Study finds Cascadia and San Andreas faults may rupture together
West Coast megaquake planning may need to cover two faults, not one. Oregon State researchers report in Geosphere that a Cascadia rupture could trigger the northern San Andreas, with sediment cores showing the faults broke together three times in 1,500 years. Per Geosphere.
New research reframes the earthquake hazard on the US West Coast from a single fault to two linked systems. Marine geologist Chris Goldfinger and colleagues at Oregon State University report in the journal Geosphere that a major earthquake on the Cascadia subduction zone could trigger a secondary rupture on the northern San Andreas fault. The team analyzed deep-sea sediment cores and found evidence that the two fault systems have ruptured together at least three times over the past 1,500 years. In some of the turbidite deposits, the second rupture appears to have followed the first within minutes or hours, raising the possibility of near-simultaneous shaking along much of the Pacific coast. The researchers are explicit that the findings do not indicate a double earthquake is imminent. They describe a rare but high-consequence scenario relevant to regional planners. Sources: Oregon State University Newsroom, Geological Society of America.