How does a longer wavelength penetrate deeper with Rayleigh waves? I'm struggling slightly to understand this idea. I've slowly been building up an explanation, so at this stage it might be just some confirmation I'm looking for, but also some guidance if I'm off with some of the understanding.
My understanding from reading some text is that Rayleigh waves decrease in amplitude exponentially with depth beneath the surface. Also the amplitude of any particular frequency component is dependent on the ratio: 
depth beneath the surface / wave length
This is where I've tried to put the puzzle together. If the amplitude is decreasing exponentially with depth, waves that have a smaller amplitude will survive for longer as the depth increases, despite initially having a lesser amplitude. With this in mind, the equation above suggests that an increased wavelength reduces the amplitude of Rayleigh waves. Thus an increased wavelength can penetrate further due to a decreased rate of decay.
Could someone either confirm or offer guidance on whether I'm on the right track? Any help would be greatly appreciated.
 A: 
Could someone either confirm or offer guidance on whether I'm on the right track?

You're not on the right track. The exponential decay with depth is a consequence of the wave itself, not of the material dissipating the wave.
A better way to look at things is that Rayleigh waves are somewhat similar to ocean waves in the deep ocean. An overly simplistic model of ocean waves is that they are sinusoidal. That isn't correct, both from a theoretical and observational point of view. Observationally, ocean waves are closer to trochoidal rather than sinusoidal. A fairly simple model of those deep water waves that explains this trochoidal nature is that ocean waves make particles of water undergo a circular motion.
This model nicely explains a phenomenon that a mere up-and-down sinusoidal model doesn't, which is that water exhibits a back-and-forth motion (divers call it "surge") at the surface. This is depicted below by an image from the hyperphysics page on ocean waves.

(source: gsu.edu) 
This rolling behavior induces smaller rotations beneath them, which in turn induces even smaller circles yet further below. The depth to which these progressively smaller circles is a function of wavelength. There is very little motion at depths deeper than half the wavelength. The image below from the same hyper physics page depicts this nicely. 

(source: gsu.edu) 

So what does this have to do with Rayleigh waves? Rayleigh waves exhibit many of the same characteristics as ocean waves. Rayleigh waves and ocean waves are surface phenomena that exhibit both an up-and-down and a back-and-forth motion. Both phenomena are nicely described by a somewhat circular motion of particles. Finally, both phenomena exhibit a roughly exponential decrease in intensity with depth that is a function of the wavelength.
There are some key differences between the two phenomena. That's to be expected; after all, one propagates through a fluid and the other propagates through an elastic solid. One key difference is that deep ocean waves are nicely modeled by circular motion, while Rayleigh waves are better described by ellipses. Another key difference is that the rotation is prograde in ocean waves but retrograde in Rayleigh waves.
The following animated gif portrays the propagation of a Rayleigh wave.

(source: mtu.edu) 
