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Slippery slope” is an all-purpose image. People use it to damn the havoc that others might set in motion.
Or it might depict the kind of “slippery slope” that lets the Earth’s tectonic plates slip along fault lines to start earthquakes.
Either image fits a public rift that is in the news out of Oklahoma. A current snarl in the quest for oil involves earthquake risk.
For many years, hydraulic fracturing (“fracking”) has helped produce more oil and gas in Oklahoma. More and more fracking produces more and more oil and gas.
In recent years, more small earthquakes also have occurred in Oklahoma.
Does the fracking trigger the small earthquakes? Statistically speaking, the answer appears to be yes.
Oklahoma always had Earth tremors, averaging about 50 per year, almost all of them minor. In the past three years, the state has had thousands of quakes, with more than 2,600 in 2013.
Most of the quakes were too slight to be felt, but a few damaged a few houses and one injured two people.
Actually, the data say that wells for disposing of wastewater from fracking may relate to quakes more than fracking itself. Lands around disposal wells have had jiggles following strong, distant earthquakes.
The next questions sharpen the debate. Do small earthquakes raise or lower the risk of a big earthquake? Could small quakes help us? Answers take time.
First, the basics: How do earthquakes start? The Earth has a molten mass inside and massive, movable rock formations (tectonic plates) nearer the surface, which play parts in volcanos and earthquakes. The Earth’s rotation, gravity and heat combine to create powerful geologic forces that tug on the Earth’s rocks.
But adjacent plates do not slip smoothly past each other; there is friction. They get stuck or “pinned” by jagged surfaces.
When adjacent plates can’t move, Earth’s forces keep building stress along the fault line between them. As in a long and mighty tug-of-war, the pressure to move keeps growing for long times, yet nothing moves.
Finally, on one grim day the plates slip, the rock moves a large amount in a moment and makes a large earthquake. Faces of suffering fill the news.
Logic suggests if the rocks could slip more easily, they would move more often and each shift would be smaller, thus safer. We might reason that many small earthquakes would relieve stress and make big quakes less severe.
We do not yet know whether nature is so obliging.
An earthquake is described by how much energy it releases.
For example, the Richter magnitude scale describes the energy from a quake, ranging from less than magnitude 2 to more than 9. People notice an earthquake of magnitude 4, but it does little harm. A magnitude 6 quake damages many buildings and can kill thousands.
The scale is such that the energy released in a magnitude 6 quake is 1,000 times greater than in a magnitude 4. In general terms, it takes thousands of small quakes to relieve enough stress to affect the most damaging quakes.
We may need many more, not fewer, small quakes to avoid one big quake.
Years hence, science might prove that starting small quakes indeed reduces the severity of big quakes. Think of the legal tangles the news will spawn.
Imagine the triggering of many small quakes to reduce losses from worse quakes. A fair portion of the deaths and damage from big quakes may end, but they are not stopped entirely. The small man-made quakes harm some properties and people.
For the losses that are not stopped and for the harm done, who will pay how much money to whom? Such is the world of risk.
John Bartlit is a member of New Mexico Citizens for Clean Air and Water.