ORCID Profile
0000-0003-2850-7818
Current Organisation
University of South Australia
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Publisher: Society of Exploration Geophysicists
Date: 1996
DOI: 10.1190/1.1443952
Abstract: Geophysical methods that use explosive seismic sources need to produce an accurate time break signal at the time of the blast. This is generally achieved with a seismic detonator, a special variety of electrical detonator (or cap) that is designed to have minimal latency between the injection of electrical current into the detonator and initiation of the explosion, as well as having a slightly higher base charge and better water resistance. A time‐break signal is obtained by either electronically controlling or monitoring the blast current. Seismic detonators are guaranteed to have better than a millisecond latency if sufficient current is injected into the leads the necessary current is usually 5 to 10 s. A millisecond tolerance is acceptable for most seismic work but may not be sufficient for shallow studies or for crosswell tomography. However, in fairness to the seismic detonator, the actual performance is generally better: Burrows (1936) and, independently, Rolland and White (1937) reported a time lag of less than 0.3 ms with a deviation of 0.1 ms. These values have changed little since the 1940s. The MK 2 from C.I.L. Inc. (a ision of I.C.I.) has an average lag of 0.3–0.4 ms (personal communication with I.C.I. explosives). Major improvements in electric detonator design have been in the areas of safety and durability. A much greater disadvantage for explosive sources are the strict regulations on the transport and storage of explosive devices (Tour, 1992). The cost of complying with these regulations may prohibit the use of explosives in small surveys or in remote areas. An ex le is the transport of explosives by aircraft: the only passengers allowed on board are those neccesary for completing the flight and for transporting the explosives. Chartering an aircraft to transport a small amount of explosive material is too costly for many geotechnical and mining geophysics surveys.
Publisher: Society of Exploration Geophysicists
Date: 06-10-2022
Abstract: The low-energy region of the gamma ray spectrum, less than 200 keV, often is either discarded or not analyzed in borehole logging or airborne radiometric surveys. There is much useful information about earth properties to be extracted from the low-energy region because it is sensitive to photoelectric absorption within the rock, a process that is highly sensitive to the atomic number of the elements within the rock. In addition, the rate of photoelectric absorption is proportional to the density of the rock. At higher energies, the spectrum is primarily sensitive to density variations only. The ratio of counts in the two energy regions may be used as a heavy mineral indicator (HMI). This ratio normalizes density effects and is primarily sensitive to variations in the average (or effective) atomic number ([Formula: see text]) of the rock. Previous work by other authors has focused on the application of this idea for wireline logging with an isotopic source and multiple scattering of copious primary gamma rays, which allows for good counting statistics in the recorded spectrum. Recent advances in gamma ray detectors and logging-while-drilling (LWD) techniques open the possibility of applying the HMI measurement to the natural gamma ray LWD logs. Drilling speeds are much slower than the running speeds of wireline tools, resulting in improved counting statistics. Using computer simulations, laboratory experiments, and field measurements, we find that the natural gamma ray spectrum, recorded while (diamond) drilling, provides sufficient counting statistics to be used for robustly calculating HMI. As iron is the most abundant and influential element in photoelectric gamma ray scattering processes in rock fabrics, we postulate that we can, in most cases, use HMI to indicate the iron content of the rocks. The HMI calculated under these conditions provides a good measure of changes in [Formula: see text] of rocks and correlates well with iron-rich sections. Our field and laboratory tests demonstrate that the HMI measures can be used as a proxy to separate many metalliferous ores from waste based on the differences in [Formula: see text].
Publisher: IEEE
Date: 06-2010
Publisher: Society of Exploration Geophysicists
Date: 03-1995
DOI: 10.1190/1.1443772
Abstract: An underground test of a seismoelectric prospecting method for massive sulfides was performed at the Mobrun Mine (Rouyn‐Noranda, Quebec) in June 1991. The method is based upon the conversion of seismic energy to high‐frequency pulses of electromagnetic radiation by sulfide minerals. The delay between shot detonation and detection of the electromagnetic radiation gives a one‐way traveltime for the acoustic wave to reach the zone of seismoelectric conversion, which when combined with P‐wave velocity allows the shot‐to‐ore zone distance to be calculated. A 0.22-kg explosive charge located within 50 m of the orebody provided the seismic excitation, and the resulting electromagnetic emissions were received by electric dipole and induction‐coil antennas. First‐arrival information from a 35‐shot survey above an orebody, the 1100 lens, provides firm evidence that short duration pulses of electromagnetic radiation are produced by the passage of acoustic waves through the orebody. The survey also demonstrated that seismoelectric conversions could be induced at shot‐to‐orebody distances of 50 m and detected at distances of up to 150 m from the orebody. Areas of seismoelectric conversion are highlighted in sections produced by plotting the position of seismic wavefronts during signal reception. The sections show anomalies that correlate with the known structure and location of the orebody and demonstrate the potential of using this seismoelectric phenomenon as an exploration tool.
