|EGS Beno Gutenberg Medallist - 2002|
in recognition of her major theoretical achievement in the modelling of surface waves and tsunamis propagation in laterally inhomogeneous media
The main fields T. Yanovskaya contributed are seismic tomography, the theory of seismic wave propagation and their inversion. On the basis of Backus-Gilbert approach T. Yanovskaya developed new, efficient methods for solving 2D tomography problem, including a new technique for azimuthal tomography, and applied them for investigation of the Earth's lithosphere structure in different regions. Her major achievement in the theory of seismic waves is the theory of surface wave propagation in laterally inhomogeneous media.
Tatiana Yanovskaya was born in 1932. She has graduated from Leningrad State University, Faculty of Physics, in 1954. In 1958 she completed the PhD course in the Institute of Physics of the Earth (Moscow), and defended the PhD thesis "Methods for determination of the source mechanism parameters from surface wave data", which she accomplished under supervision of Prof. E. Savarensky. In the period 1958-1960 she worked at the seismological station "Pulkovo", where she acquired an experience in processing the seismograms. Then, in 1960-1968 she was a junior researcher in Leningrad Division of the Mathematical Institute of the USSR Academy of Science, in the laboratory headed by Prof. G. I. Petrashen, where she worked on some problems in the theory of seismic wave propagation, mainly in the ray theory. With appearance of computers she began to study properties of seismic waves in complex structures by numerical modeling. Her main theoretical results belonged to that period are uniform asymptotic expansion of head wave field in the vicinity of the critical ray, and analysis of seismic wave field near the caustic. Also she began to work on inverse problems in seismology, and she was the first one, who proposed (with V. I. Keilis-Borok) the Monte-Carlo method for solving multiparametric problems, and applied it for inversion of travel time curve.
Beginning from 1968 she works in Leningrad (now St. Petersburg) State University, in Department of Geophysics, Faculty of Physics. She continues to work on inverse problems, and on the theory of surface waves and their inversion. In 1973 she received the second degree (Doctor of Physical and Mathematical Sci.), defending the thesis 'Determination of the structure of the transition zone between inner and outer core', where the geophysical inverse problem was solved mostly on the basis of the Monte-Carlo method. In 1982 she was awarded with the USSR State Prize for Science and Technique (with V. M. Babich, G. I. Petrashen and A. S. Alekseev).
From 1986 T. Yanovskaya is full Professor of St. Petersburg University. She delivers courses of lectures for students on fundamentals of seismology, theoretical seismology, and inverse problems in geophysics.
In the middle of 80-th she begins to be interested in studies of the upper structure of the Earth by the use of surface wave data. She works in two directions: theoretical studies of surface wave propagation in laterally inhomogeneous models, and tomography problems - reconstruction of lateral variations of the Earth crust and upper mantle from surface wave data. In studying surface wave fields in the media with weak lateral heterogeneity she modified the ray theory for harmonic waves, as well as the spatial-temporal ray theory for transient waves. Proceeding from the ray theory she could explain polarization anomalies of surface waves as an effect of lateral heterogeneity in the site of observation. To estimate surface wave fields in the media with vertical or subvertical boundaries she proposed a new method, based on the Green function technique, in which the boundary conditions are satisfied approximately. This method was applied for interpretation of the waves reflected from deep faults and from the boundaries between different tectonic units (e.g. continent -ocean). All these methods are described in the book 'Seismic surface waves in laterally inhomogeneous Earth', edited by V. I. Keilis-Borok.
On the basis of the Backus-Gilbert approach for solving 1D inverse problems she developed a method for 2D tomography both on a plane and on a spherical surface. This method is widely used now in seismological studies in different regions. She applied this method for investigation of lateral variation of the crust and upper mantle structure in the Eastern Mediterranean and Asia Minor, in the Black Sea region, and in the Central Asia. She also developed a new method for tomographic reconstruction of lateral phase velocity variations of surface waves from azimuthal anomalies.
For the great contribution to the research in seismology Tatiana Yanovskaya has been elected a Fellow of the American Geophysical Union in 1997.
Tatiana Yanovskaya participates actively in educating young seismologists from the developing countries. She was a lecturer on all six Workshops organized by the International Center for Theoretical Physics on the Theory of Seismic Wave Generation, Propagation and Inversion, beginning from 1990. Except the lectures on the theory of seismic waves and on tomography methods she distributed her computer programs for tomography to the participants from different countries, and consulted them afterwards by e-mail. This is the main reason her to be nominated as a candidate for TWAS membership.
During her visits to ICTP as a researcher she developed a method for numerical modeling of tsunami waves in realistic oceanic structures generated by offshore as well as by inland/coastal seismic sources.
Tatiana Yanovskaya is a member of Editorial Boards of the "Physics of the Solid Earth" (Russia), and of the Chinese Geophysical Journal, and also a chairperson of the Working Group "Tomography and other seismic methods" of the European Seismological Commission.
Yanovskaya, T. B.: Distribution of surface wave group velocities in the North Atlantic. Izv.AN SSSR, Fizika Zemli, 2, 3-11 (in Russian), 1982.
Yanovskaya T.B.: Solution of the inverse problem of seismology for Laterally inhomogeneous media, Geophys.J.Roy.astr.Soc., 79, 293-304, 1984.
Its, E. N. and Yanovskaya, T. B.: Propagation of surface waves in a half-space with vertical, inclined or curved interfaces. Wave motion, 7, 79-94, 1985.
Levshin A. L., Yanovskaya T. B., Lander A. V., Bukchin B. G., Barmin M. P., Ratnikova L. I., Its, E. N.: Seismic Surface Waves in a Laterally Inhomogeneous Earth 1989 (ed. Keilis-Borok V. I.) Kluwer Acad.Publ., 293p., 1989.
Yanovskaya T. B. and Roslov Yu. V.: Peculiarities of surface wave fields in laterally inhomogeneous media in the framework of ray theory. Geoph.J.Int., 99, 297-303, 1989.
Yanovskaya T. B. and Ditmar P. G.: Smoothness criteria in surface wave tomography. Geoph. J.I nt., 102, 63-72, 1990.
Yanovskaya T. B.: Uniform asymptotic representation of reflected wave field in elastic medium, in: Computational Seismology, Moscow, Nauka, 24, 185-196 (in Russian), 1991.
Yanovskaya T. B., Roslov Yu. V., and Lyskova E. L.: Quantification of earthquakes on the basis of P-wave spectra. Physics of the Solid Earth, 32, No.1: 1-12, 1996.
Yanovskaya T. B.: Ray tomography based on azimuthal anomalies, PAGEOPH., 148, 1/ 2, 319-336, 1996.
Yanovskaya T. B., Kizima E. S., and Antonova L. M.: Structure of the Black Sea and adjoining regions from surface wave data, Journal of Seismology, 2, 303-316, 1998.
Yanovskaya T. B. and Antonova L. M.: Lateral variations in the structure of the crust and upper mantle in the Asian region from data on the group velocities of Rayleigh waves, Izvestiya, Physics of the Solid Earth, 2, 25-33, 2000.
Yanovskaya T. B., Antonova L.M., Kozhevnikov V. M.: Lateral variations of the upper mantle structure in Eurasia from group velocities of surface waves, Physics of the Earth and Planet. Inter., 122, Nos.1-2, 19-32, 2000.