Converted T phases recorded on Hawaii from Polynesian nuclear tests: A preliminary report

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.