Accession Number : AD0634979

Title :   DILATANCY AND THE SEISMIC FOCAL MECHANISM,

Corporate Author : BOEING SCIENTIFIC RESEARCH LABS SEATTLE WASH

Personal Author(s) : Orowan, E.

Report Date : JAN 1966

Pagination or Media Count : 24

Abstract : In a recent paper (Reviews of Geophysics 3:1965) F. C. Frank suggested that the seismic focal stress drop might be the consequence of a mechanical instability of deformation due to dilatancy of the crust and matle. A more complete calculation shows that the instability attributed to dilatancy is a familiar general property of compacted granular masses independent of dilatancy. The rapid propagation of the seismic fault attributed to shear melting by elastic energy release would depend on the assumed absence of friction between the walls of an initial Griffith crack. Since the length of the thin Griffith crack was estimated at 5 km, friction could be absent only if the crack were filled with a pore fluid of pressure equal to the total pressure; in this case the shear strength would be zero and seismic shocks could not arise. (Author)

Descriptors :   (*SEISMOLOGY, *STRUCTURAL GEOLOGY), ROCK, DEFORMATION, PROPAGATION, SOIL MECHANICS, GEOPHYSICS

Subject Categories : Geology, Geochemistry and Mineralogy
      Seismology

Distribution Statement : APPROVED FOR PUBLIC RELEASE