THE PROBLEM OF SEISMIC REGIONALIZATION

Seismic regionalization maps, delimiting zones wherein earthquakes of given intensity are to be expected, have been prepared for many countries. Such maps of U.S.S.R., Japan, Germany, Rumania, Hungary, India, Turkey and China are included herein. Existing methods of preparing seismic zonation maps suffer the following shortcomings: 1) No information is presented on how soon an earthquake can be expected in any given zone; 2) No information is presented on the characteristics of ground motion within the zones, nor on the type of vibrations transmitted; 3) There has been insufficient accuracy in delimiting seismic regions. Consequently, a new two-stage principle of seismic regionalization has been proposed. The first stage is the preparation of a “seismicity prognosis” map outlining zones of occurrence of earthquakes of a given intensity at given depths of focus and giving the probability of their occurrence. The second stage is preparation of a seismic effect prognosis map which would give information on intensity at the surface, spectral composition, character of vibration in the near surface materials, and earthquake probability. Methods of calculating the degree of seismic activity and of calculating the probability of occurrence of earthquakes, are also discussed.—R. E. Goodman