 The United States Geological Survey ( USGS ) recorded eight aftershocks in the two hours after the main earthquake , with <unk> between 4 @.@ 3 and 5 @.@ 9 . Within the first nine hours 32 aftershocks of magnitude 4 @.@ 2 or greater were recorded , 12 of which measured magnitude 5 @.@ 0 or greater , and on 24 January USGS reported that there had been 52 aftershocks measuring 4 @.@ 5 or greater since 12 January quake . 
