Pelagic and coastal sources of P‐wave microseisms: Generation under tropical cyclones

[1] Nonlinear wave‐wave interactions generate double‐ frequency (DF) microseisms, which include both surface waves (mainly Rayleigh‐type) and compressional (P) waves. Although it is unclear whether DF surface waves generated in deep oceans are observed on land, we show that beamforming of land‐based seismic array data allows detection of DF P waves generated by ocean waves from Super Typhoon Ioke in both pelagic and coastal regions. Two distinct spectral bands associated with different P‐wave source locations are observed. The short‐period DF band (0.16– 0.35 Hz) is dominated by P waves generated in the deep ocean by local wind seas under the storm. In contrast, P waves in the long‐period DF band (0.1–0.15 Hz) are weaker and generated closer to the coast of Japan from swell interactions. The accurate identification of DF P‐wave microseism source areas is useful to monitor ocean wave‐wave interactions due to tropical cyclones and to image Earth structure using ambient seismic noise. Citation: Zhang, J., P. Gerstoft, and P. D. Bromirski (2010), Pelagic and coastal sources of P‐wave microseisms: Generation under tropical cyclones, Geophys. Res. Lett., 37, L15301, doi:10.1029/2010GL044288.