  We study resonance patterns of a spiral-shaped dielectric microcavity with
chaotic ray dynamics. Many resonance patterns of this microcavity, with
refractive indices $n=2$ and 3, exhibit strong localization of simple geometric
shape, and we call them {\em quasi-scarred resonances} in the sense that there
is, unlike the conventional scarring, no underlying periodic orbits. It is
shown that the formation of quasi-scarred pattern can be understood in ter ms
of ray dynamical probability distributions and wave properties like uncertainty
and interference.
