A five-year, collaborative, NSF FRES funded effort to
advance integrative modeling capabilties within the
megathrust context to advance the use of physics-based
models for earthquake hazard asssessment. Read more on the
MTMOD web page.
New inverse approaches to visco-elastic
earthquake deformation problems
Collaborative work on using flexible finite element frameworks for
accurate solutions to the faulting problem for forward
and inverse approaches, including for the inversion of geodetic data
for 3-D elastic property variations.
Puel, S., Becker, T.W., Villa, U., Ghattas, O., and Liu, D.:
Volcanic arc
rigidity variations illuminated by coseismic deformation of the 2011
Tohoku-oki M9, Science Adv., 10, doi:10.1126/sciadv.adl4264,
2024.
(PDF)
Puel, S., Becker, T. W., Villa, U., Ghattas, O., and Liu, D.: An
adjoint-based optimization method for jointly inverting heterogeneous
material properties and fault slip from earthquake surface deformation
data. Geophys. J. Int., doi:10.1093/gji/ggad442, 2023.
(PDF)
Puel, S., Khattatov, E., Villa U., Liu, D., Ghattas, O. and
Becker, T. W.: A Mixed, unified forward/inverse framework for earthquake
problems: Fault implementation and coseismic slip
estimate. Geophys. J. Int., 230, 733-758,
2022. (PDF)
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). We also explore the time-dependence
of crustal stress before and after the M9.
Puel, S., Becker, T.W., Villa, U., Ghattas, O., and Liu, D.:
Volcanic arc
rigidity variations illuminated by coseismic deformation of the 2011
Tohoku-oki M9, Science Adv., 10, doi:10.1126/sciadv.adl4264,
2024.
(PDF)
Becker, T. W., Hashima, A., Freed, A. M., and Sato, H.: Stress
change before and after the 2011 M9 Tohoku-oki earthquake.
Earth Planet Sci. Lett., 504, 174-184,
2018. (PDF)
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,
dynamic topography models)
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 was also involved in the
SCEC Community Stress Model (CSM) project.
SCEC IV 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. We put together a web site to allow inter-model
comparison and validation.
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 and transpressional tectonics
We explore how 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 in
particular in transpressional systems.
Conrad, E. M., Reitano, R., Faccenna, C., Becker, T. W.:
Morpho-tectonics of transpressional
systems: insights from analog modeling. Tectonics, 23,
doi:10.1029/2023TC007865, 2023. (PDF)
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)
interact is a boundary element program which
implements Okada's (1992) and Nikkhoo and Walter's (2015)
solutions for stress in an elastic half-space (Greens'
functions for constant slip on rectangular or triangular
dislocation elements) as well as Petsc enabled parallel
solves.
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)
A four year, collaborative, NSF funded Research Collaboration
Network to plan for Modeling Collaboratory for
Subduction to address the physics of megathrust and volcano
subduction systems with an eye toward decadal scale forecasting in
multi-sensor monitoring networks. Read more on the
MCS RCN web page.
Commentary on Tectonic Precursors arising out of our
COSEG 2019 workshop
Pritchard, M. E., R. M., Allen, T. W. Becker, M. D. Behn,
E. E. Brodsky, R. Bürgmann, C. Ebinger, J. T. Freymueller,
M. Gerstenberger, B. Haines, Y. Kaneko, S. D. Jacobsen, N. Lindsey,
J. J. McGuire, M. Page, S. Ruiz, M. Tolstoy, L. Wallace, W. R. Walter,
W. Wilcock, and H. Vincent: New opportunities to study earthquake
precursors. Seismol. Res. Lett., 91, 2444-2447, 2020.
(PDF)
20 years of linking seismic topography and mantle convection
Lapo Boschi, Steve Grand and I chat about the last 20 years of
linking seismic tomography and
global mantle dynamics and interdisciplinary collaboration from our perspective, sponsored by the
Modeling Collaboratory for Subduction RCN.
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 better understand the
distribution of EM1, HIMU, and high 3/4He. In particular, the high
3/4He component appears associated with a primordial, deep
mantle reservoir that is only entrained by the hottest plumes.
Koppers, A., Becker, T.W., Jackson, M., Konrad, K., Müller,
R.D., Romanowicz, B., Steinberger, B. and Whittaker, J.:
Mantle plumes and their role in Earth processes.
