James P Cull - Academia.edu (original) (raw)

Papers by James P Cull

Research paper thumbnail of Thermal conductivity probes for rapid measurements in rock

Journal of Physics E: Scientific Instruments

Probe configurations have been designed which allow thermal conductivity measurements to be made ... more Probe configurations have been designed which allow thermal conductivity measurements to be made on rocks using transient heating techniques. Two heat sources have been tested, the first is a line source which is compatible with needle probe instrumentation and the second is a ring source which can be used with small samples. Both probes can be used under field conditions.

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Research paper thumbnail of Electrical Conductivity Structure Of Central Victoria, Australia From Magnetotelluric Measurements

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Research paper thumbnail of Magnetotelluric soundings and the Levy algorithm

Explor Geophys, 1991

Standard band-averaging techniques used for representing magnetotelluric data are subject to bias... more Standard band-averaging techniques used for representing magnetotelluric data are subject to bias from spurious estimates unrelated to Gaussian noise. Consequently complex curve fitting techniques have been suggested to provide an alternative representation. Suspect bands can be eliminated and representative data can be obtained by interpolation using complex polynomials. The Levy algorithm adopted here has the additional benefit that it can be used for archiving to approximate band averages obtained using existing software.

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Research paper thumbnail of Downhole three component TEM probes

Explor Geophys, 1993

A three component transient electromagnetic (TEM) probe (VECTEM) has been constructed to eliminat... more A three component transient electromagnetic (TEM) probe (VECTEM) has been constructed to eliminate rotational ambiguities associated with data obtained along a single axis. Individual components are obtained sequentially using a surface adapter for multiplexing to any standard TEM recorder. The critical rotation angles are also indicated by this surface unit and are recorded in the data header. Data have been obtained for several sites and interpretations have been generated using filament inversion routines. The results agree in general with previous axial data and are consistent with geological constraints. However noise levels are higher than expected compared to single-component probes and anomalies confined to late windows may remain obscured.

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Research paper thumbnail of Application of Euler deconvolution and a neural network system as interpretation aids for three component downhole TEM data

Explor Geophys, 1995

The relationship between the secondary field due to a TEM source and a dipolar potential field ha... more The relationship between the secondary field due to a TEM source and a dipolar potential field has been documented (Dyck and West, 1984; Grant and West, 1965). In light of this relationship it is possible to utilise potential field interpretation aids when dealing with TEM data. Where only the axial component of the anomalous field is available, in the case of downhole TEM data, the implementation of these techniques is very restricted and may yield ambiguous model parameters, hence alternative techniques must be considered. Euler deconvolution may be used to obtain the approximate coordinates of the source even in the presence of an overburden response. A neural network system has been trained to output the dip and strike direction of a plate model using scaled field data as input. Utilising both the neural network and Euler deconvolution techniques, approximate model parameters may be computed directly from the field data. Synthetic examples are presented, showing that these techniques are applicable even in the presence of noise and conductive overburden. A field example from the Flying Doctor prospect is also presented. The computed model parameters were found to be consistent with previously published data (Cull, 1993).

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Research paper thumbnail of Simultaneous modelling of the phase and amplitude components of downhole magnetometric resistivity data

Journal of Applied Geophysics, Nov 1, 2003

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Research paper thumbnail of A Subsurface Pipeline Inspection Probe

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Research paper thumbnail of Short note: Sensor response and resolution in downhole TEM data

Explor Geophys, 1996

Downhole TEM probes can be constructed using several different types of core material. These core... more Downhole TEM probes can be constructed using several different types of core material. These cores are designed to concentrate the lines of magnetic flux associated with currents induced in a conductive target. In axial probes the resulting signal levels are greatly enhanced and anomalies associated with major targets are readily detected. However for crosshole sensors the advantages are not so evident. In particular the aspect ratio is greatly reduced in probes of reasonable diameter and flux densities can not be greatly improved. Variations in permeability as a function of frequency present a more serious problem. Data obtained at early times may become seriously distorted in any cored probes and deconvolution techniques may be required to compensate for permeability transfer functions. In these circumstances air-cored probes may be preferred but final response remains limited by self inductance.

