Thorsten W. Becker

Jackson School of Geosciences
The University of Texas at Austin

Seismology research


[news] [teaching] [group] [publications] [CV] [downloads] [contact]
[geodynamics] [seismology] [fieldwork] [downloads]
[crustal stress] [faults] [anisotropy] [tomography]
  • Earthquake source and fault system dynamics

    • Co- and post-seismic deformation after the 2011 Tohoku-oki M9 event

      Collaborative work with colleagues at Purdue and ERI, University of Tokyo. We explore the mechanics of elastic heterogeneity for co-seismic deformation, and show that post-seismic deformation may indicate the presence of Peierls creep within the subducting lithosphere, in the depth region suggested by Buffett and Becker (2012).

      • Freed, A. M., Hashima, A., Becker, T. W., Okaya, D. A., Sato, H., and Hatanaka. Y.: Resolving depth-dependent subduction zone viscosity and afterslip from postseismic displacements following the 2011 Tohoku-oki, Japan earthquake. Earth Planet. Sci. Lett., 459, 279-290, 2017. (PDF)
      • Hashima, A., Becker, T. W., Freed, A. M., Sato, H., and Okaya, D. A.: Coseismic deformation due to the 2011 Tohoku-oki earthquake: influence of 3-D elastic structure around Japan. Earth, Planet., Space, 68, 159, doi:10.1186/s40623-016-0535-9, 2016. (PDF)
    • Stick slip seismicity and roughness evolution from acoustic emission experiments

      We study stick-slip frictional sliding in laboratory experiments, focusing on natural seismicity analogs such as the spatio-temporal evolution of fore and aftershock sequences, b values, and roughness evolution as well as seismicity decay from the fault surface. A project in collaboration with GeoForschungsZentrum Potsdam and funded by NSF/USGS SCEC.

      • Goebel, T. H. W., Kwiatek, G., Becker, T.W., Brodsky, E. E. and Dresen, G.: What allows seismic events to grow big?: Insights from b-value and fault roughness analysis in laboratory stick-slip experiments. Geology, 44, 815-818, 2017. (PDF)
      • Uhl, J. T. et al.: Universal quake statistics: From compressed nanocrystals to earthquakes. Sci. Rep., 5, 16493, doi: 10.1038/srep16493, 2015. (PDF)
      • Goebel, T. H. W., Becker, T. W., Sammis, C. G., Dresen. G., and Schorlemmer, D.: Off-fault damage and acoustic emission distributions during the evolution of structurally-complex faults over series of stick-slip events. Geophys. J. Int., 197, 1705-1718, 2014. (PDF)
      • Goebel, T. H. W., Candela, T., Sammis, C. G., Becker, T. W., Dresen, G., and Schorlemmer, D.: Seismic event distributions and off-fault damage during frictional sliding of saw-cut surfaces with predefined roughness. Geophys. J. Int., 196, , 612-625, doi:10.1093/gji/ggt401, 2014. (PDF)
      • Goebel, T. H. W., Sammis, C. G., Becker, T. W., Dresen, G., and Schorlemmer, D.: A comparison of seismicity characteristics and fault structure between stick-slip experiments and nature. Pure Appl. Geophys., doi:10.1007/s00024-013-0713-7, 2013. (PDF)
      • Goebel, T. H. W., Schorlemmer, D., Becker, T. W., Dresen, G., and Sammis, C. G.: Acoustic emissions document stress changes over many seismic cycles in stick-slip experiments. Geophys. Res. Lett., 40, 2049-2054, doi:10.1002/grl.50507, 2013. (PDF)
      • Goebel, T. H. W., Becker, T. W., Schorlemmer, D., Stanchits, S., Sammis, C., Rybacki, E., and Dresen, G.: Identifying fault heterogeneity through mapping spatial anomalies in acoustic emission statistics. J. Geophys. Res., 117, B03310, doi:10.1029/2011JB008763, 2012. (PDF)
    • Stress, strain, and dynamic topography patterns in the western US and southern California

      We model the effect of crustal structure, gravitational potential energy variations, and mantle flow on the large-scale stress field, seismicity, and topography of the western United States. We also analyze seismically and geodetically imaged strain release on the smaller scales of the western US plate boundary.

