Geology Reference
In-Depth Information
Fault Displacement, Linkage, and Evolution
strike projection:
displacement versus distance
log D versus
log L
map view
A
fault growth by radial propagation
t1
t1
D=cL
n
D
max
t1
log L
L
t2
t2
t2
t3
t3
t3
distance along fault
B
fault growth by segment linkage
isolated
radial propagation
t1
segment A segment B segment C
t1
t1
A,B,C
B
A
C
t2
overlapping - interaction
A
t2
t2
A + B + C
A + B + C
t3
through-going linkage
minor pro
p
agation
t3
t
3
breached ramp
inactive splay
distance along fault
C
early propagation, then restricted
t1
t1
D
max
t1
log L
t2
t2
t2
t3
t3
t3
restricted tip
restricted tip
distance along fault
Fig. 4.12
Three models for fault growth.
A. During fault growth by radial propagation, an individual fault simply lengthens and accumulates more
displacement through time. Plots of displacement versus fault length (right column) show a steady increase in
displacement as the fault grows. The along-strike pattern of displacement versus length is approximately triangular
and assumes uniform displacement along the rupture surface in each earthquake. B. In an alternative scheme for
fault growth, small individual faults gradually link up to create one large, through-going fault. Whereas the
accumulation of displacement follows a predictable path for the individual segments, when they link up, displacement
becomes considerably less than that predicted for a fault of this length (see right-hand column). Through time, the
slip deficiencies near the points of segment linkage are reduced. Ultimately, the only indication that the large fault
resulted from linkage of smaller ones may be the presence of the perturbations to the smooth, bow-shaped
displacement near the former zones of overlap and linkage. Modified after Cartwright
et al.
(1995). C. Fault growth
with early propagation to full length followed by displacement without lengthening. Note that, for much of the fault's
lifetime, the length is fixed, so the trajectory in length-displacement space (right column) is vertical. Once the length
is fixed, the displacement profile evolves from triangular to bow-shaped.
