Ocean swell activities excite body-wave microseisms that contain
information on the Earth's internal structure. Although seismic
interferometry is feasible for exploring structures, it faces the
problem of spurious phases stemming from an inhomogeneous source
distribution. This paper proposes a new method for inferring seismic
discontinuity structures beneath receivers using body-wave microseisms.
This method considers the excitation sources of body-wave microseisms to
be spatially localized and persistent over time. To detect the P-s
conversion beneath the receivers, we generalize the receiver function
analysis for earthquakes to body-wave microseisms. The resultant
receiver functions migrate to the depth section. The detected 410- and
660-km mantle discontinuities are consistent with the results obtained
using earthquakes, thereby demonstrating the feasibility of our method
for exploring deep-earth interiors. This study is the first step toward
body-wave exploration while considering the sources of P-wave
microseisms to be isolated events.