Nature Rev. Earth & Environ., 2, 382-401,
2021. (PDF)
Jackson, M. G., Becker, T. W., and Steinberger, B.: Spatial characteristics of recycled and
primordial reservoirs in the deep mantle. Geochem., Geophys.,
Geosys., 22, doi:10.1029/2020GC009525, 2021. (PDF)
Jackson, M. G., Blichert-Toft, J., Halldórsson, S. A.,
Mundl-Petermeier, A., Bizimis, M., Kurz, M. D., Price, A. A.,
Harðardóttir, S., Willhite, L. N., Breddam, K., Becker T. W., and
Fischer, R. A.: Ancient helium and tungsten isotopic signatures
preserved in mantle domains least modified by crustal
recycling. Proc. Nat. Acad. Sci., 117, 30,993-31,001, 2020. (PDF)
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, 19, 3496-3519, doi:10.1029/2018GC007552, 2018.
(PDF)
Jackson, M. G., Becker, T. W., and Konter, J. G.: 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. G. 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)
Plume talk-back terminating subduction
We use convection models with damage rheologies to show that slabs
can not only trigger plume upwellings at the CMB, but plumes arising
along slabs may shut off subduction at the surface. This bottom-up
interaction may have been relevant particularly for the early
Earth.
Heilman, E. and Becker, T. W.: Plume-driven subduction termination
in 3-D mantle convection models. G-Cubed, 25,
doi:10.1029/2024GC011523, 2024. (PDF)
Heilman, E. and Becker, T. W.: Plume-slab interactions can shut off
subduction. Geophys. Res. Lett., 49, e2022GL099286,
2022. (PDF)
Gerya, T. V., Bercovici, D., and Becker, T. W.: Dynamic slab segmentation
due to brittle-ductile damage in the outer rise. Nature, 599,
245-250, 2021. (PDF)
Generation and character of whole mantle seismic
heterogeneity
Joint, multidisciplinary work on imaging and modeling global
isotropic and radially anisotropic mantle structure.
Hua, J., Fischer, K., Becker, T.W., Gazel, E. and Hirth, G.:
Asthenospheric low-velocity zone consistent with globally prevalent
partial melting. Nature Geosc., doi:10.1038/s41561-022-01116-9, 2023.
(PDF)
Porritt, R., Becker, T.W., Boschi, L., and Auer, L.: Multi-scale, radially anisotropic
shear wave imaging of the mantle underneath the contiguous United
States through joint inversion of USArray and global
datasets. Geophys. J. Int.,
2021. (PDF,
SI, SAVANI-US model
download)
Lai, H., Garnero, E., Grand, S., Porritt, R. W., and Becker, T. W.:
Global travel time dataset from adaptive empirical wavelet
construction. Geochem., Geophys., Geosys., 20,
doi:10.1029/2018GC007905,
2019. (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)
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)
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).
Lithospheric thickness models based on seismic tomography
We analyze seismic tomography models and describe a new method of
inferring lithospheric thickness.
Steinberger, B. and Becker, T. W.: A comparison of lithospheric
thickness models. Tectonophys.,
doi:10.1016/j.tecto.2016.08.001,
2016. (PDF)
Global (S/PMEAN) and western US
(S/PMEAN-WUS) composite tomography
model download and model comparisons
Becker, T. W.: On recent seismic tomography for the western United
States. Geochem., Geophys., Geosys., 13, Q01W10,
doi:10.1029/2011GC003977, 2012.
(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)
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)
Porritt, R., Becker, T.W., Boschi, L., and Auer, L.: Multi-scale, radially anisotropic
shear wave imaging of the mantle underneath the contiguous United
States through joint inversion of USArray and global
datasets. Geophys. J. Int.,
2021. (PDF,
SI,
SAVANI-US model
download)
Wang, W. and Becker, T. W.: Upper mantle seismic anisotropy as a
constraint for mantle flow and continental dynamics of the North
American Plate.
Earth Planet. Sci. Lett., 514, 143-155, 2019.
(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,
dynamic topography models)
Becker, T. W.: On recent seismic tomography for the
western United States. Geochem., Geophys., Geosys.,
13, Q01W10, doi:10.1029/2011GC003977,
2012. (PDF)
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).
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.
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 team 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)
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)
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.)
Regional anisotropy and lithosphere-asthenosphere interactions
We study regional shear wave splitting and receiver function based
crustal anisotropy for the North and South American Cordillera, the
the Mediterranean and Alaska, and interpret them in
terms of upper mantle, small-scale convection, slab-keel
interactions, and lithospheric deformation.
