The question has been raised again and again: Does hydraulic fracturing really cause the earth to shake, rattle and roll?

Well, apparently the answer is now "yes," though only a "very small fraction" of fracturing activities have led to earthquakes noticeable to the public, says a new report from the National Research Council, which advises the government on these kinds of matters.

Since the 1920s, a range of human activities have contributed to earthquakes, including explosions related to mining or construction, underground nuclear tests and confining reservoirs behind dams.

Sen. Jeff Bingaman, D-New Mexico, requested that the council study the matter following concern about reports of earthquakes in multiple states, including Colorado, being caused by fracturing. A group of geologists and engineers, many from Colorado, conducted the 239-page study.

The findings aren't likely to cause much of a shake-up.

Among the study's key conclusions:

1) Hydraulic fracturing does not pose a high risk for causing earthquakes that people can feel;

2) Disposal of fracturing wastewater deep into the ground poses some risk for increased earthquake activity, but very few have