Abstract
Complex fault systems are often located in regions with asymmetric
topography on one side of a fault, and these systems are very common in
Southern California. Along these fault systems, geometrical complexities
such as stepovers can impact fault rupture. Previous rupture dynamic
studies have investigated the effect of stepover widths on throughgoing
rupture, but these studies didn’t examine the influence of topography on
the rupture behavior. To investigate the effect of asymmetric topography
on rupture dynamics at stepovers, I consider three cases: 1) a flat
topography, 2) a positive (mountain) and 3) a negative (basin)
topography on only one side of the fault system outside of the stepover.
In each case, I use the 3D finite element method to compute the rupture
dynamics of these fault systems. The results show a significant time
dependent variation of the normal stress for the topography cases as
opposed to the flat surface case, which can have an important impact on
rupture propagation at the stepover. For a positive topography on the
right of the rupture propagation, there is a clamping effect behind the
rupture front that prevents the rupture to jump a wider extensional
stepover. The opposite is observed for a negative topography or for a
positive topography on the left side of the rupture propagation, where
the rupture can jump over a wider compressional stepover. These results
suggest that topography should be considered in dynamic studies with
geometric complexities such as stepovers, and perhaps bends and branched
fault systems.