Apparent Non-Double-Couple Components as Artifacts of Moment Tensor Inversion




non-double-couple component, moment tensor, moment tensor inversion, synthetic seismograms


Compilations of earthquake moment tensors from global and regional catalogs find pervasive non-double-couple (NDC) components
with a mean deviation from a double-couple (DC) source of around 20%. Their distributions vary only slightly with magnitude, faulting mechanism, or geologic environments. This consistency suggests thatfor most earthquakes, especially smaller ones whose rupture processes are expected to be simpler, the NDC components are largely artifacts of the moment tensor inversion procedure. This possibility is also supported by the fact that NDC components for individual earthquakes with Mw<6.5 are only weakly correlated between
catalogs. We explore this possibility by generating synthetic seismograms for the double-couple components of earthquakes around the
world using one Earth model and inverting them with a different Earth model. To match the waveforms with a different Earth model, the inversion changes the mechanisms to include a substantial NDC component while largely preserving the fault geometry (DC component). The resulting NDC components have a size and distribution similar to those reported for the earthquakes in the Global Centroid Moment Tensor (GCMT) catalog. The fact that numerical experiments replicate general features of the pervasive NDC components reported in moment tensor catalogs implies that these components are largely artifacts of the inversions not adequately accounting for the effects of laterally varying Earth structure.


Aki, K., & Richards, P. G. (2002). Quantitative Seismology. University Science Books.

Ammon, C. J., Lay, T., Velasco, A. A., & Vidale, J. E. (1994). Routine estimation of earthquake source complexity: The 18 October 1992 Colombian earthquake. Bulletin of the Seismological Society of America, 4(84), 1266–1271.

Beyreuther, M., Barsch, R., Krischer, L., Megies, T., Behr, Y., & and Wassermann, J. (2010). ObsPy: A Python toolbox for seismology. Seismological Research Letters, 81(3), 530–533. DOI:

Cesca, S., Buforn, E., & Dahm, T. (2006). Amplitude spectra moment tensor inversion of shallow earthquakes in Spain. Geophysical Journal International, 166(2), 839–854. DOI:

Cohee, B. P., & Beroza, G. C. (1994). Slip distribution of the 1992 Landers earthquake and its implications for earthquake source mechanics. Bulletin of the Seismological Society of America, 84(3), 692–712.

Covellone, B. M., & Savage, B. (2012). A quantitative comparison between 1D and 3D source inversion methodologies: Application to the Middle East. Bulletin of the Seismological Society of America, 102(5), 2189–2199. DOI:

Dahlen, F. A. (1982). The effect of data windows on the estimation of free oscillation parameters. Geophysical Journal International, 2(69), 537–549. DOI:

Dahlen, F., & Tromp, J. (1998). Theoretical global seismology. Princeton University Press. DOI:

Dalton, C. A., & Ekström, G. (2006). Global models of surface wave attenuation. Journal of Geophysical Research: Solid Earth, B5(111). DOI:

Domingues, A., Custodio, S., & Cesca, S. (2013). Waveform inversion of small-to-moderate earthquakes located offshore southwest Iberia. Geophysical Journal International, 192(1), 248–259. DOI:

Donner, S., Mustać, M., Hejrani, B., Tkalčić, H., & Igel, H. (2020). Seismic moment tensors from synthetic rotational and translational ground motion: Green’s functions in 1-D versus 3-D. Geophysical Journal International, 223(1), 161–179. DOI:

Duputel, Z., Rivera, L., Kanamori, H., & Hayes, G. (2018). W phase source inversion for moderate to large earthquakes (1990-2010). Geophysical Journal International, 2(189), 1125–1147. DOI:

Dziewonski, A. M., & Anderson, D. L. (1981). Preliminary reference Earth model. Physics of the Earth and Planetary Interiors, 25(4), 297–356. DOI:

Dziewonski, A. M., Chou, T. A., & Woodhouse, J. H. (1981). Determination of earthquake source parameters from waveform data for studies of global and regional seismicity. Journal of Geophysical Research: Solid Earth, B4(86), 2825–2852. DOI:

Dziewonski, A. M., Franzen, J. E., & Woodhouse, J. H. (1984). Centroid-moment tensor solutions for January-March, 1984. Physics of the Earth and Planetary Interiors, 4(34), 209–219. DOI:

Efron, B. (1979). Bootstrap Methods: Another Look at the Jackknife. Annals of Statistics, 7(1), 1–26. DOI:

Ekström, G., Nettles, M., & Dziewonski, A. (2012). The global CMT project 2004-2010: Centroid-moment tensors for 13,017 earthquakes. Physics of the Earth and Planetary Interiors, 200–201, 1–9. DOI:

Ford, S. R., Dreger, D. S., & Walter, W. R. (2010). Network sensitivity solutions for regional moment-tensor inversions. Bulletin of the Seismological Society of America, 100(5A), 1962–1970. DOI:

Frohlich, C. (1992). Triangle diagrams: ternary graphs to display similarity and diversity of earthquake focal mechanisms. Physics of the Earth and Planetary Interiors, 75(1–3), 193–198. DOI:

Frohlich, C. (1994). Earthquakes with non-double-couple mechanisms. Science, 5160(264), 804–809. DOI:

Giardini, D. (1984). Systematic analysis of deep seismicity: 200 centroid-moment tensor solutions for earthquakes between 1977 and 1980. Geophysical Journal International, 77(3), 883–914. DOI:

Gilbert, F. (1971). Excitation of the normal modes of the Earth by earthquake sources. Geophysical Journal International, 2(22), 223–226. DOI:

Gudmundsson, M. T., Jónsdóttir, K., A., H., Holohan, E. P., Halldórsson, S. A., Ófeigsson, B. G., Cesca, S., Vogfjörd, K. S., Sigmundsson, F., Högnadóttir, T., Einarsson, P., Sigmarsson, O., Jarosch, A. H., Jónasson, K., Magnússon, E., Hreinsdóttir, S., Bagnardi, M., Parks, M. M., Hjörleifsdóttir, V., … Aiuppa, A. (2016). Gradual caldera collapse at Bárdarbunga volcano, Iceland, regulated by lateral magma outflow. Science, 353(6296). DOI:

Hallo, M., & Gallovič, F. (2016). Fast and cheap approximation of Green function uncertainty for waveform-based earthquake source inversions. Geophysical Journal International, 207(2), 1012–1029. DOI:

Hamling, I. J., Hreinsdóttir, S., Clark, K., Elliott, J., Liang, C., Fielding, E., Litchfield, N., Villamor, P., Wallace, L., Wright, T. J., d’Anastasio, E., Bannister, S., Burbridge, D., Denys, P., Gentle, P., Howarth, J., Mueller, C., Palmer, N., Pearson, C., … Stirling, M. (2017). Complex multifault rupture during the Mw 7.8 Kaikōura earthquake, New Zealand. Science, 356(6334). DOI:

Hayes, G. P., Briggs, R. W., Sladen, A., Fielding, E. J., Prentice, C., Hudnut, K., Mann, P., Taylor, F. W., Crone, A. J., Gold, R., Ito, T., & Simons, M. (2010). Complex rupture during the 12 January 2010 Haiti earthquake. Nature Geoscience, 3(11), 800–805. DOI:

Hayes, G. P., Rivera, L., & Kanamori, H. (2009). Source inversion of the W-Phase: real-time implementation and extension to low magnitudes. Seismological Research Letters, 80(5), 817–822. DOI:

Hejrani, B., Tkalčić, H., & Fichtner, A. (2017). Centroid moment tensor catalogue using a 3-D continental scale Earth model: Application to earthquakes in Papua New Guinea and the Solomon Islands. Journal of Geophysical Research: Solid Earth, 122(7), 5517–5543. DOI:

Henry, C., Woodhouse, J. H., & S., D. (2002). Stability of earthquake moment tensor inversions: effect of the double-couple constraint. Tectonophysics, 356(1–3), 115–124. DOI:

Hingee, M., Tkalčić, H., Fichtner, A., & Sambridge, M. (2011). Seismic moment tensor inversion using a 3-D structural model: applications for the Australian region. Geophysical Journal International, 184(2), 949–964. DOI:

Hjörleifsdóttir, V., & Ekström, G. (2010). Effects of three-dimensional Earth structure on CMT earthquake parameters. Physics of the Earth and Planetary Interiors, 179(3–4), 178–190. DOI:

Horálek, J., Šílený, J., & Fischer, T. (2002). Moment tensors of the January 1997 earthquake swarm in NW Bohemia (Czech Republic): double-couple vs. non-double-couple events. Tectonophysics, 1–3(356), 65–85. DOI:

