Chercheurs

Sciences de la Terre / NOLET, GUUST

nolet

Position

Professor of Geosciences (Seismology)
Geosciences Azur
Université de Nice/Sophia Antipolis
Sophia Antipolis, France.

Thèmes de recherche

In the early 1990ies, Guust's work in seismic tomography culminated in the discovery that at least some lithospheric slabs penetrate beneath the limit of deep-focus seismicity, and well into the lower mantle. The 1991 publication in Nature (vol. 353, p. 37-43), with Bob Engdahl and Wim Spakman, was a mile stone since it unambiguously resolved a long-standing controversy in the geosciences community regarding the character of solid-state convection in Earth's mantle1.

Body-wave traveltime tomography is a powerful technique for imaging structure in subduction zones, but it is less useful for resolving upper mantle heterogeneity beneath continental cratons. In 1990, Pr Nolet introduced the partitioned waveform inversion method to analyze upper-mantle heterogeneity with multiple S body waves and surface waves. In collaboration with a succession of students, he used this very efficient method to obtain images of upper-mantle structure far superior to any obtained before. With Utrecht graduate student Alet Zielhuis, Nolet discovered the remarkably sharp character of the suture separating western Europe from central Europe, known as the Tornquist-Tesseyre zone, and postulated that the root of the Ukrainian shield has been eroded by the injection of volatiles from the subducted proto-Atlantic lithosphere. He and his Princeton graduate students Suzan van der Lee and Sergei Lebedev used the partition waveform method to obtain vivid images of the subducted Farallon plate beneath western North America and of the structure beneath the tectonically complex regions of eastern Asia and the western Pacific.

Despite these successes, Nolet has not lost his love for field studies. In collaboration with another Princeton graduate student Richard Allen, he recently conducted a portable passive seismic experiment in Iceland. By employing a combination of partitioned waveform inversion and traveltime tomography, they were able to place strong constraints upon the shallow structure of this classic mantle hotspot.

The partitioned waveform method ignores coupling between surface wave modes, and this approximation becomes increasingly untenable as the scale length of the 3-D heterogeneity of interest decreases. With his Utrecht graduate student Roel Snieder in 1987, Nolet developed an innovative and practical method of accounting for mode coupling and scattering, based upon the Born approximation.

This early work with Snieder led directly to Nolet's collaboration with Henk Marquering, Shu-Huei Hung, Tony Dahlen, and others at Princeton, to develop Frechet sensitivity kernels for finite-frequency travel time tomography. In collaboration with his Princeton student Raffaella Montelli and Guy Masters at the Scripps Institution of Oceanography, Nolet has recently used these so-called 'banana-doughnut' kernels to obtain global images of P-wave velocity, which strengthens the seismic evidence for deep mantle convection plumes obtained from their earlier inversions. As another example of both his creativity and breadth of skill, he is now using these plume models to estimate the heat flux from Earth's mantle, which remains one of the most critical uncertainties in our understanding of the long term thermal evolution of Earth.

Prix et récompenses

1980 Prix Lagrange, Academie Royale des Sciences, des Lettres et des Beaux Arts de Belgique

1983 Vening Meinesz prijs, Netherlands Organization for the Advancement of Pure Research

1988 Member, Academia Europaea

1988 Cecil H. and Ida Green Fellowship

1993 Fellow, American Geophysical Union

1994 Gutenberg lecturer, American Geophysical Union

1996 Corresponding member, Royal Netherlands Academy of Sciences

2006 Beno Gutenberg medal, European Geophysical Society

2006 Bownocker medal , Ohio State University

2006 Member, American Academy of Arts and Sciences

2006 EGU Beno Gutenberg Medallist "for his pioneering role in the development of digital broadband seismology and for his outstanding contributions to geophysical inverse theory and seismic tomography, which have revolutionized our understanding of the structure of the Earth's interior."

Publications

Guust Nolet, Steve Krueger and Robert M. Clouser, "Empirical Determination of Depth-Distance Corrections for mb and MW from Global Seismograph Network Stations”, Geophysical research letters - 1998, vol. 25, no9, pp. 1451-1454

Dahlen, F.A. and G. Nolet, Comment on the paper "On sensitivity kernels for wave-equation transmission tomography" by de Hoop and van der Hilst, Geophys. J. Int., 163, 949-951, 2005.

Levander, A. and G. Nolet, Perspectives on array seismology and US Array, in A. Levander and G. Nolet (eds.), Seismic Earth: Analysis of broadband seismograms, AGU Monograph Series, 1-6, 2005.

Lebedev, S., G. Nolet, T. Meier and R.D. van der Hilst, Automated multimode inversion of surface and S waveforms, Geophys. J. Int., 162, 951-964, 2005.

Montelli, R., G. Nolet, G. Masters, F.A. Dahlen and S.H.-Hung, P and PP global traveltime tomography: Rays versus waves, Geophys. J. Int., 158, 637-654, 2004a.

Montelli, R., G. Nolet, F.A. Dahlen, G. Masters, E.R. Engdahl and S.H.-Hung, Finite-frequency tomography reveals a variety of plumes in the mantle, Science, 303, 338-343, 2004b.

Montelli, R., G. Nolet and F.A. Dahlen, Comment on `Banana-doughnut kernels and mantle tomography' by van der Hilst and de Hoop, in press, Geophys. J. Int., 2006a.

Montelli, R. G. Nolet, F.A. Dahlen and G. Masters, A catalogue of deep mantle plumes: new results from finite-frequency tomography, subm. to Geochem. Geophys. Geosys. (G3), 2006b.

Nolet, G. and R. Montelli, Optimum parameterization of tomographic models, Geophys. J. Int., 161, 365-372, 2005.

Nolet, G., F.A. Dahlen and R. Montelli, Traveltimes and amplitudes of seismic waves: a re-assessment, in A. Levander and G. Nolet (eds.), Seismic Earth: Analysis of broadband seismograms, AGU Monograph Series, 37-48, 2005.

Nolet, G., Plume Imagery, in: McGraw-Hill Yearbook of Science and Technology, 240-245, 2006.

Sigloch, K. and G. Nolet, Measuring finite-frequency body wave amplitudes and travel times, subm. to Geophys. J. Int., 2005.

Zhou, Y., F.A. Dahlen and G. Nolet, Three-dimensional sensitivity kernels for surface wave observables, Geophys. J. Int., 158, 142-168, 2004.

Zhou, Y., F.A. Dahlen, G. Nolet and G. Laske, Finite-frequency effects in global surface-wave tomography, Geophys. J. Int., 163, 1087-1111, 2005.

Zhou Y., G. Nolet, F. A. Dahlen, G. Laske, Global upper-mantle structure from finite-frequency surface-wave tomography, J. Geophys. Res., 111, B04304, doi:10.1029/2005JB003677, 2006.