Greece is preparing for any scenario but experts are optimistic about the tremors that triggered an exodus of residents and visitors from the Aegean Sea island of Santorini.

Earthquakes rattled Greece’s volcanic island of Santorini every few minutes through the night and into Wednesday as authorities bolstered their emergency plans in case the temblors are a harbinger of a larger quake to come.

According to officials, more than 11,000 people have left Santorini, with around 7,000 departing by ferry and 4,000 people leaving by air. Hundreds of earthquakes have rocked the island, the strongest of which was a magnitude five tremor on Tuesday.