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

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,

Experts say the Greek island of Santorini has been hit by more than 1,000 earthquakes, but they're not linked to the region's active volcanoes.