In the early evening on March 27, 1964 a magnitude 9.2 earthquake struck beneath Alaska’s Prince William Sound, 75 miles east of Anchorage. The ground shook for over four minutes, triggering landslides and a deadly tsunami that claimed lives as far south as Crescent City, CA. The Great Alaska Earthquake was a devastating natural disaster that resulted in over 100 deaths and hundreds of millions of dollars of damage. It is the largest earthquake ever recorded in the United States, and the second largest in the world.
Credit: U.S. Geological Survey/video by Stephen M. Wessells
As described by the US Geological Survey (USGS), one positive development to emerge from this tragedy was the huge advancement in our scientific understanding of earthquakes. It is fitting then that tomorrow, on the 50th anniversary of this massive quake, the House Natural Resources Committee is holding a hearing on how earthquake science has advanced in that time. A better understanding of the causes and consequences of earthquakes can help reduce the risks to human life and property.
While major breakthroughs in seismic research have been made in the 50 years since the Great Alaska Earthquake, one topic about which more research is urgently needed is induced seismicity. Unlike earthquakes caused by natural movement in the earth’s crust, induced earthquakes are caused by human activities, including mining, water reservoirs, and energy production. As a result, they can take place in parts of the country not traditionally thought of as earthquake territory.
In particular, activities associated with oil and gas production have caused induced earthquakes, including the underground injection of fluids like brine or carbon dioxide for disposal or enhanced oil recovery and – in a handful of cases – hydraulic fracturing. Most induced earthquakes caused by oil and gas activities have been relatively small but some, like the 2011 magnitude 5.7 earthquake in Oklahoma that was triggered by wastewater injection, are large enough to cause property damage and injuries.
Researchers at the USGS found that the rate of earthquakes greater than magnitude 3.0 in the central and eastern United States has increased significantly in the past decade, from an average of 21/year from 1967 through 2000 to more than 300 in the years 2010 through 2012, with 188 occurring in 2011 alone. The researchers hypothesize that this increase in activity could be related to oil and gas production activities, including underground injection of wastewater. This trend is particularly troubling because the people, buildings, and emergency services in this part of the country – states including Arkansas, Colorado, Ohio, Oklahoma, and Texas – are less equipped to deal with seismic activity, given that natural earthquakes are less frequent and cause less shaking.
As this issue has gained national attention the pace of research has increased, but there are still big gaps in our scientific knowledge and more needs to be done. Resources need to be made available to academic institutions and government agencies, like the USGS, that have the technical abilities to research these complex issues. A better understanding of induced seismicity can help scientists develop strategies that could significantly reduce the chance that such earthquakes will occur. Regulators have a role to play too, by requiring the owners and operators of projects that have the potential to cause earthquakes to:
- Perform induced seismic hazard and risk assessments;
- Submit these assessments as part of the permit application process;
- Monitor for earthquakes, and;
- Modify or stop activities if induced seismicity occurs.
If there are places where the risks are too high and can't be mitigated, activities that could cause induced seismicity should be prohibited. Energy production must not come at the expense of public health and safety.
The anniversary of the Great Alaska Earthquake is an opportunity to focus not only on how far the science of earthquakes has advanced, but also on what gaps remain and where to focus scientific research now. We must continue to make breakthroughs in our understanding of seismic activity, both natural and induced.