Caribbean earthquake

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The Great Midwest Earthquake of 1811 | Science | Smithsonian Magazine

“The ground heaved and pitched, hurling furniture, snapping trees and destroying barns and homesteads. The shaking rang church bells in Charleston, South Carolina, and toppled chimneys as far as Cincinnati, Ohio”

“Each New Madrid earthquake had a magnitude of 7.5 or greater, making them three of the most powerful in the continental United States and shaking an area ten times larger than that affected by the magnitude 7.8 San Francisco earthquake of 1906.”

Earthquakes

"Indiana and Illinois lie in the most seismically active region east of the Rocky Mountains. This region consists of two main areas, the New Madrid Seismic Zone and the Wabash Valley Seismic Zone. These zones – or areas that are prone to earthquakes from one fault ‐ include many geologic faults that are capable of producing earthquakes. Jasper County, IN is located in close proximity to many of these potentially unstable faults."

Right now I can't help thinking about all of those tall glass and steel buildings in downtown Chicago.
 
Right now I can't help thinking about all of those tall glass and steel buildings in downtown Chicago.

Hi KathyV,

Disclaimer: I am not an engineer and may not be using accepted nomenclature or describing the events to a scholars level of understanding.

I would not worry very much about those buildings. They are built to a higher standard. It the residential homes, small buildings and highway overpasses that will fail in the Midwest. Skyscrapers are also designed to withstand high wind events. That design criteria can help them survive an earthquake. Steel is wonderful for its ability to twist, stretch, bend, and not fail--if properly connected and sized.

Out west, I watched overpasses being re-built after being felled by earthquakes. They were designed to withstand an earthquake of magnitude 8 (as I recall) on the Richter scale. Many of those same overpasses were dropped by the Northridge event. The motion was different in Northridge, and its acceleration factor was greater.

The midwestern overpasses and bridges will fall like dominos if a 6, 7 or 8 Richter scale earthquake hits this area. They will suffer long-column buckling like in the El Centro event. Or, their abutments at either end will move in the opposite direction from the bridge itself like in Sylmar, Northridge and Loma Prieta.

Modern western bridges are not attached at their abutments. They are in slip joints. After Northridge, these bridges showed signs of large scale movement at their abutments. The blind eye could gauge the slippage from 50 feet away. Most of those bridges survived. Their columns did not suffer long-column buckling (search "Cypress Structure collapse in Oakland California, Loma Prieta event).

My house is 5 years old and built by a major regional builder. It is not attached to its foundation at all. I don't mean minimally attached, I mean at all. After Homestead and Northridge, our standards out west were stepped-up again. Lateral and uplift loading hold-down features are built-in in modern western homes. Not here.

But, but, Homestead was a hurricane event...you DUMMY!

Yeah, it was. Out west, our staple sheathing nailers were banned. We had to use "hurricane" ties to connect our roof structures to shear walls and ultimately, foundations. Homestead Florida changed the UBC and the California Building Code. Seismic events and wind events can apply similar lateral loads to a structure. Roof and floor diaphragms are critical to a structures survival.

The Japanese know how to build. We learned from Kobe and other Japanese events.

I was a western project manager and builder.

Hold downs, PA's, drag trusses, and enhanced shear walls. Every engineered feature is connected to concrete, top to bottom, in western homes/buildings. Not my house in Ohio. Western homes are designed to withstand uplift and lateral motions at the same time. Not my home.

Out west, we did not build homes to survive earthquake events unscathed. We built homes to remain standing long enough for the occupants to evacuate the building. Building officials may very well condemn the homes I built after a major event. I will feel great if the occupants walked away from them, minimally injured.

cheers,
m
 
They are still experiencing aftershocks in the Caribbean, Cayman recorded a 4.4 magnitude earthquake on Wednesday.

Updated: 4.4 earthquake shakes Cayman | Cayman Compass

They say Cayman was "rattled" but no one that we know felt it. We were eating in a restaurant at the time and had no idea the aftershock occurred until the next day when I checked the USGS website, which since the "big one" I now do daily. We received over 14 aftershocks all around 4 to 4.3 the day or so after the big one, and except for one 6.1 none of us felt those either. There has been no other activity over the past couple of weeks except for Wednesday's 4.4.

Interestingly there are over 50 quakes of magnitude 2.5 or greater somewhere in the world every day. Also interesting is that Puerto Rico has been experiencing almost continual small grade quakes for the past couple of weeks (at least - just started monitoring after the CI quake).
 
"Indiana and Illinois lie in the most seismically active region east of the Rocky Mountains. This region consists of two main areas, the New Madrid Seismic Zone and the Wabash Valley Seismic Zone.

Since my early teaching days 40 years ago, my students and I have been waiting for the big one!
 
They say Cayman was "rattled" but no one that we know felt it. We were eating in a restaurant at the time and had no idea the aftershock occurred until the next day when I checked the USGS website, which since the "big one" I now do daily. We received over 14 aftershocks all around 4 to 4.3 the day or so after the big one, and except for one 6.1 none of us felt those either. There has been no other activity over the past couple of weeks except for Wednesday's 4.4.

Interestingly there are over 50 quakes of magnitude 2.5 or greater somewhere in the world every day. Also interesting is that Puerto Rico has been experiencing almost continual small grade quakes for the past couple of weeks (at least - just started monitoring after the CI quake).

Ok I DID feel the "jolt" from this one. It was quick, no shaking but like a one time Kerpow. I was sitting on a 2nd floor balcony overlooking Governors Harbour. Thought at first it was the remodeling going on downstairs, but out of character for even that.
 
We felt it too. Almost like a rumble. Nothing like the 7.7. We too are in Governor’s Harbour. Most people we know definitely felt it. Most who did not were driving.
 

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