THE MOTION OF THE GROUND IN EARTHQUAKES

The slippage along a fault that produces an earthquake radiates seismic waves; the manner in which these waves shake the ground bears on the design of buildings and other structures in the earthquake zones. Since seismic waves span such a broad spectrum of period and amplitude, many different kinds of instruments and experimental techniques are needed to capture all the information radiated by an earthquake source. Repeated geodetic surveys and seismographs can yield useful information. Models that indicate the orientation of the fault surface and the direction of the slip across the surface are discussed, as well as measures of the strength of an earthquake. A new measure of the strength of an earthquake is the seismic moment which is determined by the Fourier analysis of seismic waves of such long period that the details of the rupture are smoothed out and the entire fault appears to be a point source. The total amount of slip accumulated from a number of earthquakes over a period of time also enables the estimation of the velocity at which the tectonic plates bounding the fault are moving past each other. The gound motions are strongly influenced by the details of the rupture process, such as the speed at which the rupture travels over the fault surface, frictional strength of the fault and the drop in stress across the fault. Seismologists are now beginning to recognize that many of the problems they encounter have a statistical character. A synthesis is now being attempted of the engineers statistical view and the seismologists deterministic view.

  • Availability:
  • Corporate Authors:

    Scientific American Incorporated

    415 Madison Avenue
    New York, NY  USA  10017
  • Authors:
    • Boore, D M
  • Publication Date: 1977-12

Media Info

  • Features: Figures;
  • Pagination: p. 69-78
  • Serial:
    • Scientific American
    • Volume: 237
    • Issue Number: 6
    • Publisher: Scientific American Incorporated
    • ISSN: 0036-8733

Subject/Index Terms

Filing Info

  • Accession Number: 00173685
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Apr 26 1978 12:00AM