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I had the recollection that at least in terms of earthquake risk, the mid-Atlantic region is not nearly as bad for severe earthquakes as the Pacific, since the

I had the recollection that at least in terms of earthquake risk, the mid-Atlantic region is not nearly as bad for severe earthquakes as the Pacific, since the mid-Atlantic is an expanding / divergent fault. I.e. material gets pushed up gradually and the plates are politely moving away from one another. This is supposed to be less catastrophic compared to subduction where big stresses build up and get released suddenly when things break. Is that generally right? But of course, that is just the earthquake part, doesn't speak to the volcano or tsunami risk of big mountains erupting or falling into the ocean. I guess this current story is about the possibility of lava/ash, like what happened to the suburbs downslope of Kilauea or Soufriere Hills in the last couple years. Edit, actually watching one of the videos linked by other commenters, it looks remarkably like Molokai and people living (gulp) at the bottom of steep drop-off/valleys.

ByteJockey 5y ago
I thought transform boundaries were the big earthquake risk (not that there is none at convergent boundaries). At least that's what I remember from my 8th grade earth science class. I could be really wrong.
pid-1 5y ago
If I'm not mistaken there was an earthquake in 17xx that almost erased Lisbon. Still, it really appears that sismic activity in the Pacific is much more frequent.
- zeruch 5y ago
  It did destroy a significant portion of the city, and the rebuilding was a centerpoint of the Marquis de Pombal, whose expanding rule/influence was largely won based on his skill at using the rebuild to enact all manner of political change in a short period of time.
- Ftuuky 5y ago
  1755 earthquake (and tsunami) nearly destroyed the whole city and was probably one of the most deadliest in history. It was also one of the first quakes to be studied scientifically [0] Sooner or later it will hit Lisbon again, scientists say. As a Portuguese I'm very afraid the city is not prepared for something with an estimated magnitude of 7.7–9.0... [0] https://en.wikipedia.org/wiki/1755_Lisbon_earthquake https://en.wikipedia.org/wiki/1755_Lisbon_earthquake
  - EdwardDiego 5y ago
    I was wondering, given that quake, do Portugal's building codes now incorporate seismic standards?
    - pfdietz 5y ago
      The reconstruction of the city involved some of the first intentionally anti-seismic building methods. https://en.wikipedia.org/wiki/Pombaline_style https://en.wikipedia.org/wiki/Pombaline_style
    - Ftuuky 5y ago
      Yes but since 2020 it's moving to European construction standards [0] [0] https://en.wikipedia.org/wiki/Eurocode_8:_Design_of_structures_for_earthquake_resistance https://en.wikipedia.org/wiki/Eurocode_8:_Design_of_structur...
- mrlonglong 5y ago
  1755, and it really did obliterate the city. They had to rebuild it all, it was all gone.
nknezek 5y ago
Earth science PhD here - you're pretty much right, but Atlantic oceans can still be bad. 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-observatory/lahars-most-threatening-volcanic-hazard-cascades https://www.usgs.gov/observatories/cascades-volcano-observat... earthquake safety: https://www.calacademy.org/explore-science/how-to-prepare-for-an-earthquake https://www.calacademy.org/explore-science/how-to-prepare-fo... tsunami safety: https://www.ready.gov/tsunamis https://www.ready.gov/tsunamis

ByteJockey 5y ago

I thought transform boundaries were the big earthquake risk (not that there is none at convergent boundaries). At least that's what I remember from my 8th grade earth science class. I could be really wrong.

pid-1 5y ago

If I'm not mistaken there was an earthquake in 17xx that almost erased Lisbon. Still, it really appears that sismic activity in the Pacific is much more frequent.

zeruch 5y ago
It did destroy a significant portion of the city, and the rebuilding was a centerpoint of the Marquis de Pombal, whose expanding rule/influence was largely won based on his skill at using the rebuild to enact all manner of political change in a short period of time.
Ftuuky 5y ago
1755 earthquake (and tsunami) nearly destroyed the whole city and was probably one of the most deadliest in history. It was also one of the first quakes to be studied scientifically [0] Sooner or later it will hit Lisbon again, scientists say. As a Portuguese I'm very afraid the city is not prepared for something with an estimated magnitude of 7.7–9.0... [0] https://en.wikipedia.org/wiki/1755_Lisbon_earthquake https://en.wikipedia.org/wiki/1755_Lisbon_earthquake
- EdwardDiego 5y ago
  I was wondering, given that quake, do Portugal's building codes now incorporate seismic standards?
  - pfdietz 5y ago
    The reconstruction of the city involved some of the first intentionally anti-seismic building methods. https://en.wikipedia.org/wiki/Pombaline_style https://en.wikipedia.org/wiki/Pombaline_style
  - Ftuuky 5y ago
    Yes but since 2020 it's moving to European construction standards [0] [0] https://en.wikipedia.org/wiki/Eurocode_8:_Design_of_structures_for_earthquake_resistance https://en.wikipedia.org/wiki/Eurocode_8:_Design_of_structur...
mrlonglong 5y ago
1755, and it really did obliterate the city. They had to rebuild it all, it was all gone.

nknezek 5y ago

Earth science PhD here - you're pretty much right, but Atlantic oceans can still be bad. 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-observatory/lahars-most-threatening-volcanic-hazard-cascades https://www.usgs.gov/observatories/cascades-volcano-observat... earthquake safety: https://www.calacademy.org/explore-science/how-to-prepare-for-an-earthquake https://www.calacademy.org/explore-science/how-to-prepare-fo... tsunami safety: https://www.ready.gov/tsunamis https://www.ready.gov/tsunamis