By TAMARA AUDI – Wall Street Journal – August 18,2014
When it comes to making earthquakes, Mother Nature still packs the most powerful punch, a new study says.
Quakes believed to be caused by human activity, such as those associated with oil and gas extraction, don’t produce as much shaking as naturally occurring temblors of similar magnitudes, according to research released Monday by Susan Hough, a seismologist with the U.S. Geological Survey.
Using data collected from the public following 11 moderate earthquakes between 2011 and 2013, Ms. Hough’s study says that shaking felt from so-called induced quakes is less intense for distances beyond 6 miles from the epicenter. But shaking at the epicenter was as intense as naturally occurring quakes. That means damage from an induced quake is likely to be more concentrated at its epicenter.
“It turns out there’s a big difference between these induced earthquakes and natural earthquakes,” Ms. Hough said.Compared with naturally occurring quakes, “these induced quakes are essentially wimpy in terms of the shaking they’re creating” farther from the event, Ms. Hough said.
It is unclear why the induced quakes seemed to weaken more quickly than natural quakes, Ms. Hough said. One possible reason such quakes may release less energy is that the fault involved ruptures before it reaches its natural breaking point, she said.