Earthquakes in North America

Abstract

During the past ten years considerable progress has been made in determining the seismicity in a given area-the frequency of occurrence, and distribution of earthquakes. Earlier investigations were based almost completely on field observations, but now extensive use of instrumental records is possible. This assures much more uniform results for the whole earth. The use of seismograms in investigations of seismicity was made possible by the development of methods which permit a rapid calculation of a function of the earthquake energy from instrumental observations.

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