16 ] 7.0 4 "Antioch" 00526-05-21 May 21, 526 Antioch , Turkey (then Byzantine Empire ) 240,000 [ 17 ] 7.0 (est.) [ 18 ] Procopius (II.14.6), sources based on John of Ephesus . 5 "Gansu" 01920-12-16 December 16, 1920 Ningxia – Gansu , China 235,502 [ 19 ] 7.8 Major