Exploration Geophysics - Volume 42, Issue 4, 2011

A technique by which properties can be connected between 2D seismic lines is introduced in this paper. This interpretation workflow is then tested on a pilot area in a portion of the onshore Gippsland Basin, Australia. Calculated attributes and inverted seismic sections were fed into a 3D model in an attempt to track the sand filled channels and seals. The sealing sequence is characterised by distinctive log/seismic properties, which were modelled in 3D, and attempts are made to discuss seal potential in terms of geometry and integrity.

This paper describes a process by which seismic related properties from 2D seismic lines are extracted and a 3D property model is constructed. This interpretation workflow is then tested and described on a pilot area in the northern portion of the onshore Gippsland Basin, Australia. The primary reservoir sands in this region appear to be deposited in a channel recognised on 2D seismic lines. Seismic inversion was performed on each 2D seismic line to differentiate between geological bodies, and these inverted seismic sections were fed into a 3D model in an attempt to track the sand filled channels and seals, based on the seismic-derived attributes. The sealing sequence is characterised by distinctive log/seismic properties, which were modelled in 3D, and attempts are made to discuss seal potential in terms of geometry and integrity.

In many cultural heritage projects, it is often more important to ensure that burials are not disturbed rather than to specifically locate them. Under these circumstances, ground penetrating radar (GPR) can be used to locate modern anthropogenic fill. This may show which areas of the site are younger than the targeted graves and therefore of no archaeological interest. This approach is successfully trialled on a site in Albany, Western Australia. This approach, applied to suitable sites, could contribute to culturally sensitive non-invasive investigation of burial sites in other locations.

Geophysical techniques are a commonly used, non-invasive method for the location of unmarked graves. Contrary to popular perception, most studies rely not on directly imaging skeletal material but instead on locating the subsurface disturbance created by grave digging. This approach is effective only when sufficient contrast exists between detectable properties (such as structure, mineralogy or porosity) of the grave fill and the surrounding sediment. Resolving these features can be particularly problematic in disturbed areas where other anthropogenic fill is in place, as it is often complex in character and lacks a natural stratigraphy.

In many cultural heritage projects, it is often more important to ensure that burials are not disturbed rather than to specifically locate them. Under these circumstances, ground penetrating radar (GPR) can be used to locate modern anthropogenic fill. This may show which areas of the site are younger than the targeted graves and therefore of no archaeological interest. This approach is trialled on a site thought to contain the grave of Mokare, a significant historical figure in the colonial settlement of the Albany area in Western Australia. The delineation of a package of modern fill in the shallow subsurface in the context of the probable history of earthworks on the site demonstrates that Mokare is not buried in the surveyed location. This approach, applied to suitable sites, could contribute to culturally sensitive non-invasive investigation of burial sites in other locations.

A mesoscale petrophysics and lithological logging study has been carried out on 413 core samples of the 623 m thick Narrabeen Group succession penetrated by the Eveleigh No. 1 diamond drillhole. Mass properties, magnetic susceptibilities, and electrical estimates of mobile salt (EC 1 : 5 tests) were measured. A physical properties analysis posits a 3-fold subdivision of the succession: basal fluvio-deltaic and alluvial, upper lacustrine, and topmost fluvio-deltaic. Each division has cyclic sedimentation but from different provenances. The analysis has proved useful in the correlation of the Narrabeen Group present in a series of drillholes in the eastern part of the exposed Sydney Basin.

A mesoscale petrophysics and lithological logging study has been carried out on 413 core samples of the 623 m thick Narrabeen Group succession penetrated by the Eveleigh No. 1 diamond drillhole. Mass properties, magnetic susceptibilities, and electrical estimates of mobile salt (EC 1 : 5 tests) were measured. A physical properties analysis posits a 3-fold subdivision of the succession: basal fluvio-deltaic and alluvial, upper lacustrine, and topmost fluvio-deltaic. Each division has cyclic sedimentation but from different provenances. The analysis has proved useful in the correlation of the Narrabeen Group present in a series of drillholes in the eastern part of the exposed Sydney Basin.

Fuzzy Gustafson–Kessel cluster analysis is employed to integrate suites of disparate data sets. The fuzzy c-means algorithm is used as a reference to discuss the advantages of the Gustafson–Kessel algorithm and revise a database comprising airborne and ground-based geophysical data sets while minimising preparatory data processing required for fuzzy c-means cluster analysis.

The fuzzy partitioning Gustafson-Kessel cluster algorithm is employed for rapid and objective integration of multi-parameter Earth-science related databases. We begin by evaluating the Gustafson-Kessel algorithm using the example of a synthetic study and compare the results to those obtained from the more widely employed fuzzy c-means algorithm. Since the Gustafson-Kessel algorithm goes beyond the potential of the fuzzy c-means algorithm by adapting the shape of the clusters to be detected and enabling a manual control of the cluster volume, we believe the results obtained from Gustafson-Kessel algorithm to be superior. Accordingly, a field database comprising airborne and ground-based geophysical data sets is analysed, which has previously been classified by means of the fuzzy c-means algorithm. This database is integrated using the Gustafson-Kessel algorithm thus minimising the amount of empirical data processing required before and after fuzzy c-means clustering. The resultant zonal geophysical map is more evenly clustered matching regional geology information available from the survey area. Even additional information about linear structures, e.g. as typically caused by the presence of dolerite dykes or faults, is visible in the zonal map obtained from Gustafson-Kessel cluster analysis.