The publication of the World
Stress Map has focussed thinking
on the big picture; Zoback
[1992] showed that to first order
the world stress field is the
result of ridge-push and
continental collision resistance,
with little evidence for strong
basal tractions. Richardson
and Reding [1992] used thin-plate elastic models to show that
both shear and super-lithostatic
normal tractions on the San
Andreas and Caribbean transforms
are only 5 to 10
10
Pa, and that this value can be
explained primarily by ridge-push
effects. A collection of
surface-wave moment tensors from
51 western U.S. events confirms
the 
directions of
the World Stress Map, and shows a
convergence of tensional axes
(
) on the Mendocino
triple junction [ Patton and
Zandt, 1991].
As efforts are gradually applied to study paleostress, attention should be paid to the exhaustive study of Bergerat et al. [1992], who used joints and faults to infer a 9-stage stress history for the Colorado Plateau since the Jurassic. Another source of data can be calcite twinning in limestones, which Craddock et al. [1993] used to map the Paleozoic strain (and paleostress) field in the eastern U.S.