A Soil Velocity Model for Improved Ground Motion Simulations in the U. S. Pacific Northwest
DOI:
https://doi.org/10.26443/seismica.v4i2.1672Keywords:
Cascadia subduction zone, site characterization, Shear-wave Velocity Models, Earthquake simulationAbstract
Near-surface seismic velocity structure may significantly impact the intensity, duration, and frequency content of ground shaking during an earthquake. In this study, we compile 649 shear wave velocity (Vs) profiles throughout the U.S. Pacific Northwest and southern British Columbia (PNW) and use these measured profiles to develop a representative soil velocity model for four major Holocene soil provinces: Puget Lowlands, Willamette Valley, fill and alluvium, and `other' soils. The resulting soil velocity model shows good agreement to measured data for a wide range of site conditions, with variability between different geologic domains reflecting fundamental differences in depositional environments. We then show that using this regional soil velocity model in simulations of the 2001 M6.8 Nisqually, Washington earthquake improves the fit to observed high-frequency (≥ 0.5 Hz) ground motions in the Puget Sound region compared to simulations that do not incorporate shallow (≤ 200 m) seismic velocity structure. Overall, this work shows that incorporating localized soil velocity profiles into seismic velocity models is important for accurately estimating high-frequency ground motion and regional seismic hazard in earthquake simulations. Future earthquake simulations and hazard studies in the PNW could incorporate these soil velocity profiles to capture the region's distinct site response characteristics.
References
Ahdi, S. K., Kwak, D. Y., Ancheta, T. D., Contreras, V., Kishida, T., Kwok, A. O., Mazzoni, S., Ruz, F., & Stewart, J. P. (2022). Site parameters applied in NGA-Sub database. Earthquake Spectra, 38(1), 494–520. https://doi.org/10.1177/87552930211043536 DOI: https://doi.org/10.1177/87552930211043536
Ahdi, S. K., Stewart, J. P., Ancheta, T. D., Kwak, D. Y., & Mitra, D. (2017). Development of VS profile database and proxy‐based models for VS 30 prediction in the Pacific Northwest region of North America. Bulletin of the Seismological Society of America. https://doi.org/10.1785/0120160335 DOI: https://doi.org/10.1785/0120160335
Albuquerque Seismological Laboratory (ASL)/USGS. (1980). US Geological Survey Networks [Data set]. International Federation of Digital Seismograph Networks. https://doi.org/10.7914/SN/GS
Assaf, J., Molnar, S., & El Naggar, M. H. (2023). CPT-Vs correlations for post-glacial sediments in Metropolitan Vancouver. Soil Dynamics and Earthquake Engineering, 165, 107693. https://doi.org/10.1016/j.soildyn.2022.107693 DOI: https://doi.org/10.1016/j.soildyn.2022.107693
Assaf, J., Molnar, S., El Naggar, M. H., & Sirohey, A. (2022). Seismic site characterization in Fraser River Delta in Metropolitan Vancouver. Soil Dynamics and Earthquake Engineering, 161, 107384. https://doi.org/10.1016/j.soildyn.2022.107384 DOI: https://doi.org/10.1016/j.soildyn.2022.107384
Benito, G., & OʼConnor, J. E. (2003). Number and size of last-glacial Missoula floods in the Columbia River valley between the Pasco Basin, Washington, and Portland, Oregon. Geological Society of America Bulletin, 115, 624–638. https://doi.org/10.1130/0016-7606(2003)115<0624:nasolm>2.0.co;2 DOI: https://doi.org/10.1130/0016-7606(2003)115<0624:NASOLM>2.0.CO;2
Beyreuther, M., Barsch, R., Krischer, L., Megies, T., Behr, Y., & Wassermann, J. (2010). ObsPy: A Python Toolbox for Seismology. Seismological Research Letters, 81(3), 530–533. https://doi.org/10.1785/gssrl.81.3.530 DOI: https://doi.org/10.1785/gssrl.81.3.530
Boore, D. M., & Joyner, W. B. (1997). Site amplifications for generic rock sites. Bulletin of the Seismological Society of America, 87(2), 327–341. https://doi.org/10.1785/bssa0870020327 DOI: https://doi.org/10.1785/BSSA0870020327
