Ocean gravity waves are driven by wind and atmospheric pressure systems and generate pressure changes at the seabed [Bromirski, 2009]. These pressure fluctuations generate continuous background seismic noise, called “microseisms,” which are associated with ocean wave activity and are generally stronger in coastal areas, although they are recorded on terrestrial seismic stations throughout the world. Background seismic noise levels increase during periods of increased ocean wave activity. There are two main types of microseisms:
 Primary—These have periods of 8–20 s. They are thought to be generated in shallow water by the dynamic interaction between water waves and shoaling seafloor. They can be produced by nonlinear interactions of the ocean wave pressure signal on a sloping seafloor [Hasselmann, 1963].
 Secondary—These have periods of 3–10 s. They occur at half the primary wave period and are likely caused by the interference of opposing waves producing a standing wave [Longuet-Higgins, 1950].
 Secondary microseisms dominate over primary microseims, and their amplitudes are proportional to the square of the standing wave height. This makes them sensitive to larger waves/swell. This paper deals with the separation and location of secondary microseisms.
 There have been studies aimed at locating primary and secondary microseisms using a variety of methods. Triangulation using the time delays of arrival of Z component seismograms between station pairs has been used to locate microseism sources [Cessaro, 1994]. f-k analysis has been used with Z components recorded at arrays of stations to determine the slowness and back azimuth [Cessaro, 1994; Cessaro and Chan, 1989; Friedrich et al., 1998; Schulte-Pelkum et al., 2004; Chevrot et al., 2007]. A polarization method, assuming Rayleigh-wave propagation, to calculate the back azimuth by measuring phase differences between horizontal and vertical components has also been used [Schulte-Pelkum et al., 2004; Chevrot et al., 2007; Stutzmann et al., 2009].
 Source separation prior to application of location methods has not been studied. Here we demonstrate that this is a crucial step in the process of locating microseisms as they comprise multiple coincidently active sources. It is also important for determining the spatial and temporal heterogeneity of the microseism wavefield. Source separation will help improve transfer functions developed between land-based recordings of microseisms and wave parameters recorded at ocean buoys. The source separation algorithm used is described in section 2.1, and the location algorithm is briefly discussed in section 2.2. The algorithms are tested on synthetics (section 3) and applied to real data from Ireland, in the Northeast Atlantic (section 4).