West Virginia Highlands Voice

http://stateimpact.npr.org/pennsylvania/2012/04/04/u-s-geological-survey-links-man-made-earthquakes-to-gas-drilling/

Under­ground injec­tion of frack waste water “almost cer­tainly” caused a wave of earth­quakes from Alabama to Col­orado, accord­ing to a new report issued by the U.S. Geo­log­i­cal Sur­vey. The researchers looked at a spike in unusual seis­mic activ­ity that began in 2001.

A remark­able increase in the rate of M 3 and greater earth­quakes is cur­rently in progress in the US mid­con­ti­nent. The aver­age num­ber of M >= 3 earthquakes/year increased start­ing in 2001, cul­mi­nat­ing in a six-fold increase over 20th cen­tury lev­els in 2001. Is this increase nat­ural or manmade?

The report says the use of deep injec­tion wells to dis­pose of the waste water is the likely source of the increase in seis­mic activity.

A naturally-occurring rate change of this mag­ni­tude is unprece­dented out­side of vol­canic set­tings or in the absence of a main shock, of which there were nei­ther in this region. While the seis­mic­ity rate changes described here are almost cer­tainly man­made, it remains to be deter­mined how they are related to either changes in extrac­tion method­olo­gies or the rate of oil and gas production.

The Envi­ron­men­tal Work­ing Group has more on the USGS study.

he USGS authors said they do not know why oil and gas activ­ity might cause an increase in earth­quakes but a pos­si­ble expla­na­tion is the increase in the num­ber of wells drilled over the past decade and the increase in fluid used in the hydraulic frac­tur­ing of each well. The com­bi­na­tion of fac­tors is likely cre­at­ing far larger amounts of waste­water that com­pa­nies often inject into under­ground dis­posal wells. Sci­en­tists have linked these dis­posal wells to earth­quakes since as early as the 1960s. The injec­tions can induce seis­mic­ity by chang­ing pres­sure and adding lubri­ca­tion along faults.