      • Becker, T. W., Lowry, A. R., Faccenna, C., Schmandt, B., Borsa, A., and Yu, C. (2015): Western U.S. intermountain seismicity caused by changes in upper mantle flow. Nature, 524, 458-461. (PDF)
      • Becker, T. W., Faccenna, C., Humphreys, E. D., Lowry, A. R., and Miller, M. S.: Static and dynamic support of western U.S. topography. Earth Planet. Sci. Lett., 402, 234-246, 2014. (PDF)
      • Ghosh, A., Becker, T. W., and Humphreys, E. D.: Dynamics of the North American continent. In press at Geophys. J. Int., 2013. (PDF)
      • Bailey, I. W., Ben-Zion, Y., Becker, T. W., and Holschneider, M.: Quantifying focal mechanism heterogeneity for fault zones in central and southern California. Geophys. J. Int., 183, 267–276, 2010. (PDF)
      • Bailey, I. W., Becker, T. W., and Ben-Zion, Y.: Patterns of co-seismic strain computed from southern California focal mechanisms. Geophys. J. Int., 177, 1015-1036, 2009. (PDF).
      • Fay, N. P., Becker, T. W., and Humphreys, E. D.: Southern California Modeling of Geodynamics in 3D (SMOG3D): Toward quantifying the state of tectonic stress in the southern California crust, 2008 SCEC Annual Meeting, 1-122, 2008.
      • Becker, T. W., Bailey, I. W., and Y. Ben-Zion: Stress and strain in southern California, Southern California Earthquake Center Meeting, Palm Springs CA, September 2006. (invited)

      I am also involved in the

      • SCEC Community Stress Model (CSM) project.
        SCEC IV has committed to the development of a Community Stress Model to provide better constraints on the stress field, and with a means to formally test physical connections between observations and stress models.
    • Fault slip rates and crustal state of stress

      We construct a simple model of interseismic strain and stress accumulation on southern California faults. The joint inversion of GPS velocities and focal mechanisms for fault slip rates of the southern San Andreas contributes to an improved understanding of plate boundary processes.

      • Becker, T. W., Hardebeck, J. L., and Anderson, G.: Constraints on fault slip rates of the southern California plate boundary from GPS velocity and stress inversions. Geophys J. Int., 160, 634-650, 2005. (PDF).

    • Transform fault mechanics

      We explore how anti-symmetric crustal thinning and thickening may result along a continental transform such as the San Andreas fault, and explore other aspects of the interpretation of geodetic and seismic measures of strain-rate in terms of fault mechanics.

      • Platt, J. P. and Becker, T. W.: Kinematics of rotating panels of E-W faults in the San Andreas system: what can we tell from geodesy? Geophys. J. Int., 194, 1295-1301, 2013. (PDF)
      • Platt, J. P. and Becker, T. W.: Where is the real transform boundary in California? Geochem., Geophys., Geosys., 11(Q06013), doi:10.1029/2010GC003060, 2010. (PDF)
      • Platt, J. P., Kaus, B. J. P. and Becker, T. W.: The mechanics of continental transforms: An alternative approach with applications to the San Andreas system and the tectonics of California. Earth Planet. Sci. Lett., 274, 380-391, 2008. (PDF)
    • Slab stress state from moment tensors and geodynamic modeling

      We analyze the deep deformation state of subduction zones world wide by means of geodynamic modeling and Kostrov summation, focusing on the origin of the depth-dependent CLVD signal and how deep earthquakes can be used to constrain mantle rheology.

      • Bailey, I. W., Alpert, L. A., Becker, T. W., and Miller, M. S.: Co-seismic deformation of deep slabs based on summed CMT data. J. Geophys. Res., 117, B04404, doi:10.1029/2011JB008943, 2012. (PDF)
      • Alpert, L. A., Becker, T. W., and Bailey, I. W.: Global slab deformation and centroid moment tensor constraints on viscosity. Geochem., Geophys. Geosys., 11,(Q12006), doi:10.1029/2010GC003301, 2010. (PDF)
    • Chaos in friction

      Two state-variable rate and state friction on faults can result in deterministic chaos in the seismicity of a simple spring-slider model. The system follows the universal period doubling cascade into chaos; sliding events can, however, be predicted with some accuracy. Coupled sliders show more regular seismicity, implying a regularizing effect of interactions.

