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Artificial quakes cause less shaking, study finds

| Monday, Aug. 18, 2014, 8:21 p.m.

WASHINGTON — Man-made earthquakes, a side effect of high-tech energy drilling, cause less shaking and in general are about 16 times weaker than natural earthquakes with the same magnitude, a federal study found.

People feeling the ground move from induced quakes — those that are not natural, but triggered by injections of wastewater deep underground— report significantly less shaking than those who experience normal earthquakes of the same magnitude, according to a study by Geological Survey geophysicist Susan Hough.

Distance matters in this shaking gap, however. For people within 6 miles of the fault, artificial and natural quakes feel pretty much the same, she said.

Hough studied similar-sized man-made and natural quakes in the central and eastern United States from 2011 to 2013, comparing the reported magnitude to what people said they felt in the USGS electronic “Did You Feel It” survey. She found that while two types of temblors may have had the same magnitude as measured by seismographs, they had distinct differences in what people said they felt.

The way artificial quakes felt was equivalent on average to a natural quake that had a magnitude 0.8 smaller. So a 4.8 induced quake felt like a 4.0 quake, Hough said. The magnitude scale used by USGS and others is mathematically complex, but a drop in 0.8 magnitude translates to about 16 times less strength or energy released.

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