Gennady Aleksandrovich Sobolev (1935 – 2024)

On 6 February 2024, Gennady Aleksandrovich Sobolev, Corresponding Member of the Russian Academy of Sciences, Professor, Doctor of Physical and Mathematical Sciences, Chief Scientist of the Institute of Physics of the Russian Academy of Sciences, former President of the European Seismological Commission passed away at the 89th year of his life.

Another representative of the old academic school has left us. He was broadly educated, intelligent, shrewd, and with a tremendous energy that literally charged those around him. Bright, complex, and talented – he always attracted attention. G. A. Sobolev was a born leader. His contribution to science is incalculable. He earned the deepest respect and fondness of a vast number of geophysicists in Russia, the former USSR, and among foreign colleagues.

G. A. Sobolev was born in Smolensk on 7 April 1935 into a family of doctors. He enrolled in the Department of Geology at the Moscow State University in 1953 and graduated in 1958 with a specialisation in geophysical methods of mineral exploration. Immediately after graduation he joined the Institute of Physics of the Earth of the Academy of Sciences of the USSR in the High Pressure Laboratory under the direction of Prof. M. P. Volarovich. There G. A. Sobolev conducted a complex of laboratory and field research on developing a piezoelectric method of exploration of gold, polymetallic and piezo-quartz deposits. At this "piezoelectric" stage of scientific life, G. A. Sobolev defended his candidate's thesis in 1963, and later, in 1973, together with M. P. Volarovich, E. I. Parkhomenko and employees of geological institutions, received a State Prize of the USSR. In 1976, the development of his work led to the discovery, together with V. M. Demin and Yu. Ya. Maibuk, of the phenomenon of generation of pulsed electromagnetic radiation by natural polymetallic ore bodies, which was registered as a scientific discovery in 1982 and laid the foundation for a new field of geophysical exploration - semiconductors.

In 1965, G. A. Sobolev began research into earthquake prediction, first in Garm (Tajikistan), then in Kamchatka, where stations were set up to record variations in the electro-telluric field. With their help, anomalous field variations were detected before a number of earthquakes and investigated as precursors. The culmination of this stage was a collaborative attempt with Acad. S. A. Fedotov to make continuous short-term predictions. However, it soon became clear that without an understanding of the physics of the earthquake source, one or more forecasting methods could not guarantee reliable success.

In this connection, in the 1970s, G. A. Sobolev began to conduct laboratory experiments on modelling earthquake sources, first on high-pressure equipment for testing small rock samples, then on the unique 50,000-tonne press at the Institute of High Pressure Physics, where it was possible to deform 1-meter and larger blocks. This made it possible to place a large number of sensors of different physical fields on the sample, i.e., to solve the problem of searching for microearthquake precursors using a complex of methods. The obtained results formed the basis for the joint work of V. I. Myachkin, B. V. Kostrov and O. G. Shamina, a model of avalanche unstable fracture formation (AUF) for earthquake preparedness, which became known in the world as the IPE model. G. A. Sobolev’s collaborative work with his students and American, German, and Chinese scientists on acoustic emission from rock fracturing became a significant contribution to earthquake source physics. In 1976, G. A. Sobolev defended his doctoral thesis.

In the early 1980s, G. A. Sobolev began to test the regularities revealed by laboratory modelling under natural conditions in seismically active regions. The greatest, though modest, successes were achieved in the study of the seismic regime for medium-term forecasting. G. A. Sobolev was the architect of creating a methodology for calculating maps of expected earthquakes (the MEE algorithm) based on a set of parameters. Together with his colleagues, he developed algorithms for detecting successive stages of seismic quiescence, foreshock activation, clustering of hypocentres of small earthquakes in the focal area of an impending strong earthquake, in particular the RTL algorithm. This research provided the basis for new earthquake source models and earthquake prediction methods. For his outstanding achievements in the field of exploration geophysics and earthquake source physics, G. A. Sobolev was elected a corresponding member of the Russian Academy of Sciences in 1994. In 2011, G. A. Sobolev created the concept of earthquake prediction reflecting trigger effects.

G. A. Sobolev conducted great scientific and organisational work both in Russia and abroad. In 1990, he was elected vice-president and in 1994, President of the European Seismological Commission (ESC). He was a member of the Bureau of the Expert Committee on Earthquake Forecasting of the Council of Europe and Chairman of the Commission on Seismic Hazards and Prediction of the International Association of Seismology and Physics of the Earth's Interior (1990 – 1995). He led international projects with scientists from the USA, Germany, China, Greece, and India. From 1990 to 2004, G. A. Sobolev headed the National Geophysical Committee of the Russian Federation and was Director of the Geophysical Centre of the Russian Academy of Sciences. In 2009, G. A. Sobolev was the only Russian scientist to work in a team of international experts invited by the Italian government to analyze the state of the problem of earthquake forecasting after the catastrophic earthquake in L'Aquila. For more than a quarter of a century, Gennady Aleksandrovich held a permanent appointment as the chairman of the Scientific Council on Problems of Seismology of the Russian Academy of Sciences.

G. A. Sobolev paid great attention to the training of researchers. His students defended 15 candidate and 7 doctoral theses. The research of the leading scientific school under the leadership of G. A. Sobolev was repeatedly supported by grants from the President of the Russian Federation. He was a member of the academic councils and dissertation committees of the Institute of Physics of the Earth of the Russian Academy of Sciences, deputy editor-in-chief of the journal Volcanology and Seismology, deputy editor-in-chief of the journal Physics of the Earth. Gennady Alexandrovich devoted a lot of effort to regular seminars on physical bases of rock fracture, participation in which unites physicists and geophysicists, miners and geologists, mechanics and civil engineers. He was the initiator and constant leader of these seminars, where he delivered deep and passionate scientific presentations. He published over 400 scientific publications, 8 monographs, including one in English and one in Chinese, one scientific discovery and 21 inventions.

In recent years, G. A. Sobolev worked fruitfully and enthusiastically on the problems of causal relations between magnetic storms and earthquakes, the influence of external sources on tectonic deformations of the lithosphere and variations in seismic activity under the influence of external sources, the relationship between local geodynamics and earthquakes to improve methods of predicting catastrophic earthquakes, publishing articles in leading scientific journals, presenting results of his research at scientific conferences.

He possessed emotional fortitude, a keen sense of justice and responsibility, he knew to create a benevolent atmosphere of interpersonal working relations in a research team, he taught commitment to scientific search and painstaking unobtrusive research work.

Among the many state and scientific awards received by G. A. Sobolev, the last one – a commendation from the President of the Russian Federation – for services to the development of national science, many years of fruitful work and in connection with the 300 th anniversary of the foundation of the Russian Academy of Sciences was awarded to him on 5 February 2024.

A talented scientist who laid the foundations for several new scientific paths has left us. A devotee of science is gone, an epoch has passed. The bright memory of Gennady Aleksandrovich Sobolev will remain in our hearts forever.

Alexey Zavyalov and Alexander Ponomarev, Schmidt Institute of Earth Physics of the Russian Academy of Sciences