      • Becker, T. W.: Deterministic Chaos in two State-variable Friction Sliders and the Effect of Elastic Interactions, in GeoComplexity and the physics of earthquakes, edited by J. B. Rundle, D. L. Turcotte, and W. Klein, p. 5-26, AGU, Washington D. C., 2000. (PDF)
    • Single fault and shear zone earthquake recurrence time variations

      We study earthquake interactions using 2-D elastic models, and apply analytical and finite element methods. We show that the orientation of faults in the background stress-field can lead to variations in the seismic cycle even without fault interactions.

      • Becker, T. W. and Schmeling, H.: Earthquake recurrence time variations with and without fault zone interactions. Geophys. J. Int., 135, 165-176, 1998. (PDF)

    • Effective shear modulus of crack-filled media

      We study micro-crack interaction and the mechanical properties of a crack-filled medium using finite element and boundary element techniques. We find that interactions should be taken into account; a modified self-consistent approach is best suited to the problems under consideration.

      • Dahm, T. and Becker, T.: On the elastic and viscous properties of media containing strongly interacting in-plane cracks. Pure Applied Geophys., 151, 1-16, 1998. (PDF)
    • Boundary element package interact

      interact is a boundary element program which implements Okada's (1992) solutions for stress in an elastic half-space (Greens' functions for constant slip on rectangular dislocation elements). The interact package is modularly programmed in C and FORTRAN, GNU-licensed, and used to study geometrically complex fault systems and earthquake cycles.

      • Becker, T. W., Hardebeck, J. L., and Anderson, G.: Constraints on fault slip rates of the southern California plate boundary from GPS velocity and stress inversions. Geophys. J. Int., 160, 634-650, 2005. (PDF)
      • Becker, T. W. and Schott, B.: On boundary-element models of elastic fault interaction (abstract). Eos Trans. AGU, 83(47), Fall Meet. Suppl., Abstract NG62A-0925, 2002. (PDF)
      • download interact
  • Structural seismology/tomography

    • Generation and character of whole mantle seismic heterogeneity

      In collaboration with Lapo Boschi's group, we explore improved global radially anisotropic models. Using joint inversions, we show that the vertical coherence of mantle heterogeneity from seismic data displays some indication of slab stagnation at depths somewhat larger than 660 km. Global, visco-plastic mantle convection models show plate-like surface motions and naturally generate spherical harmonic degree-two dominated temperature heterogeneity spectra.

      • Auer, L., Boschi , L., Becker, T. W., Nissen-Meyer, T. and Giardini, D.: Savani: a variable-resolution whole-mantle model of anisotropic shear-velocity variations based on multiple datasets. J. Geophys. Res., 119, 3006-3034, doi:10.1002/2013JB010773, 2014. (PDF, model)
      • Boschi, L. and Becker, T. W.: Vertical coherence in mantle heterogeneity from global seismic data. Geophys. Res. Lett., 38, (L20306), doi:10.1029/2011GL049281, 2011. (PDF)
      • Foley, B. and Becker, T. W.: Generation of plate-like behavior and mantle heterogeneity from a spherical, visco-plastic convection model. Geochem., Geophys., Geosys., 10, Q08001, doi:10.1029/2009GC002378, 2009. (PDF)
    • Global (S/PMEAN) and western US (S/PMEAN-WUS) composite tomography model download and model comparisons

    • Plume detection, primordial reservoirs, and the origins of EM1 and high He3/4

      We analyze geodynamic and seismological models of the mantle and demonstrate that tomography images deep mantle plumes that connect to surface hotspots, if plume conduit distortion in the mantle wind is accounted for. We also analyze a range of geochemical and geophysical parameters to show that enriched mantle type of ocean island basalts (EM1 type OIBs) may be associated with a deep mantle source, along with mixing with shallow continental lithosphere material. Moreover, the high He3/4 component appears associated with a primordial, deep mantle reservoir that is only entrained by the hottest plumes.

