11:00 AM - 1:00 PM
[SSS13-P04] Oscillation of solid earth generated by the typhoon Hagibis of 2019 revealed from in-land and seafloor seismic observation networks
Keywords:Microseisms, The typhoon Hagibis of 2019
In Japan, many highly sensitive seismometers have been deployed. Their recordings include oscillations caused by non-earthquake phenomena such as human activities and meteorological phenomena. Among the oscillations, those with a period of about one second or more are called microseisms. In recent years, the relationship between the generation of microseisms and meteorological phenomena that generate wind waves and swells has been clarified. In this study, we investigate the microseisms generated by the typhoon Hagibis of 2019 which caused extensive damage in Japan.
We analyzed the continuous velocity records at Hi-net and acceleration records at S-net from October 5, 2019, to 9 days after the typhoon. We compute the RMS of the continuous records of three components every 10 minutes at the frequency bands of 0.02-0.1 Hz and 0.1-1 Hz, respectively, and investigate their spatio-temporal distributions. In addition, we investigated the temporal changes of the dominant frequency from the spectrograms for a long observation duration from the time of typhoon onset to the time of typhoon extinction at several stations.
The spatio-temporal distribution of seismic amplitude recorded both at Hi-net and S-net stations showed that the microseisms were generated and propagated in association with the typhoon movement. From the spectrograms, large amplitudes were observed in the frequency bands above and below 0.1 Hz at both land and seafloor stations during the typhoon arrival. In addition, signals in the frequency band corresponding to primary microseisms, which were previously thought to be rarely generated on the deep seafloor, were obtained from S-net stations at depths exceeding 1000 m. The spectrograms below 0.1 Hz at the ocean bottom stations showed different signal patterns from those below 0.1 Hz at the shallow-sea bottom stations. The signal pattern of the spectrogram below 0.1 Hz at the deep-sea bottom station at a depth of 1000 m was similar to that at the in-land stations, suggesting that the waves may be propagated by primary microseisms generated at the shallow seafloor.
We analyzed the continuous velocity records at Hi-net and acceleration records at S-net from October 5, 2019, to 9 days after the typhoon. We compute the RMS of the continuous records of three components every 10 minutes at the frequency bands of 0.02-0.1 Hz and 0.1-1 Hz, respectively, and investigate their spatio-temporal distributions. In addition, we investigated the temporal changes of the dominant frequency from the spectrograms for a long observation duration from the time of typhoon onset to the time of typhoon extinction at several stations.
The spatio-temporal distribution of seismic amplitude recorded both at Hi-net and S-net stations showed that the microseisms were generated and propagated in association with the typhoon movement. From the spectrograms, large amplitudes were observed in the frequency bands above and below 0.1 Hz at both land and seafloor stations during the typhoon arrival. In addition, signals in the frequency band corresponding to primary microseisms, which were previously thought to be rarely generated on the deep seafloor, were obtained from S-net stations at depths exceeding 1000 m. The spectrograms below 0.1 Hz at the ocean bottom stations showed different signal patterns from those below 0.1 Hz at the shallow-sea bottom stations. The signal pattern of the spectrogram below 0.1 Hz at the deep-sea bottom station at a depth of 1000 m was similar to that at the in-land stations, suggesting that the waves may be propagated by primary microseisms generated at the shallow seafloor.