Jechumtálová, Z., & Bulant, P. (2014). Effects of 1-D versus 3-D velocity models on moment tensor inversion in the Dobrá Voda area in the Little Carpathians region, Slovakia. Journal of Seismology, 18, 511–531. DOI:

Jechumtálová, Z., & Šílený, J. (2001). Point-source parameters from noisy waveforms: Error estimate by Monte-Carlo simulation. Pure and Applied Geophysics, 158(9), 1639–1654. DOI:

Julian, B. R., Miller, A. D., & Foulger, G. R. (1998). Non-double-couple earthquakes 1. Theory. Reviews of Geophysics, 36(4), 525–549. DOI:

Julian, B. R., & Sipkin, S. A. (1985). Earthquake processes in the Long Valley caldera area, California. Journal of Geophysical Research: Solid Earth, 90(B13), 11155–11169. DOI:

Kagan, Y. Y. (1991). 3-D rotation of double-couple earthquake sources. Geophysical Journal International, 106(3), 709–716. DOI:

Kanamori. (2008). Source inversion of W-phase: Speeding up seismic tsunami warning. Geophysical Journal International, 1(175), 222–238. DOI:

Kanamori, H., & Given, J. W. (1981). Use of long-period surface waves for rapid determination of earthquake-source parameters. Physics of the Earth and Planetary Interiors, 1(27), 8–31. DOI:

Kanamori, H., & Given, J. W. (1982). Analysis of long-period seismic waves excited by the May 18, 1980, eruption of Mount St. Helens - A terrestrial monopole? Journal of Geophysical Research: Solid Earth, 87(B7), 5422–5432. DOI:

Kanamori, H., & Rivera, L. (1993). W phase. Geophysical Research Letters, 16(20), 1691–1694. DOI:

Karaoǧlu, H., & Romanowicz, B. (2018). Inferring global upper-mantle shear attenuation structure by waveform tomography using the spectral element method. Geophysical Journal International, 3(213), 1536–1558. DOI:

Kaverina, A. N., Lander, A. V., & Prozorov, A. G. (1996). Global creepex distribution and its relation to earthquake-source geometry and tectonic origin. Geophysical Journal International, 125(1), 249–265. DOI:

Kawakatsu, H. (1991). Enigma of earthquakes at ridge-transform-fault plate boundaries distribution of non-double-couple parameter of Harvard CMT Solutions. Geophysical Research Letters, 18(6), 1103–1106. DOI:

Knopoff, L., & Randall, M. J. (1970). The compensated linear-vector dipole: A possible mechanism for deep earthquakes. Journal of Geophysical Research, 26(75), 4957–4963. DOI:

Liu, Q., Polet, J., Komatitsch, D., & Tromp, J. (2004). Spectral-element moment tensor inversions for earthquakes in southern California. Bulletin of the Seismological Society of America, 94(5), 1748–1761. DOI:

Masters, G., Woodhouse, J. H., & Freeman, G. (2011). Mineos v1.0.2 [software]. Computational Infrastructure for Geodynamics.

McNamara, D. E., Benz, H. M., Herrmann, R. B., Bergman, E. A., Earle, P., Meltzer, A., Withers, M., & Chapman, M. (2013). The Mw 5.8 Mineral, Virginia, Earthquake of August 2011 and Aftershock Sequence: Constraints on Earthquake Source Parameters and Fault Geometry. Bulletin of the Seismological Society of America, 1(104), 40–54. DOI:

Miller, A. D., Foulger, G. R., & Julian, B. R. (1998). Non-double-couple earthquakes 2. Observations. Reviews of Geophysics, 36(4), 551–568. DOI:

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), 1701–1726. DOI:

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), 922–940. DOI:

Nettles, M., & Ekström, G. (1998). Faulting mechanism of anomalous earthquakes near Bárdarbunga Volcano, Iceland. Journal of Geophysical Research: Solid Earth, 103(B8), 17973–17983. DOI:

Pang, G., Koper, K. D., Mesimeri, M., Pankow, K. L., Baker, B., Farrell, J., Holt, J., Hale, J. M., Roberson, P., Burlacu, R., Pechmann, J. C., Whidden, K., Holt, M. M., Allamm, A., & DuRoss, C. (2020). Seismic analysis of the 2020 Magna, Utah, earthquake sequence: Evidence for a listric Wasatch fault. Geophysical Research Letters, 47(18). DOI:

Phạm, T. S., & Tkalčić, H. (2021). Toward Improving Point-Source Moment-Tensor Inference by Incorporating 1D Earth Model’s Uncertainty: Implications for the Long Valley Caldera Earthquakes. Journal of Geophysical Research: Solid Earth, 126(11). DOI:

Quigley, M. C., Mohammadi, H., & Duffy, B. G. (2017). Multi-fault earthquakes with kinematic and geometric rupture complexity: how common? INQUA Focus Group Earthquake Geology and Seismic Hazards.

