The Distribution of Interseismic Locking on the Cascadia Subduction Zone Using Bayesian Methods

Special Issue: The Cascadia Subduction Zone | Bayesian Inversion of Cascadia Interseismic Locking

Authors

DOI:

https://doi.org/10.26443/seismica.v2i4.1701

Keywords:

fault locking, Bayesian inversion, subduction zone hazards, Cascadia

Abstract

We use a Bayesian probabilistic framework to invert for the kinematic locking distribution on the Cascadia Subduction Zone, constrained by surface deformation data and a prior assumption of the locking pattern. Interseismic surface deformation observations include land and seafloor GNSS data, along with decades-averaged vertical rates from spirit leveling. Using a Bayesian inversion framework, we explore a range of priors, including different updip and downdip limits and along-strike heterogeneity in locking. Data corrections account for contemporary glacial isostatic adjustment and viscoelastic effects. The mean of the locking distributions suggests a highly coupled offshore zone, transitioning to creep at a depth that varies along strike, with sensitivity to the prior. The shape of the locking distributions varies along strike, with the highest means near the deformation front and in Central Oregon. Results suggest high probability of strong locking offshore and low locking deeper than 20 km depth, which can provide insight into associated hazards. This work also highlights the importance of tradeoffs among different deformation signals. We find that the combined influence of viscoelasticity and glacial isostatic adjustment is relatively small in Cascadia, on the order of a few mm/yr vertically, indicating that elastic strain accumulation dominates the contemporary crustal deformation.

References

Blewitt, G., Hammond, W., & Kreemer, C. (2018). Harnessing the GPS Data Explosion for Interdisciplinary Science. Eos, 99. https://doi.org/10.1029/2018eo104623 DOI: https://doi.org/10.1029/2018EO104623

Bloch, W., Bostock, M. G., & Audet, P. (2023). A Cascadia Slab Model From Receiver Functions. Geochemistry, Geophysics, Geosystems, 24(10). https://doi.org/10.1029/2023gc011088 DOI: https://doi.org/10.1029/2023GC011088

Carbotte, S. M., Boston, B., Han, S., Shuck, B., Beeson, J., Canales, J. P., Tobin, H., Miller, N., Nedimovic, M., Tréhu, A., Lee, M., Lucas, M. C., Jian, H., Jiang, D., Moser, L., Anderson, C., Judd, D., Fernandez, J., Campbell, C., … Gahlawat, R. (2024). Subducting plate structure and megathrust morphology from deep seismic imaging linked to earthquake rupture segmentation at Cascadia. Science Advances, 10(23). https://doi.org/10.1126/sciadv.adl3198 DOI: https://doi.org/10.1126/sciadv.adl3198

Clark, J., Mitrovica, J. X., & Latychev, K. (2019). Glacial isostatic adjustment in central Cascadia: Insights from three-dimensional Earth modeling. Geology, 47(4), 295–298. https://doi.org/10.1130/g45566.1 DOI: https://doi.org/10.1130/G45566.1

Coreform LLC. (2018). Coreform Cubit. Computer software. http://coreform.com

Dal Zilio, L., Jolivet, R., & van Dinther, Y. (2020). Segmentation of the Main Himalayan Thrust Illuminated by Bayesian Inference of Interseismic Coupling. Geophysical Research Letters, 47(4). https://doi.org/10.1029/2019gl086424 DOI: https://doi.org/10.1029/2019GL086424

DeSanto, J. B., Schmidt, D. A., Zumberge, M., Sasagawa, G., & Chadwell, C. D. (2025). Near full locking on the shallow megathrust of the central Cascadia subduction zone revealed by GNSS-Acoustic. Earth and Planetary Science Letters, 665. https://doi.org/10.1016/j.epsl.2025.119463 DOI: https://doi.org/10.1016/j.epsl.2025.119463

Engelhart, S. E., Vacchi, M., Horton, B. P., Nelson, A. R., & Kopp, R. E. (2015). A sea-level database for the Pacific coast of central North America. Quaternary Science Reviews, 113, 78–92. https://doi.org/10.1016/j.quascirev.2014.12.001 DOI: https://doi.org/10.1016/j.quascirev.2014.12.001

Flück, P., Hyndman, R. D., & Wang, K. (1997). Three‐dimensional dislocation model for great earthquakes of the Cascadia Subduction Zone. Journal of Geophysical Research: Solid Earth, 102(B9). https://doi.org/10.1029/97jb01642 DOI: https://doi.org/10.1029/97JB01642

