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

Greece’s government declared a state of emergency on Santorini on Thursday after hundreds of undersea earthquakes shook the resort island for nearly a week. The ministry of civil protection’s announcement will provide authorities faster access to state resources.

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,