DEEP SEISMIC SOUNDING AND STUDIES OF THE STRUCTURE OF THE EARTH'S CRUST IN THE USSR A symposium on deep seismic sounding of the Earth's crust took place on 14-19 November 1960, at the Institute of Earth Physics of the Academy of Sciences of the USSR. The symposium was organized by this institute, the Council of Prospecting Geophysics of the Presidium of the Academy of Sciences of the USSR, the Geophysics Department and the All-Union Institute of Geophysical Prospecting of the Ministry of Geology and the Conservation of Natural Resources of the USSR.
Geologists and geophysicists have become increasingly interested in the internal structure of the Earth, and especially in its peripheral part, i. e., the Earth's crust and the outer mantle. This subject is also of interest to astrophysicists; although the Earth is the most accessible planet of the solar system, very little is known as yet concerning its internal structure.
Increasingly detailed and thorough studies of the crust and the mantle are required for the solution of several basic problems confronting modern science, such as the developmental trend of the Earth's crust in different geological periods, the origin and evolution of the continents and oceans, the distribution patterns of mineral resources, and many other subjects of purely scientific as well as practical importance.
The structure of the Earth's crust is investigated by means of several geological and geophysical methods, the seismic method being the principal one. Deep seismic sounding (DSS) is the most detailed of the available seismic methods for studying the Earth's crust; it is based on the study of seismic waves generated by special small-scale explosions. Application of DSS to the study of the structure of the crust on land was developed by Soviet scientists according to principles suggested by G.A. Gamburtsev, and with his direct participation. He was the first to study the internal structure of the crust by means of principles and techniques which had originated in seismic prospecting. Prior to his work these had been employed only in seismology for investigating seismic waves generated by earthquakes, and had provided very scant information. At present DSS
is being used extensively in the USSR, both for pure scientific research and for practical industrial purposes.
Outside the USSR similar studies on land are being performed on a considerably smaller scale. However, a method similar to DSS for oceans was developed for the first time by American and British scientists, and is widely used in investigating the Earth's crust within the boundaries of the World Ocean. In the USSR seismic prospecting on the seas and oceans was begun in 1956. Working methods were considerably improved by Soviet scientists who took into account experience acquired in DSS work on land as well as experience in oceanic work accumulated outside the USSR.
In recent years the Soviet Union has amassed extensive data on the application of DSS on land, in regions with different geological histories, as well as on inland and open seas, and in the transition zone from the Asian continent to the Pacific Ocean.
The symposium on deep seismic sounding organized by the Academy of Sciences of the USSR in November 1960 was necessary for discussions of the results obtained as well as of several methodical and technical difficulties which had arisen. The symposium also purported to develop and improve various aspects of the working methods, to interpret results, and finally to coordinate further work, which is being undertaken by an increasing number of organizations.
There were 190 participants representing 48 organizations, 21 of which had worked with DSS. Thirty-six papers were read and discussed.
The potentialities of DSS from a geological standpoint were considered by Associate Member of the Academy of Sciences of the USSR V. V. Belousov.
The agenda of the symposium can be divided into three principal categories: 1) working methods and methods for interpreting data obtained by DSS; 2) characteristics of deep seismic waves, and their physical nature and interpretation; 3) further development and improvement of the DSS apparatus and operating methods.