Image Processing of Geophysical Datasets Covering Central Volcanic Region Geothermal Fields

Abstract

The Central Volcanic Region of the North Island (CVR) was chosen for an investigation of the application of digital image processing techniques to geothermal studies, using large resistivity and gravity The display of such data in image format can often reveal information that is not apparent in the contour maps or profiles. Examples of the interactive computer image processing tools that have proved in this study include: filtering, contrast enhancement, histogram (anomaly highlighting), pseudo-colouring, level slicing, relief shading, and overlaying of images generated from multiple datasets. Separate datasets can be independently enhanced then combined as overlays in different colours to help identify new inter-relationships. An example is the association between many low resistivity anomalies (geothermal fields) and the edges of gravity anomalies (rift or caldera margins). Another example is the overlay of resistivity anomaliesat different depths of investigation (nominal spacings of m and rn), which reveals changes with depth in the shape, size and location of many geothermal fields in the CVR.