      • Jackson, M.G., Becker, T. W., and Konter, J. G.: Geochemistry and distribution of recycled domains in the mantle inferred from Nd and Pb isotopes in oceanic hotspots: implications for storage in the large low shear wave velocity provinces (LLSVPs) G-Cubed, doi:10.1029/2018GC007552, 2018. (PDF)
      • Jackson, M. G., Becker, T. W., and Konter, J.: Evidence for a deep mantle source for EM and HIMU domains from integrated geochemical and geophysical constraints. Earth Planet. Sci. Lett., 484, 154-167, 2018. (PDF)
      • Jackson, M. G., Konter, J. G., and Becker, T. W.: Primordial helium entrained by the hottest mantle plumes. Nature, 542, 340-343, 2017. (PDF)
      • Konter, J. and Becker, T. W.: Shallow lithospheric contribution to mantle plumes revealed by integrating seismic and geochemical data. Geochem., Geophys., Geosys., 13, Q02004, doi:10.1029/2011GC003923, 2012. (PDF)
      • Boschi, L., Becker, T. W., and Steinberger, B.: On the statistical significance of correlations between synthetic mantle plumes and tomographic models. Physics Earth Planet. Int., 260, 230-238, 2008. (PDF)
      • Boschi, L., T. W. Becker, and B. Steinberger, Mantle plumes: Dynamic models and seismic images, Geochem. Geophys. Geosyst., 8, Q10006, doi:10.1029/2007GC001733, 2007. (PDF)

    • Seismic tomography, power, validation and filtering

      We study long-period, surface wave seismograms from actual earthquakes and synthetics using the global spectral element method in order to validate and analyze different global mantle tomography models.

      • Qin, Y., Capdeville, Y., Montagner, J.-P., Boschi, L., and Becker, T. W.: Reliability of mantle tomography models assessed by spectral-element simulation. Geophys. J. Int., 177, 125-144, 2009. (PDF)

      The effects of tomographic resolution and filtering are explored in the context of global mantle circulation models; velocities between original input geodyamic model and tomo-filtered output match well.

      • Bull, A. L., McNamara, A. K., Becker, T. W., and Ritsema, J.: Global scale models of the mantle flow field predicted by synthetic tomography models. Phys. Earth Planet. Int., 182, 129-138, 2010. (PDF)

    • A comparison of seismologic and geodynamic mantle models

      We discuss several quantitative comparisons between seismological and geodynamic models of the Earth's mantle. Our global tomography analyses are compatible with whole mantle convection with reorganization of flow at 660-km due to the viscosity jump.

      • Steinberger, B., Torsvik, T. H., and Becker, T. W.: Subduction to the lower mantle - a comparison between geodynamic and tomographic models. Solid Earth, 3, 415-432, 2012. (PDF)
      • Becker, T. W. and Boschi, L.: A comparison of tomographic and geodynamic mantle models, Geochem., Geophys., Geosys., 3, 2001GC000168, 2002. (PDF)

      Additional online material is on the Becker & Boschi (2002): Correlations between models page. All tomographic models from that repository can be used directly as input for the hc mantle flow computation program, as provided in the Solid Earth Research and Teaching Environment (SEATREE).
    • Analysis of western United States regional upper mantle tomography

      • Becker, T. W.: On recent seismic tomography for the western United States. Geochem., Geophys., Geosys., 13, Q01W10, doi:10.1029/2011GC003977, 2012. (PDF)
      • Becker, T. W., Faccenna, C., Humphreys, E. D., Lowry, A. R., and Miller, M. S.: Static and dynamic support of western U.S. topography. Earth Planet. Sci. Lett., 402, 234-246, 2014. (PDF)
    • Teaching interface to seismic tomography codes

      Larry Boschi's seismic tomography codes for global body wave and surface wave inversions are available for teaching and research purposes via a GUI in the Solid Earth Research and Teaching Environment (SEATREE)

      • Milner, K., Becker, T. W., Boschi, L., Sain, J., Schorlemmer, D. and H. Waterhouse: The Solid Earth Research and Teaching Environment: a new software framework to share research tools in the classroom and across disciplines. Eos Trans. AGU, 90, 12, 2009. (PDF).
      • Waterhouse, H. D., K. Milner, T. W. Becker, J. Sain, and D. Schorlemmer: A Solid Earth Research and Teaching Environment, Opportunities and Challenges in Computational Geophysics workshop, Caltech, 2009. (PDF).
      • See also the Unified Geodynamics Earth Science Computing Environment (UGESCE) which has SEATREE preinstalled.
    • Finite frequency tomography

      We strive to analyze and evaluate enhancements in global imaging of mantle structure by means of finite frequency tomography within the constraints given by global data coverage.

