With 100% of California suffering from either drought, “extreme” drought, or “exceptional” drought, it’s time to take a closer look at one study from the journal Nature that correlated water depletion and earthquake risk.
That’s right: our drought and water use could put us at heightened risk for quakes. It’s not pretty, but it’s worth understanding more than it’s worth panicking about. So here we go with the (very scientific) language of the study:
“Our results suggest that long-term and late-summer flexural uplift of the Coast Ranges reduce the effective normal stress resolved on the San Andreas Fault. This process brings the fault closer to failure, thereby providing a viable mechanism for observed seasonality in microseismicity… and potentially affecting long-term seismicity rates for fault systems adjacent to the valley.”
“Flexural uplift” of mountain ranges refers to little height increases: in this case, just about an inch per decade. But that extra inch of “flexural uplift” could, the study argues, be the result of water depletion.
Imagine a tarp weighed down in the center with water. When the water evaporates or is sucked up somehow, the surface of the tarp rises without its weight. The earth’s surface works in the same way, rising slightly as we deplete water from it. In fact, the loss of mass due to water depletion in California has even changed our gravitational field.
As a result of flexural uplift, the balance struck by the San Andreas Fault (or the “effective normal stress” it “resolves”) gets thrown off, increasing quake risk. Seasonal patterns of small earthquakes back this up, aligning with seasonal water usage in California.
So will our big drought bring on the next “big one?” That’s unlikely, scientists say— though, ready or not, it’s coming for us someday.
[H/t: Reset SF, Nature,CBS8; photo via Flickr user Anthony Quintano]
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