Predicting the Earthquake That Could Wreck New York

From time to time, the floor shakes, in some locations extra typically and extra dramatically than others. New York shouldn’t be California. However, Brooklyn chimneys fell and home windows have been damaged in the summer season of 1884 when an earthquake struck close to Coney Island: magnitude 5, or thereabouts. (Seismometers weren’t in widespread circulation then.) Anything bigger, amid right now’s infrastructure, would trigger fairly a bit of harm. But we now have little information on how typically such an earthquake happens. “Every thousand years, every ten thousand years, every million years?” William Menke, a seismologist at Columbia’s Lamont-Doherty Observatory, requested just lately, given the potential devastation of the metropolitan area. “It makes a difference!” Many massive earthquakes have occurred on the East Coast, he defined. We simply do not know when.

Menke was climbing a mountain in Harriman State Park, close to the Ramapo fault, to attempt to fill in the gaps. He was searching for rocks whose form and placement gave him a way of existential consolation fairly than concern. “That’s what started me thinking about it,” he mentioned, arriving at a bobsleigh-sized boulder perched close to the fringe of a shallow cliff. “That has to say something significant about the amount of swings that have occurred since it was placed there. If there was too much swing, it would have fallen.” A climbing companion could not resist a futile push. The stone was deposited there, in fact, by a glacier. “Everything here smells like the Ice Age,” Menke mentioned. The final of the glaciers melted in these components about fifteen thousand years in the past. Good luck.

The two continued to climb, searching for more and more precarious rocks. Some have been too small to exclude human intervention. “You can see somebody moved those big rocks into a bench configuration,” Menke famous of an association, subsequent to the stays of a campfire. Another stone, intriguingly very heavy, landed in a crack, making it tougher to take away, and subsequently unworthy of consideration. Menke bent over the others to sketch their contours on a pocket book and measure the slope of the cornerstone, utilizing a carpenter’s stage and a bevel, which he had paid eight {dollars} for at Lowe’s. “Most of the things I do are pretty low-tech,” he mentioned. “I’ve occasionally lost things in the field and then found them six months later, a little rusty.”

Menke’s grey hair was unkempt and, like a few of the rocks he examined, seemingly defying gravity. His fixation on geology was such that he failed to note a galloping previous, though he did draw consideration to a small discoloration in the rocks at one level. “See the surface here? Something was protecting this from erosion. Were there any rocks there that rolled away? Where is it?” Using some back-of-the-envelope physics, he estimated the amount of gravitational acceleration required to send various candidates to his notebook sliding downhill. “The last one we did was on a gentler slope, and it was around gravity three,” he said. “So that would be about a magnitude seven and a half.” In contrast, a giant sea turtle-shaped rock on a steeper slope seemed likely to skied a magnitude 7. “So, it’s actually an interesting number,” Menke mentioned. “If you can rule out that there’s been any magnitude 7 earthquakes since the end of the Ice Age, that’s actually pretty significant in terms of New York’s seismic hazard.”

Proper science would require following it up with subtle digicam know-how, photogrammetry and 3-D laptop modeling. “I’ll tell you a funny story about a Greek boy,” Menke mentioned, referring to the astronomer Aristarchus, who tried to estimate the distance from the earth to the solar. “He did a pretty good job, but there was one critical piece of information he needed to know, and that was the angular diameter of the sun. It’s half a degree, and he thought it was two degrees. If he had been careful to measure things, he would have gotten the right number.” For now, although, Menke took consolation in what the free eye was telling him. Then once more, a magnitude 7 earthquake is a thousand instances extra highly effective than a magnitude 5. Think Haiti in 2010, fairly than Coney Island in 1884.

Pausing for a water break earlier than starting his descent, Menke ran his hand over one other rock and broke off a chunk of crusted stone or lichen. “Very low nutritional value,” he mentioned. “But if faced with a choice between eating rockslide and dying, you eat rockslide.” ♦