Han, S., Bangs, N. L., Carbotte, S. M., Saffer, D. M., & Gibson, J. C. (2017). Links between sediment consolidation and Cascadia megathrust slip behaviour. Nature Geoscience, 10(12), 954–959. https://doi.org/10.1038/s41561-017-0007-2 DOI: https://doi.org/10.1038/s41561-017-0007-2

Hayes, G. P., Moore, G. L., Portner, D. E., Hearne, M., Flamme, H., Furtney, M., & Smoczyk, G. M. (2018). Slab2, a comprehensive subduction zone geometry model. Science, 362(6410), 58–61. https://doi.org/10.1126/science.aat4723 DOI: https://doi.org/10.1126/science.aat4723

Jamason, P., Bock, Y., Fang, P., Gilmore, B., Malveaux, D., Prawirodirdjo, L., & Scharber, M. (2004). SOPAC Web site (http://sopac.ucsd.edu). GPS Solutions, 8(4), 272–277. https://doi.org/10.1007/s10291-004-0118-2 DOI: https://doi.org/10.1007/s10291-004-0118-2

Kemp, A. C., Cahill, N., Engelhart, S. E., Hawkes, A. D., & Wang, K. (2018). Revising Estimates of Spatially Variable Subsidence during the A.D. 1700 Cascadia Earthquake Using a Bayesian Foraminiferal Transfer Function. Bulletin of the Seismological Society of America, 108(2), 654–673. https://doi.org/10.1785/0120170269 DOI: https://doi.org/10.1785/0120170269

Konca, A. O., Avouac, J.-P., Sladen, A., Meltzner, A. J., Sieh, K., Fang, P., Li, Z., Galetzka, J., Genrich, J., Chlieh, M., Natawidjaja, D. H., Bock, Y., Fielding, E. J., Ji, C., & Helmberger, D. V. (2008). Partial rupture of a locked patch of the Sumatra megathrust during the 2007 earthquake sequence. Nature, 456(7222), 631–635. https://doi.org/10.1038/nature07572 DOI: https://doi.org/10.1038/nature07572

Li, S., & Chen, L. (2023). How Long Can the Postseismic and Interseismic Phases of Great Subduction Earthquake Sustain? Toward an Integrated Earthquake‐Cycle Perspective. Geophysical Research Letters, 50(11). https://doi.org/10.1029/2023gl103976 DOI: https://doi.org/10.1029/2023GL103976

Li, S., & Chen, L. (2024). Vertical Crustal Deformation Due To Viscoelastic Earthquake Cycles at Subduction Zones: Implications for Nankai and Cascadia. Journal of Geophysical Research: Solid Earth, 129(8). https://doi.org/10.1029/2024jb028817 DOI: https://doi.org/10.1029/2024JB028817

Li, S., Fukuda, J., & Oncken, O. (2020). Geodetic Evidence of Time‐Dependent Viscoelastic Interseismic Deformation Driven by Megathrust Locking in the Southwest Japan Subduction Zone. Geophysical Research Letters, 47(4). https://doi.org/10.1029/2019gl085551 DOI: https://doi.org/10.1029/2019GL085551

Li, S., Wang, K., Wang, Y., Jiang, Y., & Dosso, S. E. (2018). Geodetically Inferred Locking State of the Cascadia Megathrust Based on a Viscoelastic Earth Model. Journal of Geophysical Research: Solid Earth, 123(9). https://doi.org/10.1029/2018jb015620 DOI: https://doi.org/10.1029/2018JB015620

Lindsey, E. O., Mallick, R., Hubbard, J. A., Bradley, K. E., Almeida, R. V., Moore, J. D. P., Bürgmann, R., & Hill, E. M. (2021). Slip rate deficit and earthquake potential on shallow megathrusts. Nature Geoscience, 14(5), 321–326. https://doi.org/10.1038/s41561-021-00736-x DOI: https://doi.org/10.1038/s41561-021-00736-x

Lorito, S., Romano, F., Atzori, S., Tong, X., Avallone, A., McCloskey, J., Cocco, M., Boschi, E., & Piatanesi, A. (2011). Limited overlap between the seismic gap and coseismic slip of the great 2010 Chile earthquake. Nature Geoscience, 4(3), 173–177. https://doi.org/10.1038/ngeo1073 DOI: https://doi.org/10.1038/ngeo1073

