Three-Dimensional Dynamic Rupture Simulations on Partially-Creeping
Strike-Slip Faults
Abstract
Partially creeping faults exhibit complex behavior in terms of which
parts of the fault slip seismically versus aseismically. The specific
geometry of creeping versus locked fault patches may pose constraints on
rupture lengths on partially-creeping faults. We use the 3D finite
element method to conduct dynamic rupture simulations on simplified
partially-creeping strike-slip faults, to determine whether coseismic
rupture can propagate into creeping regions, and how the presence and
distribution of creeping regions affects the ability of rupture to
propagate across the whole fault. We implement rate-state friction, in
which locked zones are represented by rate-weakening behavior and
creeping zones are assigned rate-strengthening properties. We model two
simplified geometries: a locked patch at the base of a creeping fault
and a creeping patch at the surface of a locked fault. In the case of a
locked patch within a creeping fault, rupture does not propagate far
past the edges of the locked patch, regardless of its radius. The case
of a creeping patch within a locked fault is more complicated. The width
of the locked areas around the creeping patch determine whether rupture
is able to propagate around the creeping patch. Although rupture is
always able to propagate at least a small distance into the creeping
patch, if the width of the locked zone between the edge of the creeping
patch and the end of the fault is too narrow, rupture stops. This
simplified parameter study may be useful for understanding first-order
behaviors of real-world partially-creeping strike-slip faults.