Investigating the Characteristics of Microseisms Using the Australian Seismic Arrays

Earth's microseisms are continuously recorded by seismographs worldwide. Yet, studies using broadband data to analyze microseisms in Australia have been rare. Building on initial research efforts that relied on the Warramunga array in the continent's center, we expand the investigation of microseisms by utilizing seismic arrays in various locations with distinct apertures and geometries, particularly spiral-arm arrays. Motivated by expanding knowledge of short-period microseisms, which are less studied than the peak of secondary microseisms, we investigate their distribution and characteristics. We process 1-year continuous waveform data using beamforming at various periods. Using the back-projection method, we then investigate the source areas of surface waves and teleseismic P waves generated by ocean activities. We also examine the seasonal variability of microseismic sources and their relationship with the ocean wave hindcast model by comparing our observations of Rayleigh (Rg) waves with modeled Rg wave sources and juxtaposing back-projected P-waves with significant wave heights and modeled P-wave sources. Our results suggest that over interval of several months and longer, Rayleigh waves dominate from the coastlines, transitioning to higher mode Lg waves in the higher frequency bands. In contrast, P waves from the coastal and pelagic sources are observed particularly from tropical and equatorial regions. We also identify new patterns of body waves from the Southern Hemisphere perspective, which includes P waves arriving from French Polynesia islands and core phases from North Atlantic Ocean. Our study highlights the importance of utilizing multiple arrays and elucidates the critical roles of the frequency range and bathymetry.