Booth, D. B. (1994). Glaciofluvial infilling and scour of the Puget Lowland, Washington, during ice-sheet glaciation. Geology, 22(8), 695. https://doi.org/10.1130/0091-7613(1994)022<0695:giasot>2.3.co;2 DOI: https://doi.org/10.1130/0091-7613(1994)022<0695:GIASOT>2.3.CO;2
Booth, D. B., Troost, K. G., Clague, J. J., & Waitt, R. B. (2003). The Cordilleran Ice Sheet. In The Quaternary Period in the United States (pp. 17–43). Elsevier. https://doi.org/10.1016/s1571-0866(03)01002-9 DOI: https://doi.org/10.1016/S1571-0866(03)01002-9
Borcherdt, R. D. (1970). Effects of local geology on ground motion near San Francisco Bay. Bulletin of the Seismological Society of America, 60(1), 29–61. https://doi.org/10.1785/BSSA0600010029
Bretz, J. H. (1969). The Lake Missoula Floods and the Channeled Scabland. The Journal of Geology, 77(5), 505–543. https://doi.org/10.1086/627452 DOI: https://doi.org/10.1086/627452
Burns, W. J., & Coe, D. E. (2012). Missoula Floods – Inundation Extent and Primary Flood Features in the Portland Metropolitan Area, Clark, Cowlitz, and Skamania Counties. Oregon Department of Geology and Mineral Industries Interpretative Map Series, 1(8).
Delorey, A. A., & Vidale, J. E. (2011). Basin Shear-Wave Velocities beneath Seattle, Washington, from Noise-Correlation Rayleigh Waves. Bulletin of the Seismological Society of America, 101(5), 2162–2175. https://doi.org/10.1785/0120100260 DOI: https://doi.org/10.1785/0120100260
Ely, G. P., Jordan, T., Small, P., & Maechling, P. J. (2010). A VS30-Derived Near-Surface Seismic Velocity Model.
Frankel, A., Carver, D., Cranswick, E., Meremonte, M., Bice, T., & Overturf, D. (1999). Site response for Seattle and source parameters of earthquakes in the Puget Sound Region. Bulletin of the Seismological Society of America, 89(2), 468–483. https://doi.org/10.1785/bssa0890020468 DOI: https://doi.org/10.1785/BSSA0890020468
Frankel, A., & Grant, A. (2020). Site Response, Basin Amplification, and Earthquake Stress Drops in the Portland, Oregon Area. Bulletin of the Seismological Society of America, 111(2), 671–685. https://doi.org/10.1785/0120200269 DOI: https://doi.org/10.1785/0120200269
Frankel, A., Wirth, E., Marafi, N., Vidale, J., & 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. https://doi.org/10.1785/0120180034 DOI: https://doi.org/10.1785/0120180034
Frankel, A.D., Carver, D. L., & Williams, R. A. (2002). Nonlinear and Linear Site Response and Basin Effects in Seattle for the M 6.8 Nisqually, Washington, Earthquake. Bulletin of the Seismological Society of America, 92(6), 2090–2109. https://doi.org/10.1785/0120010254 DOI: https://doi.org/10.1785/0120010254
Frankel, Arthur D., Stephenson, W. J., Carver, D. L., Williams, R. A., Odum, J. K., & Rhea, S. (2007). Seismic Hazard Maps for Seattle, Washington, Incorporating 3D Sedimentary Basin Effects, Nonlinear Site Response, and Rupture Directivity (Open-File Report No. 2007–1175). US Geological Survey. https://doi.org/10.3133/ofr20071175 DOI: https://doi.org/10.3133/ofr20071175
Friedman Alvarez, C. D., Stephenson, W. J., Leeds, A. L., & Lindberg, N. S. (2024). Miscellaneous microtremor array datasets from the Puget Lowland, Washington State [U.S. Geological Survey data release]. https://doi.org/10.5066/P9M5344V
Geyin, M., & Maurer, B. W. (2023). U.S. National VS30 Models and Maps Informed by Remote Sensing and Machine Learning. Seismological Research Letters. https://doi.org/10.1785/0220220181 DOI: https://doi.org/10.1785/0220220181
Joyner, W. B., & Boore, D. M. (1988). Measurement, characterization, and prediction of strong ground motion. Earthquake Engineering and Soil Dynamics II, Proc. Am. Soc. Civil Eng. Geotech. Eng. Div. Specialty Conf, 27–30.
