Comment on ‘ ‘ Source of the great tsunami of 1 April 1946 : a landslide in the upper Aleutian forearc ’ ’ , by G . J . Fryer

In a recent contribution, Fryer et al. (2004) have proposed to interpret many features of the 1946 Aleutian earthquake and tsunami as evidence for a major earthquake-triggered landslide. In particular, in support of their model, they claim that the T phase observed at Hawaiian Volcano Observatory (HVO) was generated at the time of the main shock, and dispute our earlier interpretation (Okal et al., 2003a; hereafter Paper I) that it is about 29 min late in this respect and was actually generated by the first major aftershock, occurring 27 min after and 86 km to the North of the main shock. The scope of the present Comment is strictly limited to the issue of the interpretation of the T phase at HVO. In particular, we elect, at this point, not to comment on any aspect regarding the characteristics of the far-field tsunami, which may be addressed in a later contribution; this should not, however, be taken as an endorsement of Fryer et al.’s model (Fryer et al., 2004) for the specific properties of the Ugamak slide, or more generally for the generation of the tsunami. We simply wish to address several points raised specifically in Section 8 of Fryer et al. (2004): (i) respond to their claim that our timing of the T wave train is wrong; (ii) correct the false impression left by their work that T phase amplitudes should be in direct relation to those of P waves, and (iii) emphasize that