Millions of people in the U.S. felt the effect of a powerful earthquake that struck Mexico on Sunday morning. Tremors reached north as far as Las Vegas with residents reporting swaying buildings and choppy swimming pools. The 7.2 magnitude quake was centred 60 km southeast of the border city Mexicali, where two people were killed and others remain trapped in their homes. A state of emergency has been declared there. It is the strongest quake to hit the area in decades.