Kelsey, H. M., Sherrod, B. L., Blakely, R. J., & Haugerud, R. A. (2012). Holocene faulting in the Bellingham forearc basin: Upper‐plate deformation at the northern end of the Cascadia subduction zone. Journal of Geophysical Research: Solid Earth, 117(B3). https://doi.org/10.1029/2011jb008816 DOI: https://doi.org/10.1029/2011JB008816
Kolaj, M., Adams, J., & Halchuk, S. (2020). The 6th generation seismic hazard model of Canada. 17th World Conference on Earthquake Engineering, 1–12.
Kourehpaz, P., Molina Hutt, C., Marafi, N. A., Berman, J. W., & Eberhard, M. O. (2020). Estimating economic losses of midrise reinforced concrete shear wall buildings in sedimentary basins by combining empirical and simulated seismic hazard characterizations. Earthquake Engineering & Structural Dynamics, 50(1), 26–42. https://doi.org/10.1002/eqe.3325 DOI: https://doi.org/10.1002/eqe.3325
Lowe, C., Dehler, S. A., & Zelt, B. C. (2003). Basin architecture and density structure beneath the Strait of Georgia, British Columbia. Canadian Journal of Earth Sciences, 40(7), 965–981. https://doi.org/10.1139/e03-030 DOI: https://doi.org/10.1139/e03-030
Marafi, N. A., Eberhard, M. O., Berman, J. W., Wirth, E. A., & Frankel, A. D. (2019). Impacts of Simulated M9 Cascadia Subduction Zone Motions on Idealized Systems. Earthquake Spectra, 35(3), 1261–1287. https://doi.org/10.1193/052418eqs123m DOI: https://doi.org/10.1193/052418EQS123M
Marafi, N. A., Grant, A., Maurer, B. W., Rateria, G., Eberhard, M. O., & Berman, J. W. (2021). A generic soil velocity model that accounts for near-surface conditions and deeper geologic structure. Soil Dynamics and Earthquake Engineering, 140, 106461. https://doi.org/10.1016/j.soildyn.2020.106461 DOI: https://doi.org/10.1016/j.soildyn.2020.106461
McPhee, D. K., Langenheim, V. E., Wells, R. E., & Blakely, R. J. (2014). Tectonic evolution of the Tualatin basin, northwest Oregon, as revealed by inversion of gravity data. Geosphere, 10(2), 264–275. https://doi.org/10.1130/ges00929.1 DOI: https://doi.org/10.1130/GES00929.1
Minervini, J. M., O’Connor, J. E., & Wells, R. E. (2003). Maps Showing Inundation Depths, Ice-Rafted Erratics, and Sedimentary Facies of Late Pleistocene Missoula Floods in the Willamette Valley, Oregon (Open-File Report No. 2003–408). US Geological Survey. https://doi.org/10.3133/ofr2003408 DOI: https://doi.org/10.3133/ofr2003408
Molnar, S., Cassidy, J. F., Olsen, K. B., Dosso, S. E., & He, J. (2014). Earthquake Ground Motion and 3D Georgia Basin Amplification in Southwest British Columbia: Deep Juan de Fuca Plate Scenario Earthquakes. Bulletin of the Seismological Society of America, 104(1), 301–320. https://doi.org/10.1785/0120110277 DOI: https://doi.org/10.1785/0120110277
Petersen, M. D., Shumway, A. M., Powers, P. M., Field, E. H., Moschetti, M. P., Jaiswal, K. S., Milner, K. R., Rezaeian, S., Frankel, A. D., Llenos, A. L., Michael, A. J., Altekruse, J. M., Ahdi, S. K., Withers, K. B., Mueller, C. S., Zeng, Y., Chase, R. E., Salditch, L. M., Luco, N., … Witter, R. C. (2023). The 2023 US 50-State National Seismic Hazard Model: Overview and implications. Earthquake Spectra, 40(1), 5–88. https://doi.org/10.1177/87552930231215428 DOI: https://doi.org/10.1177/87552930231215428
