Exploration Geophysics (EXPLOR GEOPHYS)

Publisher: CSIRO Publishing

Journal description

Exploration Geophysics publishes excellent research in geophysics, reviews, technical papers and significant case histories in minerals, petroleum, mining and environmental geophysics, and is an official publication of the Australian Society of Exploration Geophysicists (ASEG). Authors and readers are professional earth scientists specialising in the practical application of the principles of physics and mathematics to solve problems in a broad range of geological situations. They are variously in industry, government and academic research institutions. All papers are peer reviewed. Four issues are published each year in both print and online versions and some issues include special sections of particular topics, or collections of papers from the regular ASEG Conferences. We also publish a joint issue as Mulli-Tamsa with the Korean Society of Exploration Geophysicists and as Butsuri-Tansa with the Society of Exploration Geophysicists of Japan; this issue goes to all three societies.

Current impact factor: 0.55

Impact Factor Rankings

2015 Impact Factor Available summer 2015
2013 / 2014 Impact Factor 0.554
2012 Impact Factor 0.667
2011 Impact Factor 0.634
2010 Impact Factor 0.619
2009 Impact Factor 0.404

Impact factor over time

Impact factor
Year

Additional details

5-year impact 0.79
Cited half-life 9.60
Immediacy index 0.07
Eigenfactor 0.00
Article influence 0.38
Website Exploration Geophysics website
ISSN 0812-3985
OCLC 180103031
Material type Periodical, Internet resource
Document type Internet Resource, Computer File, Journal / Magazine / Newspaper

Publisher details

CSIRO Publishing

  • Pre-print
    • Author can archive a pre-print version
  • Post-print
    • Author can archive a post-print version
  • Conditions
    • On author's personal repository or institutional repository
    • Must link to publisher version
    • Published source must be acknowledged
    • Publisher's version/PDF cannot be used
  • Classification
    ​ green

