Characteristics of body wave microseism observed at northern continental Asia

Abstract:

It has been understood that most of microseism observed at land is generated at coastal region by the ocean wave activity and propagates into the continent as the Rayleigh wave. However, it has also been reported that microseism could be generated at mid ocean and propagate as the body waves, such as P, PP and PKP phases. In this study, we analyzed microseisms with seismic records from seismic stations that are located at northern continental Asia. These included seismic arrays and a local dense network at South Korea, Kazakhstan, and China. First, we computed seismic noise spectra in the frequency band between 0.01 and 0.4 Hz. Second, the back-azimuth and the phase velocity of the microseism were measured from the frequency-wavenumber (FK) analysis. Although each data set was recorded at different time periods, the results show similar patterns. Non-transient microseism peak around the 0.2 Hz frequency was observed coherently at all data of winter season. The FK analysis shows that this microseism propagated with the phase velocities of around 12, 11, and 21 km/s at South Korea, China, and Kazakhstan, respectively. The back-projection of the FK result shows that these body wave microseisms were mostly generated at the northern part of the Pacific.