aftershock
noun [ C ] uk/ˈɑːf.tə.ʃɒk/ us/ˈæf.tɚ.ʃɑːk/
（地震后的）余震
a sudden movement of the earth's surface that often follows an earthquake and is less violent than the first main movement
The initial earthquake was followed by a series of aftershocks. 初震后又发生了一系列的余震。