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

The threat of a more major earthquake seems to have subsided on the most visited of the Greek islands but experts disagree on the origin of the tremors that have caused 11,000 of the 15,000 permanent residents to flee.

It welcomes around 3 million visitors per year, but between January 26 and February 8, the Seismology Laboratory of the University of Athens has registered a staggering 12,800 earthquakes in the Santorini-Amorgos zone, the strongest of these was last night at a magnitude of 5.3.