Publisher: MDPI AG
Date: 28-06-2018
DOI: 10.3390/MIN8070276
Publisher: Elsevier BV
Date: 2011
Publisher: Society of Exploration Geophysicists
Date: 19-08-2015
Publisher: Informa UK Limited
Date: 09-2016
DOI: 10.1071/EG15117
Publisher: Informa UK Limited
Date: 03-1992
DOI: 10.1071/EG992201
Publisher: Society of Exploration Geophysicists
Date: 2008
DOI: 10.1190/1.3064078
Publisher: American Geophysical Union (AGU)
Date: 2013
DOI: 10.1029/2012JB009448
Publisher: Society of Exploration Geophysicists
Date: 2008
DOI: 10.1190/1.3063940
Publisher: Society of Exploration Geophysicists
Date: 07-2009
DOI: 10.1190/1.3167783
Publisher: Society of Exploration Geophysicists
Date: 19-08-2015
Publisher: Informa UK Limited
Date: 03-2016
DOI: 10.1071/EG14086
Publisher: Informa UK Limited
Date: 03-1992
DOI: 10.1071/EG992281
Publisher: Wiley
Date: 04-07-2018
Publisher: Society of Exploration Geophysicists
Date: 09-2012
Abstract: Seismic imaging in hard rock environments is gaining wider acceptance as an exploration technique and as a mine-planning tool. To date, 13 successful case studies have been acquired in Australia. The images generated from hard rock targets exhibit large levels of complexity and their interpretations remain an active area of study. To assist the imaging and better understand the source of the reflections observed, vertical seismic profiling (VSP) can be employed. This technique is not readily applied to hard rock environments because cost and operational issues often prove prohibitive. We propose the use of hydrophone arrays as a cost effective solution to VSP acquisition. We highlight the key challenges in using these receivers and propose solutions to overcome them. By careful acquisition methodologies and refined signal processing techniques, the tube waves that have up to now compromised the use of hydrophones for VSP acquisition can be effectively mitigated. We show that the data acquired with hydrophones compare favorably to that acquired with conventional 3C geophones. The data acquired with hydrophones come at a fraction of the cost and deployment time required for conventional acquisition procedures. Our results show that hydrophone vertical seismic acquisition is a viable, cost effective, and efficient solution that should be employed more routinely in hard rock environments to enhance the value of the surface data sets being acquired.
Publisher: Society of Exploration Geophysicists
Date: 2004
DOI: 10.1190/1.1845111
Publisher: Society of Exploration Geophysicists
Date: 2008
DOI: 10.1190/1.3064080
Publisher: Informa UK Limited
Date: 06-2001
DOI: 10.1071/EG01107
Publisher: Society of Exploration Geophysicists
Date: 2004
DOI: 10.1190/1.1851111
Publisher: Informa UK Limited
Date: 06-2005
DOI: 10.1071/EG05245
Publisher: Society of Exploration Geophysicists
Date: 2008
DOI: 10.1190/1.3064087
Publisher: Society of Exploration Geophysicists
Date: 09-2011
Abstract: An unexpected result of ground-penetrating radar (GPR) surveys in the Great Victoria Desert (South Australia) was the lack of returning signal in what appeared to be a favorable environment for GPR, with dry silica sand and calcrete aggregates in the near surface. We found that the dielectric response of the dry sand s les had much higher dielectric losses than comparable sands from Western Australia and that the dielectric losses are controlled by the presence of iron oxide minerals, although iron concentrations themselves are only around 0.4%. The s les contained over 90% quartz, with subsidiary amounts of carbonates, kaolin, and smectite occurring with the iron oxide minerals as a coating on the quartz grains. An acid washing procedure removed the reducible iron oxide minerals from the clay coating but left the clays substantially unaltered. Subsequent dielectric and magnetic analysis of the s les indicates that the iron oxide minerals removed during the washing process are responsible for the reduction of GPR penetration at 250 MHz from approximately 10 m to only 1 m.