      • Boschi, L., Becker, T. W., Soldati, G., and Dziewonski, A. M.: On the relevance of Born theory in global seismic tomography. Geophys. Res. Lett., 33, L06302, doi:10.1029/2005GL025063, 2006. (PDF).
    • NSF-CD project Program to Investigate Convective Alboran Sea System Overturn (PICASSO)

      We were part of a multi-institutional, multi-disciplinary continental dynamics research effort funded by NSF-CD to study subduction dynamics and lithospheric delamination mechanisms in the westernmost terminus of the Tethyan collision.
      • Main PICASSO project web page
      • Conference presentation summarizing some of the USC led findings:
        • Miller, M. S.: Pockets, conduits, channels, and plumes: links to volcanism and orogeny in the western Meditteranean. Presentation at CIDER 2016, (video)
      • Geodynamics group project publications
        • Sun, D., Miller, M. S., Holt, A. F., and Becker, T. W.: Hot upwelling conduit beneath the Atlas Mountains, Morocco. Geophys. Res. Lett., 41, 8037-8044, doi:10.1002/2014GL061884, 2014. (PDF, supp. mat.)
        • Faccenna, C., Becker, T. W., Auer, L., Billi, A., Boschi, L., Brun, J.-P., Capitanio, F. A., Funiciello, F., Horvath, F., Jolivet, L., Piromallo, C., Royden, L., Rossetti, F., and Serpelloni, E.: Mantle dynamics in the Mediterranean. Rev. Geophys., 52, doi:10.1002/2013RG000444, 2014. (PDF)
        • Miller, M. S. and Becker, T. W.: Reactivated lithospheric-scale discontinuities localize dynamic uplift of the Moroccan Atlas Mountains. Geology, doi:10.1130/G34959, 2014. (PDF)
          • Miller, M. S. and Becker, T. W.: Reactivated lithospheric-scale discontinuities localize dynamic uplift of the Moroccan Atlas Mountains: Comment - Reply. Geology, 42, 338, 2014. (PDF)
          • Nature Geoscience highlight by Whitchuch
        • Alpert, L. A., Miller, M. S., Becker, T. W., and Allam, A. A.: Structure beneath the Alboran from geodynamic flow models and seismic anisotropy. J. Geophys. Res., 118, 4265--4277, doi:10.1002/jgrb.50309, 2013. (PDF)
        • Faccenna, C., Becker, T. W., Jolivet, L., and Keskin, M.: Mantle convection in the Middle East: Reconciling Afar upwelling, Arabia indentation and Aegean trench rollback. Earth Planet. Sci. Lett., 375, 254-269, 2013. (PDF)
        • Miller, M. S., Allam, A. A., Becker, T. W., Di Leo, J., and Wookey, J.: Constraints on the geodynamic evolution of the westernmost Mediterranean and northwestern Africa from shear wave splitting analysis. Earth Planet. Sci. Lett., 375, 234-243, 2013. (PDF)
        • Becker, T. W. and Faccenna, C.: Mantle conveyor beneath the Tethyan collisional belt. Earth Planet. Sci. Lett., 310, 453-461, 2011. (PDF)
        • Faccenna, C. and Becker, T. W.: Shaping mobile belts by small-scale convection. Nature, 465, 602-605, 2010. (PDF)
  • Seismic anisotropy and upper mantle dynamics

    • Seismic anisotropy from global mantle flow LPO model

    • A comprehensive reference frame for present-day plate motions

      We show that a spreading-aligned absolute plate motion reference frame can be constructed and fits a number of observations, including azimuthal anisotropy and hotspot motions, well. This has implications for transform fault weakness, passive spreading, and trench motions statistics.
      • Schaeffer, A., Lebedev, S., and Becker, T. W.: Azimuthal seismic anisotropy in the Earth's upper mantle and the thickness of tectonic plates. Geophys. J. Int., 207, 901-933, 2016. (PDF, supp. mat.)
      • Becker, T. W., Schaeffer, A. J., Lebedev, S., and Conrad, C. P.: Toward a generalized plate motion reference frame. Geophys. Res. Lett., 42, doi:10.1002/2015GL063695, 3188-3196, 2015. (PDF, supp. mat.)
      • download plate velocities in new reference frame
    • Regional anisotropy and lithosphere-asthenosphere interactions

      We study regional shear wave splitting for the northern margins of the South American plate, the Alboran-Atlas-Canary system, and the Mediterranean and western U.S. mobile belts, and interpret them in terms of upper mantle, small-scale convection and slab-keel interactions.

