Santorini earthquakes

ZZZZZZZ

"Emergency crews deployed on Santorini as an earthquake swarm worries Greek experts | AP News" https://apnews.com/article/greece-santorini-earthquake-volcano-8e5f6a16a3d6458aa86f3d0d06928292.

Crazy what's happening there....such a beautiful island too. 😧

broknsymetry

A candidate for the mythical island of Atlantis. There used to be a lot more there.

Astyanax

broknsymetry A candidate for the mythical island of Atlantis. There used to be a lot more there.

...but there isn't anymore. So "there's no 'there there' ". 😉

Somewhat-Reticent

Better a swarm of micro-quakes than one big one.

real_aurgathor

Somewhat-Reticent

Somewhat-Reticent Better a swarm of micro-quakes than one big one.

Among other things, a swarm of micro quakes could be indicative of a magma chamber that is being recharged.

real_aurgathor

The precursor of Santorini blew up around 1600 BCE, wiping out a Minoan settlement there and seriously disrupting life on nearby islands. The eruption was estimated to be level 7, though slightly less powerful than the 1815 eruption of Mount Tambora. In comparison, the Mount St. Helens eruption was level 5 and the Mount Pinatubo eruption was level 6.

So they definitely have a notable precedent, but explosions even at level 5 are very rare.

Heat84

real_aurgathor The precursor of Santorini blew up around 1600 BCE, wiping out a Minoan settlement there and seriously disrupting life on nearby islands. The eruption was estimated to be level 7, though slightly less powerful than the 1815 eruption of Mount Tambora. In comparison, the Mount St. Helens eruption was level 5 and the Mount Pinatubo eruption was level 6.

So they definitely have a notable precedent, but explosions even at level 5 are very rare.

Don't forget Krakatoa. That was way bigger than any of those.

real_aurgathor

Heat84

Heat84 Don't forget Krakatoa. That was way bigger than any of those.

Nope. Even though Krakatoa was very loud, it was only a VEI level 6 while Tambora was a 7.

It's the amount of ejected material that counts, and Krakatoa is estimated at 18 - 25 km³ while Tambora was around 150 - 200 km³.

real_aurgathor

Some interesting readings in news:

Thousands of earthquakes have been recorded since Sunday, with Wednesday's the most significant yet.
"We are in the middle of a seismic crisis," Dr Gasnas said.
Dr Margarita Segou from the British Geological Survey described the quakes as happening every day "in pulses".
She says this "swarm-like behaviour" means that when a more significant earthquake strikes, for example a magnitude four, the "seismicity is increased for one to two hours, and then the system relaxes again".
But seismologists have told the BBC it is difficult to be sure. Authorities have warned the activity could go on for weeks.
Experts also do not know whether this chain of quakes are foreshocks leading up to a large earthquake or their own event.
Professor Joanna Faure Walker, an earthquake geology expert at UCL's Institute of Disaster Risk Reduction, said some large earthquakes do experience foreshocks - elevated levels of small to moderate seismic events - before the main shock.
But what is happening now are not volcanic earthquakes, say Dr Ganas. Volcanic earthquakes have a characteristic signature of low frequency wave forms and these have not been exhibited here.

https://www.yahoo.com/news/long-could-santorini-seismic-crisis-202032223.html

I hope he's right and these are not volcanic earthquakes, especially since elsewhere, there is this somewhat dubious claim:

Greece, sitting on multiple fault lines, is one of Europe's most earthquake-prone countries. But the high seismic activity in the area of Santorini is unprecedented, seismologists have said, warning that it could last weeks or months.

https://www.yahoo.com/news/greece-declares-state-emergency-due-135023449.html

Not sure what, or when counts as a precedent of "high seismic activity", but there's a page with this content:

The Minoan eruption was a catastrophic volcanic eruption that devastated the Aegean island of Thera (also called Santorini) circa 1600 BCE. It destroyed the Minoan settlement at Akrotiri, as well as communities and agricultural areas on nearby islands and the coast of Crete with subsequent earthquakes and paleotsunamis. With a Volcanic Explosivity Index (VEI) of 7, it resulted in the ejection of approximately 28–41 km³ (6.7–9.8 cu mi) of dense-rock equivalent (DRE). The eruption was one of the largest volcanic events in human history.

https://en.wikipedia.org/wiki/Minoan_eruption

While VEI level 7 eruptions are exceedingly rare, even a level 5 (i.e. Mt. St. Helens) can wreak havoc on a relatively small island.

Somewhat-Reticent

Pumping water into the ground can facilitate micro-quakes and mitigate bigger shakes.

real_aurgathor

Somewhat-Reticent

The first part is definitely true as we know from fracking induced quakes, but I'm kinda doubtful about the second one.

Earth quakes can have a number of different causes, and there's not much humans can do with quakes that originate from fault lines at tectonic plate boundaries such as the Cascadia subduction zone.