  We present a detonating failed deflagration model of Type Ia supernovae. In
this model, the thermonuclear explosion of a massive white dwarf follows an
off-center deflagration. We conduct a survey of asymmetric ignition
configurations initiated at various distances from the stellar center. In all
cases studied, we find that only a small amount of stellar fuel is consumed
during deflagration phase, no explosion is obtained, and the released energy is
mostly wasted on expanding the progenitor. Products of the failed deflagration
quickly reach the stellar surface, polluting and strongly disturbing it. These
disturbances eventually evolve into small and isolated shock-dominated regions
which are rich in fuel. We consider these regions as seeds capable of forming
self-sustained detonations that, ultimately, result in the thermonuclear
supernova explosion. Preliminary nucleosynthesis results indicate the model
supernova ejecta are typically composed of about 0.1-0.25 Msun of silicon group
elements, 0.9-1.2 Msun of iron group elements, and are essentially carbon-free.
The ejecta have a composite morphology, are chemically stratified, and display
a modest amount of intrinsic asymmetry. The innermost layers are slightly
egg-shaped with the axis ratio ~1.2-1.3 and dominated by the products of
silicon burning. This central region is surrounded by a shell of silicon-group
elements. The outermost layers of ejecta are highly inhomogeneous and contain
products of incomplete oxygen burning with only small admixture of unburned
stellar material. The explosion energies are ~1.3-1.5 10^51 erg.