Publications in this journal

  • [Show abstract] [Hide abstract]
    ABSTRACT: Passive seismic sources can generally be divided into transient sources and noise sources. Noise sources are particularly the continuous, random small bursts, like background noise. The virtual-shot gathers obtained by the traditional cross-correlation algorithm from passive seismic data not only contain primaries, but also include surface-related multiples. Through estimating primaries by sparse inversion, we can directly obtain primaries from passive seismic data activated by transient sources, which are free of surface-related multiples. The problem of estimating primaries from passive seismic data activated by noise sources has not been discussed to date. First, by introducing the optimisation problem via the L1-norm constraint, this paper makes the traditional method of estimating primaries by sparse inversion from passive seismic data activated by transient sources improved, which overcomes the time-window problem. During the sparse inversion, the sparsifying transform, S = C2⊗W, is introduced. In the sparsifying-transform domain, the transformed data is more sparse, so the solution becomes more accurate. Second, this paper proposes estimating primaries from passive seismic data activated by noise sources. In the case of the sparse assumption not holding, we use the least-squares method based on the principle of minimum energy to estimate primaries from passive seismic data using the noise sources. Finally, we compare the primaries estimated from passive seismic data using transient sources and noise sources and analyse the characteristics of the estimated primaries obtained from two passive seismic data.
    Exploration Geophysics 11/2015; 46(2):184. DOI:10.1071/EG14079
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    ABSTRACT: Rapid interpretation of large airborne transient electromagnetic (ATEM) datasets is highly desirable for timely decision-making in exploration. Full solution 3D inversion of entire airborne electromagnetic (AEM) surveys is often still not feasible on current day PCs. Therefore, two algorithms to perform rapid approximate 3D interpretation of AEM have been developed. The loss of rigour may be of little consequence if the objective of the AEM survey is regional reconnaissance. Data coverage is often quasi-2D rather than truly 3D in such cases, belying the need for `exact' 3D inversion. Incorporation of geological constraints reduces the non-uniqueness of 3D AEM inversion. Integrated interpretation can be achieved most readily when inversion is applied to a geological model, attributed with lithology as well as conductivity. Geological models also offer several practical advantages over pure property models during inversion. In particular, they permit adjustment of geological boundaries. In addition, optimal conductivities can be determined for homogeneous units. Both algorithms described here can operate on geological models; however, they can also perform `unconstrained' inversion if the geological context is unknown. VPem1D performs 1D inversion at each ATEM data location above a 3D model. Interpretation of cover thickness is a natural application; this is illustrated via application to Spectrem data from central Australia. VPem3D performs 3D inversion on time-integrated (resistive limit) data. Conversion to resistive limits delivers a massive increase in speed since the TEM inverse problem reduces to a quasi-magnetic problem. The time evolution of the decay is lost during the conversion, but the information can be largely recovered by constructing a starting model from conductivity depth images (CDIs) or 1D inversions combined with geological constraints if available. The efficacy of the approach is demonstrated on Spectrem data from Brazil. Both separately and in combination, these programs provide new options to exploration and mining companies for rapid interpretation of ATEM surveys.
    Exploration Geophysics 10/2015; 46(1). DOI:10.1071/EG14046
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    ABSTRACT: Magnetic and electromagnetic (EM) results from two helicopter EM surveys, a time-domain (VTEM) and AFMAG (ZTEM), are compared over the Nuqrah sedimentary exhalative (SEDEX) massive sulphide deposits in the Western Arabian Shield of the Kingdom of Saudi Arabia. The magnetic and EM data from both surveys map the major controlling structures that host the Nuqrah North and South deposits. Neither Nuqrah deposits stand out as distinctive aeromagnetic anomalies, but both EM surveys define the massive sulphide mineralised vent and bedded portions of the SEDEX orebodies. ZTEM is interpreted to be more capable in defining the larger, lower conductance and less mineralised distal portions of the SEDEX system. The modelled ZTEM also defines a down-dip extension of the Nuqrah South zone below a depth of 750 m.
    Exploration Geophysics 09/2015; 46(1). DOI:10.1071/EG14028
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    ABSTRACT: Forward modelling of airborne time-domain electromagnetic (ATDEM) responses is frequently used to compare systems and design surveys for optimum detection of expected mineral exploration targets. It is a challenging exercise to display and analyse the forward modelled responses due to the large amount of data generated for three dimensional models as well as the system dependent nature of the data. I propose simplifying the display of ATDEM responses through using the dimensionless quantity of signal-to-noise ratios (signal:noise) instead of respective system units. I also introduce the concept of a three-dimensional signal:noise nomo-volume as an efficient tool to visually present and analyse large amounts of data. The signal:noise nomo-volume is a logical extension of the two-dimensional conductance nomogram. It contains the signal:noise values of all system time channels and components for various target depths and conductances integrated into a single interactive three-dimensional image. Responses are calculated over a complete survey grid and therefore include effects of system and target geometries. The user can interactively select signal:noise cut-off values on the nomo-volume and is able to perform visual comparisons between various system and target responses. The process is easy to apply and geophysicists with access to forward modelling airborne electromagnetic (AEM) and three-dimensional imaging software already possess the tools required to produce and analyse signal:noise nomo-volumes.
    Exploration Geophysics 09/2015; 46(1). DOI:10.1071/EG14026
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    ABSTRACT: In order to get the correct amplitudes of the secondary field measurements, the correct value for the primary signal must be subtracted from the input signal where both secondary and primary are recorded together. This is due to the secondary signals being measured while the transmitter is on. The onboard data system approximates the transmitter signal by the total signal value in the last window, it being assumed that the secondary signal has decayed to a negligible value at that delay time. The result of subtracting too much from the secondary signal and adding this excess to the primary signal is that the secondary signals are no longer sums of simple exponential decay functions. A procedure is described to estimate the decay functions as well as the offset to be subtracted from the initial estimate of the primary.
