the work of conducting continuous observation of earthquakes and processing materials according to standard programs and methods. Observations are conducted by a network of seismological stations. The chief objective of seismological services is to determine systematically the principal parameters of earthquake foci, including coordinates of the focus, time of occurrence of the shock at the focus, and energy characteristics. Seismograms and initial bulletins from seismological stations provide raw data for correlation.
Seismological services are conducted by agencies in many countries of the world, for example, by the Integrated System for Seismic Observations (ESSN), in the USSR, by the U.S. Geological Survey in the USA, and by the Japan Meteorological Agency (JMA) in Japan. National seismological centers correlate observation data from seismological services in individual countries. Regional seismological services are organized for the detailed study of seismic activity. Current trends in the development of seismological services include the establishment of autonomous, unmanned seismological stations and grouping systems equipped for telemetric data transmission, the recording of data in digital form, and the extensive correlation of data by computer.
International seismological service is provided by the International Seismological Centre in Great Britain, where data from most of the world’s seismological stations are correlated. Raw data on the arrival time and amplitudes of seismic waves are transmitted from the stations to the seismological center in special form. The siesmological data are then processed by computer. As a result, the coordinates of the earthquake focus and the magnitude of the earthquake are systematically determined.
Data from seismological observations are used to study seismicity, the structure of the earth, and processes at the foci of earthquakes.
With the development of knowledge of the structure of the earth, the foci of earthquakes, and methods of evaluating seismic danger, the objectives of seismological services broaden. An example is the introduction of the systematic determination of additional parameters of earthquake foci, such as the mechanism and dimensions of the focus. Future aspects may include statistical generalizations about earthquakes and the compilation of special seismological tables of the characteristics of seismic wave propagation.
Seismological service data are published in Seismologicheskie biulleteni seti opornykh seismicheskikh stantsii SSSR (Seismological Bulletins of the USSR Network of Reference Seismic Stations, since 1962), Zemletriaseniia v SSSR (Earthquakes in the USSR: yearbook, since 1964), Bulletin of the International Seismological Centre (Edinburgh, since 1967), and The Seismological Bulletin of the Japan Meteorological Agency (Tokyo, since 1951).
N. V. KONDORSKAIA and Z. I. ARANOVICH