A magnitude 5.1 earthquake struck very close to Pakistan's capital of Islamabad, the U.S. Geological Survey (USGS) said on Friday. Although the quake had a moderate magnitude, its epicenter was only 10 miles northeast of the populous city. It struck at 1:59 a.m. on Saturday and was very shallow, only 16.2 miles deep, the USGS said. A magnitude 5.1 quake is capable of causing considerable damage.