Publisher: Society of Exploration Geophysicists
Date: 2008
DOI: 10.1190/1.3064082
Publisher: Elsevier BV
Date: 07-2017
Publisher: Society of Exploration Geophysicists
Date: 11-1996
DOI: 10.1190/1.1444093
Abstract: Field experiments carried out at a site near Vancouver, Canada have shown that a shallow lithologic boundary can be mapped on the basis of its seismoelectric response.As seismic waves cross the boundary between organic‐rich fill and impermeable glacial till, they induceelectric fields that can be measured at the surfacewith grounded dipole receivers. Sledgehammer and blasting cap seismic sources, positioned up to 7 m away from the interface, have produced clear seismoelectric conversions. Two types of seismoelectric signals are observed. The primary response is distinguished by near simultaneous arrivals at widely separated receivers. Its arrival time is equal to the time required for a seismic P‐wave to travel from the shotpoint to the fill/till boundary. On the surface, its maximum litude (about 1 mV/m) ismeasured by dipoles located within a few meters of the shotpoint. At greater distances, the litude of the primaryarrival decays rapidly with offset, and secondary seismoelectric arrivals become dominant. They differ from the primary response in that their arrival times increasewith dipole offset, and they appear to be generatedin the immediate vicinity of each dipole sensor. Our studies show that the responses cannot be attributedto piezoelectricity or to resistivity modulation in the presence of a uniform telluric current. We infer that seismically induced electrokinetic effects or streamingpotentials are responsible for the seismoelectric conversion,and a simple electrostatic model is proposed to account for the two types of arrivals. Although our experimentswere small in scale, the results are significant in that they suggest that the seismoelectric method may be used to map the boundaries of permeable formations.
Publisher: Society of Exploration Geophysicists
Date: 2002
DOI: 10.1190/1.1816945
Publisher: Informa UK Limited
Date: 03-2005
DOI: 10.1071/EG05073
Publisher: Society of Exploration Geophysicists
Date: 05-08-2014
Publisher: Elsevier BV
Date: 07-2017
Publisher: Society of Exploration Geophysicists
Date: 11-2007
DOI: 10.1190/1.2773780
Abstract: We have acquired a [Formula: see text] seismoelectric section over an unconfined aquifer to demonstrate the effectiveness of interfacial signals at imaging interfaces in shallow sedimentary environments. The seismoelectric data were acquired by using a [Formula: see text] accelerated weight-drop source and a 24-channel seismoelectric recording system composed of grounded dipoles, pre lifiers, and seismographs. In the shot records, interfacial signals were remarkably clear they arrived simultaneously at offsets as far as [Formula: see text] from the seismic source. The most prominent signal was generated at the water table at a depth of approximately [Formula: see text] and had peak litudes on the order of [Formula: see text]. A weaker response was generated at a shallower interface that is interpreted to be a water-retentive layer. The validity of these two laterally continuous events, and of other discontinuous events indicative of vadose-zone heterogeneity, is corroborated by the presence of reflections exhibiting similar characteristics in a ground-penetrating radar profile acquired along the same line.
Publisher: American Geophysical Union (AGU)
Date: 10-2009
DOI: 10.1029/2008JB005939
Publisher: Wiley
Date: 13-12-2011
Publisher: American Geophysical Union (AGU)
Date: 03-2014
DOI: 10.1002/2013WR014331
Publisher: Society of Exploration Geophysicists
Date: 02-2010
DOI: 10.1190/1.3304819
Abstract: The CO2CRC Otway Project conducted under the Australian Cooperative Research Centre for Greenhouse Gas Technologies is the first of its kind, where [Formula: see text] is injected into a depleted gas reservoir. The use of depleted gas fields for [Formula: see text] storage and or enhanced gas recovery is likely to become globally adopted. Therefore, the CO2CRC project provides important experience for monitoring under these conditions. However, injection of [Formula: see text] into a depleted gas reservoir (residual gas saturation zone in this case) does not present a favorable condition for the application of geophysical monitoring techniques, and particularly seismic methods.
Publisher: Elsevier BV
Date: 08-2017
Publisher: Society of Exploration Geophysicists
Date: 07-2015
Abstract: The integration of different geophysical data has the potential to provide more accurate estimate of subsurface rock properties. Several methodologies and attempts have been developed over the years with the objective of reducing exploration risk. We have developed a cooperative joint-inversion approach intended to facilitate recovery of acoustic impedance (AI) using seismic and magnetotelluric (MT) data. In this approach, the MT data provided a pathway for iteratively building large-scale low-frequency information content not directly recoverable from the seismic data themselves. The MT data provided complementary information to seismic, especially in seismically complex terrains such as overthrust belts, subbasalt and subsalt, carbonate reefs or for targets below deep cover containing limestone, concretionary layers, or basalt. On the other hand, the seismic data provided structural information necessary to derive accurate resistivity models from MT inversion and small-scale features during seismic impedance inversion. The connections between resistivity and the elastic property of rocks are obtained from petrophysical relationships derived from available borehole data, or if not available, from empirical relationships. We tested our technique on synthetic and field data. The application of cooperative joint inversion to 3D seismic and MT data sets acquired in a mineral province made it possible to recover AI distribution across a wide range of geologic environments. The resulting rock property images provided a direct link to geology that is exceedingly difficult, if not impossible, to extract from the in idual data sets.
Publisher: Society of Exploration Geophysicists
Date: 19-08-2015
No related grants have been discovered for Anton Kepic.