Fig. 7

Beamforming results for P-wave signals using the broadband seismic stations in Southern California with about 150 stations. (top) The beam for the P-wave source is tracking the center of Hurricane Ioke (white square box). (middle) The P-wave beam (dark red) is on the east side of the center of Hurricane Sandy in 2012 (white square box). (bottom) When Sandy was moving north off the east coast of the USA, there was also an independent P-wave signal from a low-pressure system (storm) in the northern Pacific Ocean. They typically create signals between about 0.15 Hz and 0.25 Hz, in the frequency band of the secondary microseism