Petersson, N. A., Sjogreen, B., Tang, H., & Pankajakshan, R. (2023). geodynamics/sw4: SW4, version 3.0 [Software]. Zenodo. https://doi.org/10.5281/ZENODO.8322590
Rekoske, J. M., Moschetti, M. P., & Thompson, E. M. (2021). Basin and Site Effects in the U.S. Pacific Northwest Estimated from Small-Magnitude Earthquakes. Bulletin of the Seismological Society of America, 112(1), 438–456. https://doi.org/10.1785/0120210029 DOI: https://doi.org/10.1785/0120210029
Roten, D., Olsen, K. B., & Takedatsu, R. (2019). Numerical Simulation of M9 Megathrust Earthquakes in the Cascadia Subduction Zone. Pure and Applied Geophysics, 177(5), 2125–2141. https://doi.org/10.1007/s00024-018-2085-5 DOI: https://doi.org/10.1007/s00024-018-2085-5
Shi, J., & Asimaki, D. (2018). A Generic Velocity Profile for Basin Sediments in California Conditioned on VS30. Seismological Research Letters, 89(4), 1397–1409. https://doi.org/10.1785/0220170268 DOI: https://doi.org/10.1785/0220170268
Somala, S. N., Parla, R., & Mangalathu, S. (2022). Basin effects on tall bridges in Seattle from M9 Cascadia scenarios. Engineering Structures, 260, 114252. https://doi.org/10.1016/j.engstruct.2022.114252 DOI: https://doi.org/10.1016/j.engstruct.2022.114252
Stephenson, W. J., Reitman, N. G., & Angster, S. J. (2017). P- and S-wave velocity models incorporating the Cascadia subduction zone for 3D earthquake ground motion simulations, Version 1.6—Update for Open-File Report 2007–1348 (Open-File Report No. 2017–1152). US Geological Survey. https://doi.org/10.3133/ofr20171152 DOI: https://doi.org/10.3133/ofr20171152
Stone, I., Wirth, E. A., & Frankel, A. D. (2021). Structure and QP–QS Relations in the Seattle and Tualatin Basins from Converted Seismic Phases. Bulletin of the Seismological Society of America, 111(3), 1221–1233. https://doi.org/10.1785/0120200390 DOI: https://doi.org/10.1785/0120200390
Stone, I., Wirth, E. A., & Frankel, A. D. (2022). Topographic Response to Simulated Mw 6.5–7.0 Earthquakes on the Seattle Fault. Bulletin of the Seismological Society of America, 112(3), 1436–1462. https://doi.org/10.1785/0120210269 DOI: https://doi.org/10.1785/0120210269
Stone, I., Wirth, E. A., Grant, A., & Frankel, A. D. (2023). 3D Wave Propagation Simulations of Mw 6.5+ Earthquakes on the Tacoma Fault, Washington State, Considering the Effects of Topography, a Geotechnical Gradient, and a Fault Damage Zone. Bulletin of the Seismological Society of America, 113(6), 2519–2542. https://doi.org/10.1785/0120230083 DOI: https://doi.org/10.1785/0120230083
Su, F., Aki, K., Teng, T., Zeng, Y., Koyanagi, S., & Mayeda, K. (1992). The relation between site amplification factor and surficial geology in central California. Bulletin of the Seismological Society of America, 82(2), 580–602. https://doi.org/10.1785/BSSA0820020580 DOI: https://doi.org/10.1785/BSSA0820020580
