Centre of the earthquake (5)
I believe the answer is:
heart
'centre of the earthquake' is the definition.
'heart' can be an answer for 'centre' (synonyms). I am unsure of the 'of the earthquake' bit.
'centre of the' is the wordplay.
'centre of' becomes 'hear' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
'hear'+'t'='HEART'
Can you help me to learn more?
(Other definitions for heart that I've seen before include "Vital organ - centre - courage" , "the name of a prison in Midlothian!" , "Nucleus" , "It's in the chest" , "Red card" .)