Tag Archives: tsunami surges

Reality of a mega quake on the Juan de Fuca fault would equal multiple Katrinas, and for some the best plan is to run

Mathew 24:7 For nation will rise against nation, and kingdom against kingdom, and there will be famines and earthquakes in various places.

Important Takeaways:

  • A Disaster the Size of Multiple Katrinas Is Building Off Washington’s Coast
  • Someday — next week, next year, maybe next century — a sudden and deadly marine shock will strike the Northwest coast: what locals call the Big One, a circa 9.0-magnitude offshore earthquake generating tsunami surges reaching 60 feet high or more
  • The offshore Juan de Fuca Plate, is what’s left of a continent-sized plate that has for the past 200 million years been intermittently sliding under the larger North American Plate, an actual continent, in a process called subduction
  • The Washington coast is the likeliest target zero for the next megaquake and tsunami.
  • The sliding-under movement of subduction is very different from the side-to-side grinding of the San Andreas Fault to the south. There, frequent movements, experienced as earthquakes, release tectonic tension before it builds to catastrophic levels. Along the Subduction Zone, however, this tension builds for hundreds of years and releases with explosive force. When the Juan de Fuca Plate jams farther under the North American Plate, it will push it up 30 feet or more and displace vast quantities of seawater. And a tsunami will be born.
  • The last Cascadia earthquake, with an estimated magnitude of 9.0, occurred around 9 p.m. on Jan. 26, 1700, a date known precisely thanks to meticulous Japanese records…
  • They’ve now identified more than 40 earthquakes along the subduction zone in the past 10,000 years, nearly all in the 8.2 to 9.2 magnitude range — one every 240 years on average
  • The smallest had an estimated magnitude of 7.5, the same as the devastating recent quake in Turkey and Syria.
  • “Megaquakes” of 8.7-plus magnitude, capable of generating large tsunamis, have averaged 430-year intervals.
  • Five appear to have reached the magnitude (9.1) of Japan’s 2011 Tōhoku (Fukushima) Earthquake and the 2004 Sumatran quake whose tsunami killed 228,000 people in 11 countries.
  • After 323 quiet years, another could strike anytime.
  • According to new draft data from that agency, 112,555 residents of the four counties lining Washington’s ocean coast and Strait of Juan de Fuca live in the inundation zone — land that tsunami waves will overrun.
  • Earlier benchmarks suggest that 23 percent will be unable to reach higher ground in time and 18 percent — perhaps 20,000 people, more than 10 times the number who died in Katrina — will be washed out to sea or crushed by debris.
  • These estimates don’t account for the tens of thousands of tourists and nonresident workers who would likely be in the area if the tsunami struck during the day, or the 63,000 inundation-zone residents zone along Puget Sound and the inner straits, or an estimated 1,100 people across the region who would die in the initial shaking.

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