Everybody knows it’s coming, later — or maybe much sooner. There’s been a resurgence of earthquake interest recently, with the 50th anniversary of the Great Alaska Earthquake on March 27. That 9.2-magnitude event lasted four minutes — an eternity when the ground is rocking — and killed 147 people. It also solidified the then-shaky theory of plate tectonics.
Now, a new book by Camas native John Dvorak updates our understanding of earthquakes and how they behave.
In “Earthquake Storms: The Fascinating History and Volatile Future of the San Andreas Fault,” Dvorak notes that it’s been just over 300 years since the last major seismic event along the Cascadia Subduction Zone. That zone marks the shifting, shuddering boundary between two enormous tectonic plates, and it’s not far from here, off the Pacific Northwest coast.
Fifteen major earthquakes have occurred in the zone in the past 3,000 years, Dvorak writes, and it’s typical for a big one to hit every 120 years or so. To put it plainly, we’re overdue. Furthermore, Dvorak draws causal connections between Cascadia quakes and quakes along the far more famous San Andreas fault, which runs almost the entire length of western California.
Every time but one, those 15 Cascadia quakes “were followed soon after by rupture of the San Andreas fault. Such a cause-and-effect sequence has been a surprise and shows scientists how a single large earthquake could lead to many more large, regional earthquakes.”
Call it an earthquake storm. Quakes tend to cluster and set one another off, Dvorak writes. Since it’s been hundreds of years since Cascadia shook hard, and since relative calm has followed a series of big quakes along San Andreas in the 1800s and up to 1906 — when San Francisco was mostly destroyed by one — Dvorak concludes that huge seismic pressures are building in both places.
But don’t worry, California won’t topple into the ocean. Rather, it’ll disintegrate: “The San Andreas Fault and its many subsidiary faults are slowly tearing California apart, so that much of what is California today will be transformed into a collection of islands that are destined to be rafted northward across the Pacific.”
An earthquake storm has been underway since 1939 in northern Turkey, where 13 big ones have hit, and another has brought 10 major quakes to central China since 1893, Dvorak writes.
“Earthquake Storms” isn’t all prediction of devastation. It also examines colorful early earthquake scientists — such as mountain namesake Josiah Whitney, who was “puzzled by many geologic peculiarities in California,” especially weathered granite and marine sediment sitting side by side. Now we know they came together due to sliding and folding plates.
Perhaps appropriately, the inventor of the earthquake scale used throughout the last century, Charles Richter, had an unpredictable, devastating temper. “And there seemed to be only two ways he could control his rages,” Dvorak writes: “Either by intense calculations of seismic wave paths or by attending nudist colonies.”
Dvorak has led a colorful life too: he studied aeronautical engineering and then planetary geophysics before studying volcanoes with the U.S. Geological Survey in locations as far flung as Italy and Indonesia — not to mention Mount St. Helens during its “Big One” in 1980. Today, Dvorak operates a large telescope at the mountaintop Mauna Kea Observatories in Hawaii.
Bits ‘n’ Pieces appears Fridays and Saturdays. If you have a story you’d like to share, email bits@columbian.com.
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