People in Pakistani cities hundreds of kilometres apart felt the 7.2 magnitude earthquake at it hit just before 2030GMT on Tuesday.
People sought refuge in the streets as the tremors shook buildings from Quetta to Karachi and Lahore.
There've been few initial reports of casualties or damage.
The full impact of the quake was expected to become clearer during Wednesday.
Several people were said to have been hurt as the roofs of their homes collapsed.
SOUNDBITE: Maria, Karachi resident, saying (Urdu):
"I was sleeping when the quake struck and I felt my bed shaking. It felt as if somebody was knocking at the door. I rushed to check the door, then I saw everyone running out saying an earthquake had hit. I got out of the house along with the children. It was very scary. We were praying to God for mercy."
The U.S. Geological Survey put the epicentre 55 kilometres west of Dalbandin.
It said the quake was more than 80 kilometres underground in Baluchistan province, near the Afghan and Iranian frontiers.
Such a powerful earthquake is capable of causing widespread damage and loss of life if it's at a shallow depth and close to major population centres.
In 2005 a quake of 7.6 magnitude killed more than 70, 000 people in Pakistan.