Seismic Imaging Using Electromagnetic Vibrators - Storm versus Lightning

Brodic, Bojan; Kunder, Richard de; Ras, Paul; Berg, J. Van den; Malehmir, Alireza

doi:10.3997/2214-4609.201902406

Cited by 8 publications

(4 citation statements)

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“…a sudden impact produced by a weight drop) should be employed to generate seismic wave fields with sufficient energy and frequency bandwidth (e.g. Brodic et al, 2019;Pertuz et al, 2020). The adequate energy ensures the wave fields propagate down to the depth of targets and travel back to the surface.…”

Section: Introductionmentioning

confidence: 99%

Reverse time migration (RTM) imaging of iron oxide deposits in the Ludvika mining area, Sweden

Ding

Malehmir

2021

Solid Earth

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Abstract. To discover or delineate mineral deposits and other geological features such as faults and lithological boundaries in their host rocks, seismic methods are preferred for imaging the targets at great depth. One major goal for seismic methods is to produce a reliable image of the reflectors underground given the typical discontinuous geology in crystalline environments with low signal-to-noise ratios. In this study, we investigate the usefulness of the reverse time migration (RTM) imaging algorithm in hardrock environments by applying it to a 2D dataset, which was acquired in the Ludvika mining area of central Sweden. We provide a how-to solution for applications of RTM in future and similar datasets. When using the RTM imaging technique properly, it is possible to obtain high-fidelity seismic images of the subsurface. Due to good amplitude preservation in the RTM image, the imaged reflectors provide indications to infer their geological origin. In order to obtain a reliable RTM image, we performed a detailed data pre-processing flow to deal with random noise, near-surface effects, and irregular receiver and source spacing, which can downgrade the final image if ignored. Exemplified with the Ludvika data, the resultant RTM image not only delineates the iron oxide deposits down to 1200 m depth as shown from previous studies, but also provides a better inferred ending of sheet-like mineralization. Additionally, the RTM image provides much-improved reflection of the dike and crosscutting features relative to the mineralized sheets when compared to the images produced by Kirchhoff migration in the previous studies. Two of the imaged crosscutting features are considered to be crucial when interpreting large-scale geological structures at the site and the likely disappearance of mineralization at depth. Using a field dataset acquired in hardrock environment, we demonstrate the usefulness of RTM imaging workflows for deep targeting mineral deposits.

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Section: Introductionmentioning

confidence: 99%

Reverse time migration (RTM) imaging of iron oxide deposits in the Ludvika mining area, Sweden

Ding

Malehmir

2021

Solid Earth

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“…The source provides a flat amplitude response capable of a 2–200‐Hz bandwidth at a peak force of approximately 7 kN. Earlier tests with the source were done at a sedimentary rock setting and inside mining tunnels (Brodic et al ., 2021a, 2021b; Donoso et al ., 2021), while in this study we validated the source on the surface at a hardrock site, more specifically, an iron oxide deposit located near Blötberget in central Sweden (Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

“…In this study, we present first-hand results from a prototype linear-synchronous-motor-based (electrically driven) broadband seismic source (Noorlandt et al, 2015;Brodic et al, 2019aBrodic et al, , 2019bBrodic et al, and 2021aBrodic et al, , 2021b, used as a surface seismic source for mineral exploration. The source provides a flat amplitude response capable of a 2-200-Hz bandwidth at a peak force of approximately 7 kN.…”

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Broadband seismic source data acquisition and processing to delineate iron oxide deposits in the Blötberget mine‐central Sweden

Pertuz

Malehmir

Bos³

et al. 2021

Geophysical Prospecting

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A prototype electromagnetic vibrator, referred to here as E‐Vib, was upgraded and developed for broadband hardrock and mineral exploration seismic surveys. We selected the iron oxide mine in Blötberget, central Sweden, for a test site in 2019 for the newly developed E‐Vib because of the availability of earlier seismic datasets (from 2015 to 2016) for verification of its performance for hardrock imaging purposes. The two‐dimensional data acquisition consisted of a fixed geometry with 550 receiver locations spaced at every 5 m, employing both cabled and wireless seismic recorders, along an approximately 2.7 km long profile. The E‐Vib operated at every second receiver station (i.e. 10 m spacing) with a linear sweep of 2–180 Hz and with a peak force of 7 kN. The processing workflow took advantage of the broadband signal generated by the E‐Vib in this challenging hardrock environment with varying ground conditions. The processed seismic section shows a set of reflections associated with the known iron oxide mineralization and a major crosscutting reflection interpreted to be from a fault system likely to be crosscutting the mineralization. The broadband source data acquisition and subsequent processing helped to improve signal quality and resolution in comparison with the earlier workflows and data where a drophammer seismic source was used as the seismic source. These results suggest new possibilities for the E‐Vib source for improved targeting in hardrock geological settings.

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“…CC BY 4.0 License. generate seismic wavefields with sufficient energy and frequency bandwidth (e.g., Brodic et al, 2019;Pertuz et al, 2020). The adequate energy ensures the wavefields propagate down to the depth of targets and travel back to the surface.…”

Section: Introductionmentioning

confidence: 99%

Reverse time migration (RTM) imaging of iron-oxide deposits in the Ludvika mining area, Sweden

Ding¹,

Malehmir²

2020

Preprint

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Abstract. To discover or delineate mineral deposits and other geological features such as faults and lithological boundaries in their host rocks, seismic methods are a qualified choice, given their resolution power at depth. One major goal for seismic methods is to produce a reliable image of the subsurface given the typical discontinuous geology in crystalline environment with low signal-to-noise ratio. In this study, we investigate the usefulness of reverse time migration (RTM) imaging algorithm in hardrock environment by applying it to a legacy 2D dataset, which was acquired in the Ludvika mining area of central Sweden. We provide a how-to solution for applications of RTM in future and similar datasets. When using the RTM imaging technique properly, it is possible to obtain high-fidelity seismic images of the subsurface. Due to good amplitude preservation in the RTM image, the imaged reflectors provide indications to infer their geological origin. Aside from the chosen seismic imaging algorithm, we illustrate that two other important factors for successful RTM imaging workflows are the suitable acquisition and careful data pre-processing. Exemplified with the Ludvika legacy data, the RTM method allows imaging the iron-oxide deposits at a great level of detail down to 1200 m depth as shown from previous studies. It also provides much-improved images of the lithological contacts and crosscutting features relative to the mineralized sheets. Some of the imaged crosscutting features are considered to be crucial when interpreting large-scale geological structures of the site and the likely disappearance of mineralization at depth. The RTM imaging workflows have the potential to be used on hardrock seismic data and for deep targeting mineral deposits, a key message we would like to deliver in this article.

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Seismic Imaging Using Electromagnetic Vibrators - Storm versus Lightning

Cited by 8 publications

References 0 publications

Reverse time migration (RTM) imaging of iron oxide deposits in the Ludvika mining area, Sweden

Reverse time migration (RTM) imaging of iron oxide deposits in the Ludvika mining area, Sweden

Broadband seismic source data acquisition and processing to delineate iron oxide deposits in the Blötberget mine‐central Sweden

Reverse time migration (RTM) imaging of iron-oxide deposits in the Ludvika mining area, Sweden

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