Recent research indicates a potential synchronization between two major fault systems on North America’s West Coast: the Cascadia subduction zone and the San Andreas fault. This finding may suggest that an earthquake on one fault could trigger seismic activity on the other.
Study Insights on Cascadia and San Andreas Faults
Chris Goldfinger, a marine geologist from Oregon State University, led a study revealing important insights into these fault systems. The research team drilled deep-sea sediment cores, analyzing geological data spanning 3,100 years. They examined turbidites—layers formed by underwater landslides triggered by earthquakes—and found noticeable similarities in timing and structure across both fault systems.
Notable Historical Events
The team identified three instances within the last 1,500 years where the Cascadia and northern San Andreas faults experienced ruptures that occurred just minutes to hours apart. One such event was traced back to 1700. This synchronization could have serious implications for hazard planning in the region.
Implications for Hazard Preparedness
- A significant earthquake on one fault could cause the entire country to divert resources for emergency response.
- Simultaneous earthquakes on both faults may present a compounded crisis affecting major cities like San Francisco, Portland, Seattle, and Vancouver.
Goldfinger noted the importance of this research in terms of preparedness for severe seismic events. “Expecting one fault to move could mean multiple urban areas face emergencies simultaneously,” he stated.
Historical Context and Methodology
The origins of this research trace back to a 1999 oceanographic cruise that unwittingly led to the study of both faults. The research team initially targeted the Cascadia zone but ended up 55 miles south of Cape Mendocino in the San Andreas zone due to a navigational error. There, they discovered unique sediment layering, which played a crucial role in their findings.
They found an unusual layering pattern: coarse sediment atop fine sediment, a reversal of typical turbidite structure. This phenomenon, described as “doublets,” indicates that both fault systems experienced earthquakes in close succession rather than one being a mere aftershock of the other.
Collaborative Research and Contributions
The study included contributions from various institutions and experts. Authors included Ann Morey, Christopher Romsos, and Bran Black from Oregon State University’s College of Earth, Ocean, and Atmospheric Sciences, along with researchers from NOAA and the University of Washington. Internationally, researchers from Germany and Spain also participated.
Understanding the relationship between the Cascadia and San Andreas faults provides valuable insights for assessing and preparing for seismic risks along the West Coast of North America.
