Imaging Earth Structure and Microseism Sources Using Seismic Array Observations of Oceanic Storms

Storms over deep oceans generate microseismic P waves that can be observed over teleseismic distance by land-based arrays. Using data from the Southern California Seismic Network (SCSN), we demonstrate that travel-time anomalies beneath an array can be obtained from storm-generated P waves via noise cross-correlation across the array stations. This suggests using tropical cyclones as additional sources in teleseismic body-wave tomography. We also show that P-wave microseism sources, where ocean wave interactions due to storms occur, can be imaged seismologically via beamforming. Our results show double frequency (DF) microseism origins 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 from swell interactions.