University of Tasmania, Australia

Ambient seismic energy is the background ‘hum’ that is recorded on seismic instruments.

Image 1: Hilary Goh, UTAS Earth Sciences Honours graduate and KUTh Energy Ltd geologist pictured during an early field deployment.  Photo credit: Anya Reading

Ambient seismic energy is the background ‘hum’ that is recorded on seismic instruments. We can use this constantly arriving energy to investigate 1) ocean wave activity and 2) the nature of buried tectonic structure. Deductions of wind speed and wave height occurring in Southern Ocean storms, made using satellite observations, are independently cross examined using seismic data from permanent and temporary seismic arrays located on the Australian mainland and in Tasmania. Storm activity in the southern ocean may be increasing with implications for modelling carbon dioxide uptake in the global system. Energy produced by ocean wave activity and recorded on land allows the seismic shear wavespeed beneath the recording stations to be determined. Data from pairs of stations are combined, through an interferometric processing technique, to produce a waveform function which is used to infer buried structure in the top few km of the Earth’s crust. Combined with other seismic data from distant earthquakes, this allows the tectonic structure of southeastern Australia and its controversial and dynamic history of plate tectonic evolution to be found. Improving our knowledge of buried structure is also possible at a more detailed scale which assists in the exploration for geothermal energy resources.

Image 2: Small, portable, 3-component seismic sensors enable quality recordings of incoming ocean energy to be made. The signals enable a broad range of research from southern ocean wave activity to tectonic structure and evolution to be carried out through the use of ambient seismic energy. Photo Credit: Anya Reading.

New Ph.D. students may be recruited into this broad area which includes current support through several separate successful ARC grants. Students should have a good Honours degree including any combination of earth sciences subjects, physics, mathematics and/or computing and an interest in either further field data acquisition or computer program development. On-going studies are focussing on ocean wave studies and resolving controversies in Tasmania’s tectonic history with varied research training opportunities in fundamental and applied geophysics available for suitable candidates. Interested applicants should contact Anya Reading, the Project Leader, for more details regarding currently available areas for graduate research.

Image 3: Seismic array response summary for incoming seismic energy back azimuths and horizontal slowness values recorded at a permanent seismic array in Northern Territory, Australia, during the Austral winter. Response maxima located near the centre originate from deep ocean wave activity while the bright spot at lower left originates from wave activity in the Great Australian Bight.

Image 4: Red and blue contour cross section shows slow to fast seismic wavespeed variations along a transect in central Tasmania. The transect can be used to constrain models of deep geological structure and hence enhance our knowledge of the complex plate tectonic evolution of southeastern Australia.