Loveless, J. P., & Meade, B. J. (2011). Spatial correlation of interseismic coupling and coseismic rupture extent of the 2011 MW= 9.0 Tohoku-oki earthquake: COUPLING AND TOHOKU-OKI SLIP. Geophysical Research Letters, 38(17). https://doi.org/10.1029/2011gl048561 DOI: https://doi.org/10.1029/2011GL048561

Matsu’ura, M., Noda, A., & Fukahata, Y. (2007). Geodetic data inversion based on Bayesian formulation with direct and indirect prior information: Geodetic data inversion based on Bayesian formulation. Geophysical Journal International, 171(3). https://doi.org/10.1111/j.1365-246x.2007.03578.x DOI: https://doi.org/10.1111/j.1365-246X.2007.03578.x

McCaffrey, R., King, R. W., Payne, S. J., & Lancaster, M. (2013). Active tectonics of northwestern U.S. inferred from GPS‐derived surface velocities. Journal of Geophysical Research: Solid Earth, 118(2), 709–723. https://doi.org/10.1029/2012jb009473 DOI: https://doi.org/10.1029/2012JB009473

McCaffrey, R., Qamar, A. I., King, R. W., Wells, R., Khazaradze, G., Williams, C. A., Stevens, C. W., Vollick, J. J., & Zwick, P. C. (2007). Fault locking, block rotation and crustal deformation in the Pacific Northwest. Geophysical Journal International, 169(3). https://doi.org/10.1111/j.1365-246x.2007.03371.x DOI: https://doi.org/10.1111/j.1365-246X.2007.03371.x

McCrory, P. A., Blair, J. L., Waldhauser, F., & Oppenheimer, D. H. (2012). Juan de Fuca slab geometry and its relation to Wadati‐Benioff zone seismicity. Journal of Geophysical Research: Solid Earth, 117(B9). https://doi.org/10.1029/2012jb009407 DOI: https://doi.org/10.1029/2012JB009407

Métois, M., Socquet, A., & Vigny, C. (2012). Interseismic coupling, segmentation and mechanical behavior of the central Chile subduction zone. Journal of Geophysical Research: Solid Earth, 117(B3). https://doi.org/10.1029/2011jb008736 DOI: https://doi.org/10.1029/2011JB008736

Miller, M., Johnson, D., Rubin, C., Dragert, H., Endo, E., & Humphreys, E. (1997). GPS monitoring of the Cascadia Margin: The Pacific Northwest Geodetic Array (PANGA). Eos Trans AGU, 78, 46.

Miller, M. M., Johnson, D. J., Rubin, C. M., Dragert, H., Wang, K., Qamar, A., & Goldfinger, C. (2001). GPS‐determination of along‐strike variation in Cascadia margin kinematics: Implications for relative plate motion, subduction zone coupling, and permanent deformation. Tectonics, 20(2), 161–176. https://doi.org/10.1029/2000tc001224 DOI: https://doi.org/10.1029/2000TC001224

Minson, S. E., Simons, M., & Beck, J. L. (2013). Bayesian inversion for finite fault earthquake source models I—theory and algorithm. Geophysical Journal International, 194(3). https://doi.org/10.1093/gji/ggt180 DOI: https://doi.org/10.1093/gji/ggt180

Minson, S. E., Simons, M., Beck, J. L., Ortega, F., Jiang, J., Owen, S. E., Moore, A. W., Inbal, A., & Sladen, A. (2014). Bayesian inversion for finite fault earthquake source models – II: the 2011 great Tohoku-oki, Japan earthquake. Geophysical Journal International, 198(2). https://doi.org/10.1093/gji/ggu170 DOI: https://doi.org/10.1093/gji/ggu170

Nalbant, S., McCloskey, J., Steacy, S., NicBhloscaidh, M., & Murphy, S. (2013). Interseismic coupling, stress evolution, and earthquake slip on the Sunda megathrust. Geophysical Research Letters, 40(16), 4204–4208. https://doi.org/10.1002/grl.50776 DOI: https://doi.org/10.1002/grl.50776

Newton, T., Weldon, R., Miller, I., Schmidt, D., Mauger, G., Morgan, H., & Grossman, E. (2021). An Assessment of Vertical Land Movement to Support Coastal Hazards Planning in Washington State. Water, 13(3), 281. https://doi.org/10.3390/w13030281 DOI: https://doi.org/10.3390/w13030281

