Published In
Bulletin of the Seismological Society of America
Document Type
Article
Publication Date
4-1-2024
Abstract
Earthquake‐induced landslides can record information about the seismic shaking that generated them. In this study, we present new mapping, Light Detection and Ranging‐derived roughness dating, and analysis of over 1000 deep‐seated landslides from the Puget Lowlands of Washington, U.S.A., to probe the landscape for past Seattle fault earthquake information. With this new landslide inventory, we observe spatial and temporal evidence of landsliding related to the last major earthquake on the Seattle fault ∼1100 yr before present. We find spatial clusters of landslides that correlate with ground motions from recent 3D kinematic models of Seattle fault earthquakes. We also find temporal patterns in the landslide inventory that suggest earthquake‐driven increases in landsliding. We compare the spatial and temporal landslide data with scenario‐based ground motion models and find stronger evidence of the last major Seattle fault earthquake from this combined analysis than from spatial or temporal patterns alone. We also compare the landslide inventory with ground motions from different Seattle fault earthquake scenarios to determine the ground motion distributions that are most consistent with the landslide record. We find that earthquake scenarios that best match the clustering of ∼1100‐year‐old landslides produce the strongest shaking within a band that stretches from west to east across central Seattle as well as along the bluffs bordering the broader Puget Sound. Finally, we identify other landslide clusters (at 4.6–4.2 ka, 4.0–3.8 ka, 2.8–2.6 ka, and 2.2–2.0 ka) in the inventory which let us infer potential ground motions that may correspond to older Seattle fault earthquakes. Our method, which combines hindcasting of the surface response to the last major Seattle fault earthquake, using a roughness‐aged landslide inventory with forecasts of modeled ground shaking from 3D seismic scenarios, showcases a powerful new approach to gleaning paleoseismic information from landscapes.
Rights
This work was authored as part of the Contributor's official duties as an Employee of the United States Government and is, therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
Locate the Document
DOI
10.1785/0120230079
Persistent Identifier
https://archives.pdx.edu/ds/psu/42040
Citation Details
Herzig, E., Duvall, A., Booth, A., Stone, I., Wirth, E., LaHusen, S., Wartman, J., & Grant, A. (2023). Evidence of Seattle Fault Earthquakes from Patterns in Deep-Seated Landslides. Bulletin of the Seismological Society of America, 114(2), 1084–1102.