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WASHINGTON – The western United States is overdue for a huge earthquake and tsunami much like the one that devastated Japan last week, and is nowhere near ready to cope with the disaster, experts say.
A volatile, horseshoe-shaped area known as the Pacific Ring of Fire has recently erupted with quakes in Chile, Japan, Mexico and New Zealand, and seismologists say it is just a matter of time before the next big one hits.
"From the geological standpoint, this earthquake occurs very regularly," said geotechnical engineer Yumei Wang, who is the geohazards team leader at the Oregon Department of Geology.
"With the Cascadia fault, we have records of 41 earthquakes in the last 10,000 years with an average of 240 years apart. Our last one was 311 years ago so we are overdue," she said.
If 'The Big One' hits, Madin said, "Buildings and bridges would sway back and forth, back and forth, and its hard for structures to tolerate repeated shaking for a long period of time. Most of the earthquakes in California last 20 seconds or 30 seconds, but we are talking about two plus minutes of shaking." The reason for the longer shaking: the Cascadia is 600 miles long, and it will take that to make its way from the bottom of the fault line to the top. Madin said, "We pretty much have to plan on Portland being two cities after this hits." He said our bridges would not be able to survive that much shaking.
Structural engineer, Kent Yu, specializes in earthquake structures at Portland based Degenkolb Engineers. He said, "We are living on borrowed time." Yu said all of Portland's bridges would likely collapse. He said 60 percent of buildings in downtown Portland would not be left standing, because they are not designed for earthquakes.
The observed horizontal strain rates indicate that strain is accumulating everywhere along the CSZ from Cape Mendocino to the Strait of Juan de Fuca. These observations do not indicate whether the strain will ultimately be released by a single great M$\sim $9 earthquake, by a sequence of smaller M$\sim $8 earthquakes, or by some other scenario. However, we find no evidence that the megathrust is segmented by shallow regions where strain is not accumulating, so the hypothesis that the strain could be released by a single great earthquake cannot be rejected. Measurements by recent GPS surveys and permanent GPS stations installed since 1996 [e.g.,Khazaradze et al., 1999], should soon provide greater spatial resolution of deformation and strain accumulation along the CSZ.
Originally posted by borutp
Nevada quake...just updated from 3.2 to 3.5....
I know it is small but anyway....
Originally posted by DaddyBare
Thanks for the link to your thread...
And like the guy from the video said
it might be Calif that gets it in light of the recent fish die off as well as whales coming into shore down in San Diego
guess we'll know but this time next week right?
A conventional model for strain accumulation at a subduction zone assumes that the plate interface slips at the long-term convergence rate at great depths but is fully or partially locked at shallower depths [Savage, 1983]. A model with 10$^circ $ dipping megathrust, a 100-km wide locked zone and a 75-km wide transition zone, where aseismic slip increases linearly with depth until it equals the plate convergence rate, adequately explains crustal shortening and vertical uplift observations in western Washington [Savage et al., 1991]. Similar models are consistent with deformation observations in Vancouver Island, vertical uplift along the CSZ margin, and thermal modeling [Flück et al., 1997].
Horizontal deformation within the southern CSZ is more poorly known. Between 1987 and 1999, the U. S. Geological Survey (USGS) used GPS to recover the positions of survey benchmarks in this region previously measured by triangulation, trilateration, or GPS techniques. We use these observations to estimate horizontal strain rates, which indicate that strain is accumulating everywhere along the CSZ from Cape Mendocino to the Strait of Juan de Fuca and do not rule out the possibility that the entire CSZ could rupture in a major M$sim $9 earthquake [Murray and Lisowski, 2000].