A new study warns that a massive earthquake along the Cascadia subduction zone could cause significant land sinking, dramatically increasing flood risks in coastal areas from Northern California to Washington. The study, published in the journal Proceedings of the National Academy of Sciences, highlights the potential for land to sink by up to 6.6 feet, expanding flood-prone areas by 116 square miles, which is more than twice the size of San Francisco.
The Cascadia subduction zone, which stretches from Northern California to Canada’s Vancouver Island, is known for its potential to unleash powerful earthquakes. The last megaquake in the area, a magnitude 9 event, occurred in 1700. Scientists predict that the next great earthquake, with a magnitude of 8 or higher, could drastically alter shorelines and infrastructure, leaving lasting impacts on coastal populations and ecosystems.
According to the study, the Humboldt Bay region, including areas around Eureka and Arcata, is particularly vulnerable. The study’s lead author, Dr. Tina Dura, told the Los Angeles Times that the subsidence caused by such an earthquake would persist for decades or centuries, altering flood plains long after the initial shaking.
Currently, over 8,000 people live in flood-prone areas along the Cascadia coastal region. A high level of subsidence could nearly triple this number to more than 22,000, with nearly 36,000 structures threatened. The study emphasizes the need for comprehensive planning to address both earthquake and climate impacts on coastal resilience.
The Lost Coast Outpost reported that the study underscores the importance of considering earthquake-triggered land subsidence in flood hazard analyses. As sea levels rise due to climate change, the combined effects of earthquake subsidence could significantly increase flood exposure in the coming decades.
The study calls for urgent action from residents and government officials to prepare for these potential risks, including reconsidering the placement of critical infrastructure in areas likely to become part of the expanded flood plain.
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