Ringler, A. T., Anthony, R. E., Aster, R. C., Ammon, C. J., Arrowsmith, S., Benz, H., Ebeling, C., Frassetto, A., Kim, W.-Y., Koelemeijer, P., Lau, H. C. P., Lekić, V., Montagner, J. P., Richards, P. G., Schaff, D. P., Vallee, M., & Yeck, W. (2022). Achievements and prospects of global broadband seismographic networks after 30 years of continuous geophysical observations. Reviews of Geophysics, 3(60). DOI:

Rodríguez-Cardozo, F., Hjörleifsdóttir, V., K., J., Iglesias, A., Franco, S. I., Geirsson, H., Trujillo-Castrillón, N., & M., H. (2021). The 2014-2015 complex collapse of the Bárðarbunga caldera, Iceland, revealed by seismic moment tensors. Journal of Volcanology and Geothermal Research, 416. DOI:

Rösler, B., & Stein, S. (2022). Consistency of Non-Double-Couple Components of Seismic Moment Tensors with Earthquake Magnitude and Mechanism. Seismological Research Letters, 93(3), 1510–1523. DOI:

Rösler, B., Stein, S., & Hough, S. E. (2022). On the documentation, independence, and stability of widely used seismological data products. Frontiers in Earth Science, 10(988098). DOI:

Rösler, B., Stein, S., & Spencer, B. D. (2021). Uncertainties in Seismic Moment Tensors Inferred from Differences Between Global Catalogs. Seismological Research Letters, 92(6), 3698–3711. DOI:

Rösler, B., Stein, S., & Spencer, B. D. (2023). When are Non-Double-Couple Components of Seismic Moment Tensors Reliable? Seismica, 2(1). DOI:

Ross, A., Foulger, G. R., & Julian, B. R. (1996). Non-double-couple earthquake mechanisms at the Geysers geothermal area, California. Geophysical Research Letters, 23(8), 877–880. DOI:

Rößler, D., Krüger, F., & Rümpker, G. (2007). Retrieval of moment tensors due to dislocation point sources in anisotropic media using standard techniques. Geophysical Journal International, 169(1), 136–148. DOI:

Ruhl, C. J., Morton, E. A., Bormann, J. M., Hatch-Ibarra, R., Ichinose, G., & Smith, K. D. (2021). Complex Fault Geometry of the 2020 Mww 6.5 Monte Cristo Range, Nevada, Earthquake Sequence. Seismological Research Letters, 92(3), 1876–1890. DOI:

Saloor, N., & Okal, E. A. (2018). Extension of the energy-to-moment parameter Θ to intermediate and deep earthquakes. Physics of the Earth and Planetary Interiors, 274, 37–48. DOI:

Sandanbata, O., Kanamori, H., Rivera, L., Zhan, Z., Watada, S., & Satake, K. (2021). Moment tensors of ring-faulting at active volcanoes: Insights into vertical-CLVD earthquakes at the Sierra Negra caldera, Galápagos Islands. Journal of Geophysical Research: Solid Earth, 126(6). DOI:

Sawade, L., Beller, & Tromp, J. (2022). Global centroid moment tensor solutions in a heterogeneous earth: the CMT3D catalogue. Geophysical Journal International, 231(3), 1727–1738. DOI:

Scognamiglio, L., Tinti, E., Casarotti, E., Pucci, S., Villani, F., Cocco, M., Magnoni, F., Michelini, A., & Dreger, D. (2018). Complex fault geometry and rupture dynamics of the Mw 6.5, 30 October 2016, Central Italy earthquake. Journal of Geophysical Research: Solid Earth, 123(4), 2943–2964. DOI:

Shapiro, S. S., & Wilk, M. B. (1965). An analysis of variance test for normality (complete samples). Biometrika, 52(3/4), 591–611. DOI:

