Geophysical surveys

, Volume 3, Issue 4, pp 297–329 | Cite as

Classical focal mechanism techniques for body waves

  • David S. Brumbaugh


The initial motion of primary body waves and polarization directions of secondary body waves have been applied successfully to the study of the mechanism operating at the earthquake focus. Equal area plots of these body wave characteristics resulted in radiation patterns that were compared to patterns due to theoretical focal mechanism sources. Such an approach indicated that a double couple force is the source mechanism operating at earthquake foci. This can be physically represented by faulting at the focus. This seems likely because of the relation between earthquakes and fault motion in shallow earthquakes. The possibility of other mechanisms operating in deep focus earthquakes has not been ruled out.

The technique of solving for fault plane orientation/motion in equal area plots ofP-wave first motion andS-wave polarization, has been a powerful tool in areas where fault motions cannot be directly observed in studying tectonics. Such an approach has been used to test the theory of global tectonics. This approach has resulted in the confirmation of the suggested mechanics of plate motion, and the results of plate motion, such as spreading of the sea floor from mid-oceanic ridges and underthrusting of lithospheric plates at the sites of oceanic trenches.


Trench Fault Plane Focal Mechanism Plate Motion Body Wave 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© D. Reidel Publishing Co. 1979

Authors and Affiliations

  • David S. Brumbaugh
    • 1
  1. 1.Northern Arizona UniversityFlagstaffUSA

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