Based on a massive archive of thousands of sea-floor soil samples analyzed meticulously for years, scientists report that there have been 19 mega-earthquakes in the last 10,000 years. A mega-earthquake is considered one whose impact is global, or hemispherical. The frequency of mega-earthquakes is approximated at an average of one every 500 years. Two places have been identified by experts where a mega-earthquake may occur soon. Curiously, both are within the American continent.
One is in Cascadia in Northern California. The last mega-quake here was circa 1700. The nearest population center is Seattle, a mere 150 kilometers away. The Cascadia fault line is a 1,000-kilometer stretch along the Pacific coast where extreme tectonic forces are colliding. An area the size of Ireland has moved very slowly by 10 meters against the continent since the 1700 disaster.
What baffles scientists is the fact that the Cascadia fault line moves only exactly every 14 months. The rest of the time, it is in deep slumber. Such regular movements release energy, which helps dissipate a future mega-quake. But scientists believe these are not enough to contain the next mega-earthquake, which will churn a series of 15-meter-tall tsunamis across the entire Pacific.
Computer simulations predict rapid shaking of the ground. If protracted for five minutes, this extended tremor will liquefy the soil, which will easily bring down the most earthquake-proof skyscrapers of Seattle. The predicted Cascadia mega-earthquake is called “skyscraper killer.”
The predicted epicenter is 50-meter inland. Scientists predict that a mega-earthquake will extend all the way to British Columbia and Southern California. It will encompass other population centers, such as Portland in Oregon and Vancouver in Canada. The tremor will reach speeds of 11,000 kilometers per hour on land, and three kilometers per second in the sea. It will reach Seattle in 30 seconds, Hawaii in four hours, and Japan in eight hours. Multiple tsunamis will occur for many hours, even a day. Thousands of aftershocks are predicted to occur within the span of a year.
This will “resurrect” many dead volcanoes along the western seaboard of the American continent, dominated by the notorious Mt. St. Helens, which exploded recently. The Cascadia mega-earthquake can be called “the volcano catalyst.”
The second predicted mega-earthquake is in Memphis, Tennessee, which is ironically not an earthquake prone area. There are no geological signs of upheavals, only serene plains and valleys. The last mega-earthquake here occurred in 1811. Earthquakes had been occurring every 500 years since 40 to 50 AD. In 1811, the ground shook on and off for months, with three or four large quakes on top of thousands of aftershocks affecting a 1,000-kilometer area. Water spewed like geysers from large fissures as much as 30 feet high. These “geysers” left remnants today of three feet of sand across large areas.
The predicted epicenter is below the Mississippi River, whose course will be reversed to flood the upstream area for kilometers in case of a quake. Excavations revealed part of the series of disturbances for the last thousands of years, where extensive ground liquefaction was a prominent feature.
Using a new technology combining sonar and x-ray, “geo-phones” have discovered a complex labyrinth of crisscrossing faults deep in the ground. Many of these are hidden beneath the Mississippi River. Memphis itself is close to a major fault line. An earthquake of magnitude 6 is predicted in the next 50 to 90 years. In 1811, for a year, there were major quakes four times a week out of 200 mini-earthquakes of magnitudes of 1.5 to 4.
Mega-earthquakes of global extent have been prophesied — Marian messages, Nostradamus. The problem is the two Ps, namely prayer and preparedness. Prayer can “defer” or reverse the wrath of the Lord, but people mostly pray only when it is too late.
About preparedness, major population centers are mostly never ready for such a massive eventuality. Even Kobe is just “half-ready,” if we are to talk of the sheer volume of casualties in a mega-disaster.
(Sources: National Geographic documentary, Wikipedia)