Open AccessA Note on the Mechanics of Seismic Faulting
Author(s) -
Berg C. A.
Publication year - 1967
Publication title -
geophysical journal of the royal astronomical society
Language(s) - English
Resource type - Journals
eISSN - 1365-246X
pISSN - 0016-8009
DOI - 10.1111/j.1365-246x.1967.tb06227.x
Subject(s) - crust , crack closure , slip (aerodynamics) , shear (geology) , geology , coulomb , mechanics , drop (telecommunication) , plasticity , fracture mechanics , kinetic energy , shock (circulatory) , geotechnical engineering , materials science , geophysics , classical mechanics , physics , engineering , composite material , petrology , medicine , telecommunications , quantum mechanics , thermodynamics , electron
Summary In the following paper an infinitely long shear crack lying in an infinitely deep elastic solid is considered as a model of a strike slip fault. The faces of the crack are stuck together by friction which increases linearly with the depth measured from the surface of the Earth. It is shown that if the interaction between the crack surfaces is just dry friction, with a drop from static to kinetic friction, the crack cannot produce a seismic shock. The case in which the interaction between the crack surfaces is Coulomb frictional failure (soil plasticity) with an initial cohesive strength is considered, and it is shown that if the cohesive strength undergoes a static to kinetic drop and then reheals under static conditions, the crack can produce more than one seismic shock provided that the loading on the Earth's crust increases in time. The depth to which the crack will propagate downward into the Earth under a given driving stress acting on the crust is given. The conclusion of this note is that if a shear crack in the crust is to give rise to seismic shocks, the interaction between the crack faces must entail some cohesive strength (i. e. a kinetic drop in dry friction is insufficient to produce shocks) and if the crack is to continue to produce shocks while the loading on the Earth does not increase indefinitely, the crack must penetrate deeply enough into the crust to influence the compliance of the crust as a whole.