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,

Repeated earthquakes are rattling Greece’s volcanic island of Santorini. Scientists say the quakes aren't related to a slight increase in volcanic activity that has also been registered recently.