Linked Earthquake and Tsunami Hazard Modeling on Puget Sound’s Crustal Faults
Description:
Shallow tectonics in the U.S. Pacific Northwest result in north-south compression in the Puget Sound region of Washington State. Much of this shortening is accommodated by deformation along shallow (depths ≤ 35 km), generally east-west striking crustal faults. Many of these crustal faults, including the Seattle Fault (SF) and Saddle Mountain Fault (SMF), underlie the Puget Sound and have produced earthquakes of ~M6.5–7.8 with subsequent tsunamis throughout the Holocene. Recent paleoseismic investigations found that the SF and SMF either ruptured separately within a span of six months or ruptured together as a combined, multifault rupture with an estimated magnitude of M7.8. An M7.8 multifault rupture is significantly larger than the previously-estimated upper bound for an SF earthquake (M7.5) and is not currently included in seismic hazard estimates for the region.
Here, we develop 3-D linked earthquake/tsunami simulations of potential multifault and single fault earthquake scenarios along the SF and SMF to quantify the range of expected shaking and tsunamigenesis, as well as the time-dependent impacts of these cascading hazards. We run 3-D physics-based kinematic ground motion simulations using the code SPECFEM3D Cartesian to generate synthetic seismograms resulting from these potential crustal fault earthquake scenarios. The results demonstrate that an M7.8 earthquake in the Puget Sound region would result in more ground shaking over a wider area and would put a much larger region at risk. Next, we simulate and propagate the tsunami waves that result from our synthetic earthquakes and seafloor displacements. To model these tsunamis, we use the GeoClaw and Method of Splitting Tsunamis (MOST) modeling softwares. Our “linked” earthquake and tsunami simulations allow for a time-dependent analysis of earthquake ground shaking and tsunami inundation from Puget Sound area crustal faults. This study aims to advance critical knowledge of seismic processes and hazards that may inform engineering standards and emergency response efforts, so as to better protect human life and infrastructure.
Session: Accuracy and Variability of Physics-based Ground Motion Modeling [Poster]
Type: Poster
Date: 4/15/2025
Presentation Time: 08:00 AM (local time)
Presenting Author: Julia
Student Presenter: Yes
Invited Presentation:
Poster Number: 83
Authors
Julia Grossman Presenting Author Corresponding Author juliagro@uw.edu University of Washington |
Erin Wirth emoriarty@usgs.gov U.S. Geological Survey |
Audrey Dunham adunham@usgs.gov U.S. Geological Survey |
Ian Stone istone@usgs.gov U.S. Geological Survey |
Randall LeVeque rjl@uw.edu University of Washington |
Loyce Adams lma3@uw.edu University of Washington |
Yong Wei yong.wei@noaa.gov University of Washington, National Oceanic and Atmospheric Administration |
Christopher Moore christopher.moore@noaa.gov National Oceanic and Atmospheric Administration |
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Linked Earthquake and Tsunami Hazard Modeling on Puget Sound’s Crustal Faults
Category
Accuracy and Variability of Physics-based Ground Motion Modeling