A rare earthquake in the upper mantle of subcontinental lithospheric mantle of North America

Authors

DOI:

https://doi.org/10.26443/seismica.v5i1.2999

Keywords:

Mantle earthquakes, focal mechanism, waveform analysis

Abstract

Earthquakes occurring in stable continental mantle lithosphere are extremely rare, with a small number of cases restricted to northern Australia, the India-Asia collision zone, and western North America. Here, we use a combination of regional seismic waveform modelling and teleseismic array data to confirm the location of a small (Mw 4.1) earthquake from September 2025 under northern Utah, whose depth places it firmly below the local Moho, and into the continental mantle. This joins other reported small-magnitude seismicity under the eastern Rocky Mountains, principally in Utah and Wyoming, who’s causative mechanism remains enigmatic. The focal mechanism of this earthquake is consistent with those of other reported mantle seismicity, but contrasts with the shallower crustal stress field, indicating that seismicity in the mantle in this region may not reflect the shallow crustal geodynamics of the region, and is unlikely to be playing a role in supporting long-term stresses.

References

Albuquerque Seismological Laboratory/USGS. (1990). United States National Seismic Network. International Federation of Digital Seismograph Networks. https://doi.org/10.7914/SN/US

Albuquerque Seismological Laboratory/USGS. (2003). Intermountain West Seismic Network. International Federation of Digital Seismograph Networks. https://doi.org/10.7914/SN/IW

Albuquerque Seismological Laboratory/USGS. (2013). Central and Eastern US Network. International Federation of Digital Seismograph Networks. https://doi.org/10.7914/SN/N4

Arora, N. S., Russell, S., & Sudderth, E. (2012). NET-VISA: Network Processin Vertically Integrated Seismic Analysis. Bulletin of the Seismological Society of America, 103. https://doi.org/10.1785/0120120107 DOI: https://doi.org/10.1785/0120120107

Bassin, C. (2000). The current limits of resolution for surface wave tomography in North America. Eos Trans. AGU, 81, F897.

Becker, T. W., Lowry, A. R., Faccenna, C., Schmandt, B., Borsa, A., & Yu, C. (2015). Western US intermountain seismicity caused by changes in upper mantle flow. Nature, 524(7566), 458–461. https://doi.org/10.1038/nature14867 DOI: https://doi.org/10.1038/nature14867

Bedrosian, P. A., & Frost, C. D. (2023). Geophysical extent of the Wyoming Province, western USA: Insights into ancient subduction and craton stability. Bulletin, 135(3–4), 725–742. https://doi.org/10.1130/B36417.1 DOI: https://doi.org/10.1130/B36417.1

Brigham Young University-Idaho. (2001). BYU-Idaho Network. International Federation of Digital Seismograph Networks. https://doi.org/10.7914/SN/RC

Cao, Z., & Liu, L. (2024). Western US intraplate deformation controlled by the complex lithospheric structure. Nature Communications, 15(1), 3917. https://doi.org/10.1038/s41467-024-48223-2 DOI: https://doi.org/10.1038/s41467-024-48223-2

Chen, W.-P., & Molnar, P. (1983). Focal depths of intracontinental and intraplate earthquakes and their implications for the thermal and mechanical properties of the lithosphere. Journal of Geophysical Research: Solid Earth, 88(B5), 4183–4214. https://doi.org/10.1029/JB088iB05p04183 DOI: https://doi.org/10.1029/JB088iB05p04183

Colorado Geological Survey. (2016). Colorado Geological Survey Seismic Network. International Federation of Digital Seismograph Networks. https://doi.org/10.7914/SN/C0

Craig, T., & Heyburn, R. (2015). An enigmatic earthquake in the continental mantle lithosphere of stable North America. Earth and Planetary Science Letters, 425, 12–23. https://doi.org/10.1016/j.epsl.2015.05.048 DOI: https://doi.org/10.1016/j.epsl.2015.05.048

Craig, T. J., Copley, A., & Jackson, J. (2012). Thermal and tectonic consequences of India underthrusting Tibet. Earth and Planetary Science Letters, 353–354. https://doi.org/10.1016/j.epsl.2012.07.010 DOI: https://doi.org/10.1016/j.epsl.2012.07.010

Craig, T. J., Jackson, J., Priestley, K., & Ekstrom, G. (2023). A Cautionary Tale: examples of the mis-location of small earthquake beneath the Tibetan plateau by routine approaches. Geophysical Journal International, 233. https://doi.org/10.1093/gji/ggad025 DOI: https://doi.org/10.1093/gji/ggad025