      • Jolivet, L., Faccenna, C., Becker, T. W., Tesauro, M., Sternai, P., and Bouihol, P.: Mantle flow and deforming continents: From India-Asia convergence to Pacific subduction. Tectonics, doi:10.1029/2018TC005036, 2018. (PDF)
      • Porritt, R. W., Becker, T. W., and Monsalve, G.: Seismic anisotropy and slab dynamics from SKS splitting recorded in Colombia. Geophys. Res. Lett., 41, doi:10.1002/2014GL061958, 2014. (PDF)
      • Faccenna, C., Becker, T. W., Auer, L., Billi, A., Boschi, L., Brun, J.-P., Capitanio, F. A., Funiciello, F., Horvath, F., Jolivet, L., Piromallo, C., Royden, L., Rossetti, F., and Serpelloni, E.: Mantle dynamics in the Mediterranean. Rev. Geophys., 52, doi:10.1002/2013RG000444, 2014. (PDF)
      • Miller, M. S. and Becker, T. W.: Reactivated lithospheric-scale discontinuities localize dynamic uplift of the Moroccan Atlas Mountains. Geology, 42, 35-38, 2014. (PDF)
      • Miller, M. S., Allam, A. A., Becker, T. W., Di Leo, J., and Wookey, J.: Constraints on the geodynamic evolution of the westernmost Mediterranean and northwestern Africa from shear wave splitting analysis. Earth Planet. Sci. Lett., 375, 234-243, 2013. (PDF)
      • Alpert, L. A., Miller, M. S., Becker, T. W., and Allam, A. A.: Structure beneath the Alboran from geodynamic flow models and seismic anisotropy. J. Geophys. Res., 118, 1-13, doi:10.1002/jgrb.50309, 2013. (PDF)
      • Faccenna, C., Becker, T. W., Jolivet, L., and Keskin, M.: Mantle convection in the Middle East: Reconciling Afar upwelling, Arabia indentation and Aegean trench rollback. Earth Planet. Sci. Lett., 375, 254-269, 2013. (PDF)
      • Miller, M. S. and Becker, T. W.: Mantle flow deflected by interactions between subducted slabs and cratonic keels. Nature Geosc., 5, 726-730, 2012. (PDF)
      • Becker, T. W., Schulte-Pelkum, V., Blackman, D. K., Kellogg, J. B., and O'Connell, R. J.: Mantle flow under the western United States from shear wave splitting, Earth Planet. Sci. Lett., 247, 235-251, 2006. (PDF)
    • Review articles on seismic anisotropy

    • Radial anisotropy as a constraint for regional tectonics, mantle rheology, and volatile content

      We explore radial anisotropy by means of improved global and regional imaging and forward models based on stochastic and mantle flow computations. The geoynamic models are able to match both global radial anisotropy averages and most of the anomaly patterns. The mismatch between seismology and geodynamic reference, residual anisotropy, yields information on the frozen-in structure of the oceanic and continental lithosphere and the volatile content and dynamics of the asthenosphere.

      • seismic anisotropy from global mantle flow model download
      • Auer, L., Becker, T. W., Boschi, L., and Schmerr, N.: Thermal structure, radial anisotropy, and dynamics of oceanic boundary layers. Geophys. Res. Lett., 42, 9740-9749, doi:10.1002/2015GL06624, 2015. (PDF)
      • Auer, L., Boschi , L., Becker, T. W., Nissen-Meyer, T. and Giardini, D.: Savani: a variable-resolution whole-mantle model of anisotropic shear-velocity variations based on multiple datasets. J. Geophys. Res., 119, 3006-3034, doi:10.1002/2013JB010773, 2014. (PDF, model)
      • Schaefer, J. F., Boschi, L., Becker, T. W. and Kissling, E.: Radial anisotropy in the European mantle: Tomographic studies explored in terms of mantle flow. Geophys. Res. Lett., 38 (L23304), doi:10.1029/2011GL049687, 2011. (PDF).
      • Becker, T. W., Kustowski, B. and Ekström, G.: Radial seismic anisotropy as a constraint for upper mantle rheology. Earth Planet. Sci. Lett., 267, 213-237, 2008. (PDF, model)
    • Anisotropy provides a speed limit for net rotations

      We show that anisotropy constrains net rotations of the lithosphere to be smaller than in some hotspot reference frame models, and that spreading-aligned plate motion reference frames are consistent with azimuthal anisotropy.

