Love wave

Better sensitivity has been reported (32,33) with a surface guided wave, known as a Love wave. A shear horizontal wave is directed along the surface on top of the device a layer is deposited in which the acoustic waves are carried at a lower velocity. 

Another approach to obtaining a sturdy sensor substrate and a transverse particle motion to permit operation in liquids is the use of a structure that supports Love waves [85,86]. These waves are guided in a layer that is thin compared with the wavelength on a thick substrate. With the proper choice of materials one may also be able to achieve a significant degree of temperature compensation in this device. 

The seismic wave generated by an explosion is a compression wave the vibration is parallel to the direction of propagation of the wave. On the surface, the initial movement of this wave corresponds to a lifting of the ground. However, this is not the only propagation mode for seismic waves. Three other types are possible shear wave. Love wave and Rayleigh wave. 

The Rayleigh and Love waves propagate at the surface of the Earth. Because of their mechanism, which is essentially symmetrical, and in contrast to earthquakes, the explosions generate very few surface waves. The amplitude of the surface waves enables the magnitude of an earthquake on the Richter scale to be calculated. An earthquake of = 7.0 (approximately 30 earthquakes of magnitude greater than this value occur per year in the world) causes ground displacements of approximately 100 pm at 10,000 km. This is not the case for explosions, for which the surface waves are almost undetectable their amplitude is only a few micrometres at 1000 kilometres from a 100-kt explosion. 

Finally, Kirkwood Crampin (1981) showed that particle-motion anomalies are diagnostic of anisotropy and that the variations with period can be used to estimate the approximate depth of the anisotropic layer. This is best done using fundamental quasi-Love waves visible on the radial and vertical components, as they will not be contaminated by the later arriving Rayleigh waves (Yu Park 1994). 

Fig. 5. Love- and Rayleigh-wave interstation phase velocities (IPV) (continuous lines) predicted from the best-fit model derived from the Rayleigh-wave observation. The observed Love- and Rayleigh-wave IPVs are shown for comparison. It should be noted that the Love waves have higher velocities than those predicted in the period range 38-62 s (i.e. in the upper mantle).

Schlensog, M., Schlensog, M. D., Gronewold, T., Tewes, M., Famulok, M., Quandt, E. (2004). A Love-wave biosensor using nucleic acids as ligands. Sens Actual B 101, 308-315. 

Jakoby, B. Ismail, G.M. Byfield, M.P. Vellekoop, M.J. A novel molecularly imprinted thin film applied to a Love wave gas sensor. Sens. Actuat. 1999, 76, 93-97. 

In a bounded medium, such as thick metal plates, surface waves (Love waves and Rayleigh waves) occur. If the thickness of the plate is of the order of a few wavelengths, Lamb waves (plate waves) can propagate. These can be either symmetric or asymmetric. Generally, if the solid has moderate symmetry, unique waveforms can propagate, for example, tube waves. 

Love-Wave, Shear-Horizontal SAW and Acoustic Plate Mode Sensors... 

Love Wave Wave formed by the combination of secondary waves and primary waves on the surface causes the ground to oscillate from side to side perpendicular to the propagation direction of the wave and is the most destructive. 

Love Waves Seismic waves that occur in a side-to-side motion. 

Eigenvalue problems for the Rayleigh and Love wave modes... 

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