Investigating the Characteristics of Microseisms using the Australian
Seismic Arrays
Abstract
Earth’s microseisms are continuously recorded by seismographs worldwide.
Yet, studies using broadband digital 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 and with distinct apertures and geometries, particularly
spiral-arm arrays. Motivated by expanding knowledge of microseismic
sources, we investigate the distribution and characteristics of
microseisms. We process one-year continuous waveform data using
beamforming at various periods. Using the back-projection, we then
investigate the plausible source areas of surface waves and teleseismic
P-waves generated by ocean activity. 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 modelled Rg wave sources and juxtaposing the back-projected
P-waves with significant wave heights. Our results suggest that over the
time interval of several months and longer, Rayleigh waves are the
dominant component arriving from the nearby coastlines. They show a
transition to higher mode Lg waves in the higher frequency bands. In
contrast, on the time scale of days and weeks, teleseismic P-waves from
the coastal and pelagic sources are observed particularly from the
tropical and equatorial regions. We also identify new patterns of body
waves from the perspective of the Southern Hemisphere. Our study
highlights the importance of utilizing multiple arrays and elucidates
the critical roles of the frequency range and bathymetry.