ATHENS, Greece — The Greek government's chief seismologist says the frequency of earthquakes affecting Santorini and nearby islands has eased in recent days, but the outlook for continued tremors in the coming weeks remains uncertain.

"Unfortunately, for now, we must wait. These seismic sequences do not end quickly. They follow their own timeline," seismologist Costas Papazachos told state-run ERT radio on Monday.

"Hopefully, this particular sequence will surprise us in a positive way and resolve itself sooner rather than later," he said.

A state of emergency has been declared on Santorini and the nearby islands of Ios, Amorgos, and Anafi, after a series of undersea earthquakes this month — sometimes felt every few minutes — prompted thousands of residents and workers to move to the Greek mainland.

Schools on the islands remain closed for a third week, while security services have set up rescue teams and backup power generators as part of precautionary measures.

The government announced on Monday that an emergency port facility was being established on Santorini in case of a wide-scale evacuation.

Papazachos, a professor of geophysics at the University of Thessaloniki, said Santorini, a volcanic island shaped by catastrophic eruptions, did not face danger from its dormant volcano, but noted that magma was affecting the tremors.

"The root cause of the activity is the interaction of tectonic and magmatic processes," he said.

"That does not mean that the molten material — the magma — will manage to break through 8 kilometers of crust and reach the surface, causing a new volcanic eruption."

Scientists are developing a clearer picture after gathering data from multiple sensors, Papazachos said, but added that "we do not have a definitive forecast, as it is too early to assess the current slight de-escalation of seismic activity".

"We have encountered many surprises," he said.

Earthquakes of up to magnitude 5.1 were recorded on Monday in the undersea area bordered by the four islands — which are under a state of emergency.

Agencies via Xinhua