Simplify the following text for a Grade 4 native English-speaking person.
Original: The Nankai megathrust has five distinct segments ( A-E ) that can rupture independently , the segments have ruptured either singly or together repeatedly over the last 1,300 years . Megathrust earthquakes on this structure tend to occur in pairs , with a relatively short time gap between them .
Simplified: The Nankai megathrust has five parts ( A-E ) that can break one by one .