Here is my explanation that I use for my understanding of this text of dead ones being thrown up and people coming out of the tombs to inform others.
We know that Mathew used many texts from the Hebrew Scriptures to reveal to Jews that Jesus was the Messiah. We know that Jesus and the apostles used the Septuagint that translated the Jewish text from Hebrew into Greek about 250 years before Christ. We know that the Masoretes after JC, endeavored to thwart Mathew’s use of the Hebrew Scriptures to give support that Jesus was the Messiah.
Reading The Apostolic Bible, Polyglot (ie The Septuagint interlinear from Greek to English) I came across this text of Psalms 68:6 which the interlinear in English reads: “God settles simple people in a house; leading out the prisoners being shackled in courage; in like manner the ones being greatly embittered, dwelling in tombs.”
The Greek word for “tombs” (#5028) is the same word in the Greek scripture for tombs. Except in some places it uses another word that has be translated as “memorial tombs”
In the Hebrew interlinear the word translated as “tombs“ in the Septuagint is translated as “dry land” (#6707).
In the scriptures Jesus healed demon possessed people who were living in the grave yards. It seems among the tombs, the "embittered" ones sought refuge, also people who were about to die sought refuge there. (The average person avoided the dead and graveyards. They would become unclean if they went there.) The earthquake shook them up, revived them to go back into the city and tell people what had happened.
So at Jesus death, the embittered ones, the ones as good as dead, sprung up with energy and went into the city and told others what had happened.
belbab