California has been the focus of most of Hollywood’s disaster films: there are the succinctly named Earthquake (1974) and Volcano (1977), and most recently San Andreas (2015), about America’s most famous fault line. Now a second fault line in the Pacific Northwest (PNW) – the Cascadia subduction zone – is making its way into the public imagination following a much talked about New Yorker article.
In the PNW, the oceanic Juan de Fuca tectonic plate meets the North America plate and the two are pressed together causing the oceanic plate to subduct, that is, move under the North America plate. The North America plate, however, has become wedged against the Juan de Fuca plate and this builds pressure. This pressure will eventually have to be released and this will probably happen in the form of what geophysicists call “the big one”: an earthquake that is calculated to be between 8.0 and 9.2 on the Richter scale.
Normally when a science news story takes over the collective imagination, scientists step in to assuage people’s fears and abate their excitement. This is not the case this time around. The Cascadia subduction zone has a recurrence interval – the average number of years between earthquakes – of 243 years. And while 243 years is only an average, PNW’s last large-scale, fault line-triggered earthquake occurred in January 1700. As such, Cascadia’s next earthquake is (a) probably overdue and, (b) given the growing pressure at the fault line, will most likely be a “big one”.
The glimmer of hope is that geologists can use the mineral deposit makeup of the PNW to predict the more vulnerable regions in the area and are actively trying to push the science on predicting where the epicenter of fault-line earthquakes will be located. But, for now their advice can be summarized in a single word: prepare.
Many thanks to Dr. Brendan Meade, Professor of Earth and Planetary Sciences at Harvard University, for providing his expertise and commentary on the subject
Kathryn Schulz’s The Really Big One
A selection of articles on the Cascadia subduction zone from Seattle Times
A Reddit AMA about the Kathryn Schulz article with earthquake experts from the Seattle region