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For the most part, completely true. Subduction zone quakes are the most powerful (as compared with the San Andreas, which is for the most part a strike-slip fault). Several comments about the article.Originally posted by Carolinian
- He mentions that the area of free movement on the San Andreas divides the San Andreas into smaller segments. Many geologists do not agree with that premise. The reasoning, which I think is quite sound, is that we can establish how much energy is being stored per mile along the fault based on the overall movement of the San Andreas. We also can determine how much energy is being dissipated by the smaller movements in the "free movement" portion of the fault, and there is a large discrepancy between the two numbers. The activity in the area appears to be far short of what is needed to dissipate the energy.
- While the San Andreas is a strike-slip fault, as it traverses the Los Angeles basin it is in an east-west dogleg. Since the movement of the two crustal plates is mostly north-south, this means that in the LA Basin the two sides of the fault are butting into each other instead of sliding past each other. This creates "thrust" faulting, which is the same type of movement that occurs in a suduction zone quake. This is also why the mountains associated with the San Andreas Fault in the dogleg area (notably the San Bernardino, San Gabriel, San Jacinto, and Santa Ynez ranges) include all of the tallest peaks along entire length of the San Andreas.
I'm not saying that the the LA Basin is likely to see an 8.9 subduction zone quake; the area of thrust faulting simply isn't that great. But it does mean that the San Andreas hazards in the LA Basin are greater than those generally associated with strike-slip faults, and the portion of the San Andreas that is in the LA Basin is the portion would be expected to generate the most violent shaking on the fault.
- He is incorrect when he suggests that Portland and Seattle having the same tsunami risk form a subduction zone quake as Sendai. Both Portland and Seattle are separated from the coast by the Coast and Olympic Mountains. Any tsunami approaching those cities would have to pass through watergaps that would severely constrict and restrain the flow of water (for Seattle that is the Strait of Juan de Fuca, as well as the various narrows in the San Juan Islands; for Portland that is the river bluffs between Astoria and Portland). The amount of water getting past these points would be reduced, and the tsunami would be slowed down, providing additional response time.
The tsunami would be devastating in communities right on the Pacific Cost - all low-lying land in towns such as Newport, Coos Bay, and Eureka would be totally devastated. Towns that face directly onto the Strait of Juan de Fuca will also be devastated - while the Straits will slow down the tsunami and reduce it's flow, the restriction will cause water to stack up within the Straits themselves. So Victoria and Port Angeles will likely be completely destroyed.
- Among Vancouver (BC), Seattle, and Portland, Vancouver is likely to receive more damage because Vancouver has somewhat more direct exposure to ocean. Seattle would receive the least impact because it has the most upstream flow restrictions and it has less low-lying lands along the waterfront.
Along the Columbia River, Longview/Kelson would likely have significant damage; being located at what would be the discharge from the water gap and having extensive low-lying land, water would likely come through the gap with considerable velocity and hit Longview and Kelso without having much time for the energy to dissipate. But as the water that did get through the gap headed to Portland it would face an ever widening river channel area with lots of land over which the force would dissipate. St. Helens, OR and Kalama, WA would probably have a lot of damage.
“Maybe you shouldn't dress like that.”
“This is a blouse and skirt. I don't know what you're talking about.”
“You shouldn't wear that body.” -
Same for here, the New Madrid fault.RCI Member Since 24-Aug-1989/150-plus Exchanges***THE TIMESHARE GRIM REAPER~~~Exchanging/Searching/SW Florida/MO/AR/IA/Consumer Advocacy/Estate Planning/Sports/Boating/Fishing/Golf/Lake-living/Retirement****Sometimes ya just gotta be a dickComment
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If I was placing money on where the next big earthquake will occur, I would bet that it will be here, along the New Madrid fault. It wouldn't take a magnitude 8 earthquake to cause signficant damage because most of the buildings there aren't built to withstand an earthquake. Arkansas has been having a slew of small tremors for quite some time, and they seem to be increasing in intensity. So there appears to be some pressure building in the area. And many geologists believe the area is long overdue for a big quake.Originally posted by JLB View PostComment
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I was gonna say that, but it is felt that is because of natural gas drilling in the area . . . slake wells precisely. That is not far from here, and one of our nephews is on one of the crews . . . one of the two nephews that did Katrina cleanup.Originally posted by longtimer View Post
Arkansas Earthquakes Decline After 'Fracking' Injection Well Closures
We have earthquake insurance. Always have had it here.RCI Member Since 24-Aug-1989/150-plus Exchanges***THE TIMESHARE GRIM REAPER~~~Exchanging/Searching/SW Florida/MO/AR/IA/Consumer Advocacy/Estate Planning/Sports/Boating/Fishing/Golf/Lake-living/Retirement****Sometimes ya just gotta be a dickComment
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Glad to hear the incidence of ground shaking is declining. Stay safe! Hopefully you also have a emergency preparedness plan just in case.Originally posted by JLB View PostComment
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Yup, bend over and . . . well . . .Originally posted by longtimer
RCI Member Since 24-Aug-1989/150-plus Exchanges***THE TIMESHARE GRIM REAPER~~~Exchanging/Searching/SW Florida/MO/AR/IA/Consumer Advocacy/Estate Planning/Sports/Boating/Fishing/Golf/Lake-living/Retirement****Sometimes ya just gotta be a dickComment
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