They've been big in the news for the last year and a half: earthquakes.
First, the M7 in January that leveled Port-Au-Prince and killed tens, perhaps hundreds of thousands. Then the M8.8 off of Chile in March that had all of us glued to our televisions one Saturday afternoon, waiting for a tsunami to strike Hawaii. Followed by an M7 near Christchurch NZ last September that would be the start of a remarkable and devastating sequence that is still ongoing, and then finally the big M9 off of Japan on March 11th of this year that may have killed an energy industry, in addition to drowning tens of thousands of people, and likely hampering an already weak global economic recovery.
It just so happens that I've found a couple of books that are quite accessible to the layperson in explaining this terrifying phenomenon. One discusses the threat to the Pacific Northwest, but not in fear mongering tones, and the other explains why predicting earthquakes remains beyond our grasp.
Cascadia's Fault: The Earthquake and Tsunami That Could Devastate North America
The title is pretty lurid, yes? But don't let that stop you. It's an incredibly excellent and level headed story on how the scientific consensus behind the threat the Cascadia subduction zone grew to what it is today. It's part detective story, part science story. And the best part of all is that it was written by a Canadian journalist (Jerry Thompson) who knew what he was talking about because he did his science homework. We all know I have issues with that, when they don't.
For the unaware, the West Coast is a plate boundary, well, a series of plate boundaries. In California (to roughly Cape Mendocino), the boundary is dominated by the infamous San Andreas Fault. This is where the North American Plate and the Pacific Plate meet, and they grind past each other. North of Cape Mendocino, it gets a bit more complex. Here, three plates meet at a triple junction--the Pacific, the North American, and the Juan de Fuca. The Juan de Fuca is the remnant of what was once a vast tectonic plate that North America has overridden over the last few dozen million years. On a front stretching from northern California to the Alaska/British Columbia border, the Juan de Fuca is subducting beneath North America, which gives the Pacific Northwest its spectacular geography. Volcanoes, mountains, and earthquakes.
Except there really aren't any earthquakes, and that was a puzzle. I mean there are quakes, deep ones in the Puget Sound area, and shallow ones elsewhere. The triple junction off of Cape Mendocino is quite active. Everyone knew about the San Andreas. Heck, it even has its own Twitter account. By and large, though, Cascadia is aseismic and people also assumed that Cascadia was dead. Early on one couldn't even find the signature of a trench (it's covered in sediment that's washed off of North America). Even then, from the 1960s to the early 1980s, Cascadia was assumed to be different than all of the other subduction zones ringing the Pacific, and elsewhere. Jerry Thompson highlights this deftly, through interviews, and primary sources.
How did they start to realize the threat? First, surveyors noted that coastal Oregon and Washington were deforming (in this case, actively rising). Deformation is a sign that strain is building and the fault is locked up tight. Then, up and down the coast, sunken forests were discovered, indicating that the land had dropped suddenly, as what happens in a large, subduction zone earthquake. These were coupled with many Native legends about the night the sea suddenly rushed in after the earth violently wrenched and writhed. Radiometric dating dated the most recent big drop to roughly 300 years ago. And there it sat until that most recent big drop, up and down the coast was connected to a tsunami in Japan that came out of nowhere and puzzled people all along the Japanese coast (coasts that would be scoured clean 311 years later in March of 2011). The quake was dated to late January, 1700. Tracking the time backwards we actually have a precise time and date for the last big Cascadia earthquake--January 26, 1700, 9pm local (Pacific, obviously) time.
As an aside, I have a textbook that was published shortly before the date was pinned down, which describes Cascadia as an enigma.
From there more data came in. Marine scientists went up and down the trench, tracking underwater landslides and mudslides off of the continental shelf. From their data they've determined a sequence of massive earthquakes have occurred, 41 in total, dating back over 10,000 years. Cascadia ain't dead by a long shot, merely sleeping. 19 of those 41 quakes ruptured the entire length of the zone, from SE Alaska/British Columbia to California, indicating the zone is segmented. It can go in a single pop, or it can break in bits (although those breaks can be huge quakes in their own right), and an infamous example of this is the Nankai Trough off of Southern Japan. Unfortunately, the Japanese mono-focus on this trough (deadly as it can be) led them to not fully appreciate other threats until it was too late.
The chapter where he describes the scenario quake isn't sensationalist in the least.
Also, a companion film to this would be the documentary "Shockwave", which the author also wrote.
Other nits include a lack of footnotes, although there is an extensive bibliography in the back, for those who want to read more.
I highly recommend this one, even though it has a forward that is word-for-word an article that caused me to rant earlier this year. Consider skipping over it. If you live in the Pacific Northwest especially within 300 vertical feet of the sea, this is one you probably should have in your library.
Predicting the Unpredictable: The Tumultuous Science of Earthquake Prediction
Dr. Susan Hough has written a fascinating survey on earthquake prediction. It certainly would be nice to be able to predict them, given the massive destruction and disruption they cause. At best we can forecast, but that leads to media articles stating "Fault X is overdue for a massive quake", which is not exactly correct.
The best forecast is admittedly vague. We can say that "Fault X has large quakes every 150 years, but this is an average, and even though Fault X's last quake was 160 years ago, this does not necessarily mean it's overdue because the clock isn't regular" which is not what the public really wants. They want precision, and that gives rise to hacks like @quakeprediction on Twitter, and the irritating buttload of supermoon and superflare and cosmic alignment people who think they have something that science has missed, or deliberately isn't telling them. Precision is what is wanted.
Hough does a great job at discussing the various methods throughout history. As recently as the 1970s, the US Government felt it could predict earthquakes, and had a USGS team working on it. The Soviets felt they had a method. The Chinese continue to crow they had a successful prediction in 1975 (Hough spends a chapter dissecting their claims as very murky). A spectacular failure in 1980, after a scientist predicted that Lima, Peru would absolutely be leveled, pretty much sealed the fate of this program (and it didn't help that a fairly anti-science US administration came along in 1981, although Hough doesn't say this.) Most of these methods were failures, although some may have promise, radon emissions possibly being one of them. She's good at noting those methods of prediction that may have promise.
Her main conclusion though, I felt, is that we really need to make sure the buildings we live and work in are safe, a conclusion she and Dr. Roger Bilham write about inAfter the Earth Quakes: Elastic Rebound on an Urban Planet , another book I highly recommend. She also declines to completely dismiss earthquake prediction, as perhaps someday we'll get it.
Both books are available in Kindle form, for those who like that.