    Exploration Geophysics 08/2015; 46(1). DOI:10.1071/EG14029
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    ABSTRACT: A regional scale TEMPEST208 airborne electromagnetic survey was flown in north-east Namibia in 2011. With broad line spacing (4 km) and a relatively low-powered, fixed-wing system, the approach was intended to provide a regional geo-electric map of the area, rather than direct detection of potential mineral deposits. A key component of the geo-electric profiling was to map the relative thickness of the Kalahari sediments, which is up to 200 m thick and obscures most of the bedrock in the area. Knowledge of the thickness would allow explorers to better predict the costs of exploration under the Kalahari. An additional aim was to determine if bedrock conductors were detectable beneath the Kalahari cover. The system succeeded in measuring the Kalahari thickness where this cover was relatively thin and moderately conductive. Limitations in depth penetration mean that it is not possible to map the thickness in the centre of the survey area, and much of the northern half of the survey area. Additional problems arise due to the variable conductivity of the Kalahari cover. Where the conductivity of the Kalahari sediment is close to that of the basement, there is no discernable contrast to delineate the base of the Kalahari. Basement conductors are visible beneath the more thinly covered areas such as in the north-west and south of the survey area. The remainder of the survey area generally comprises deeper, more conductive cover and for the most part basement conductors cannot be detected. A qualitative comparison with VTEM data shows comparable results in terms of regional mapping, and suggests that even more powerful systems such as the VTEM may not detect discrete conductors beneath the thick conductive parts of the Kalahari cover.
    Exploration Geophysics 08/2015; 46(1). DOI:10.1071/EG14022
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    ABSTRACT: An airborne time domain electromagnetic (TEM) system with high resolution and great depth of exploration is desired for geological mapping as well as for mineral exploration. The MULTIPULSE technology enables an airborne TEM system to transmit a high power pulse (a half-sine, for instance) and one or multiple low power pulse(s) (trapezoid or square) within a half-cycle. The high power pulse ensures good depth of exploration and the low power pulse allows a fast transmitter current turn off and earlier off-time measurement thus providing higher frequency signals, which allows higher near-surface resolution and better sensitivity to weak conductors. The power spectrum of the MULTIPULSE waveform comprising a half-sine and a trapezoid pulse clearly shows increased power in the higher frequency range (〉 ~2.3 kHz) compared to that of a single half-sine waveform. The addition of the low power trapezoid pulse extends the range of the sensitivity 10-fold towards the weak conductors, expanding the geological conductivity range of a system and increasing the scope of its applications. The MULTIPULSE technology can be applied to standard single-pulse airborne TEM systems on both helicopter and fixed-wing. We field tested the HELITEM MULTIPULSE system over a wire-loop in Iroquois Falls, demonstrating the different sensitivity of the high and low power pulses to the overburden and the wire-loop. We also tested both HELITEM and GEOTEM MULTIPULSE systems over a layered oil sand geologic setting in Fort McMurray, Alberta, Canada. The results show comparable shallow geologic resolution of the MULTIPULSE to that of the RESOLVE system while maintaining superior depth of exploration, confirming the increased geological conductivity range of a system employing MULTIPULSE compared to the standard single-pulse systems.
    Exploration Geophysics 08/2015; 46(1). DOI:10.1071/EG14027
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    ABSTRACT: We compare time domain systems of different waveform shape, power and receiver sampling times using a wire loop conductor model to define a comprehensive `geobandwidth' that shows the strength of the response over a range of time constants, analogous to a range of conductance. Frequency domain EM responses can also be calculated as a function of time constant for a wire loop model, giving a consistent comparison method for all time domain waveforms and frequency domain. Arbitrary waveforms can be modelled as a sum of simple short ramps, and the geobandwidth determined numerically. Peak time constant (time constant of peak response) or equivalent frequency can be determined analytically or numerically. The frequency content of a time-domain EM system can be characterised by the peak time constant or the equivalent frequency. The results of these calculations are used to compare response amplitude across a wide range of geological target conductance. Systems can be compared on the basis of signal or signal/noise ratio.
    Exploration Geophysics 06/2015; 46(1). DOI:10.1071/EG14032
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    Exploration Geophysics 03/2015; 46(1). DOI:10.1071/EG14105
  • Exploration Geophysics 01/2015; DOI:10.1071/EG15019
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    Exploration Geophysics 01/2015; DOI:10.1071/EG15033
  • Exploration Geophysics 01/2015; 46(2):213. DOI:10.1071/EG13091
  • Exploration Geophysics 01/2015; DOI:10.1071/EG14123
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    ABSTRACT: Time-domain induced polarisation (TDIP) methods are routinely used for near-surface evaluations in quasi-urban environments harbouring networks of buried civil infrastructure. A conventional technique for improving signal to noise ratio in such environments is by using analogue or digital low-pass filtering followed by stacking and rectification. However, this induces large distortions in the processed data. In this study, we have conducted the first application of wavelet based denoising techniques for processing raw TDIP data. Our investigation included laboratory and field measurements to better understand the advantages and limitations of this technique. It was found that distortions arising from conventional filtering can be significantly avoided with the use of wavelet based denoising techniques. With recent advances in full-waveform acquisition and analysis, incorporation of wavelet denoising techniques can further enhance surveying capabilities. In this work, we present the rationale for utilising wavelet denoising methods and discuss some important implications, which can positively influence TDIP methods.
    Exploration Geophysics 01/2015; DOI:10.1071/EG13077
  • Exploration Geophysics 01/2015; DOI:10.1071/EG15002
  • Exploration Geophysics 01/2015; DOI:10.1071/EG14111