Induced Seismicity: Man-Made Earthquakes

In California, more renewable energy comes from geothermal energy than solar and wind, combined. Today, a new technology known as Enhanced Geothermal Systems has the potential to extract even more heat and consequently energy to power steam turbines, but it’s not without challenges, including man-made earthquakes which are a consequence of breaking up rock more than a mile below the earth’s surface. Such earthquake activity is referred to as "induced seismicity" and can occur in other fields of energy production, including oil and natural gas production and hydropower.

Although most of these earthquake events are miniscule, registering less than a 2.0 in magnitude, occasionally, they can result in larger magnitude earthquakes, especially when the engineering activity which precipitates them occurs within the proximity of active fault zones.

In the U.S., the buzz over Enhanced Geothermal Systems (EGS) started ratcheting up after the publication of a 2006 Department of Energy study investigating its potential, spearheaded by researchers at M.I.T. Among their findings was that EGS could meet 10% of the U.S.' electricity supply by 2050. Ten percent doesn't seem to be that much but it would represent a 40-fold increase over the current amount of geothermal power being harnessed nationally and if realized, it could significantly boost the nation's efforts to wean itself off its carbon-heavy diet, with more than 60% of energy consumption in the U.S. currently coming from coal and petroleum.

Today, the Department of Energy is spending millions of dollars to fund seven demonstration EGS projects, including a grant of $5.5 million Calpine's to develop the EGS field featured in our QUEST story on induced seismicity. Calpine has invested $9.5 million of its own money on the project, an impressive sum it's willing to spend to demonstrate the success of this green, renewable technology.

Here is how Calpine Senior Vice President Mike Rogers described the project's energy potential to me: "We expect to produce between 5 to 7 megawatts of additional steam (which is) enough for a small city, say, 6,000 people (and) depending on what we find, possibly up to 50 megawatts in that part of the field." Calpine has measured a temperature of 725 degrees Fahrenheit at a depth of 11,000 feet at their new enhanced geothermal project site. That's roughly 300 degrees warmer than their other geothermal fields at the Geysers, and with more heat comes more energy potential.

Calpine is working with Ernie Majer of the Lawrence Berkeley National Laboratory to monitor the risk of induced seismicity with additional, around-the-clock seismic monitoring next to their EGS production and injection wells located in the northwestern region of the Geysers.

The company is proud of their efforts to reach out to nearby communities such as the town of Anderson Springs that are impacted by the year-round geothermal activities at the Geysers. Not only has Calpine created a seismic monitoring committee comprised of representatives from the Lawrence Berkeley National Laboratory, USGS and community members to review recent earthquake activity in the vicinity of the Geysers, they also have set up a hotline to report earthquake activity and an annual fund which communities can use to pay for repairs to buildings and homes possibly damaged by earthquakes.

It should also be noted that Calpine has the support of some prominent members of Anderson Springs for the development of their EGS demonstration project. Jeff Gospe, the President of Anderson Springs Community Alliance, wrote a letter of support for the project in September 2010 to Sonoma County District Supervisor Paul Kelly. Although Jeff and other community members still have concerns about seismicity in the southern portion of the Geysers, Jeff maintains that the work on the EGS demonstration project is an example of "pro-community geothermal development" that is far enough away to pose little risk to residents of the town.

In the course of my research on the story, I discovered several international EGS projects, including two that are online in France and Germany. Given the concern with nuclear energy in the wake of the Fukushima Daiichi disaster in Japan, and the phasing out of nuclear energy programs in Germany, Italy and Switzerland, the need for more renewable energy sources like geothermal power becomes more pressing.

But as nuclear energy also reveals, no matter how green the energy source is, its exploitation must be safe for the public to get behind it.

As Ernie Majer of Lawrence Berkeley National Laboratory told me, "Over the past 20 years, it started out as the (geothermal energy) industry almost ignored induced seismicity. But as the recent issues have come up, the industry has finally said, 'Alright, we need to deal with this properly and we need to take it very seriously.'"