The spatial variability of the regional crustal stress in northern Chile
is resolved. We infer a margin-parallel compressive crustal stress
regime along the coastal region, similar to crustal stress observations
in Cascadia and Japan. The Andean Precordillera shows a distinct stress
field associated with a strike-slip faulting regime. These results are
constrained by over a decade of observations, for which earthquake
catalogs report thousands of events in the continental crust. We present
focal mechanisms for 817 of these crustal earthquakes, including
mechanism qualities. The best mechanisms were grouped and inverted to
infer the stress-field variability. We interpret the margin-parallel
compression to be caused by the concave shape of the margin and the
locking of the plate interface. The inferred strike-slip regime in the
Andes agrees with previous studies and has been proposed to be mostly
caused by local stresses imposed by a thicker crust.