Overview

• The Geosphere paper led by Oregon State’s Chris Goldfinger reports repeated “doublet” signatures linking Cascadia megathrust events to subsequent northern San Andreas ruptures over millennia.
• Evidence for 1700 points to a magnitude ~9 Cascadia quake followed hours to days later by a northern San Andreas event estimated near magnitude 7.9.
• An inverted turbidite sequence near Noyo Canyon supports a distant Cascadia-triggered fine layer overlain by coarser sands from a nearby San Andreas quake.
• The authors identify multiple intervals with this pattern and note 1906 as the only major northern San Andreas earthquake in the last 2,500 years not preceded by a Cascadia event, with no evidence for the reverse triggering.
• Scientists emphasize the linkage is a hypothesis based on geologic proxies with limited timing resolution, yet emergency planners are weighing the compounded risks of near-concurrent West Coast disasters.