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#           Rainfall triggers more deep-seated landslides than Cascadia earthquakes in the Oregon Coast Range, USA      

      September 16, 2020    

The coastal Pacific Northwest USA hosts thousands of deep-seated landslides. Historic landslides have primarily been triggered by rainfall, but the region is also prone to large earthquakes on the 1100-km-long Cascadia Subduction Zone megathrust. Little is known about the number of landslides triggered by these earthquakes because the last magnitude 9 rupture occurred in 1700 CE. Here, we map 9938 deep-seated bedrock landslides in the Oregon Coast Range and use surface roughness dating to estimate that past earthquakes triggered fewer than half of the landslides in the past 1000 years. We find landslide frequency increases with mean annual precipitation but not with modeled peak ground acceleration or proximity to the megathrust. Our results agree with findings about other recent subduction zone earthquakes where relatively few deep-seated landslides were mapped and suggest that despite proximity to the megathrust, most deep-seated landslides in the Oregon Coast Range were triggered by rainfall.

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April 26, 2019

####                 GeoMapping for Integrated Science              

Earthquake Hazards Program, Landslide Hazards Program, National Cooperative Geologic Mapping Program, Earthquake Science Center, Geologic Hazards Science Center, Geology, Minerals, Energy, and Geophysics Science Center, Geosciences and Environmental Change Science Center, Pacific Coastal and Marine Science Center, Big Sur Landslides

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April 26, 2019

####   GeoMapping for Integrated Science

Learn More

#### Sean Lahusen, PhD

##### Research Geologist

Geology, Minerals, Energy, and Geophysics Science Center

slahusen@usgs.gov

1-888-275-8747

#### Alex Grant

##### Research Civil Engineer

Earthquake Hazards Program

agrant@usgs.gov

650-329-5205

## Related Content

link

April 26, 2019

####                 GeoMapping for Integrated Science              

Earthquake Hazards Program, Landslide Hazards Program, National Cooperative Geologic Mapping Program, Earthquake Science Center, Geologic Hazards Science Center, Geology, Minerals, Energy, and Geophysics Science Center, Geosciences and Environmental Change Science Center, Pacific Coastal and Marine Science Center, Big Sur Landslides

link

April 26, 2019

####   GeoMapping for Integrated Science

Learn More

#### Sean Lahusen, PhD

##### Research Geologist

Geology, Minerals, Energy, and Geophysics Science Center

slahusen@usgs.gov

1-888-275-8747

#### Alex Grant

##### Research Civil Engineer

Earthquake Hazards Program

agrant@usgs.gov

650-329-5205

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####               Earthquake Science Center          

350 N. Akron RoadMoffett Field, CA94035United States

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