On February 27, 2010, just after 3:30 in the morning local time, a 430-mile fault snapped off the coast of Chile, displacing up to 30 feet of the seabed and coast. GPS units in the city of Conception were rendered inaccurate by 10 feet in a manner of minutes, as the city jumped to the west. It also knocked the Earth about a bit on its axis. A tsunami flooded a wide swath of the coastline and rolled across the Pacific, causing evacuations in Hawaii.
On March 11, 2011, just after quarter-to-three on a Friday afternoon local time, a significant section of the Pacific Ocean suddenly jumped beneath the Japanese island of Honshu. It thrust parts of the island eastward by nine feet, generated massive tsunami that killed 20,000 people and damage all around the Pacific Ocean, dramatically swayed skyscrapers across Japan, South Korea, and even China, caused a nuclear power plant crisis that affected hundreds of thousands more, and like the Chilean quake knocked the Earth about a bit on its own axis
April 12, 2012 bought a pair of giant quakes off Indonesia. Unique in their own right, they represent the beginning of a new tectonic boundary as Australia continues to plow its way northward into Indonesia (and then eventually into the Philippines and then ultimately, mainland China.) They thankfully did not cause the chaos, death, and destruction the other two massive quakes did.
The seismic waves from these quakes ripped across North America, unfelt by human beings. However as they did so, the feather-touch of their passing tickled a number of regions already under strain from an anthropogenic cause- Fluid-injection, from gas and oil extraction- and other regions under strain from natural causes. The regions lit up with small earthquakes in the days that followed. However, more interestingly, in Texas, Oklahoma, and Colorado, these tiny earthquakes were harbingers of larger moderate (and in Colorado and Oklahoma, damaging) quakes that occurred, in September, November, and August of 2011, respectively.
A group of new studies adds to an increasingly growing body of research that a variety of human activities can and do create earthquakes.
The continued bad news? Injecting waste-water into the ground can cause earthquakes. The silver lining? Sometimes we get a tool to see them coming or stop the larger quakes from happening by ceasing activity, provided you have a large and distant earthquake to provide remote triggering.
Now it’s not that this is news to anyone paying attention. This has been known for the better part of 60 years. However with gas and oil extraction increasing across the United States in addition to an expansion of green geothermal energy production we're seeing this happen more and more, and it's a problem.
A recent dramatic increase in seismicity in the midwestern United States may be related to increases in deep wastewater injection. Here, we demonstrate that areas with suspected anthropogenic earthquakes are also more susceptible to earthquake-triggering from natural transient stresses generated by the seismic waves of large remote earthquakes. Enhanced triggering susceptibility suggests the presence of critically loaded faults and potentially high fluid pressures. Sensitivity to remote triggering is most clearly seen in sites with a long delay between the start of injection and the onset of seismicity and in regions that went on to host moderate magnitude earthquakes within 6 to 20 months. Triggering in induced seismic zones could therefore be an indicator that fluid injection has brought the fault system to a critical state.
This is the abstract for the
most interesting, and
more widely reported study. For the Texas quake, they found a sharp increase of seismicity in the Cogdell field near the town of Snyder immediately after the March 2011 megaquake, culmanating in an Mw 4.3 quake in September of that year.
In Oklahoma near the town of Prauge, which has experienced a broad, widespread, remarkable, and alarming increase in seismicity beginning in 2009 (see my previous diary on the subject for more), the trigger appears to have been the Chilean earthquake after almsot 20 years of injection and no earthquakes. That earthquake seems to have set the stage for one M4 to occur just mere hours after the distant quake caused much destruction in Chile. That M4 may have triggered a later M5, which then triggered the large M5.7 quake that was felt across much of the Midwest, and destroyed 14 homes. Had it been under an urban center like Oklahoma City, things could have been far worse. It's perhaps "good" that the injection wells near the epicenter are in a rural area. The 2011 Japanese quake did not cause any new swarms but the 2012 Indonesia quakes appear to have triggered and uptick.
There are still small quakes occuring in the area to date.
In Colorado near Trinidad, a seismic swarm that occured in 2011 is possibly related to coal-bed methane extraction and reinjection of the produced water back into the ground. The study found the correlation was the weakest of the three "fracked" areas, but they still managed to find a statistically significant uptick after the two massive quakes off of Indonesia in 2012, and a statistically significant uptick in 2010 after the Chilean quake.
All three of these areas in Texas, Oklahoma, and Colorado were significant because of their very long histories of fluid injection for energy production. Unlike other areas, like Arkansas, Ohio, and even elsewhere in Colorado, the seismicity began almost within days of the onset of injection. In these areas there were long delays between the start of our activity and the start of the seismic activity. It suggests to me (and the researchers themselves) a chain like this:
1. the faults were fairly close to failure.
