Volcanologists fear tremors could trigger “powerful earthquake”

The Azores island of São Jorge has been rattled by more than 14,000 small earthquakes in the past seven days.

Since admitting to “higher than normal seismic activity” on March 21, the island has been on major alert: populations in the most vulnerable areas have been evacuated to less affected parts of the island; over 1500 residents have already left the island – and President Marcelo has even visited (yesterday) to ‘transmit a sense of calm’, telling people the situation was ‘under control’.

Says Reuters: “Arriving by helicopter, Portugal’s President Marcelo Rebelo de Sousa visited Sao Jorge on Sunday to attend a briefing about the situation and calm the local population. He also visited a historic tower that survived the 1808 eruption.

“Later on Sunday, Rebelo de Sousa interacted with locals in Calheta, a town on the eastern part of the island where people have sought safety. Most of the seismic activity has been in the western side of Sao Jorge.

“He drank a traditional Azorean spirit, kissed and hugged members of the crowd and took selfies with them”.

And then he left. But the island keeps shaking.

Dozens of soldiers have been mobilised; large tents with beds erected “that could accommodate 100 people in case of an evacuation” while island municipalities have also transformed various facilities into temporary reception centers, says Reuters.

Major Rodolfo Romeiro told the news agency that more resources will be arriving during the week.

Meantime, an exercise by Civil Protection, dubbed “Touro 22” – due to have begun at the beginning of April – has been delayed, and will only be rescheduled once this seismic crisis has passed.

This year’s exercise was designed to test ‘articulation’ between the various civil protection agents in a scenario of a red level weather event (meaning intense rain, wind and “maritime agitation”), particularly in the area of Santa Maria.

Now hopes are that the São Jorge isn’t visited by something far worse.

As volcanologists have been saying, the greatest fear is that the situation this far is very similar to what happened in La Palma, in the Spanish Canary islands, last year.

A sudden increase in seismic activity was the first sign that the Cumbre Vieja volcano was about to blow – and blow it did, for a total of 85 days in which thousands of homes, businesses and crops were lost.

Civisa – the Azores ‘sismo volcanico’ monitoring and information centre – has registered five further quakes today, all in the western part of the island, around Velas, Santo Amaro, Rosais, Urzelina.

For now they are low level quakes, measuring at the most between 3-4 on the Richter Scale.

According to the scale 3-4 are ‘small’ or ‘light’: once quakes reach level 5 they are considered ‘moderate’, and from 6 upwards they are “large” (7-7.9, “important” (8-8.9), “exceptional” (9-9.9) and “extreme” (over 10).

The island’s last volcanic eruption, in 1808, wiped out the parish of Urzelina (indeed the volcano is called the Urzelina Volcano), causing over 30 deaths and producing a basalt field of volcanic rock extending to the Ponta da Urzelina. 

The eruption was the last sub-aerial event observed in the Azores, explains Wikipedia; “most recent eruptions have occurred along submarine vents, with the Capelinhos eruption (1957–58) starting as a submarine eruption (that eventually grew into a sub-aerial event) and the 1998–2001 Serreta eruption being exclusively submarine (never breaking the surface)”.

The entire archipelago is volcanic, each island with its own distinct geomorphological characteristics. In São Jorge’s case, it was formed from fissural eruptions over thousands of years.

For now, the Civil Protection level of alert is at 4 (the top level being 6, which means ‘eruption underway’). Level 4 means there is a serious possibility of eruption, Civil Protection’s regional secretary Clelio Meneses has told Lusa. “What we are doing is preparing for the worst case scenario,” he said.

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