The northwestern coast of the United States could experience major ground subsidence following an earthquake. A recent study reveals the combined impact of this phenomenon and rising sea levels due to climate change.
Researchers modeled the consequences of a major earthquake in the Cascadia subduction zone. According to their findings, the ground could sink by up to 6.5 feet (2 meters), worsening flood risks in coastal areas.
The study highlights the interaction between post-seismic subsidence and sea level rise. By 2100, these two factors could triple the area of flood-prone zones in the region.
Tina Dura, a coastal geologist at Virginia Tech, emphasizes the persistence of subsidence. Unlike tsunamis or shaking, this phenomenon can last for decades, even centuries, permanently altering coastal landscapes.
The Cascadia subduction zone has not experienced a major earthquake since 1700. Since then, the coastline has been rising slightly each year, partially offsetting sea level rise. However, this trend is expected to reverse by 2030.
Researchers compared flooding scenarios with and without an earthquake. A magnitude 8 earthquake today would affect an additional 116 square miles (300 km²), while by 2100, an extra 143 square miles (370 km²) would be at risk.
Critical infrastructure, such as wastewater treatment plants and airports, would be particularly vulnerable. The study underscores the importance of preparing emergency plans that account for these new risks.
Published in
PNAS, these results provide a more comprehensive view of the challenges ahead for Pacific Northwest coastal communities.
What is a subduction zone?
A subduction zone is a region where an oceanic tectonic plate slides beneath a continental plate. This process is responsible for many earthquakes and volcanoes.
In the case of the northwestern U.S. coast, the Juan de Fuca Plate is diving beneath the North American Plate. This interaction is responsible for the formation of the Cascade Range.
Earthquakes in these zones can be particularly powerful, like the magnitude 9.5 earthquake that struck Chile in 1960. They are often accompanied by coastal ground subsidence.
Understanding these mechanisms is essential for anticipating natural hazards and protecting nearby populations.