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Structural Features Stand Out in CET Grid Analysis

by Virginia Heffernan on March 9, 2016 applied

The Newer Volcanics Province is a complex of volcanic centres formed by the East Australia hotspot across south-eastern Australia.

[Click to enlarge]

Figure 1: Rose diagrams showing the azimuth frequency of the faults, weighted by fault length.

Researchers at Monash University are using grid analysis techniques to determine the structural controls on the Newer Volcanics Province in south-eastern Australia.

PhD candidate Jackson van den Hove recently produced an unbiased 2D structural interpretation of gravity and magnetic data from the 50,000 km2 basaltic volcanic field, where controls are poorly understood, by running the data through CET Grid Analysis, an extension of Geosoft Oasis montaj developed by the University of Western Australia’s Centre for Exploration Targeting.

“The analysis allows us to determine what crustal structures, if any, provide a control on the location of emplacement,” says van den Hove, whose thesis is supervised by Laurent Ailleres and Robin Armit of the School of Earth, Atmosphere and Environment at Monash University’s Melbourne campus.  “It provides information on geodynamic and tectonic factors that may allude to the cause and location of volcanic activity, as well as having implications for hazard analysis for potential future eruptions.”

The analysis included grids for both Bouguer gravity and reduced to pole magnetic anomalies. Van den Hove used upward continuation (extrapolating measurements at a lower elevation to higher levels) to emphasize regional scale faults and remove noise and short wavelength magnetic anomalies associated with basaltic lavas. Applying the standard deviation texture analysis feature along and the phase symmetry method allowed him to identify laterally continuous line-like features in the gridded datasets.

The resulting Rose diagrams (Fig 1) show the azimuth frequency of the faults, weighted by fault length. The trends identified by automated edge detection, or worming, closely matched previously mapped fault fabrics in the area.

Van den Hove says CET Grid Analysis, with its standardized step-by-step approach, is a rapid and unbiased means of analysing linear trends within gridded geophysical data. The tool could help anyone who faces the hurdle of interpreting geophysical datasets for areas that are geologically poorly constrained by steering the initial interpretation and providing validity to final geophysical maps.

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