Craig, T., Kelemen, P., Hacker, B., & Copley, A. (2020). Reconciling geophysical and petrological estimates of the thermal structure of southern Tibet. Geochemistry, Geophysics, Geosystems, 21(8), e2019GC008837. https://doi.org/10.1029/2019GC008837 DOI: https://doi.org/10.1029/2019GC008837

EarthScope Consortium. (1986). Global Seismograph Network — II. International Federation of Digital Seismograph Networks. https://doi.org/10.7914/SN/II

Federal Institute for Geosciences and Natural Resources (BGR). (1976). German Regional Seismic Network. International Federation of Digital Seismograph Networks. https://doi.org/10.25928/mbx6-hr74

Frohlich, C., Gan, W., & Herrmann, R. B. (2015). Two deep earthquakes in Wyoming. Seismological Research Letters, 86(3), 810–818. https://doi.org/10.1785/0220140197 DOI: https://doi.org/10.1785/0220140197

Hanan, B. B., Shervais, J. W., & Vetter, S. K. (2008). Yellowstone plume–continental lithosphere interaction beneath the Snake River Plain. Geology, 36(1), 51–54. https://doi.org/10.1130/G23935A.1 DOI: https://doi.org/10.1130/G23935A.1

Hutchings, S. J., Koper, K. D., Burlacu, R., Zeng, Q., Lin, F.-C., & Zandt, G. (2025). Upper mantle earthquakes along the edge of the Wyoming Craton. Geophysical Research Letters, 52(9), e2024GL114073. https://doi.org/10.1029/2024GL114073 DOI: https://doi.org/10.1029/2024GL114073

Hutchings, S. J., Koper, K. D., & Pang, G. (2026). A seismically active shear zone in the uppermost mantle beneath the Canadian Rockies. Geophysical Research Letters, 53(1), e2025GL117818. https://doi.org/10.1029/2025GL117818 DOI: https://doi.org/10.1029/2025GL117818

Idaho National Laboratory. (1972). INL Seismic Monitoring Program. International Federation of Digital Seismograph Networks. https://doi.org/10.7914/SN/IE

Institute of Geophysical Research (KNDC). (1994). Kazakhstan Network. International Federation of Digital Seismograph Networks. https://doi.org/10.7914/SN/KZ

ISC. (2026). International Seismological Centre On-line Bulletin [Data set]. International Seismological Centre. https://doi.org/10.31905/D808B830 DOI: https://doi.org/10.31905/D808B830

Kind, R., Yuan, X., & Kumar, P. (2012). Seismic receiver functions and the lithosphere–asthenosphere boundary. Tectonophysics, 536, 25–43. https://doi.org/10.1016/j.tecto.2012.03.005 DOI: https://doi.org/10.1016/j.tecto.2012.03.005

Koper, K. D., Hutchings, S. J., Burlacu, R., Whidden, K., Springer, V., Tibi, R., & Pang, G. (2026). The 10 September 2025 M w 4.1 Earthquake in Northeastern Utah, United States: An Archetypal Continental Mantle Event. The Seismic Record, 6(2), 167–177. https://doi.org/10.1785/0320260006 DOI: https://doi.org/10.1785/0320260006

Li, A., & Dave, R. (2016). Destroying a Craton by Plate Subduction, Small-scale Convection, and Mantle Plume: Comparison of the Wyoming Craton and the North China Craton. AGU Fall Meeting Abstracts, 2016, T21F-02.

Lindenfeld, M., & Rümpker, G. (2011). Detection of mantle earthquakes beneath the East African Rift. Geophysical Journal International, 186(1), 1–5. https://doi.org/10.1016/j.tecto.2012.07.010 DOI: https://doi.org/10.1111/j.1365-246X.2011.05048.x

McCafferty, A. E., San Juan, C. A., Lawley, C. J. M., Graham, G. E., Gadd, M. G., Huston, D. L., Kelley, K. D., Paradis, S., Peter, J. M., & and Czarnota, K. (2023). National-scale geophysical, geologic, and mineral resource data and grids for the United States, Canada, and Australia: Data in support of the tri-national Critical Minerals Mapping Initiative (ver 1.1, March 2025) [Data release]. https://doi.org/10.5066/P970GDD5

