The popular Greek tourist island of Santorini has experienced thousands of near-constant earthquakes since Jan. 25, prompting more than 13,000 of the island’s 15,500 residents to leave the island, according to The New York Times.

Scientists have detected several thousand earthquakes, the vast majority of them with small magnitudes, in just over two weeks near Greece’s volcanic island of Santorini.

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