Scientists have conducted an unprecedented study, mapping one of the most dangerous regions on Earth in unparalleled detail. The Cascadia subduction zone, a 600-mile geologic boundary off the Pacific Northwest coast, has the potential to unleash a catastrophic 9.0-magnitude earthquake and generate a tsunami with waves as high as 40 feet.

To better understand the geological conditions and prepare for the inevitable event, a 235-foot ship embarked on a 41-day expedition along the coasts of Oregon, Washington, and British Columbia in the summer of 2021. Equipped with a 9-mile-long waterproof cable featuring 1,200 specialized microphones, the researchers sent sound waves deep into the ocean and used the resulting data to create a comprehensive map of the underwater geology.

Published in the journal Science Advances, the findings will provide valuable insights into potential earthquake and tsunami scenarios, enabling policymakers to implement enhanced building codes for better protection of vulnerable populations. The entire area from Northern California to Vancouver Island is at risk, but the study revealed that the fault off the coast of Washington, characterized by a flat, smooth surface that extends farther onshore, may face increased vulnerability.

Erin Wirth, a seismologist with the United States Geological Survey who was not involved in the study, expressed enthusiasm about incorporating the newly obtained results into her work to accurately predict shaking estimates. The knowledge gained from this study will undoubtedly contribute to more precise forecasting and preparedness efforts.

The history of the Cascadia subduction zone indicates that it has been relatively calm for hundreds of years. However, historical records from various sources, including Japanese historical accounts and Native American oral histories, document an earthquake on January 26, 1700, accompanied by a tsunami. Analysis of tree rings from submerged "ghost forests" corroborated this date and provided further evidence of the occurrence of a magnitude-9 quake more than three centuries ago.

The Cascadia subduction zone is categorized as a "megathrust" fault, where the Juan de Fuca tectonic plate subducts beneath the North American continental plate. While the plates move at the rate of fingernail growth, they periodically get stuck, accumulating stress that can lead to seismic events. Significant earthquakes and tsunamis, such as the 2011 Tohoku earthquake in Japan and the 2004 Indian Ocean earthquake, have occurred at similar subduction zones.

The lack of recent earthquake activity in the Cascadia subduction zone has made it challenging for seismologists to gather detailed information. Suzanne Carbotte, a marine seismologist at Columbia Climate School's Lamont-Doherty Earth Observatory and the study's lead author, compared the previous understanding of the fault zone to having impaired vision. However, the newly obtained data has removed those limitations, revealing a fault surface that is far more complex than previously envisioned.

While this study is just the beginning of a wealth of scientific papers expected to emerge from the new dataset, several significant findings have already been made. Notably, a flat and smooth section of the fault spanning Washington state up to southern Vancouver Island has been identified. Similar fault systems worldwide often generate the largest and most destructive earthquakes, making this section of the Cascadia subduction zone particularly worrisome. Moreover, the fault in this region is shallower and closer to the surface than previously assumed, increasing its potential hazard.

The study also discovered four individual segments along the fault, raising the question of whether the entire fault will rupture simultaneously or if separate segments might rupture progressively. Seismologists anticipate that either scenario could be a major natural disaster, with potential differences in magnitude and destructive power.

Scientists and researchers are already beginning to utilize this extensive dataset to deepen their understanding of tsunami formation. Kelin Wang, a research scientist for the Geological Survey of Canada, emphasized the wealth of information contained within the dataset and its potential for multidimensional analysis.

As the scientific community delves further into this groundbreaking study, policymakers, engineers, and coastal communities can use this knowledge to implement critical measures aimed at enhancing preparedness and mitigating the devastating impact of an inevitable megaquake and tsunami event in the Pacific Northwest.