The May 1 edition of Time magazine included an article by Bryan Walsh entitled “The Seismic Link Between Fracking and Earthquakes”. The first line of the story claims “New research indicates that wastewater disposal wells—and sometimes fracking itself—can induce earthquakes.” Pretty scary, right? Later in the article, Mr. Walsh notes that “Environmentalists who seek to block shale oil development in the Golden State [California] have seized on fears of fracking-induced quakes, and a bill in the state legislature would establish a moratorium on fracking until research shows it can be done safely.” Is this really prudent?
First, a little background. Earthquakes are conventionally measured according to the Richter Scale, which was developed in the 1930s by Charles Francis Richter and which measures the amplitude of the seismic wave generated by the earthquake, in other words the displacement of the earth. Richter set the zero point of the scale at the smallest disturbance that instruments could record at the time. The strongest earthquakes ever recorded, such as the 2011 earthquake in Japan, the 1964 Alaskan earthquake or the 1960 Valdivia earthquake in Chile, measured between 9 and 10 on the Richter scale. The Richter Scale, however, is logarithmic. In other words, the wave amplitude of a magnitude 9.0 earthquake is 10 times the amplitude of a magnitude 8.0 earthquake, which in turn is 10 times the amplitude of a magnitude 7.0 earthquake and so on. The total energy released by the earthquake varies with the 1.5th power of the amplitude of the wave. Therefore, a magnitude 9.0 quake involves an energy release 31.6 times (10 to the 1.5th) that of an 8.0 quake. Bear in mind that this energy release does not occur at the surface like a bomb, but deep underground. Much of the energy is dissipated downward into the Earth’s crust.
This definition creates an extremely wide scale for measuring earthquakes. For example, a magnitude 9.0 earthquake releases a trillion times as much energy as a magnitude 1.0 earthquake. Here’s a brief guide to the earthquake scale.
The magnitude 9.5 Tohoku Earthquake that hit Japan in 2011 resulted from a shift in the tectonic plate about 40 miles offshore at a depth of nearly 20 miles below the sea floor. The severe shaking and the massive tsunami that followed killed 15,000 people, destroyed over 100,000 buildings and damaged another million or so, including several nuclear power plants. This event was a true catastrophe, but it required an energy release of about 2.5 billion tons of TNT – equivalent to detonating a substantial share of the US thermonuclear arsenal all at once.
The magnitude 8.0 earthquake that devastated San Francisco in 1906 released the energy of a single large thermonuclear weapon. This event was severe, but the devastation resulted as much from the poor quality construction of the city’s buildings and massive fires as from the quake itself.
The 2010 earthquake in Haiti measured 7.0 on the scale, killing over 100,000 people and destroying the flimsy infrastructure of much of the country. The energy release of this quake was about 500,000 tons of TNT –equivalent to a small thermonuclear bomb. In addition to the poor quality of buildings and overcrowding of the populace, the damage was intensified by the proximity of the epicenter, which was only 16 miles from the capital city of Port-au-Prince and only 8 miles underground.
In August, 2011 a magnitude 6.0 earthquake hit the Washington DC area. This was one of the largest earthquakes ever to hit the US east of the Rocky Mountains, and involved an energy release of about 15,000 tons of TNT – about the size of the Hiroshima bomb. There were no casualties and only a modest amount of property damage – including cracks in the Washington Monument that closed the structure for nearly three years.
So far, we are discussing events that can, under some circumstances, cause serious damage and loss of life, particularly in crowded areas. Smaller earthquakes, however, are rarely so serious.
Quebec and Ontario suffered a magnitude 5.0 quake on June 23, 2010. The quake, equivalent to the detonation of 500 tons of high explosive, had an epicenter about 35 miles from Ottawa at a depth of about 10 miles. Although the effect was felt for hundreds of miles, there were no casualties and little property damage other than a few cracked windows. Most of the disruption caused by the earthquake resulted from indirect effects such as closing schools, suspending public transportation for inspections and overloaded phone lines.