Nikkhoo, M., & Walter, T. R. (2015). Triangular dislocation: an analytical, artefact-free solution. Geophysical Journal International, 201(2), 1119–1141. https://doi.org/10.1093/gji/ggv035 DOI: https://doi.org/10.1093/gji/ggv035

Nocquet, J.-M. (2018). Stochastic static fault slip inversion from geodetic data with non-negativity and bound constraints. Geophysical Journal International, 214(1), 366–385. https://doi.org/10.1093/gji/ggy146 DOI: https://doi.org/10.1093/gji/ggy146

Patton, J., Williams, T., Anderson, J., Hemphill-Haley, M., Burgette, R., Weldon II, R., McPherson, R., & Leroy, T. (2023). 20th to 21st century relative sea and land level changes in Northern California: Tectonic land level changes and their contribution to sea-level rise. Tektonika, 1(1). https://doi.org/10.55575/tektonika2023.1.1.6 DOI: https://doi.org/10.55575/tektonika2023.1.1.6

Pearson, A. E. R., & Schmidt, D. (2026). Datasets associated with the publication The Distribution of Interseismic Locking on the Cascadia Subduction Zone Using Bayesian Methods . Zenodo. https://doi.org/10.5281/zenodo.21479776

Pollitz, F. F. (2025). 3D Viscoelastic Models of Slip‐Deficit Rate Along the Cascadia Subduction Zone. Journal of Geophysical Research: Solid Earth, 130(1). https://doi.org/10.1029/2024jb029847 DOI: https://doi.org/10.1029/2024JB029847

Protti, M., González, V., Newman, A. V., Dixon, T. H., Schwartz, S. Y., Marshall, J. S., Feng, L., Walter, J. I., Malservisi, R., & Owen, S. E. (2013). Nicoya earthquake rupture anticipated by geodetic measurement of the locked plate interface. Nature Geoscience, 7(2), 117–121. https://doi.org/10.1038/ngeo2038 DOI: https://doi.org/10.1038/ngeo2038

Satake, K., Shimazaki, K., Tsuji, Y., & Ueda, K. (1996). Time and size of a giant earthquake in Cascadia inferred from Japanese tsunami records of January 1700. Nature, 379(6562), 246–249. https://doi.org/10.1038/379246a0 DOI: https://doi.org/10.1038/379246a0

Sato, D. S., Hori, T., & Fukahata, Y. (2025). Differentiating Frictionally Locked Asperities From Kinematically Coupled Zones. Journal of Geophysical Research: Solid Earth, 130(10). https://doi.org/10.1029/2024jb030357 DOI: https://doi.org/10.1029/2024JB030357

Savage, J. C. (1983). A dislocation model of strain accumulation and release at a subduction zone. Journal of Geophysical Research: Solid Earth, 88(B6). https://doi.org/10.1029/jb088ib06p04984 DOI: https://doi.org/10.1029/JB088iB06p04984

Savage, J. C., Svarc, J. L., Prescott, W. H., & Murray, M. H. (2000). Deformation across the forearc of the Cascadia subduction zone at Cape Blanco, Oregon. Journal of Geophysical Research: Solid Earth, 105(B2), 3095–3102. https://doi.org/10.1029/1999jb900392 DOI: https://doi.org/10.1029/1999JB900392

Schmalzle, G. M., McCaffrey, R., & Creager, K. C. (2014). Central Cascadia subduction zone creep. Geochemistry, Geophysics, Geosystems, 15(4), 1515–1532. https://doi.org/10.1002/2013gc005172 DOI: https://doi.org/10.1002/2013GC005172

Seyler, C. E., Kirkpatrick, J. D., Savage, H. M., Hirose, T., & Faulkner, D. R. (2020). Rupture to the trench? Frictional properties and fracture energy of incoming sediments at the Cascadia subduction zone. Earth and Planetary Science Letters, 546. https://doi.org/10.1016/j.epsl.2020.116413 DOI: https://doi.org/10.1016/j.epsl.2020.116413

Sherrill, E. M., Johnson, K. M., & Jackson, N. M. (2024). Locating Boundaries Between Locked and Creeping Regions at Nankai and Cascadia Subduction Zones. Journal of Geophysical Research: Solid Earth, 129(10). https://doi.org/10.1029/2024jb029346 DOI: https://doi.org/10.1029/2024JB029346

