UW Earthquake Hazard and Risk Resources

About M9 Simulations

Background

With funding support from the National Science Foundation, a United States Geological Survey and University of Washington team studied the impacts of large magnitude, megathrust earthquakes on the Cascadia subduction zone (The M9 Project). The researchers used physics-based simulations to generate possible ground motions for the entire Pacific Northwest region during a magnitude-9 (M9) event. The simulations used a deterministic, finite difference approach for long periods (i.e., > 1 s) and a stochastic approach for short periods (i.e., < 1 s). The finite difference portion of the simulations used a 3-D seismic velocity model for the Cascadia subduction zone, which includes realistic subduction geometry and several sedimentary basins. Ground motions were generated for thirty possible earthquake rupture scenarios of a magnitude-9 CSZ earthquake. More information on the simulations can be found in the following reference:

  • Frankel, A., Wirth, E., Marafi, N., Vidale, J., and Stephenson, W. (2018), Broadband Synthetic Seismograms for Magnitude 9 Earthquakes on the Cascadia Megathrust Based on 3D Simulations and Stochastic Synthetics, Part 1: Methodology and Overall Results. Bulletin of the Seismological Society of America, 108 (5A), 2347–2369. doi: https://doi.org/10.1785/0120180034

An additional 20 simulations were conducted to evaluate the sensitivities of the computed ground motions to model assumptions.

  • Wirth, E. A., Frankel, A. D., Marafi, N., Vidale, J. E., and Stephenson, W. J. (2018), Broadband Synthetic Seismograms for Magnitude 9 Earthquakes on the Cascadia Megathrust Based on 3D Simulations and Stochastic Synthetics, Part 2: Rupture Parameters and Variability. Bulletin of the Seismological Society of America, 108 (5A), 2370–2388. doi: https://doi.org/10.1785/0120180029

These simulated motions have been used to estimate the vulnerability of idealized structural systems and reinforced-concrete core-wall building to M9 motions.

  • Marafi, Nasser, Eberhard, Marc O., Berman, Jeff, Wirth, E.A. and Frankel, A.D. (2019), Impacts of Simulated M9 Cascadia Subduction Zone Motions on Idealized Systems. Earthquake Spectra. doi: https://doi.org/10.1193/052418EQS123M
  • Marafi, Nasser, Makdisi, A.J., Eberhard, Marc O., and Berman, Jeff (2019), Impacts of M9 Cascadia Subduction Zone Earthquake and Seattle Basin on Performance of RC Core-Wall Buildings. Journal of Structural Engineering, ASCE. In press, 6/2019.

The extents and spacings of the grids for which motions are available are described here.

The coordinates of the stations are listed here.

Acknowledgments

The simulations were the result of a collaboration between researchers at the University of Washington and United States Geological Survey (USGS) with the financial support from the National Science Foundation (Award Number 1331412). This web service tool was developed by Nasser A. Marafi with the support of the USGS (USGS External Grant G19AP00049) and is publically available here.

Disclaimer of Liability

Neither the University of Washington, nor the USGS, nor the National Science Foundation, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, data and tools provided. Users of this information, data, and tools are responsible for assessing their accuracy and proper use.