The largest aftershocks of an earthquake over the years around the world we've observed tend to be about one magnitude unit less than the main shock, more likely within months, but it could be years.

我们所观测到的世界上地震发生后强度最大的余震通常要比主震小一级，一般是在几个月内发生，但也可能是在几年后。

youdao

The largest aftershocks of an earthquake over the years around the world we've observed tend to be about one magnitude unit less than the main shock, more likely within months, but it could be years.

余震发生的时间和地点都有很大差异。余震可以在主震发生后的一个月或者几天之内发生。但也可能会在几十年之内发生。

youdao

Russia has been busy helping Japan recover from its March 11 natural disaster, when a 9.0 magnitude earthquake struck the main island of Japan.

FORBES: Russia Extends Hand in US Southern Tornado Disaster

Its most destructive on record was an 8.4 magnitude earthquake on Sept. 1, 1923 on the main, central, island of Honshu.

FORBES: China Sends Rescue Workers to Quake Ravaged Japan-Xinhua