Shirzaei, M., Freymueller, J., Törnqvist, T. E., Galloway, D. L., Dura, T., & Minderhoud, P. S. J. (2020). Measuring, modelling and projecting coastal land subsidence. Nature Reviews Earth & Environment, 2(1), 40–58. https://doi.org/10.1038/s43017-020-00115-x DOI: https://doi.org/10.1038/s43017-020-00115-x

Thatcher, W. (1984). The earthquake deformation cycle at the Nankai Trough, southwest Japan. Journal of Geophysical Research: Solid Earth, 89(B5), 3087–3101. https://doi.org/10.1029/jb089ib05p03087 DOI: https://doi.org/10.1029/JB089iB05p03087

Wang, K., Hu, Y., & He, J. (2012). Deformation cycles of subduction earthquakes in a viscoelastic Earth. Nature, 484(7394), 327–332. https://doi.org/10.1038/nature11032 DOI: https://doi.org/10.1038/nature11032

Wang, K., & Tréhu, A. M. (2016). Invited review paper: Some outstanding issues in the study of great megathrust earthquakes—The Cascadia example. Journal of Geodynamics, 98, 1–18. https://doi.org/10.1016/j.jog.2016.03.010 DOI: https://doi.org/10.1016/j.jog.2016.03.010

Wang, L., Hainzl, S., Zöller, G., & Holschneider, M. (2012). Stress‐ and aftershock‐constrained joint inversions for coseismic and postseismic slip applied to the 2004 M6.0 Parkfield earthquake. Journal of Geophysical Research: Solid Earth, 117(B7). https://doi.org/10.1029/2011jb009017 DOI: https://doi.org/10.1029/2011JB009017

Wang, P., Engelhart, S. E., Wang, K., Hawkes, A. D., Horton, B. P., Nelson, A. R., & Witter, R. C. (2013). Heterogeneous rupture in the great Cascadia earthquake of 1700 inferred from coastal subsidence estimates. Journal of Geophysical Research: Solid Earth, 118(5), 2460–2473. https://doi.org/10.1002/jgrb.50101 DOI: https://doi.org/10.1002/jgrb.50101

Wells, R. E., & McCaffrey, R. (2013). Steady rotation of the Cascade arc. Geology, 41(9). https://doi.org/10.1130/g34514.1 DOI: https://doi.org/10.1130/G34514.1

Wells, R. E., & Simpson, R. W. (2014). Northward migration of the Cascadia forearc in the northwestern U.S. and implications for subduction deformation. Earth, Planets and Space, 53(4). https://doi.org/10.1186/bf03352384 DOI: https://doi.org/10.1186/BF03352384

Wirth, E. 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, E. 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

Yousefi, M., Milne, G. A., & Latychev, K. (2021). Glacial isostatic adjustment of the Pacific Coast of North America: the influence of lateral Earth structure. Geophysical Journal International, 226(1), 91–113. https://doi.org/10.1093/gji/ggab053 DOI: https://doi.org/10.1093/gji/ggab053

Zhu, M. (2023). The Liu-Han Altar: Between a Literati Spirit-Writing Altar and Popular Religion. In Communicating with the Gods. BRILL. https://doi.org/10.1163/9789004677906_010 DOI: https://doi.org/10.1163/9789004677906_010

Zumberge, J. F. (1999). Automated GPS Data Analysis Service. GPS Solutions, 2(3), 76–78. https://doi.org/10.1007/pl00012760 DOI: https://doi.org/10.1007/PL00012760

Seismica cover image for Volume 2, Number 4: The Cascadia Subduction Zone: Grand Challenges and Research Frontiers. Image shows a hemispherical white dome on a four-legged stand on a rocky mountain peak. In the far distance, a series of sharp rocky and snowy peaks stretches toward the setting sun which is refracted through thin clouds.

Downloads

Additional Files

Published

2026-09-02

How to Cite

Pearson, A., & Schmidt, D. (2026). The Distribution of Interseismic Locking on the Cascadia Subduction Zone Using Bayesian Methods: Special Issue: The Cascadia Subduction Zone | Bayesian Inversion of Cascadia Interseismic Locking. Seismica, 2(4). https://doi.org/10.26443/seismica.v2i4.1701

Issue

Vol. 2 No. 4: Special Issue: the Cascadia Subduction Zone

Section

Special Issue: the Cascadia Subduction Zone

License

Copyright (c) 2023 Anna Pearson, David Schmidt

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 International License.

Funding data