Friday, April 5, 2024

East Coast Earthquakes - a fun summary

 We have actually had a good earthquake in a population zone.  So far, all eastern earthquakes (in the past 100 years) have been in pockets of nowhere.  This resulted in no pennies from heaven for studying these things.

There we have it - the east coast - dead as a dodo bird, so they think.

This is a passive margin, the Atlantic Ocean is spreading where you see all those cracks.  The East Coast is sinking.  Crazy people are calling that the 'rise of sea level'.  Sheesh.

It was very active in historic times, and now it isn't.  Is that a good thing?  No, the sinking of the coast is a wobbly curve like all things, but it isn't measured in great detail.  It goes faster and slower.  I'm thinking that I would be happy if the rate of sinking increased, and we went back to our old rate of earthquakes.  This new one could be a sign, but it really isn't.

If we get more earthquakes, then it could mean something, or not.

But, the good point is that we have an earthquake near buildings.  There may be lots of unmeasured cracking for the neighbours.  We we went to the near-field of the last earthquake in New Brunswick, the rock was exploding under our feet (royal we).  We should get that now.

These earthquakes are generally 'explosive' because they happen in granite, not mushed-up California rock.  A completely different animal.  That's why I went to Peak Ground Velocity only.  No use measuring peak acceleration here (pga).

The pga in the east is ridiculously high at high frequencies.  That's because pga is not anchored in physics, but is always used by earthquake engineers.  That's like assuming the convective atmosphere is a greenhouse with the glass in.  It really has the glass out.

Now, people will say we don't have to study (or worry about) earthquakes on the east coast.  Pooey I say.  We have 10 times less chance of 40 cm/s (like Taiwan) but will have 10 times more impact (cost and lives) because we don't do anything.  Think of that bridge jammed up like all New York bridges.  Think of the absolutely decrepit NY subway.  Think of all the buildings on the verge of falling down.  That's my life, I always look at these things, and knock myself to sleep with happy pills and my good stuff.

ps.  everything in New Jersey was delayed for inspections.  These are totally useless, except for political rear-covering.  These types of earthquakes are felt at 0.5 mm/s.  You might have a stone fall at 1 cm/s.  Really bad buildings are damaged at 20 cm/s and modern buildings tilt at 40 cm/s.  I put instruments in nuclear plants for the express reason of not closing them at 1 mm/s, but I can't say the effort really worked.  If you know the pgv, then you can figure out the damage.  At 40 cm/s you need instruments in the building to figure out if there is damage.  Needless to say, nobody does this.

ps. OMG, clange caused this earthquake!  Now I can put it all together.  Or maybe it was a response to the trumpy bible.  Who knows?

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