A state of emergency was declared on Santorini Thursday after a magnitude 5.2 earthquake shook the Greek island late Wednesday. The tremor is the latest — and strongest — in a series of quakes that have struck the island since last week,

The Greek island has a long history of earthquakes, but what is causing the recent series of quakes has scientists perplexed.

Greece has declared a state of emergency on Santorini because of the hundreds of undersea earthquakes that have shaken the resort island for nearly a week