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Abstract

Structural complexity is common at the terminations of earthquake surface ruptures;
similar deformation may therefore be expected at the end zones of earthquake ruptures at
depth. The 8.2 km long Glacier Lakes fault (GLF) in the Sierra Nevada is a left-lateral
strike-slip fault with a maximum observed displacement of 125 m. Within the fault,
pseudotachylytes crosscut cataclasites, showing that displacement on the GLF was
accommodated at least partly by seismic slip. The western termination of the GLF is
defined by a gradual decrease in the displacement on the main fault, accompanied by a
1.4 km wide zone of secondary faulting in the dilational quadrant of the GLF. The
secondary faults splay counterclockwise from the main fault trace forming average angles
of 39 degrees with the main fault. Slip vectors defined by slickenlines plunge more steeply west
for these splay faults than for the GLF. Static stress transfer modeling shows that the
orientations of the splays, and the plunge of displacement on those splays, are consistent
with displacement on the main fault. The GLF termination structure shows that structural
complexity is present at the terminations of faults at seismogenic depths and therefore
ruptures that propagate beyond fault terminations, or through step overs between two
faults, will likely interact with complex secondary fault structures. Models of dynamic
rupture propagation must account for the effect of preexisting structures on the elastic
properties of the host rock. Additionally, aftershock distributions and focal mechanisms
may be controlled by the geometry and kinematics of structures present at fault
terminations.

Item Type:	Article
Authors/Creators:	Kirkpatrick, JD and Shipton, ZK and Evans, JP and Micklethwaite, S and Lim, SJ and McKillop, P
Keywords:	fault; damage zone; earthquake; rupture; termination; pseudotachylyte, Tectonophysics: Rheology and friction of fault zones; Structural Geology: Dynamics and mechanics of faulting; Seismology: Earthquake dynamics; Structural Geology: Kinematics of crustal and mantle deformation; Physical Properties of Rocks: Fracture and flow.
Journal or Publication Title:	Journal of Geophysical Research - Solid Earth
ISSN:	0148-0227
DOI / ID Number:	https://doi.org/10.1029/2007JB005311
Additional Information:	Copyright 2008 by the American Geophysical Union.
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