SEOUL - An annual hush descended upon South Korea on Thursday as hundreds of thousands of students sat the crucial national college entrance exam, delayed for a week by a rare earthquake.

Educational authorities had to change four exam sites at Pohang, affecting about 2,000 candidates, after a 5.4-magnitude quake shook the southern city a week ago.

More than 60 minor aftershocks have hit Pohang throughout the past week, forcing 1,500 residents to stay in shelters.