Estimating the Acoustic Intensity of Typhoon Shanshan at Very Low Frequencies

Double frequency (DF) microseisms (0.12-0.4 Hz) are believed to be generated by nonlinear interaction between ocean waves traveling in opposite directions, and are often more energetic than the single frequency microseisms. Based on the traveling time for long period (LP) DF microseismic signals generated by typhoon Shanshan to the closest seismic stations, the mean velocity is estimated to be on the order of 20 m/s suggesting that the LPDF signals are generated near the coastal area. The typhoon intensity is estimated as a function of time. It seems to show a cubic power dependence on the maximum wind speed, in agreement with the previous finding based on data at 10-50 Hz.