A quantitative evaluation of the microseismic activities in the far field

 This paper presents a derivation of the governing equations for microseisms in the far field in a visco-elastic half-space generated by ocean waves. The equations are for small amplitudes and for the range of microseismic frequencies associated with the first order bottom pressure effects of the generating shallow water swell. We apply the equations to a fairly hard rock geology and we calculate the frequency spectral amplitude components of microseisms as a function of depth below the Earth’ s surface in the far field. Further, by analysing the Rayleigh denominator (Burridge, 1972), usually derived from the governing equations, we verify that microseismic signals propagating away from the generating source are damped. In this consideration, we derived the limiting values of the damping coefficient to ensure effective damping of microseismic oscillations as function of the material shear wave speed.