How long could the "seismic crisis" on Santorini last?

Santorini, and other Greek islands in the region, are in the midst of an "unprecedented" seismic swarm or crisis, which is the name for a sudden increase in the number of earthquakes in a given area.

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Photo: Reuters
Photo: Reuters
Disclaimer: The translations are mostly done through AI translator and might not be 100% accurate.

"We moved all our mattresses to the living room," says Georgia Nomiku.

A resident of Santorini fears the consequences of ongoing earthquakes on the Greek island, popular among tourists for its picturesque views.

But this past week, this idyll was shattered by thousands of earthquakes.

Santorini, and other Greek islands in the region, are in the midst of an "unprecedented" seismic swarm or crisis, which is the name for a sudden increase in the number of earthquakes in a given area.

About three-quarters of the island's 15.000 residents were evacuated when authorities declared a state of emergency after a magnitude 5,2 earthquake, the largest ever recorded, shook the island on Wednesday.

New, albeit smaller, earthquakes were felt again on Thursday.

The "clusters" of earthquakes have puzzled scientists, who say the pattern is unusual because they are not linked to any major quake.

So what's going on?

What's happening in Santorini?

Experts agree that the island is experiencing what the Greek prime minister called an "extreme and complex geological phenomenon."

"This is truly unprecedented, we have never seen anything like this in modern times in Greece," says Dr. Athanasios Ganas, director of research at the National Observatory in Athens.

Santorini lies on the so-called Hellenic volcanic arc - a chain of islands created by volcanoes.

But it has not experienced any major eruptions in recent times, and none since the 1950s, so the reason for the current crisis is unclear.

Experts say they are seeing numerous earthquakes within a relatively small area, which does not fit the pattern of a mainshock-aftershock sequence, says Dr. Ganas.

He said this started with the eruption of the volcano on Santorini last summer.

Then in January there was a "surge" of seismic activity with minor earthquakes recorded.

This activity escalated last week.

Thousands of earthquakes have been recorded since Sunday, and the largest one so far struck on Wednesday.

"We are in the middle of a seismic crisis," said Dr. Ganas.

Dr Margarita Segou from the British Geological Survey (BGS) described earthquakes as something that happens every day "in pulses".

She says this "swarm-like behavior" means that when a major earthquake hits, such as a magnitude four, "seismicity increases for one to two hours, and then the system relaxes again."

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How much longer will it last?

In short, it's impossible to say.

People are hoping that Wednesday's earthquake, which struck overnight, will be the largest to hit the island.

But seismologists tell the BBC it's hard to be sure.

Authorities have warned that these activities could take weeks.

Experts don't even know if this chain of earthquakes is just a prelude to a major earthquake or an event in itself.

Professor Joanna Faure Walker, an expert in earthquake geology at the Institute for Disaster Risk Reduction at University College London, said some large earthquakes have foreshocks - heightened levels of small to moderate seismic events - before the main shock.

But what's happening now are not volcanic earthquakes, claims Dr. Ganas.

Volcanic earthquakes have a characteristic, recognizable low-frequency wave shape, and they didn't happen here.

Dr Segou told the BBC that she and her colleagues analysed previous earthquakes in the region using machine learning - a data analysis method that can make predictions - to find out how the 2002 and 2004 earthquakes in the region ended.

The magnitude of those earthquakes was not as intense as those felt now, she says.

But the "identifying characteristic" of how they started and how they ended could help paint a picture of what patterns to look for.

Meanwhile, additional police and military forces have been sent to the island to help deal with any major earthquake.

Nomiko, who is the president of the Santorini city government, said her family remained, but that they had all packed small bags, "ready to go if anything happens."

But some islanders say they are not at all bothered by the earthquakes.

"I'm not afraid at all," said one Santorini resident, who decided to stay on the volcanic island despite thousands of her neighbors fleeing the ongoing earthquakes.

Chantal Metakides insists she will not join her compatriots.

"For five hundred years this house has survived earthquakes and volcanic eruptions, and it still stands tall," she told AFP news agency, adding that "there is no reason for anything to change."

Watch the video: A game can save you in the event of an earthquake

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