Azores – Evacuations Begin as Seismic Crisis Unfolds in Atlantic

How can you tell when it's a "big one" vs a normal one?

edit link: https://en.wikipedia.org/wiki/Cumbre_Vieja_tsunami_hazard

At least that's what I remember from my 8th grade earth science class. I could be really wrong.

Still, it really appears that sismic activity in the Pacific is much more frequent.

Most earthquakes are caused by tectonic plate motion.

The biggest earthquakes (>M9, e.g. Japan 2011) occur at subduction zones where an oceanic plate collides with and dives underneath a continental plate. Japan, South&Central America, New Zealand, and Malaysia are the biggest and most common examples. Two plates pushing against each other allow large energy to build, which can be released suddenly and catastrophically.

Large earthquakes (M7-8, e.g. San Francisco 1906) can still occur along strike-slip faults, where two plates are sliding past each other. However, because the plates are sliding, these faults usually cannot build enough energy for extremely large earthquakes (>M9.0). San Andreas fault in California is the most well known strike-slip fault and runs through both LA and SF, and has caused plenty of damage partly because the faults run directly through population centers.

The Azores lie on top of strike slip and expanding (normal) faults. Thus, they are not likely to experience the largest earthquakes (M9), but could be hit but a M8 which can still be devastating, especially if buildings are not constructed with earthquake safety in mind.

In addition, there is a high risk of any earthquake triggering an underwater landslide since the Azores are a mid-ocean island chain. This could cause a tsunami which could damage far-away locations.

As far as lava/ash risk -- generally the biggest risk is from explosive eruptions forming into a fast-moving cloud of ash and mud called a "pyroclastic flow" or "lahar". [1] These can travel faster than a car and blanket everything in their path in a boiling, burning cloud. Think Mt St Helens or Mt Vesuvius. However, only certain types of volcanoes are at risk of this type of eruption -- Hawaii for example erupts as smooth, oozing lava flows -- and I don't know if the Azores are at risk for this kind of eruption.

Notes on safety:

For earthquake safety, the best cure is preparation. Most injuries and death occur from items falling on top of people during the shaking. Secure shelves and items on walls. Avoid living in structures on poles as they are prone to collapse (e.g. apartments with parking garage on first level). Avoid living in marshy areas or seaside land constructed with landfill (due to liquefaction) or on steep slopes (due to landslides).

For tsunamis, if there is a warning, head to high ground further inland if possible, or move to upper stories of the roof of structures.

[1] https://www.usgs.gov/observatories/cascades-volcano-observat... earthquake safety: https://www.calacademy.org/explore-science/how-to-prepare-fo... tsunami safety: https://www.ready.gov/tsunamis

I hope that everyone is able to stay safe and get through this alright.

People have been living in the Azores since the 1400s.

I'm willing to bet that the risk from volcanic eruption in the Azores is considerably less than the risk from, say, traffic accidents in a major mainland city.

https://youtu.be/U1SSlulfFKg

We've been to the Azores. I really wish these people are safe. We want to return there again soon.

If you want agriculture, there's no place better than near a volcano (which is one reason for big death tolls, when they blow their tops).

I lived in Uganda, and that country is surrounded by volcanoes (I think they are all dormant). The soil is jet-black, and it is a gorgeous, lush nation.

The Reader view (F9) in Firefox fixed it.

If we learned anything from the global pandemic (covid-19), the world would do better by building and strengthening institutions like WHO and CDC to solve global problems.

This is very much something we understand quite well. You're seeing volcanic activity on a volcanic island on a plate boundary. Basically, this is the geological "normal" for this area that's been going on much longer than human civilization.

It's fair to be worried about increased human population in areas that are affected by this, but it's not in any way something caused by civilization's toll on the environment or even something we "don't understand" in some way. There's _tons_ that we don't understand in detail, but the broad brush strokes of volcanoes at a mid ocean ridge is something we understand relatively well. Note that the evacuation is beginning _before_ the eruption due to both local seismic monitoring of the sub-surface and space-borne monitoring of deformation at the surface.