Monsalve, G., Sheehan, A., Schulte-Pelkum, V., Rajaure, S., Pandey, M., & Wu, F. (2006). Seismicity and one-dimensional velocity structure of the Himalayan collision zone: Earthquakes in the crust and upper mantle. Journal of Geophysical Research: Solid Earth, 111(B10). https://doi.org/10.1029/2005JB004062 DOI: https://doi.org/10.1029/2005JB004062

Mooney, H. M. (1970). Upper mantle inhomogeneity beneath New Zealand: seismic evidence. Journal of Geophysical Research, 75(2), 285–309. https://doi.org/10.1029/JB075i002p00285 DOI: https://doi.org/10.1029/JB075i002p00285

National Institute for Earth Physics (NIEP). (1994). Romanian Seismic Network. International Federation of Digital Seismograph Networks. https://doi.org/10.7914/SN/RO

Natural Resources Canada. (1975). Canadian National Seismograph Network. International Federation of Digital Seismograph Networks. https://doi.org/10.7914/SN/CN

NORSAR. (1971). NORSAR Station Network. International Federation of Digital Seismograph Networks. https://doi.org/10.21348/d.no.0001

Paul, H., Sunilkumar, T. C., Naresh, B., & Ravi Kumar, M. (2025). Minor Lithospheric Mantle Earthquakes Beneath the South Indian Shield: Implications for Continental Mantle Rheology. Journal of Geophysical Research: Solid Earth, 130(10), e2025JB031522. https://doi.org/10.1029/2025JB031522 DOI: https://doi.org/10.1029/2025JB031522

Priestley, K., Jackson, J., & McKenzie, D. (2008). Lithospheric structure and deep earthquakes beneath India, the Himalaya and southern Tibet. Geophysical Journal International, 172(1), 345–362. https://doi.org/10.1111/j.1365-246X.2007.03636.x DOI: https://doi.org/10.1111/j.1365-246X.2007.03636.x

Prieto, G. A., Froment, B., Yu, C., Poli, P., & Abercrombie, R. (2017). Earthquake rupture below the brittle-ductile transition in continental lithospheric mantle. Science Advances, 3(3), e1602642. https://doi.org/10.1126/sciadv.1602642 DOI: https://doi.org/10.1126/sciadv.1602642

Reyners, M., Eberhart-Phillips, D., & Stuart, G. (2007). The role of fluids in lower-crustal earthquakes near continental rifts. Nature, 446, 1075–1078. https://doi.org/10.1038/nature05743 DOI: https://doi.org/10.1038/nature05743

Rigo, A., Adam, C., Grégoire, M., Gerbault, M., Meyer, R., Rabinowicz, M., Fontaine, F., & Bonvalot, S. (2015). Insights for the melt migration, the volcanic activity and the ultrafast lithosphere delamination related to the Yellowstone plume (Western USA). Geophysical Journal International, 203(2), 1274–1301. https://doi.org/10.1093/gji/ggv360 DOI: https://doi.org/10.1093/gji/ggv360

Rost, S., & Thomas, C. (2002). Array seismology: Methods and applications. Reviews of Geophysics, 40(3), 2–1. https://doi.org/10.1029/2000RG000100 DOI: https://doi.org/10.1029/2000RG000100

Schulte-Pelkum, V., Monsalve, G., Sheehan, A. F., Shearer, P., Wu, F., & Rajaure, S. (2019). Mantle earthquakes in the Himalayan collision zone. Geology, 47(9), 815–819. https://doi.org/10.1130/G46378.1 DOI: https://doi.org/10.1130/G46378.1

Shen, W., & Ritzwoller, M. H. (2016). Crustal and uppermost mantle structure beneath the United States. Journal of Geophysical Research: Solid Earth, 121(6), 4306–4342. https://doi.org/10.1002/2016JB012887 DOI: https://doi.org/10.1002/2016JB012887

Shinevar, W. J., Golos, E. M., Jagoutz, O., Behn, M. D., & Van der Hilst, R. D. (2023). Mantle thermochemical variations beneath the continental United States through petrologic interpretation of seismic tomography. Earth and Planetary Science Letters, 602, 117965. https://doi.org/10.1016/j.epsl.2022.117965 DOI: https://doi.org/10.1016/j.epsl.2022.117965

Shinevar, W. J., Jagoutz, O., & Behn, M. D. (2022). WISTFUL: Whole-rock interpretative seismic toolbox for ultramafic lithologies. Geochemistry, Geophysics, Geosystems, 23(8), e2022GC010329. https://doi.org/10.1093/petrology/egy048 DOI: https://doi.org/10.1029/2022GC010329

