Relative Tsunami Hazard From Segments of Cascadia Subduction Zone For M w 7.5–9.2 Earthquakes

• Published in: Geophysical research letters Vol. 48; no. 16
• Main Authors: Salaree, Amir, Huang, Yihe, Ramos, Marlon D., Stein, Seth
• Format: Journal Article
• Language: English
• Published: 28.08.2021
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2021GL094174

Abstract Tsunamis from earthquakes of various magnitudes have affected Cascadia in the past. Simulations of M w 7.5–9.2 earthquake constrained by earthquake rupture physics and geodetic locking models show that M w ≥ 8.5 events initiating in the middle segments of the subduction zone can create coastal tsunami amplitudes comparable to those from the largest expected event. Our rupture and tsunami simulations reveal that the concave coastline geometry of the Pacific Northwest coastline focuses tsunami energy between latitudes 44° and 45° in Oregon. The possible coastal tsunami amplitudes are largely insensitive to the choice of slip model for a given magnitude. These results are useful for identifying the most hazardous segments of the subduction zone and demonstrate that a worst‐case rupture scenario does not uniquely yield the worst‐case tsunami scenario at a given location. Plain Language Summary Offshore earthquakes along the Pacific Northwest coast of the U.S. and Canada (Cascadia region) can have magnitudes as high as 9.2, as was probably the case for an earthquake in the year 1700 CE that resulted in a large tsunami in Cascadia and across the Pacific Ocean. To learn more about the future tsunami hazard in the region, we design computer models of tsunamis from a wide range of earthquake scenarios. We find that almost regardless of the earthquake source details, events larger than magnitude 8.5 near the coast of Oregon can create large and widespread tsunamis along the US west coast. These are consequences of the geometry of offshore earthquake faulting and the concave shape of coastline in the region. Key Points A M w  = 8.5 event in central Cascadia (Oregon) can create coastal tsunami amplitudes comparable to those from the largest possible event The concave coastline contributes to larger coastal tsunami amplitudes in central Cascadia The choice of slip model does not significantly affect the distribution of coastal tsunami amplitudes in Cascadia