A state of emergency has been declred in Santorini, a volcanic island and popular tourist destination in Greece, as an 'earthquake swarm' that began earlier this month continues. Since 31 January, more than 800 tremors with a magnitude of three and above have been recorded.

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,