Schulte-Pelkum, V., Becker,
T. W., Behr, W. M., and Miller, M. S.:
Tectonic inheritance during plate boundary evolution in southern
California constrained from seismic anisotropy.
Geochem., Geophys., Geosys., 22, doi:10.1029/2021GC010099,
2021. (PDF)
Schulte-Pelkum, V., Cain, J. S, Jones II, J. V., and Becker, T. W:
Imaging the tectonic grain of the Northern Cordillera orogen using
Transportable Array receiver functions.
Seismol. Res. Lett., 91, 3086-3105, 2020.
(PDF, SI)
Wang, W. and Becker, T. W.: Upper mantle seismic anisotropy as a
constraint for mantle flow and continental dynamics of the North
American Plate.
Earth Planet. Sci. Lett., 514, 143-155,
2019. (PDF)
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,
37, 2887-2914, 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. and Becker, T. W.: Reactivated lithospheric-scale
discontinuities localize dynamic uplift of the Moroccan Atlas
Mountains: Comment - Reply. Geology, 42, 338,
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,
velocity grids)
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 and chapters on seismic anisotropy
Becker, T. W. and Lebedev, S.: Dynamics of the upper mantle in
light of seismic anisotropy. In Mantle Convection and Surface
Expressions, Cottaar, S.. et al., eds., AGU, Washington DC,
doi:10.1002/9781119528609.ch10, 2020.
(PDF)
Long, M. D. and Becker, T. W.: Mantle dynamics and seismic
anisotropy. Earth Planet Sci. Lett., 297, Frontiers, 341-354,
2010. (PDF).
Becker, T. W.: Seismic anisotropy. In Encyclopedia of
Solid Earth Geophysics, Gupta, H. (Ed.), doi:10.1007/978-90-481-8702-7_51,
p. 1070-1081, Springer, 2010.
(PDF, HTML)
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 and melt content and
viscosity of the asthenosphere.
Hua, J., Fischer, K., Becker, T.W., Gazel, E. and Hirth, G.:
Asthenospheric low-velocity zone consistent with globally prevalent
partial melting. Nature Geosc., 16, 175-181, 2023.
(PDF)
Porritt, R., Becker, T.W., Boschi, L., and Auer, L.: Multi-scale, radially anisotropic
shear wave imaging of the mantle underneath the contiguous United
States through joint inversion of USArray and global
datasets. Geophys. J. Int., 265, 1730--1746,
2021. (PDF,
SI,
SAVANI-US 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, and CPO field studies.
Bernard, R., Behr, W. M., Becker, T. W., and Young, D.:
Relationships between olivine CPO and deformation parameters in
naturally deformed rocks and implications for mantle seismic
anisotropy. Geochem., Geophys., Geosys., 20, 1-27,
doi:10.1029/2019GC008289, 2019.
(PDF)
Becker, T. W., Lebedev, S., and Long, M. D.: On the relationship
between azimuthal anisotropy from shear wave splitting and surface
wave tomography. J. Geophys. Res., 117, B01306,
doi:10.1029/2011JB008705, 2012.
(PDF)
Becker, T. W., Browaeys, J. T., and Jordan, T. H.: Stochastic Analysis
of Shear Wave Splitting Length Scales. Earth
Planet. Sci. Lett., 259, 526-540, 2007. (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)
We study upper mantle fabrics from field samples and theoretical
texturing models and mantle convection models. We also explore the
role of mechanical anisotropy for boundary layer flow.
Previously NSF-CSEDI funded.
Liu, D., Puel, S., Becker, T. W., and Moresi, L. N.: Analytical and numerical
models of viscous anisotropy: A toolset to constrain the role of
mechanical anisotropy for regional tectonics and fault loading.
Geophys. J. Int., 239, 950-963, 2024.
Bernard, R., Behr, W. M., Becker, T. W., and Young, D.:
Relationships between olivine CPO and deformation parameters in
naturally deformed rocks and implications for mantle seismic
anisotropy. Geochem., Geophys., Geosys.,
doi:10.1029/2019GC008289, 2019.
(PDF)
Wang, W. and Becker, T. W.: Upper mantle seismic anisotropy as a
constraint for mantle flow and continental dynamics of the North
American Plate.
Earth Planet. Sci. Lett., 514, 143-155,
2019. (PDF)
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)