CNN)Several million earthquakes occur annually, but most are unnoticed because they're so small, the U.S. Geologic Survey says.
Here are five things to know about those quakes.
1. Are the Ecuador and Japan earthquakes related?
It's way too early to tell, said Paul Caruso, a geophysicist with the U.S. Geological Survey
"It's one day after the Ecuador earthquake and two days after the Japanese earthquake, so no real research has been done on these quakes as far as they're being connected," he said Sunday...
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