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Research paper thumbnail of Acquisition and signal processing of ground-penetrating radar for shallow exploration and open-pit mining

Explor Geophys, 1992

The Australian Mineral Industries Research Association (AMIRA) has sponsored Monash University to... more The Australian Mineral Industries Research Association (AMIRA) has sponsored Monash University to investigate the acquisition and signal processing of ground-penetrating radar (GPR) for shallow exploration and open-pit mining. This project had three objectives: (1) to acquire high-quality GPR data sets for shallow exploration and surface mining applications under a variety of geological conditions; (2) to develop signal-processing techniques to enhance radar profiles prior to detailed interpretation; (3) to assess the accuracy of GPR and associated processing techniques through comparisons with independent measurements. Over one hundred kilometres of data were recorded at the various sponsors sites in a wide variety of geological conditions for different economic targets. Several examples are presented to demonstrate: 1) the hand-carried and vehicle-towed acquisition techniques, 2) target detection at depths down to 25 m, 3) the benefits of signal processing for good and poor quality data, 4) the use of dielectric measurements, petrophysical modelling and frequency-dependent synthetic radargrams, 5) the application of seismic interpretation concepts. The project has demonstrated commercially acceptable rates of GPR data acquisition where the penetration is satisfactory. Some of the unfavourable Australian geological conditions for radar have also been identified. Although signal processing techniques have extended the applicable range of the radar technique, additional hardware enhancements have been identified to improve the commercial application of radar. The next stage is to assess the economic feasibility of radar by comparison with competing techniques such as drilling.

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Research paper thumbnail of Time domain electromagnetic analysis and inspection system for conduits

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Research paper thumbnail of Spectral acoustic techniques for joint and fracture characterization

Explor Geophys, 1995

An ultrasonic pulse transmission method was used on a large block of gabbro (18 � 18 � 30 cm), at... more An ultrasonic pulse transmission method was used on a large block of gabbro (18 � 18 � 30 cm), at low normal stresses (0.01?15 MPa) and low frequencies (0.02?1 Mhz) in order to determine the transmission coefficient of a simulated fracture. The contact stiffness was measured directly and spectral ratios of the received signals calculated for comparison with predictions from the displacement discontinuity model. The agreement between the measured and derived spectral ratios was significantly better for the rough surface, indicating that the model provides a better approximation for natural fractures than for smooth interfaces. The model predictions also improved at lower frequencies, suggesting that spectral analysis of seismic data might yield useful information about the presence and stress state of fractures in the field.

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Research paper thumbnail of Subsurface pipeline inspection probe

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Research paper thumbnail of Implications for geothermal profiling from magnetotelluric data

Explor Geophys, 1991

Laboratory studies of the temperature dependence of the electrical conductivity of rock materials... more Laboratory studies of the temperature dependence of the electrical conductivity of rock materials can be used to relate electrical conductivity to temperature in the Earth. Electrical conductivity models advanced for central and southeastern Australia are compared with profiles predicted from such laboratory measurements, and are then used to generate representative magnetotelluric response curves. The response curves differ sufficiently to give confidence in their use to detect gross conductivity changes at depth. Observed data from Broken Hill and Ivanhoe, NSW, are interpreted to indicate a temperature contrast in the upper mantle of some 200�C between these two sites (hotter to the east beneath Ivanhoe). The temperature at these large depths is a vital factor in constraining models of crustal underplating and intrusion.

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Research paper thumbnail of Heat Flow and Regional Geophysics in Australia

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Research paper thumbnail of Heat‐flow data in western Victoria

Http Dx Doi Org 10 1046 J 1440 0952 2001 00840 X, Nov 8, 2010

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Research paper thumbnail of Geothermal models and mantle rheology in Australia

Tectonophysics, Aug 1, 1989

... Estimates for an isolated group con sidered by O'Reilly and Griffin (1985) are con siste... more ... Estimates for an isolated group con sidered by O'Reilly and Griffin (1985) are con sistent with conduction models based on a surface heat flow of 90110 mW m2 (BG, Fig. ... The join MgSi04 CaMgSiO at 30 kb pressure and its application to pyrox enes from kimberlite. J. Geophys. ...

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Research paper thumbnail of High definition gravity surveys and density modelling for kimberlite exploration

Exploration Geophysics

Gravity data obtained at Hiles Lagoon, near Terowie, indicates the presence of a subtle gravity l... more Gravity data obtained at Hiles Lagoon, near Terowie, indicates the presence of a subtle gravity low. The 5 mm s-2 gravity low over the lagoon possesses roughly circular dimensions with a diameter of approximately 200 m and is the likely response of a concealed kimberlite pipe. These results are of particular interest since previous aeromagnetic and aeroradiometric geophysical surveys have had little success in detecting a kimberlite pipe at Hiles Lagoon. Density determinations typical of weathered Australian kimberlites and shales were employed to create a structural model of a kimberlite pipe and the surrounding country rock. Resulting gravity raster images from the kimberlitic model allow us to confidently interpret the field response as a kimberlite pipe and justify the application of the gravimetric technique as a tool for detailed exploration.

