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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.

Citation Information

Publication Year 2020
Title Rainfall triggers more deep-seated landslides than Cascadia earthquakes in the Oregon Coast Range, USA
DOI 10.1126/sciadv.aba6790
Authors Sean R LaHusen, Alison R Duvall, Adam M. Booth, Alex R. R. Grant, Benjamin A Mishkin, David R. Montgomery, William Struble, Joshua J. Roering, Joseph Wartman
Publication Type Article
Publication Subtype Journal Article
Series Title Science Advances
Index ID 70214589
Record Source USGS Publications Warehouse
USGS Organization Earthquake Science Center

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