Sloan, R., & Jackson, J. (2012). Upper-mantle earthquakes beneath the Arafura Sea and south Aru Trough: Implications for continental rheology. Journal of Geophysical Research: Solid Earth, 117(B5). https://doi.org/10.1029/2011JB008992 DOI: https://doi.org/10.1029/2011JB008992

Soosalu, H., Key, J., White, R. S., Knox, C., Einarsson, P., & Jakobsdóttir, S. (2010). Lower-crustal earthquakes caused by magme movement beneath Askja volcano on the north Iceland rift. Bulletin of Volcanology, 72. https://doi.org/10.1007/s00445-009-0297-3 DOI: https://doi.org/10.1007/s00445-009-0297-3

Tape, W., & Tape, C. (2012). Angle between principal axis triples. Geophysical Journal International, 191(2), 813–831. https://doi.org/10.1111/j.1365-246X.2012.05658.x DOI: https://doi.org/10.1111/j.1365-246X.2012.05658.x

Thielmann, M. (2018). Grain size assisted thermal runaway as a nucleation mechanism for continental mantle earthquakes: Impact of complex rheologies. Tectonophysics, 746, 611–623. https://doi.org/10.1016/j.tecto.2017.08.038 DOI: https://doi.org/10.1016/j.tecto.2017.08.038

University of Utah. (1962). University of Utah Regional Seismic Network. International Federation of Digital Seismograph Networks. https://doi.org/10.7914/SN/UU

University of Utah. (1983). Yellowstone National Park Seismograph Network. International Federation of Digital Seismograph Networks. https://doi.org/10.7914/SN/WY

U.S. Bureau of Reclamation. (1985). US Bureau of Reclamation Seismic Networks. In International Federation of Digital Seismograph Networks.

USGS. (2017). Advanced National Seismic System (ANSS) Comprehensive Catalog of Earthquake Events and Products [Data set]. U.S. Geological Survey. https://doi.org/10.5066/F7MS3QZH

Various Institutions. (1965). International Miscellaneous Stations. International Federation of Digital Seismograph Networks. https://doi.org/10.7914/vefq-vh75

Vasyura-Bathke, H., Dettmer, J., Steinberg, S., Andreasand Heimann, Isken, M., Zielke, O., Mai, P. M., Sudhaus, H., & Jónsson, S. (2019). BEAT - Bayesian Earthquake Analysis Tool. V. 1.0 [Software]. https://doi.org/10.5880/fidgeo.2019.024

Woo, J.-U., & Chen, T. (2025). Mantle Earthquakes: Deep Quakes Beneath the Moho in the Wyoming Craton. The Seismic Record, 5(4), 363–373. https://doi.org/10.1785/0320250032 DOI: https://doi.org/10.1785/0320250032

Xiao, H., Marshak, S., DeLucia, M., & Song, X. (2025). Moho depth (crustal thickness) variations under the northeastern midcontinent of North America, based on H-κ- c receiver-function analysis. Earth and Planetary Science Letters, 658, 119289. https://doi.org/10.1016/j.epsl.2025.119289 DOI: https://doi.org/10.1016/j.epsl.2025.119289

Zandt, G., & Richins, W. (1979). An upper mantle earthquake beneath the middle Rocky Mountains in NE Utah. Earthquake Notes, 50(4), 69–70.

Zhang, H., Ravat, D., & Lowry, A. R. (2020). Crustal composition and Moho variations of the central and eastern United States: Improving resolution and geologic interpretation of EarthScope USArray seismic images using gravity. Journal of Geophysical Research: Solid Earth, 125(3), e2019JB018537. https://doi.org/10.1029/2019JB018537 DOI: https://doi.org/10.1029/2019JB018537

Zhao, D., Liang, X., Toyokuni, G., Hua, Y., & Xu, Y.-G. (2024). Cause of enigmatic upper-mantle earthquakes in central Wyoming. Seismological Research Letters, 95(4), 2497–2505. https://doi.org/10.1785/0220230333 DOI: https://doi.org/10.1785/0220230333

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2026-06-03

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Fitton, B., Craig, T., & Rost, S. (2026). A rare earthquake in the upper mantle of subcontinental lithospheric mantle of North America. Seismica, 5(1). https://doi.org/10.26443/seismica.v5i1.2999

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Vol. 5 No. 1 (2026)

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Fast Reports

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Copyright (c) 2026 Benedict Fitton, Timothy J. Craig, Sebastian Rost

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