Two-layered Liquid Half Space

point source in liquid layer over liquid half space.

Ewing. Elastic waves in layered media, Page 126

The dispersive waves observed by Ewing[35] and Worzel and Ewing[211] in experiments on explosion sounds in shallow water (10 to 20 fathoms) were first interpreted by Pekeris[116].

Ewing. Elastic waves in layered media, Page 149

The result of Pekeris for two layered liquid layers have often been found application to studies on explosion sound transmission in shallow water, implying absence of rigidity of ocean-bottom materials. This is not surprising since core samples consist of unconsolidated sediments almost everywhere.

아마도 여기서 말하는 rigidity는 $\mu$를 의미하는 것 같다.

Ewing. Elastic waves in layered media, Page 6

Ideal fluid. If the rigidity $\mu$ vanishes, the medium is an ideal fluid.