We study a 2D quasi-static discrete {\it crack} anti-plane model of a
tectonic plate with long range elastic forces and quenched disorder. The plate
is driven at its border and the load is transfered to all elements through
elastic forces. This model can be considered as belonging to the class of
self-organized models which may exhibit spontaneous criticality, with four
additional ingredients compared to sandpile models, namely quenched disorder,
boundary driving, long range forces and fast time crack rules. In this
''crack'' model, as in the ''dislocation'' version previously studied, we find
that the occurrence of repeated earthquakes organizes the activity on
well-defined fault-like structures. In contrast with the ''dislocation'' model,
after a transient, the time evolution becomes periodic with run-aways ending
each cycle. This stems from the ''crack'' stress transfer rule preventing
criticality to organize in favor of cyclic behavior. For sufficiently large
disorder and weak stress drop, these large events are preceded by a complex
space-time history of foreshock activity, characterized by a Gutenberg-Richter
power law distribution with universal exponent B=1±0.05. This is similar
to a power law distribution of small nucleating droplets before the nucleation
of the macroscopic phase in a first-order phase transition. For large disorder
and large stress drop, and for certain specific initial disorder
configurations, the stress field becomes frustrated in fast time : out-of-plane
deformations (thrust and normal faulting) and/or a genuine dynamics must be
introduced to resolve this frustration