Impacts

Earthquakes

California is the second most seismically active state in the United States, after Alaska.1  The state contains over 15,000 fault lines, including the San Andreas Fault, which stretches for 810 miles and has been responsible for earthquakes up to 7.9 in magnitude.  Because of its history of highly active tectonic plates, the Monterey Shale formation is highly variable both in thickness and composition, and is full of fractures, folds and fault lines.  Given California’s complex geological context, it is especially important to understand how the full lifecycle of oil and gas extraction may impact seismicity and induce fracking earthquakes.

An aerial view of the San Andreas fault. California is particularly seismically active and susceptible to fracking earthquakes

An aerial view of the San Andreas Fault. (Credit: Ikluft/Creative Commons)

What is Induced Seismicity?

Induced seismicity is earthquake activity that occurs above the rate of naturally occurring seismicity due to human activity.  The injection of large volumes of water into the earth at high pressures – such as in hydraulic fracking – has been directly linked to inducing seismic events.  Experts believe that added pressure of injected water lubricates existing faults, which can separate them enough to release the energy that causes tremors.2  The vast majority of earthquakes caused by human activity are too small to be felt, but there have been instances of large earthquakes being triggered by water injection.3  It’s estimated that half of all 4.5 magnitude or above earthquakes in the past decade may have been induced by injection of water into the earth.4

The Mechanisms for induced earthquakes, including fracking earthquakes

Mechanisms for Inducing Earthquakes. (Source: Earthquakes Science Center, USGS)

Fracking Can Trigger Earthquakes

Multiple studies have concluded that injection increases the likelihood that large earthquakes elsewhere will set off earthquakes near the injection site. Instances of remote triggering happen when faults are “critically loaded” with high pressures of fluid.5

Wastewater InjectionOklahoma Case Study. Oklahoma has been one of main areas of fracking earthquakes in the US.

Experts agree that the largest threat of earthquakes comes not from the fracking process itself, but from the underground storage of the wastewater it produces. The Division of Oil, Gas, and Geothermic Resources (DOGGR) reports that oil and gas wells in California produced 3,083,038,501 barrels of water in 2012 – approximately 16 times more than the volume of produced oil.6  This massive amount of water needs somewhere to go. Wastewater from fracking contains toxic chemicals used in fracking fluid, as well as natural contaminants from deep underground, including total dissolved solids (e.g., salts, barium, strontium), organic pollutants (e.g., benzene, toluene) and normally occurring radioactive material, such as Radium.7  As a result, wastewater is unfit for use until it has been treated extensively – a process which is cost prohibitive in most cases due to the high salt content of the water, which can be up to ten times saltier than sea water.  Learn more about the challenges of wastewater.

Seismic Risk in California

Many of California’s injection wells are located within miles of active fault lines. The following map, courtesy of FracTracker, shows hydraulic fracturing activity (in red) and injection wells (in yellow), in relation to California’s fault lines.

Regulation of Seismic Risk

In general, regulations on wastewater disposal have been primarily concerned with protecting drinking water, not with mitigating the potential for seismic activity.8 Because of insufficient seismic monitoring data, geologists do not know how close wastewater injection or fracking can occur to an existing fault without presenting a hazard, and there is currently no regulation about the distance wells must be from a fault line in California.  Additionally, there is little understanding of the cumulative impact that many small earthquakes may have on larger faults.  Learn more about current regulation of fracking in California.

Economic Impact of Earthquakes

Wastewater injection can lead to fracking earthquakes. This home was damaged by a magnitude 5.7 quake

Oklahoma home damaged by a magnitude 5.7 earthquake linked to wastewater injection. (Source: Sue Ogrocki/AP)

There is extensive research showing that waste water injection can cause both large and small earthquakes.  The largest earthquake that has been potentially linked to wastewater injection had an estimated magnitude of 5.6-5.7.9  An earthquake of that magnitude can cause up to $4 billion in damage. Even a medium sized earthquake can cause millions of dollars indamage in a highly populated area.  With the current regulatory framework in California the oil companies inherently responsible for such an earthquake would not be held accountable for damages.

Scientific Studies on Fracking & Earthquakes

In the past year, several papers have been published in major scientific journals that have directly linked injection of wastewater to increases in seismic activity, either caused by injection or triggered by large earthquakes elsewhere. The following table summarizes the most up-to-date research on the topic.

Title Publication Authors Year Finding
Anthropogenic Seismicity Rates and Operational Parameters at the Salton Sea Geothermal Field  Science Emily E. Brodsky and Lia J. Lajoie 2013 An analysis of water injection near the Salton Sea Geothermal Field, located directly over the San Andreas Fault, found that there was a linear relationship between the number of earthquakes and the net production and injection rates of a nearby geothermal plant. For every 500m gallons of water injected into the ground monthly, there is an earthquake, on average, every 11 days.
Enhanced Remote Earthquake Triggering at Fluid-Injection Sites in the Midwestern United States Science Nicholas J. van der Elst et al. 2013 Long-term fluid injection was shown to have a destabilizing effect on geology.  When large earthquakes in Chile and Japan happened in 2010 and 2011, they set off other large earthquakes near far-flung injection sites, possibly because faults were loaded to the breaking point by high-pressured fluids.
Induced seismicity associated with fluid injection into a deep well in Youngstown Ohio Journal of Geophysical Research  Won-Young Kim* 2013 Wastewater disposal in Pennsylvania caused at least 108 earthquakes in nearby Ohio, a state that had not experienced even one recorded earthquake from 1776 until 2011. The largest quake recorded had a magnitude of 3.9.
Injection-Induced Earthquakes Science William Ellsworth, Jessica Robertson, and Christopher Hook 2013 As wastewater injection has come into wider use in the Central and Eastern United States, the rate of earthquakes with a magnitude of 3.0 or higher has increased by nearly 5 times in recent years. From 1967 to 2000 the area registered only 21 earthquakes per year on average but from 2010 to 2012 over 300 earthquakes were recorded. Concluded that the location of these earthquakes coincided with the locations of injection wells.
Potentially induced earthquakes in Oklahoma USA: Links between wastewater injection and the 2011 Mw 5.7 earthquake sequence Geology Katie M. Keranen et al. 2013 Linked a 5.7 magnitude earthquake in Oklahoma to injection wells and determined that the first earthquake triggered a second, larger event. Additionally, the long period of injection activity suggests that the increased probability for earthquakes can persist for decades after injection occurs.
Man-Made Earthquakes U.S. Geological Survey William Ellsworth, Jessica Robertson, and Christopher Hook 2013 As wastewater injection has come into wider use in the Central and Eastern United States, the rate of earthquakes with a magnitude of 3.0 or higher has increased by nearly 5 times in recent years. From 1967 to 2000 the area registered only 21 earthquakes per year on average but from 2010 to 2012 over 300 earthquakes were recorded. Scientists found that the location of these earthquakes coincided with the locations of injection wells.
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