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,

Greece has declared a state of emergency on Santorini after hundreds of undersea earthquakes shook the resort island for nearly a week.

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