“Suddenly,

There was a great earthquake.”

 

καὶ ἰδοὺ σεισμὸς ἐγένετο μέγας·

 

Matthew is the only one who has any activity at the tomb.  In the 3 other gospel stories, the woman or women found that the tomb was empty.  Thus, Matthew uniquely said that suddenly there was a great seismic earthquake (καὶ ἰδοὺ σεισμὸς ἐγένετο μέγας).  Matthew also uniquely had an earthquake at the death of Jesus, chapter 27:54.  Now he had another earthquake at the resurrection of Jesus.  These earthquakes symbolized that something important was happening.