We present a preliminary study of T waves from Polynesian nuclear tests at
Mururoa, recorded on digital stations of the Hawaii Volcano Observatory net
work, following their conversion to seismic waves at the southern shore of
the Island of Hawaii, and subsequent propagation to the recording stations.
We show that seismograms are composed of several packets, which can be int
erpreted as resulting from T --> P and T --> S conversions, and which featu
re distinct spectral characteristics. As the distance from the shoreline to
the station increases, the relative importance of the several wave packets
changes; a prominent shadow for T --> P is found at 8-12 km from the shore
. This pattern is affected by the local crustal structure; in a favorable c
ase, propagation in deep, low-attenuation layers resulted in a clear record
as far as 76 km from the shoreline. While these results are generally robu
st, they can be moderately affected by a change of location of the source i
nside Mururoa Atoll.