Analysis On Microseism Characteristics By Typhoon 'Hagibis' Using Land And Ocean-Bottom Seismometers

We use seismic data recorded at OLDEST-1 Pacific Array ocean-bottom seismometers (OBSs) in the Western Pacific and land seismometers in Japan by the typhoon HAGIBIS in 2019 to study spatial background noise level changes. While noise levels in both the single-frequency microseisms (SFMs) and the double-frequency microseisms (DFMs) increase in the land seismometers by HAGIBIS, changes in the SFMs due to the typhoon are barely observed in the OBSs. The changes in the long-period DFMs (LPDFMs) are smaller than those in the short-period DFMs (SPDFMs) in the OBSs, because the LPDFMs may be affected by the intensity of the typhoon and the distance to the typhoon. The LPDFMs begin to increase earlier than the SPDFMs in the land seismometers because of relatively rapid attenuation of SPDFMs in the land, but the opposite case is observed for the OBSs. We also compare the DFMs with the significant wave height (SWH) using Pearson's correlation coefficient and find that the SPDFMs are more correlated with the SWH than the LPDFMs. This may indicate that the SWH is the main cause for the SPDFMs.