According to the report, gas-drilling and related activities can lead to human-induced earthquakes when those activities cause changes in fluid pressures or in underground stresses, especially in areas where there are geologic faults.

However, the report says even experts don't have enough information to reliably predict when this can happen.

"While the general mechanisms that created induced seismic events are well understood, we are currently unable to accurately predict the magnitude or occurrence of such events due to the lack of comprehensive data on complex natural rock systems and the lack of validated predictive models," the report said.

Also, the report said current regulations and practices don't necessarily go far enough.

For example, it said, some drilling-wastewater injection wells "normally do not have a detailed geologic review performed and often data are not available to make such a review.

"Thus, although fluid pressure in the injection zone and the fracturing pressure of the injection zone can be measured after the disposal well is drilled, the location of possible faults is often not known as part of standard well siting and drilling procedures," the report said.

The report urges closer monitoring and development of new guidelines, but says more drilling and related activities will have to be used to come up with such protocols.

"Practices that consider induced seismicity both before and during the actual operation of an energy project can be employed in the development of a 'best practices' protocol specific to each energy technology and site location," the report said.

Reach Ken Ward Jr. at kw...@wvgazette.com or 304-348-1702.

Read the report here.

The National Research Council said the practice of hydraulic fracturing to release gas reserves is, by itself, not a major risk for triggering "seismic events" large enough for humans to feel.

Of greater concern, the council said, is underground injection of wastewater from the increased drilling in formations such as the Marcellus Shale and the proposed injection deep underground of carbon dioxide emitted by coal-fired power plants.

Still, seismic events traced to various energy production activities -- from Marcellus drilling to coal mining -- amounted to only 154 worldwide during the past century, compared to a global average of about 14,450 earthquakes every year, the report said.

Because of the timing, though, Friday's report did not consider more recent peer-reviewed science, especially an April paper by a U.S. Geological Survey expert who said he found a "remarkable increase" in the rate of earthquakes. USGS seismologist William Ellsworth said these changes were "almost certainly manmade" and linked to "either changes in extraction methodologies or the rate of oil and gas production."

In West Virginia, industry officials and state regulators have dismissed any connection between the gas-drilling boom and a string of small earthquakes recorded in Braxton County in 2010. Citizen groups in that area, and other parts of the state impacted by the Marcellus rush, have included potential quakes among their lists of concerns.

The new report was written by a panel of experts appointed by the National Research Council, which is part of the National Academy of Science, a nonprofit that provides scientific advice to the government.

According to the report, gas-drilling and related activities can lead to human-induced earthquakes when those activities cause changes in fluid pressures or in underground stresses, especially in areas where there are geologic faults.

However, the report says even experts don't have enough information to reliably predict when this can happen.

"While the general mechanisms that created induced seismic events are well understood, we are currently unable to accurately predict the magnitude or occurrence of such events due to the lack of comprehensive data on complex natural rock systems and the lack of validated predictive models," the report said.

Also, the report said current regulations and practices don't necessarily go far enough.

For example, it said, some drilling-wastewater injection wells "normally do not have a detailed geologic review performed and often data are not available to make such a review.

"Thus, although fluid pressure in the injection zone and the fracturing pressure of the injection zone can be measured after the disposal well is drilled, the location of possible faults is often not known as part of standard well siting and drilling procedures," the report said.

The report urges closer monitoring and development of new guidelines, but says more drilling and related activities will have to be used to come up with such protocols.

"Practices that consider induced seismicity both before and during the actual operation of an energy project can be employed in the development of a 'best practices' protocol specific to each energy technology and site location," the report said.

Reach Ken Ward Jr. at kw...@wvgazette.com or 304-348-1702.