Thanks, some of the supposed scholars that have chimed in may wish to review your notes.
Have heard that here in US the Cascadia subduction zone is ripe for some action. You agree?
We all joke about things, and speculation is what makes us us.
Throw a ribeye on for me and let's shake up the 'viros. This has all the hallmarks of good science.
Earthquakes are not my specialty, so I will defer to folks who have studied not only earthquakes, but the sediments that result from earthquake events. One type of these is called a turbidite, a deposit that results from a slurry of sediment moving downhill and coming to rest under water. These have a classic coarse at the bottom, finest sized sediment at the top, and grading upward appearance, and are separated by ordinary very fine sediments that make it far offshore before settling to the bottom. The record of these only reliably goes back in this region as an earthquake indicator to the last ice age, because during the ice age sea levels were far lower, and rivers dumped into the ocean down river channels that are submarine canyons and estuaries today, leaving sediments which resulted from storms when sea level was lower, and make the record less clear in terms of what can be attributed to earthquakes during the ice age and before.
Correlating turbidites believed to have been caused by earthquakes and tsunami sediments onshore with a fairly high rate of correlation and closely matching carbon dates, gives an historical record reaching back to the last ice age of major earthquake events.
Using that information:
Oregon State University researchers determined:
“Over the past 10,000 years, there have been 19 earthquakes that extended along most of the margin, stretching from southern Vancouver Island to the Oregon-California border,” Goldfinger noted. “These would typically be of a magnitude from about 8.7 to 9.2 – really huge earthquakes.
“We’ve also determined that there have been 22 additional earthquakes that involved just the southern end of the fault,” he added. “We are assuming that these are slightly smaller – more like 8.0 – but not necessarily. They were still very large earthquakes that if they happened today could have a devastating impact.”
Using interval analysis, basically determining the average time between earthquakes and attempting to apply that to the last historically known earthquake there (1700, by Japanese records of harvested rice crops destroyed in the warehouses by the tsunami) the zone is considered 'overdue' for a major earthquake, but probabilities for one in the next 50 years are given at 40 percent. Because stresses build over time, even though the mechanisms which cause that buildup are not necessarily constant and steady, the time interval is one indicator of increasing risk, with the assumption that stress on the fault zone has increased, much as it has in the past.
According to one of the co-authors of the study, Jay Patton,
“By the year 2060, if we have not had an earthquake, we will have exceeded 85 percent of all the known intervals of earthquake recurrence in 10,000 years,” Patton said. “The interval between earthquakes ranges from a few decades to thousands of years. But we already have exceeded about three-fourths of them.”
Now, one of the flaws in the concept of uniformitarianism is that though processes operate under the same fundamental physical laws, processes don't necessarily operate at the same speed or intensity over time, and that is what makes predictions so problematical. That said, the general indication is that earthquake risk for the region is increasing, and with the historical frequency for major earthquakes higher (with slightly less severe earthquakes) in the south part of the zone, that is where the next earthquake seems more likely.
As yet, the experts won't predict an earthquake at some given time and place, mainly because they could easily end up in a 'cry wolf' situation. Failure to predict would make them the subject of potentially life-threatening animosity, predictions that did not manifest themselves would cost millions or billions in lost revenues and likely many lives in the ensuing panic, so they just don't go there. I don't blame them.
Here , for those who are interested is a link to the study abstract with other links to reference studies and the main paper (USGS):
Turbidite Event History—Methods and Implications for Holocene Paleoseismicity of the Cascadia Subduction Zone
