In 2015, the New Yorker published “The Really Big One”, a story that brought public awareness to the dangers posed by the Cascadia subduction zone. The Cascadia subduction zone is a large fault that lies underwater, just off the coasts of Washington, Oregon, and Northern California. As a scientist and professor who researches this fault and its dangers, I really appreciated the large impact this article had in raising awareness of the importance of preparing for the next large earthquake here, especially among the many residents who live in this region. The New Yorker article, and plenty of ongoing scientific research, suggests that we need to prepare for the possibility of a major earthquake in this region—but we also need more research to help with this preparation.
Weighing the probabilities of earthquakes—room for uncertainty
The Cascadia subduction zone has the capacity for a magnitude 9.0 earthquake, the same size as the devastating Japanese earthquake that occurred in 2011. The 2011 Japan earthquake caused a large tsunami, widespread destruction, and an ongoing nuclear disaster. We expect the next great Cascadia earthquake will have similar effects, hopefully minus the nuclear disaster. This fault directly threatens the urban areas of Seattle, Washington and Portland, Oregon, in addition to the many more residents in rural and suburban areas of California, Oregon, and Washington. In a 2013 report, The Cascadia Region Working Group estimates that if a magnitude 9.0 earthquake were to happen in the near future in this region, “the number of deaths could exceed 10,000”, and “more than 30,000 people could be injured”, with economic losses “upwards of $70 billion”.
It is very difficult to predict when this next great Cascadia earthquake will occur. A recent report published by the U. S. Geologic Survey estimates the probability of a magnitude 9.0 earthquake at roughly 10% in the next 50 years. The probability of a somewhat smaller, but still very destructive earthquake in the southern section of Cascadia (located just offshore, stretching from Cape Mendocino, CA to Florence, OR) is roughly 40% over the same timeframe. These probabilities are high enough to be scary—and to indicate the urgency of preparing for a a major earthquake disaster in this region.
These probability numbers represent decades of scientific progress and breakthroughs in studies of fault behavior, but they are not as useful as they could be. What the public and emergency managers want to know is “Will a destructive earthquake occur in the next 50 years, or not?”. The best answer we currently have is these probabilities. What that really means is, “we don’t know, so prepare just in case”.
While the New Yorker article raised awareness, over time this fades and people go about their usual lives. It is really difficult to maintain vigilance making sure you are personally prepared for a major earthquake at all times for the next 50 years, especially when there’s a good chance nothing will happen. Therefore, it would be really great to put some more certainty in those probabilities. If we can revise these probabilities closer to 0% (no chance of an earthquake) or 100% (definitely going to be an earthquake) we can reduce uncertainty when planning for the future.
The public depends on earthquake research
Increased certainty can only come from increased scientific understanding of this fault, and the mechanics of faults in general, which is at best only partially understood. We are also monitoring this fault for long-term changes that might indicate a large earthquake is imminent.
Making progress improving earthquake forecasts for Cascadia is a multi-disciplinary research problem. Scientists like myself use techniques such as numerical models of friction on faults to study the rupture process, laboratory experiments to study fault behavior, field geology studies to look at the signatures of past earthquakes, and data-driven studies using multiple instruments planted all along the subduction zone.
The vast majority of these studies are publicly funded using federal funding from the U.S. Geological Survey and National Science Foundation. The instruments we use were placed as part of a major scientific initiative called Earthscope, which was featured by Popular Science as the #1 “Most Ambitious Experiment in the Universe Today”. Earthscope is funded completely by the National Science Foundation, and funding is scheduled to end soon. The future of the critical scientific instrumentation in Cascadia is currently uncertain. These instruments have been, and continue to be, vital in improving our understanding of the mechanics of the Cascadia subduction zone and the size and timing of the next large earthquake there.
Budget cuts and uncertainty have a large effect on this field. The U.S. Geological Survey, under the recently released Trump budget blueprint, is going to take a 15% cut. The National Science Foundation is not specifically mentioned in the blueprint, but the working assumption among scientists is a 10% cut. While the cuts certainly hinder our efforts to study the Cascadia subduction zone, even the uncertainty is a hindrance to this science, as funding proposals take 6 months or more to receive an answer because of budget uncertainty. For scientists to do our jobs and give emergency managers and the public the best available information, it is critical that we continue to receive federal research funding.
Noel M. Bartlow is an Assistant Professor in the Department of Geological Sciences at the University of Missouri. She is a geophysicist who studies slow earthquakes and frictional locking in subduction zones. She earned her Ph.D. in Geophysics from Stanford University in 2013, and completed a postdoctoral fellowship at the University of California–San Diego’s Scripps Institution of Oceanography before joining the University of Missouri faculty in 2016. She is currently the principal investigator for the National Science Foundation funded project, “Collaborative Research: Improving models of interseismic locking and slow slip events in Cascadia and New Zealand.”
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