New Delhi, June 26 -- The two powerful earthquakes that struck Venezuela's northern coast, killing more than 180 people, were an event known as a "doublet."

Doublet earthquakes happen when a pair of similar-sized quakes hit close in location and time, according to the U.S. Geological Survey. On Wednesday evening, a 7.2 magnitude quake hit first, followed by a magnitude 7.5 just 39 seconds later.

The deadly one-two punch toppled buildings in Venezuela's capital, Caracas and beyond. Some 1,500 people were injured and thousands were reported missing. The coastal region of La Guaira, which is north of Caracas, experienced some of the heaviest damage and casualties, officials said.

How rare are doublets?

While not as common as a typical ea...