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Research paper thumbnail of Condition assessment of cast iron and asbestos cement pipes by in-pipe probes and selective sampling for estimation of remaining life

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Research paper thumbnail of Structural Controls on the Hydrothermal System of Villarrica: Evidence from Self-Potential Measurements

Geological studies at Volcan Villarrica have investigated the volcanic history of this part of th... more Geological studies at Volcan Villarrica have investigated the volcanic history of this part of the Andes southern volcanic zone but have revealed little information about the hydrothermal and magmatic circulation system. Hydrothermal circulation, and the extent over which it is active on volcanoes, has connotations to hazard mitigation as areas within the hydrothermal cell are often less competent and more prone to failure. A self- potential survey was conducted over a period of three months on two sub-parallel transects from the summit of the volcano. Initial results suggest fluid circulation is occurring. The survey detected a strong amplitude dipolar anomaly reaching a value of -2.7 volt, the minimum in the self potential data indicating the transitional zone from a hydrothermal to hydrological regime of fluid circulation. This anomaly is believed to be a result of a combination of rapid fluid disruption, electro-kinetic, and thermoelectric effects within and surrounding the magm...

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Research paper thumbnail of Two-dimensional Analysis of MT Data across Northern Victoria, Australia

MT soundings were carried out in 2008, in northern Victoria, Australia, as a continuing collabora... more MT soundings were carried out in 2008, in northern Victoria, Australia, as a continuing collaboration research of 2007 between Republic of Korea, Australia, and Japan. The main purpose of this research is to investigate electrical conductivity structure and thus help understanding of tectonic structure in central Victoria, which is believed to be closely linked to mineralization and magmatic processes of this region. The survey area is located in western Lachlan Fold Belts, which is the part of Tasman Fold Belts in southeastern Australia. An MT profile of 2008 is almost parallel to the one of 2007 and approximately 50 km away. The 2D inversion result of MT data also shows that the position of conductivity discontinuity near surface are well matched with the positions of major faults, such as Avoca Fault, which is the structural boundary between Stawell and Bendigo Zones, and Heathcote Fault Zone, which marks the boundary between Bendigo and Melbourne Zones. It is also confirmed from...

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Research paper thumbnail of Thermal conductivity probes for rapid measurements in rock

Journal of Physics E: Scientific Instruments

Probe configurations have been designed which allow thermal conductivity measurements to be made ... more Probe configurations have been designed which allow thermal conductivity measurements to be made on rocks using transient heating techniques. Two heat sources have been tested, the first is a line source which is compatible with needle probe instrumentation and the second is a ring source which can be used with small samples. Both probes can be used under field conditions.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Electrical Conductivity Structure Of Central Victoria, Australia From Magnetotelluric Measurements

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Magnetotelluric soundings and the Levy algorithm

Explor Geophys, 1991

Standard band-averaging techniques used for representing magnetotelluric data are subject to bias... more Standard band-averaging techniques used for representing magnetotelluric data are subject to bias from spurious estimates unrelated to Gaussian noise. Consequently complex curve fitting techniques have been suggested to provide an alternative representation. Suspect bands can be eliminated and representative data can be obtained by interpolation using complex polynomials. The Levy algorithm adopted here has the additional benefit that it can be used for archiving to approximate band averages obtained using existing software.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Downhole three component TEM probes

Explor Geophys, 1993

A three component transient electromagnetic (TEM) probe (VECTEM) has been constructed to eliminat... more A three component transient electromagnetic (TEM) probe (VECTEM) has been constructed to eliminate rotational ambiguities associated with data obtained along a single axis. Individual components are obtained sequentially using a surface adapter for multiplexing to any standard TEM recorder. The critical rotation angles are also indicated by this surface unit and are recorded in the data header. Data have been obtained for several sites and interpretations have been generated using filament inversion routines. The results agree in general with previous axial data and are consistent with geological constraints. However noise levels are higher than expected compared to single-component probes and anomalies confined to late windows may remain obscured.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Application of Euler deconvolution and a neural network system as interpretation aids for three component downhole TEM data

