ANU seismologists used two 50-by-50-kilometre spiral arrays in Australia to detect PKP waves-seismic core waves created by powerful cyclones in the North Atlantic that traverse the Earth's center and reach the Australian continent during its summer months. The study pinpointed two primary signal source regions in Greenland and Newfoundland.
Abhay Pandey, an ANU PhD student and co-author of the study, highlighted the significance of this detection method. "This method, particularly in the context of exploring other planets and icy moons, can be used to identify planets with a core, including those that don't have plate tectonics or volcanoes, as well as planets that don't experience quakes, providing valuable data for future exploration," he said.
Professor Hrvoje Tkalcic, another study co-author and ANU seismologist, emphasized the broader potential of this approach: "If we can land a seismometer array on the surface of a small planet without quakes, the method might be handy for scanning their interiors by using the atmospheric and hidden ocean signals that resemble the ones from our study."
The research team utilized two custom spiral-arm arrays installed in remote regions of Queensland and Western Australia. These arrays, specially designed for this project, enabled the detection of microseismic, long-wave-period signals that would otherwise be too faint to capture.
Microseismic noise, a phenomenon where seismic waves are generated by the interaction between the ocean and the Earth's solid surface, was a critical focus of the study. The team used advanced array-seismology techniques to identify the North Atlantic Ocean as the origin of these signals, specifically pointing to regions near the southern tip of Greenland and the deeper North Atlantic.
"We combined data from multiple days to identify the regions where the signals were strongest, providing insights into the source and transmission of the seismic waves," Pandey added.
The study also revealed the complexity of detecting these signals, noting that the weak amplitudes often fall below the threshold of individual sensors, requiring specialized instrument designs and remote locations for effective observation. Factors influencing these detections include storm intensity, ocean depth, seafloor shape, distance to the source, frequency band used, and sensor types.
"Our study used a seismic period band of four to six seconds, which is crucial for detecting the signals of interest," Pandey explained. This approach provides a fresh alternative for probing the deep structure of the Earth, particularly beneath the geologically stable Australian continent.
Research Report:Detection of Seismic Core Phases from the Northern Atlantic Cyclones on the Australian Spiral-Arm Arrays
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