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Group 2 – FARM | Poster Abstracts
unconditional uniform averaging (the averaging applied at each grid point of the fault), four
single-point criterion averaging (the averaging applied at a grid point if certain criteria at that point
are met), and four 9-point criterion averaging (the averaging applied at a grid point if certain
criteria at that point and 8 neighboring grid points are met).
The selected best smoothing algorithm was then tested for convergence for two distinct physical
rupture propagation configurations.
The improved algorithm for the numerical modeling of rupture propagation has been
implemented in the 3D causal hybrid viscoelastic FD-FE method and computer code for the
numerical modeling of rupture and wave propagation.
2-065
RUPTURE PROPAGATION ACROSS FAULTS WITH LINKED STEPOVERS: A
GEOMETRICAL PARAMETER STUDY Lozos JC, Oglesby DD, and Duan B
Segmented faults with stepovers are ubiquitous, and occur at a variety of scales, ranging from
small stepovers on the San Jacinto Fault to the large-scale stepover on the San Andreas Fault
between Tejon Pass and San Gorgonio Pass. Because this type of fault geometry is so prevalent,
understanding how earthquake rupture propagates through such systems is important for
evaluating seismic hazard. In the present study, we systematically investigate how far rupture will
propagate through a fault with a linked (i.e., continuous fault) stepover, based on the length of the
linking fault segment and the angle that connects the linking segment to adjacent segments.
We conducted dynamic models of such systems using the two-dimensional finite element method
(Duan and Oglesby 2007). The fault system in our models consists of three segments: two parallel
10km-long faults linked at a specified angle by a linking segment of 500m, 1km, 2km, or 3km. This
geometry was modeled both as a extensional system and a compressional system depending on the
direction of shear.
We observed several distinct rupture behaviors, with systematic differences between
compressional and extensional cases. Both shear directions rupture straight through the stepover
for very shallow stepover angles. In compressional systems with steeper angles, rupture may jump
ahead from the linking segment onto the far segment; whether or not rupture on this segment
reaches critical patch size and slips fully is also a function of angle and stepover length. In some
compressional cases, if the angle is steep enough and the stepover short enough, rupture may jump
over the step entirely and propagate down the far segment without touching the linking segment.
In extensional systems, rupture jumps from the nucleating segment onto the linking segment at
shallow angles, but at steeper angles, rupture propagates through without jumping. Rupture
propagates through a wider range of angles in extensional cases. In both extensional and
compressional cases, for each stepover length there exists a maximum angle through which rupture
can fully propagate; this maximum angle decreases asymptotically to a minimum value as the
stepover length increases.
2-066
A FINITE DIFFERENCE METHOD FOR IRREGULAR GEOMETRIES: APPLICATION
TO DYNAMIC RUPTURE ON ROUGH FAULTS Belanger D, and Dunham EM
We have developed a finite difference method to solve dynamic rupture problems in irregular
geometries. Our objective is to connect properties of high frequency radiation produced during slip
on rough faults to statistical measures of fault roughness. To handle irregular geometries, we
2008 SCEC Annual Meeting | 175