Shuler, A., Ekström, G., & Nettles, M. (2013). Physical mechanisms for vertical-CLVD earthquakes at active volcanoes. Journal of Geophysical Research: Solid Earth, 118(4), 1569–1586. DOI:

Shuler, A., Nettles, M., & Ekström, G. (2013). Global observation of vertical-CLVD earthquakes at active volcanoes. Journal of Geophysical Research: Solid Earth, 118(1), 138–164. DOI:

Šílený, J. (2004). Regional moment tensor uncertainty due to mismodeling of the crust. Tectonophysics, 383(3–4), 133–147. DOI:

Šílený, J., Campus, P., & Panza, G. F. (1996). Seismic moment tensor resolution by waveform inversion of a few local noisy records - I. Synthetic tests. Geophysical Journal International, 126(3), 605–619. DOI:

Šílený, J., & Vavryčuk, V. (2002). Can unbiased source be retrieved from anisotropic waveforms by using an isotropic model of the medium? Tectonophysics, 1–3(356), 125–138. DOI:

Silver, P. G., & Jordan, T. H. (1982). Optimal estimation of scalar seismic moment. Geophysical Journal International, 70(3), 755–787. DOI:

Sipkin, S. A. (1986). Interpretation of non-double-couple earthquake mechanisms derived from moment tensor inversion. Journal of Geophysical Research: Solid Earth, B1(91), 531–547. DOI:

Stierle, E., Bohnhoff, M., & Vavryčuk, V. (2014). Resolution of non-double-couple components in the seismic moment tensor using regional networks-II: application to aftershocks of the 1999 Mw 7.4 Izmit earthquake. Geophysical Journal International, 3(169), 1878–1888. DOI:

Stierle, E., Vavryčuk, V., Šílený, J., & Bohnhoff, M. (2014). Resolution of non-double-couple components in the seismic moment tensor using regional networks-I: a synthetic case study. Geophysical Journal International, 3(169), 1869–1877. DOI:

Tréhu, A. M., Nábêlek, J. L., & Solomon, S. C. (1981). Source characterization of two Reykjanes Ridge earthquakes: Surface waves and moment tensors; P waveforms and nonorthogonal nodal planes. Journal of Geophysical Research: Solid Earth, B3(86), 1701–1724. DOI:

Vackář, Burjánek, J., Gallovič, F., Zahradník, J., & Clinton, J. (2017). Bayesian ISOLA: new tool for automated centroid moment tensor inversion. Geophysical Journal International, 2(210), 693–705. DOI:

Vasyura-Bathke, H., Dettmer, J., Dutta, R., Mai, P. M., & Jonsson, S. (2021). Accounting for theory errors with empirical Bayesian noise models in nonlinear centroid moment tensor estimation. Geophysical Journal International, 225(2), 1412–1431. DOI:

Vavryčuk, V. (2002). Non-double-couple earthquakes of 1997 January in West Bohemia, Czech Republic: evidence of tensile faulting. Geophysical Journal International, 2(149), 364–373. DOI:

Vera Rodriguez, I., Gu, Y. J., & Sacchi, M. D. (2011). Resolution of seismic-moment tensor inversions from a single array of receivers. Bulletin of the Seismological Society of America, 101(6), 2634–2642. DOI:

Wald, D. J., & Heaton, T. H. (1994). Spatial and temporal distribution of slip for the 1992 Landers, California, earthquake. Bulletin of the Seismological Society of America, 84(3), 668–691. DOI:

Wang, X., & Zhan, Z. (2020). Moving from 1-D to 3-D velocity model: automated waveform-based earthquake moment tensor inversion in the Los Angeles region. Geophysical Journal International, 220(1), 218–234. DOI:

Yang, J., Zhu, H., Lay, T., Niu, Y., Ye, L., Lu, Z., Luo, B., Kanamori, H., Huang, J., & Li, Z. (2021). Multi-fault opposing-dip strike-slip and normal-fault rupture during the 2020 Mw 6.5 Stanley, Idaho earthquake. Geophysical Research Letters, 48(10). DOI:

Zhu, L., & Zhou, X. (2016). Seismic moment tensor inversion using 3D velocity model and its application to the 2013 Lushan earthquake sequence. Physics and Chemistry of the Earth, Parts A/B/C, 95, 10–18. DOI:

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How to Cite

Rösler, B., Stein, S., Ringler, A., & Vackář, J. (2024). Apparent Non-Double-Couple Components as Artifacts of Moment Tensor Inversion. Seismica, 3(1).