Here in the Pacific Northwest, we get a lot of buzz about The Big One - which, assuming we haven't all been killed by man-made global warming - will strike at any time and kill us all. The Cascadia subduction zone, an area where the Pacific plate is diving under the North American plate is due to break loose at any time, and we're "overdue" for a mega-quake. So there's a lot of "planners" planning and a lot of quake-proofing and a lot of lip-flapping over here.
But we're hardly alone: the central United States is also planning for a giant earthquake; the city of Memphis paid $64 million to remove nine floors of the Memphis VA in order to reduce the risk of collapse in a catastrophic earthquake. Back in the winter of 1811-1812, three large quakes occurred in the then-sparsely populated area, but there are a lot more people around today, and so there's a whole lot of retrofitting going on.
The shocks occurred on what today is the least understood seismic zone in the United States. And depending who you ask, another major earthquake here represents either a towering threat for which the Central U.S. is woefully unprepared, or a wildly overhyped phantom costing taxpayers hundreds of millions of dollars in needless infrastructure improvements.
The thing is, yes, there are faults under the surface. There are subsurface faults everywhere. But faults aren't what produce earthquakes; strain does that.
Along the San Andreas, the ground is warping at a rate of 40 millimeters per year.
So there's a lot of strain down there, where again, the Pacific plate is diving under the North American plate. And that is not happening in the Midwestern USA. In fact, movement there is between zero and 2 millimeters per year - most of which is related to fragments of the Juan de Fuca plate returning to Earth's mantle, and water movement in the Mississippi River. And of course, until 12,000 years ago, the area was covered in ice sheets more than a mile thick - which was doubtless due to man-made global cooling....
In any event, all of that ice compressed the substrate, and now that the ice is gone, it's still slowly uncompressing. Is all of this cause for worry and expensive retrofitting measures?
In the words of geologist Charles Richter himself who once scoffed, “I don’t know why people in California or anywhere worry so much about earthquakes. They are such a small hazard compared to things like traffic.”
“A good number to remember is that earthquakes kill about 10 people a year in the United States,” Stein says. “Which is about the same as skateboards.”
If it seems as though there's far too much worry about earthquakes in the USA - and far too much spent on remediation, you may be onto something:
In Chile, home to the largest earthquakes in recorded history, the Nazca Plate is diving under South America at 80 millimeters per year, or twice that of California.
They certainly have reason to be concerned, as do those of us living on the Ring of Fire. But the American Midwest? Not so much. There is, however, a lot of money to be made in the business of scaring people to death.