title: Apollo 12 seismic signal: indication of a deep layer of powder.
abstract: The seismic signal caused by the Apollo 12 lunar module is interpreted in terms of propagation between source and receiver through a layer of powder in which sound velocity increases with depth. This increase, which is due to compaction, extends over several kilometers and leads to a concentration of seismic waves toward the surface. Computer simulations with the use of ray acoustics and on the assumption of a randomly undulating lunar surface approximate well the observed signal. Seismic amplitudes are greatly enhanced in such a medium compared to solid rock, so that the observed signal requires less power to be transmitted than previously estimated.
authors.forename: T
authors.initials: T
authors.lastname: Gold
authors.forename: S
authors.initials: S
authors.lastname: Soter