Explor Geophys, 1995

The relationship between the secondary field due to a TEM source and a dipolar potential field ha... more The relationship between the secondary field due to a TEM source and a dipolar potential field has been documented (Dyck and West, 1984; Grant and West, 1965). In light of this relationship it is possible to utilise potential field interpretation aids when dealing with TEM data. Where only the axial component of the anomalous field is available, in the case of downhole TEM data, the implementation of these techniques is very restricted and may yield ambiguous model parameters, hence alternative techniques must be considered. Euler deconvolution may be used to obtain the approximate coordinates of the source even in the presence of an overburden response. A neural network system has been trained to output the dip and strike direction of a plate model using scaled field data as input. Utilising both the neural network and Euler deconvolution techniques, approximate model parameters may be computed directly from the field data. Synthetic examples are presented, showing that these techniques are applicable even in the presence of noise and conductive overburden. A field example from the Flying Doctor prospect is also presented. The computed model parameters were found to be consistent with previously published data (Cull, 1993).

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Simultaneous modelling of the phase and amplitude components of downhole magnetometric resistivity data

Journal of Applied Geophysics, Nov 1, 2003

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A Subsurface Pipeline Inspection Probe

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Short note: Sensor response and resolution in downhole TEM data

Explor Geophys, 1996

Downhole TEM probes can be constructed using several different types of core material. These core... more Downhole TEM probes can be constructed using several different types of core material. These cores are designed to concentrate the lines of magnetic flux associated with currents induced in a conductive target. In axial probes the resulting signal levels are greatly enhanced and anomalies associated with major targets are readily detected. However for crosshole sensors the advantages are not so evident. In particular the aspect ratio is greatly reduced in probes of reasonable diameter and flux densities can not be greatly improved. Variations in permeability as a function of frequency present a more serious problem. Data obtained at early times may become seriously distorted in any cored probes and deconvolution techniques may be required to compensate for permeability transfer functions. In these circumstances air-cored probes may be preferred but final response remains limited by self inductance.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Acquisition and signal processing of ground-penetrating radar for shallow exploration and open-pit mining

Explor Geophys, 1992

The Australian Mineral Industries Research Association (AMIRA) has sponsored Monash University to... more The Australian Mineral Industries Research Association (AMIRA) has sponsored Monash University to investigate the acquisition and signal processing of ground-penetrating radar (GPR) for shallow exploration and open-pit mining. This project had three objectives: (1) to acquire high-quality GPR data sets for shallow exploration and surface mining applications under a variety of geological conditions; (2) to develop signal-processing techniques to enhance radar profiles prior to detailed interpretation; (3) to assess the accuracy of GPR and associated processing techniques through comparisons with independent measurements. Over one hundred kilometres of data were recorded at the various sponsors sites in a wide variety of geological conditions for different economic targets. Several examples are presented to demonstrate: 1) the hand-carried and vehicle-towed acquisition techniques, 2) target detection at depths down to 25 m, 3) the benefits of signal processing for good and poor quality data, 4) the use of dielectric measurements, petrophysical modelling and frequency-dependent synthetic radargrams, 5) the application of seismic interpretation concepts. The project has demonstrated commercially acceptable rates of GPR data acquisition where the penetration is satisfactory. Some of the unfavourable Australian geological conditions for radar have also been identified. Although signal processing techniques have extended the applicable range of the radar technique, additional hardware enhancements have been identified to improve the commercial application of radar. The next stage is to assess the economic feasibility of radar by comparison with competing techniques such as drilling.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Time domain electromagnetic analysis and inspection system for conduits

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Spectral acoustic techniques for joint and fracture characterization

Explor Geophys, 1995

An ultrasonic pulse transmission method was used on a large block of gabbro (18 � 18 � 30 cm), at... more An ultrasonic pulse transmission method was used on a large block of gabbro (18 � 18 � 30 cm), at low normal stresses (0.01?15 MPa) and low frequencies (0.02?1 Mhz) in order to determine the transmission coefficient of a simulated fracture. The contact stiffness was measured directly and spectral ratios of the received signals calculated for comparison with predictions from the displacement discontinuity model. The agreement between the measured and derived spectral ratios was significantly better for the rough surface, indicating that the model provides a better approximation for natural fractures than for smooth interfaces. The model predictions also improved at lower frequencies, suggesting that spectral analysis of seismic data might yield useful information about the presence and stress state of fractures in the field.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Subsurface pipeline inspection probe

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Implications for geothermal profiling from magnetotelluric data

