Simplify the following text for a Grade 7 native English-speaking person.
Original: The quake 's epicenter was 70 m from the northern Thai city of Chiang Rai , north of Mae Sai and southeast of Kentung .
Simplified: The quake 's epicentre was 70 m from the northern Thai city of Chiang Rai , north of Mae Sai and southeast of Kentung .