Thompson, M., Wirth, E. A., Frankel, A. D., Renate Hartog, J., & Vidale, J. E. (2020). Basin Amplification Effects in the Puget Lowland, Washington, from Strong-Motion Recordings and 3D Simulations. Bulletin of the Seismological Society of America, 110(2), 534–555. https://doi.org/10.1785/0120190211 DOI: https://doi.org/10.1785/0120190211
United States Geological Survey, O. D. of G. and M. I., Washington Department of Natural Resources. (2025). Quaternary fault and fold database for the United States. https://www.usgs.gov/natural-hazards/earthquake-hazards/faults
University of Washington. (1963). Pacific Northwest Seismic Network - University of Washington [Dataset]. International Federation of Digital Seismograph Networks. https://doi.org/10.7914/SN/UW
Washington Division of Geology and Earth Resources. (2016). Surface geology, 1:100,000–GIS data [Dataset]. In Washington Division of Geology and Earth Resources Digital Data Series DS-18 (Vol. 1). http://www.dnr.wa.gov/publications/ger_portal_surface_geology_100k.zip
Washington Geological Survey. (2021). Shear wave database–GIS data: Washington Geological Survey Digital Data Series 17, version 1.3 [Dataset]. https://fortress.wa.gov/dnr/geologydata/publications/data_download/ger_portal_shear_wave.zip.
Wirth, E.A., Alex R Grant, Ian P Stone, William J Stephenson, & Arthur D Frankel. (2025). Data for A 3-D Seismic Velocity Model for Cascadia with Shallow Soils & Topography, Version 1.7 [Dataset]. U.S. Geological Survey. https://doi.org/10.5066/P14HJ3IC
Wirth, E.A., Grant, A. R., Stone, I. P., Stephenson, W. J., & Frankel, A. D. (2025). Three-dimensional seismic velocity model for the Cascadia Subduction Zone with shallow soils and topography, version 1.7: U.S (Open-File Report No. 2025–1045). https://doi.org/10.3133/ofr20251045
Wirth, Erin A., & Frankel, A. D. (2019). Impact of Down‐Dip Rupture Limit and High‐Stress Drop Subevents on Coseismic Land‐Level Change during Cascadia Megathrust Earthquakes. Bulletin of the Seismological Society of America, 109(6), 2187–2197. https://doi.org/10.1785/0120190043 DOI: https://doi.org/10.1785/0120190043
Wirth, Erin A., Frankel, A. D., Marafi, N., Vidale, J. E., & 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. https://doi.org/10.1785/0120180029 DOI: https://doi.org/10.1785/0120180029
Wirth, Erin A., Grant, A., Marafi, N. A., & Frankel, A. D. (2020). Ensemble ShakeMaps for Magnitude 9 Earthquakes on the Cascadia Subduction Zone. Seismological Research Letters, 92(1), 199–211. https://doi.org/10.1785/0220200240 DOI: https://doi.org/10.1785/0220200240
Yeh, T.-Y., & Olsen, K. B. (2024). Simulation of 0–7.5 Hz physics-based nonlinear ground motions for maximum credible earthquake scenarios at the Long Valley Dam, CA. Earthquake Spectra, 40(2), 1479–1506. https://doi.org/10.1177/87552930231226135 DOI: https://doi.org/10.1177/87552930231226135
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