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Influence of Material Contrast on Fault Branching Behavior

Nora DeDontney, James R. Rice, & Renata Dmowska

Published 2011, SCEC Contribution #1487

Material contrasts across faults are a common occurrence,
and it is important to understand if these material contrasts
can influence the path of rupture propagation. Here we examine
numerical models of rupture propagation through one
type of geometric complexity, that of a fault branch stemming
from a planar main fault on which rupture initiates.
This geometry, with a material contrast across the main
fault, could be representative of either a mature strike-slip
fault or a subduction zone interface. We consider branches
in both the compressional and extensional quadrants of the
fault, and material configurations in which the branch fault
is in either the stiffer or the more compliant material and
configurations with no material contrast. We find that there
are regimes in which this elastic contrast can influence the
rupture behavior at a branching junction, but there are also
stress states for which the branch activation will not depend
on the orientation of the mismatch. For the scenarios
presented here, both compressional and extensional side
branches are more likely to rupture if the branch is on the
side of the fault with the more compliant material versus the
stiffer material. The stresses induced on the branch fault, by
rupture traveling on the main fault, are different for the two
orientations of material contrast. We show how the interactions between rupture on the two faults determine which
faults are activated.

DeDontney, N., Rice, J. R., & Dmowska, R. (2011). Influence of Material Contrast on Fault Branching Behavior. Geophysical Research Letters, Submitted April 2011, L14305. doi: 10.1029/2011GL047849.