      • Becker, T. W., Schaeffer, A. J., Lebedev, S., and Conrad, C. P.: Toward a generalized plate motion reference frame. Geophys. Res. Lett., 42, doi:10.1002/2015GL063695, 3188-3196, 2015. (PDF, supp. mat., model)
      • Becker, T. W.: Azimuthal seismic anisotropy constrains net rotation of the lithosphere. Geophys. Res. Lett., 35, L05303, doi:10.1029/2007GL032928, 2008. (Correction: 2008GL033946, PDF)
      • Becker, T. W., Ekström, G., Boschi, L., and Woodhouse, J.: Length scales, patterns, and origin of azimuthal seismic anisotropy in the upper mantle as mapped by Rayleigh waves. Geophysical J. Int., 171 451-462, 2007. (PDF)
    • Length scales and origin of upper mantle anisotropy

      We analyze the lateral variations in anisotropic length scales as inferred from SKS splitting and azimuthal anisotropy tomography. Older continental regions appear more coherent than younger, geologically active units. We interpret this finding using surface waves and geodynamic models and explore different methods of predicting shear wave splitting from tomography

    • Mantle flow, lattice preferred orientation (LPO) fabrics, and viscous anisotropy

      We study upper mantle fabrics from different mineral physics texturing models and mantle convection simulations with lateral viscosity variations. Texturing methods are found to differ strongly in terms of the treatment of recrystallization and predictions of mechanical anisotropy. Flow modeling results indicate that scaling relationships exist between hexagonal anisotropy parameters, and that natural samples follow the same trends as synthetics. We also explore the role of mechanical anisotropy for boundary layer flow. Previously NSF-CSEDI funded.

      • seismic anisotropy from global mantle flow model download
      • Becker, T. W.: Superweak asthenosphere in light of upper-mantle seismic anisotropy, Geochem., Geophys., Geosys., 18, 1986-2003, doi:10.1002/2017GC006886, 2017. (PDF)
      • Schaeffer, A., Lebedev, S., and Becker, T. W.: Azimuthal seismic anisotropy in the Earth's upper mantle and the thickness of tectonic plates. Geophys. J. Int., 207, 901-933, 2016. (PDF, supp. mat.)
      • Auer, L., Becker, T. W., Boschi, L., and Schmerr, N.: Thermal structure, radial anisotropy, and dynamics of oceanic boundary layers. Geophys. Res. Lett., 42, 9740-9749, doi:10.1002/2015GL066246, 2015. (PDF)
      • Becker, T. W., Conrad, C. P., Schaeffer, A. J., and Lebedev, S.: Origin of azimuthal seismic anisotropy in oceanic plates and mantle. Earth Planet. Sci. Lett., 401, 246-250, 2014. (PDF, model)
      • Becker, T. W. and Kawakatsu, H.: On the role of anisotropic viscosity for plate-scale flow. Geophys. Res. Lett., 38, L17307, doi:10.1029/2011GL048584, 2011. (PDF)
      • Castelnau, O., Blackman, D. K. and Becker, T. W.: Numerical simulations of texture development and associated rheological anisotropy in regions of complex mantle flow. Geophys. Res. Lett, 36, L12304, doi:10.1029/2009GL038027, 2009. (PDF)
      • Becker, T. W., Ekström, G., Boschi, L., and Woodhouse, J.: Length scales, patterns, and origin of azimuthal seismic anisotropy in the upper mantle as mapped by Rayleigh waves. Geophysical J. Int., 171 451-462, 2007. (PDF)
      • Becker, T. W., Chevrot, S., Schulte-Pelkum, V., and Blackman, D. K.: Statistical properties of seismic anisotropy predicted by upper mantle geodynamic models. J. Geophys. Res., 111, B08309, doi:10.1029/2005JB004095, 2006. (PDF).
      • Becker, T. W., Kellogg, J. B., Ekström, G., and O'Connell, R. J.: Comparison of azimuthal seismic anisotropy from surface waves and finite-strain from global mantle-circulation models, Geophys. J. Int., 155, 696-714, 2003. (PDF)

[news] [teaching] [group] [publications] [CV] [downloads] [contact]
[geodynamics] [seismology] [fieldwork] [downloads]
[crustal stress] [faults] [anisotropy] [tomography]
Updated: September 25, 2018. (c) JSG Geodynamics, 2018.