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I've read letters and newspaper articles talking about the New Madrid quakes from 1811-12. The one that referenced church bells ringing in Boston caused by the quake told me what I need to know. The plate east of the Mississippi transmits the quake over a very large area. When that sucker hits again, there's going to be major shaking in a huge swath of densely populated areas.

To my knowledge these areas have NOT built to what is typically thought of as California earthquake standards. When we discussed this topic a while back, one person challenged these thoughts. I don't remember the particulars, but I do believe there is serious cause for concern.

The buildings in the mid-west are not built to any earthquake standards. From memory, there are 4 earthquake zones for design. Almost all of the mid-west is in the lowest earthquake zone -- ie. no additional design required. There is a small zone of elevated earthquake danger around New Madrid, but it does not extend to any really large City's.

From a book I read about it once, there have been many earthquakes in the area at about 100 year intervals. The longer between earthquakes, the larger it is. We are overdue.

I read a lot about the New Madrid quakes. I think the scientists don’t even want to imagine how bad a quake so severe as the worst of 1811-12 could be. There is something called Reelfoot Lake formed when a large chunk of land in Tennessee dropped about 20 feet.

https://www.reelfoot.com/new_madrid_earthquake.htm [This site has vivid descriptions from that time.]

https://en.wikipedia.org/wiki/1811%E2%80%931812_New_Madrid_earthquakes [ This article has a number of clickable links.]

http://www.new-madrid.mo.us/102/Earthquakes-of-1811-1812 [This is the official New Madrid town site. Click the words “Strange happenings during the earthquakes” in the green box to the left.]
After reading these links, all I can say is Heaven help the poor people in the Mississippi basin if they are ever hit with comparable quakes with current buildings.

I was in a 7.5 in Mexico City (1957) which only killed about 150 people and collapsed very few buildings. That earthquake had a rolling quality like being on a NY subway train , and lasted for around a minute+. Mexico City is located on a mud lake bed so it quakes and oscillates rather than shudders. I was in the Mineral, VA earthquake (5.5), and where I was it was probably about 4. The wall and bed shuddered very intensely for about 15 seconds. The area where I was has hard clay on bedrock.

While researching this topic I found that Caracas, Venezuela had experienced a severe earthquake during that time that killed 20,000 people. These major earth convulsions can be felt over a wide area and affect different faults at the same or near same times. The great Lisbon earthquake and tsunami occurred about a month before the worst earthquake in Boston, USA. The great Pelee volcano eruption in Martinique that killed over 30,000 people was a day after one in nearby St. Vincent that killed 2 to 4,000. And during that year Santa Maria in Guatemala killed 5,000 and at least 2 other Caribbean Plate volcanoes were also active.