2. people then came along and forced fluid in the ground, raising further the strain, over a period of decades.
3. distant massive earthquakes "troubled the waters" so to speak, observed as a swarm of microseismicity above the local background levels within days of the "troubling."
4. the faults then failed.
This is a problem. Although the study doesn't mention it, there are fields similiar to the three researched nationwide. It tells me that if you're going to force liquid into the ground, you're going to have to have extensive and widespread seismic monitoring. Or better yet, don't do it at all.
Geothermal power is a growing energy source; however, efforts to increase production are tempered by concern over induced earthquakes. Although increased seismicity commonly accompanies geothermal production, induced earthquake rate cannot currently be forecast based on fluid injection volumes or any other operational parameters. We show that at the Salton Sea Geothermal Field, the total volume of fluid extracted or injected tracks the long-term evolution of seismicity. After correcting for the aftershock rate, the net fluid volume (extracted-injected) provides the best correlation with seismicity in recent years. We model the background earthquake rate with a linear combination of injection and net production rates that allows us to track the secular development of the field as the number of earthquakes per fluid volume injected decreases over time.
I've found it interesting that the study for the abstract above is
not as widely reported. I'll leave that to you all to speculate why (Green is automatically good?) but yes, geothermal energy production uses the same type of fluid injection down into the earth to create steam which then creates electricity, and yes,
it too can create earthquakes. This is
pretty well known.
This study took a look at the seismicity surrounding the geothermal plants in the Salton Trough in Southern California. The facility--and the Salton Trough---sit next to the diffuse terminus of the San Andreas Fault. From here south through the Gulf of California, the plate boundary moves from two plates sliding past each other to two plates spreading apart.
This area is quite seismically active.
This study found a very clear correlation. If the plants stuck perhaps 500 million gallons into the ground per month, an earthquake occured on average every 11 days. Thousands of small tremors have been observed in the area over a 30 year period. This is especially concerning considering the location. Southern California awaits "The Big One." Which fault will generate it we can't really know until it happens but the segment of the San Andreas from the Salton Sea to Palmdale has not ruptured in perhaps 300 years. It isn't known if the geothermal energy production is capable of triggering the currently "stuck" San Andreas and adjacent faults but further research is needed.
Movers and Shakers
We tend to view earthquakes as unpredictable phenomena caused by naturally shifting stresses in Earth's crust. In reality, however, a range of human activity can also induce earthquakes. Ellsworth (p. 10.1126/science.1225942) reviews the current understanding of the causes and mechanics of earthquakes caused by human activity and the means to decrease their associated risk. Notable examples include injection of wastewater into deep formations and emerging technologies related to oil and gas recovery, including hydraulic fracturing. In addition to directly causing increased local seismic activity, activities such as deep fluid injection may have other ramifications related to earthquake occurrence. Van der Elst et al. (p. 164; see the news story by Kerr) demonstrate that in the midwestern United States, some areas with increased human-induced seismicity are also more prone to further earthquakes triggered by the seismic waves from large, remote earthquakes. Improved seismic monitoring and injection data near deep disposal sites will help to identify regions prone to remote triggering and, more broadly, suggest times when activities should, at least temporarily, be put on hold.
The last
paper of this group was a review paper. It reiterates much of the above but points out even more activities that can induce quakes. I found the case of Paradox Valley, Colorado very interesting. There, a project to keep salt water out of the Dolores River and eventually the Colorado too is creating earthquakes, as the briny water is injected deep into the ground. Here, the government agency responsible has taken steps to reduce the number of quakes occuring because of their activities. In other areas of the world
large and deep resevoirs can induce earthquakes as they fill or even a number of years later, along with
groundwater extraction. These activities change the "pore pressure" which can increase the strain in nearby faults which then can slip, triggering earthquakes.
The papers are all behind paywalls. They are:
1. Anthropogenic Seismicity Rates and Operational Parameters at the Salton Sea Geothermal Field
2. Injection-Induced Earthquakes
3. Enhanced Remote Earthquake Triggering at Fluid-Injection Sites in the Midwestern United States
Another piece related is: Some Earthquakes Warn That They Are About to Strike. All were published in the latest issue of Science.
As I've noted in the past this is not well regulated. US Federal regulations do not require operators of fracking wells, injection wells, geothermal plants, or the like to report on anything beyond what's required for various laws controlling safe and clean drinking water (and we know how well they do that.) That their wells may trigger quakes, they're not required to do anything about that. There are over 30,000 injection wells nationwide; most are not a problem. The handful that are still require regulation. Ellsworth (the author of the review paper) suggests traffic light systems that automatically shut down injection when quake numbers reach a certain count. I'd say don't inject in the first place but realistically that just isn't going to happen in the short-to-medium term.