I personally experienced two magnitude 5.0 earthquakes in Los Angeles. In both cases, the effects were so subtle that they were difficult to perceive. In one case, we were on the 11th floor of a hotel, which seemed to sway slightly. People on the first floor of the structure were unaware that anything at all had happened. In the other case, our door latch rattled a bit, which I originally attributed to the wind blowing through the window.
Magnitude 4.0 quakes involve an energy release equivalent to about 15 tons of TNT – about the size of the largest conventional bomb dropped in World War II. Such quakes are fairly common. For example, the world experiences on average one earthquake each year of magnitude 8.0 or higher and about 10,000 per year between magnitude 4.0 and 4.9. When such quakes occur in the US, the press generally reports that the local population was aware of the quake and occasionally frightened by the sensation, but that there were no casualties or property damage.
A magnitude 3.0 earthquake is generally described by those who feel it as similar to a heavy truck driving by. Indoor objects can rattle a bit near the quake’s epicenter, but people outdoors rarely notice the effect at all.
A magnitude 2.0 earthquake involves an energy release equivalent to about 15 kilograms (35 pounds) of heavy explosive, set off underground. Except for people directly above the epicenter of a very shallow event, most people would be completely unaware of an earthquake of this size. As a good benchmark, Seattle fans cheered, shouted and stomped their feet when the Seahawks beat the New Orleans Saints on Monday Night Football last December. The activity was measured as a Magnitude 2.0 earthquake on the University of Washington seismograph.
A magnitude 1.0 quake is equivalent to the detonation of a stick of dynamite several thousand feet underground. Only under unusual circumstances would anyone be aware of such an event, which could be recorded only on a sensitive instrument. The Los Angeles Earthquake Tracker (which you can find at http://earthquaketrack.com/v/la/recent) generally records about 7 earthquakes in the 1.0-2.0 range every single day.
The zero point on the scale, as established by Richter, is defined as a wave amplitude of one micron (one millionth of a meter) at a distance of 100 kilometers from the event. The energy required for such an event is equivalent to a box of kitchen matches ignited several miles underground.
Using the term “earthquake” without qualification is equivalent to using the term “rainstorm” to describe everything from a sprinkle to Hurricane Sandy. We therefore need to be careful and precise when we discuss the effects of fracking. We should also remember that we are discussing the effects not of hydraulic fracturing itself, but of the reinjection into the ground of the waste water used in hydraulic fracturing.
A number of news outlets, including NBC News, have run stories over the last few months about a possible linkage between earthquakes and waste water injection in Ohio. The strongest earthquake under evaluation was a magnitude 3.9 quake near Youngstown. Based on the scale outlined above, such an event should be classified as perceptible but harmless. Most “quakes” attributed to fracking are in the 1.0-2.0 range. According to the Time article, “In Ohio, officials this month established new guidelines that would allow regulators to halt active hydraulic fracturing if seismic monitors detect a quake with a magnitude of 1.0 or higher.” State governments of course have a responsibility to look after the public welfare. It seems to me, however, that the proper metric is whether fracking causes injury and damage, not whether it causes disturbances that can only be perceived by sensitive instruments. If we are going to regard such events as serious enough to require policy intervention, then we had better be prepared to regulate football fans and the UPS truck driving through your neighborhood.
Perhaps the real point here can be found in the proposed California moratorium on fracking “until research shows it can be done safely.” This bill is typical of the approach environmentalists often use to oppose things they don’t like. Often called “the precautionary principle”, the idea is that nothing should be permitted until proven safe. Sounds fair, but nothing can actually be proven safe. Things can be proven dangerous through a single example of harm directly related to the thing under evaluation. Even hundreds of examples of safe water injection, however, don’t prove that the next case won’t cause a problem. Companies should be allowed to produce natural gas, and mineral rights owners should be allowed to profit from those rights, unless and until a clear threat to public safety has been demonstrated. Otherwise, we will never do anything.