not cause a catastrophic event for the surrounding area as a nuclear bomb would because a body is made of more inert elements such as carbon, nitrogen, and oxygen, rather than unstable elements like uranium and plutonium as used in bombs. Nevertheless, the more intert explosion does shake the earth.
In conjunction, it is thought that the "tribulation" period in Revelation (as we think of it) does not start until the opening of the Sixth Seal -- that with the great earthquake across the world. The prior five seals are seen as having been occuring over the earth since Jesus ascended to rule at the Father's "right hand." It pictures Christ's rule and control over things for the past 2000 years in spite of all the bad things in the world of oppressive rulers, war, death, plague, and economic oppression. So, according to this theory, what kicks off the great earthquake of the Sixth Seal of Revelation? You guessed it! The resurrection of all of the dead in Christ from Adam to the present day, and the transformation of the alive in Christ at that time -- all into immortal bodies! Can you imagine the severity of earthquakes that would cause all across the globe? Would probably also kick off other quakes at natural fault lines and eruptions from natural weak places in the earth's crust such as volcanoes and etc.
Also noted was that the scriptures say that it is the resurrection and transformation into immortal bodies that occurs in the "twinkling of an eye" (instantaneously) not the rapture. The rapture, being caught up into the air to meet Jesus at his return, occurs less rapidly. So, there could be a small period of time between a beliver's transformation into an immortal body and his being caught up into the air to meet the Lord. During that time, apparently all hell will be breaking loose on the earth, but that won't hurt a transformed believer who can no longer die or be injured! Until Jesus comes to get him, he can hang out and watch. If he's from around here, he'll probably say: "Ain't Skeert!"

[information from Earthquake Resurrection by David W. Lowe]