Explor Geophys, 1991

Laboratory studies of the temperature dependence of the electrical conductivity of rock materials... more Laboratory studies of the temperature dependence of the electrical conductivity of rock materials can be used to relate electrical conductivity to temperature in the Earth. Electrical conductivity models advanced for central and southeastern Australia are compared with profiles predicted from such laboratory measurements, and are then used to generate representative magnetotelluric response curves. The response curves differ sufficiently to give confidence in their use to detect gross conductivity changes at depth. Observed data from Broken Hill and Ivanhoe, NSW, are interpreted to indicate a temperature contrast in the upper mantle of some 200�C between these two sites (hotter to the east beneath Ivanhoe). The temperature at these large depths is a vital factor in constraining models of crustal underplating and intrusion.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Heat Flow and Regional Geophysics in Australia

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Heat‐flow data in western Victoria

Http Dx Doi Org 10 1046 J 1440 0952 2001 00840 X, Nov 8, 2010

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Geothermal models and mantle rheology in Australia

Tectonophysics, Aug 1, 1989

... Estimates for an isolated group con sidered by O'Reilly and Griffin (1985) are con siste... more ... Estimates for an isolated group con sidered by O'Reilly and Griffin (1985) are con sistent with conduction models based on a surface heat flow of 90110 mW m2 (BG, Fig. ... The join MgSi04 CaMgSiO at 30 kb pressure and its application to pyrox enes from kimberlite. J. Geophys. ...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of High definition gravity surveys and density modelling for kimberlite exploration

Exploration Geophysics

Gravity data obtained at Hiles Lagoon, near Terowie, indicates the presence of a subtle gravity l... more Gravity data obtained at Hiles Lagoon, near Terowie, indicates the presence of a subtle gravity low. The 5 mm s-2 gravity low over the lagoon possesses roughly circular dimensions with a diameter of approximately 200 m and is the likely response of a concealed kimberlite pipe. These results are of particular interest since previous aeromagnetic and aeroradiometric geophysical surveys have had little success in detecting a kimberlite pipe at Hiles Lagoon. Density determinations typical of weathered Australian kimberlites and shales were employed to create a structural model of a kimberlite pipe and the surrounding country rock. Resulting gravity raster images from the kimberlitic model allow us to confidently interpret the field response as a kimberlite pipe and justify the application of the gravimetric technique as a tool for detailed exploration.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Condition assessment of cast iron and asbestos cement pipes by in-pipe probes and selective sampling for estimation of remaining life

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Structural Controls on the Hydrothermal System of Villarrica: Evidence from Self-Potential Measurements

Geological studies at Volcan Villarrica have investigated the volcanic history of this part of th... more Geological studies at Volcan Villarrica have investigated the volcanic history of this part of the Andes southern volcanic zone but have revealed little information about the hydrothermal and magmatic circulation system. Hydrothermal circulation, and the extent over which it is active on volcanoes, has connotations to hazard mitigation as areas within the hydrothermal cell are often less competent and more prone to failure. A self- potential survey was conducted over a period of three months on two sub-parallel transects from the summit of the volcano. Initial results suggest fluid circulation is occurring. The survey detected a strong amplitude dipolar anomaly reaching a value of -2.7 volt, the minimum in the self potential data indicating the transitional zone from a hydrothermal to hydrological regime of fluid circulation. This anomaly is believed to be a result of a combination of rapid fluid disruption, electro-kinetic, and thermoelectric effects within and surrounding the magm...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Two-dimensional Analysis of MT Data across Northern Victoria, Australia

MT soundings were carried out in 2008, in northern Victoria, Australia, as a continuing collabora... more MT soundings were carried out in 2008, in northern Victoria, Australia, as a continuing collaboration research of 2007 between Republic of Korea, Australia, and Japan. The main purpose of this research is to investigate electrical conductivity structure and thus help understanding of tectonic structure in central Victoria, which is believed to be closely linked to mineralization and magmatic processes of this region. The survey area is located in western Lachlan Fold Belts, which is the part of Tasman Fold Belts in southeastern Australia. An MT profile of 2008 is almost parallel to the one of 2007 and approximately 50 km away. The 2D inversion result of MT data also shows that the position of conductivity discontinuity near surface are well matched with the positions of major faults, such as Avoca Fault, which is the structural boundary between Stawell and Bendigo Zones, and Heathcote Fault Zone, which marks the boundary between Bendigo and Melbourne Zones. It is also confirmed from...

Bookmarks Related papers MentionsView impact