Subsonic and intersonic shear rupture of weak planes with a velocity weakening cohesive zone. Samudrala, O.; Huang, Y.; and Rosakis, A. J. J. Geophys. Res., Aug, 2002.
doi  abstract   bibtex   
[1] A substantial effort has been devoted in the past toward modeling earthquake source mechanisms as dynamically extending shear cracks. Most of the attention was focused on the subsonic crack speed regime. Recently, a number of reports have appeared in the seismological literature citing evidence of intersonic rupture speeds during shallow crustal earthquakes. In the first part of this paper, we discuss direct experimental observations of intersonic in-plane shear crack growth along a weak plane joining two homogeneous, isotropic, linear elastic plates. Associated with the primary intersonic crack and at locations behind the propagating shear crack tip, a series of secondary tensile cracks, at a steep angle to the shear crack plane, were also observed. Motivated by these observations, subsonic and intersonic mode II crack propagation with a velocity weakening cohesive zone is analyzed in the main body of the paper. A cohesive law is assumed wherein the cohesive shear traction is either a constant or decreases linearly with the local slip rate, the rate of decrease governed by a slip rate weakening parameter. The cohesive shear traction is assumed to vanish when the crack tip sliding displacement reaches a characteristic breakdown slip. It is shown that a positive energy flux into the rupture front is possible in the entire intersonic regime. The influence of shear strength and of the weakening parameter on the crack propagation behavior is investigated. Crack tip stability issues are also addressed, and favorable speed regimes are identified. Estimates of the slip rate weakening parameter are obtained by using the theoretical model to predict the angle of the secondary cracks. The rest of the parameters are subsequently estimated by comparing the isochromatic fringe patterns (contours of maximum in-plane shear stress) predicted by the solution with those recorded experimentally.
@article{samudrala2002a,
	Abstract = {[1] A substantial effort has been devoted in the past
toward modeling earthquake
source mechanisms as dynamically extending shear cracks. Most of the
attention was focused on the
subsonic crack speed regime. Recently, a number of reports have appeared
in the seismological
literature citing evidence of intersonic rupture speeds during shallow
crustal earthquakes. In the
first part of this paper, we discuss direct experimental observations of
intersonic in-plane shear
crack growth along a weak plane joining two homogeneous, isotropic,
linear elastic plates.
Associated with the primary intersonic crack and at locations behind the
propagating shear crack
tip, a series of secondary tensile cracks, at a steep angle to the shear
crack plane, were also
observed. Motivated by these observations, subsonic and intersonic mode
II crack propagation with a
velocity weakening cohesive zone is analyzed in the main body of the
paper. A cohesive law is
assumed wherein the cohesive shear traction is either a constant or
decreases linearly with the
local slip rate, the rate of decrease governed by a slip rate weakening
parameter. The cohesive
shear traction is assumed to vanish when the crack tip sliding
displacement reaches a characteristic
breakdown slip. It is shown that a positive energy flux into the rupture
front is possible in the
entire intersonic regime. The influence of shear strength and of the
weakening parameter on the
crack propagation behavior is investigated. Crack tip stability issues
are also addressed, and
favorable speed regimes are identified. Estimates of the slip rate
weakening parameter are obtained
by using the theoretical model to predict the angle of the secondary
cracks. The rest of the
parameters are subsequently estimated by comparing the isochromatic
fringe patterns (contours of
maximum in-plane shear stress) predicted by the solution with those
recorded experimentally.},
	Author = {Samudrala, O. and Huang, Y. and Rosakis, A. J.},
	Date-Modified = {2010-05-27 13:33:03 -0700},
	Doi = {10.1029/2001JB000460},
	Journal = {J. Geophys. Res.},
	Month = {Aug},
	Number = {B8},
	Title = {Subsonic and intersonic shear rupture of weak planes with a velocity weakening cohesive zone},
	Volume = {107},
	Year = {2002},
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