Enhancing hardrock seismic images: Reprocessing of high resolution seismic reflection data from Vihanti, Finland

Heinonen, Suvi; Heikkinen, Pekka; Kousa, Jukka; Kukkonen, Ilmo; Snyder, David B.

doi:10.1016/j.jappgeo.2013.03.004

Cited by 11 publications

(8 citation statements)

References 24 publications

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“…This dependence of the moduli on the time frame of crack closure can result in dispersion in cracked rocks even at low porosities. As seismic methods become more commonly used in crystalline rocks (e.g., Chan & Schmitt, 2015;Hajnal et al, 2010;Heinonen et al, 2013;Koivisto et al, 2012;Malehmir et al, 2012;Milkereit et al, 1996;Schijns et al, 2009;White & Malinowski, 2012), which typically exhibit these low aspect ratio cracks, the importance of quantifying the dispersion caused by cracks increases (Sun et al, 2009). However, there have been very few direct experimental observations of dispersion in low-porosity rocks with low aspect ratio cracks.…”

Section: Introductionmentioning

confidence: 99%

Shear Modulus Dispersion in Cracked and Fluid‐Saturated Quartzites: Experimental Observations and Modeling

2018

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The effect of pore fluids on acoustic wave dispersion in rocks with low aspect ratio crack porosity is important for the interpretation of laboratory and field observations in hard rock mineral exploration environments. Here we make laboratory measurements of shear modulus dispersion at frequencies 0.01–1 Hz and at 1 MHz with different saturating fluids (dry, argon, and water saturated) in two thermally cracked quartzite samples with ~2% total porosity. Measurements are made across a range of effective pressures (10–150 MPa), with the resulting very low permeabilities of the samples varying from 1–300 × 10−21 m2. Moduli across the 0.01–1 Hz band were typically independent of frequency. The shear moduli measured at sub‐Hz frequencies are unaffected by fluid saturation, as expected for the saturated isobaric (Gassmann) regime. In marked contrast, water saturation of the cracked rocks results in very large increases in the shear moduli measured at 1 MHz and low effective pressures, indicative of saturated isolated conditions. Thus, at an effective pressure of 20 MPa, the shear moduli for the two water‐saturated quartzites increase by 74% and 98% from 1 Hz to 1 MHz. The contrast in elastic moduli between dry and water‐saturated conditions is well represented by the theoretical model developed by Walsh and others. The observed dispersion highlights the need for care in seismological application of results obtained at MHz frequencies from laboratory ultrasonic measurements.

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Section: Introductionmentioning

confidence: 99%

Shear Modulus Dispersion in Cracked and Fluid‐Saturated Quartzites: Experimental Observations and Modeling

2018

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“…Poor DMO performance has also previously been observed on similar types of data (e.g. Heinonen et al, 2013;Juhlin et al, 2010) and has been attributed to the complexity of the structures and the crookedness of the acquisition profile. Therefore, in the vicinity of the fault we present stacked seismic sections that were obtained using only NMO corrections to enhance reflections assumed to originate from the fault or structures associated with it.…”

Section: Data Processingmentioning

confidence: 57%

“…Preliminary commercially processing of the data did not clearly image the Suasselkä fault and in order to improve the clarity of the seismic images we have supplemented an otherwise standard processing flow with specialized techniques such as cross-dip analysis. The new processing presented here is built on the experience of previous seismic studies on PG faults in northern Sweden (Juhlin and Lund, 2011;Juhlin et al, 2010) and on reprocessing of other HIRE seismic data (Heinonen et al, , 2013Koivisto et al, 2012). Thus, we expected that reprocessing of the Suurikuusikko seismic data would provide more detailed information about the geometry of the Suasselkä fault in the upper few kilometers of the crust.…”

Section: Introductionmentioning

confidence: 99%

Constraints on the geometry of the Suasselkä post-glacial fault, northern Finland, based on reflection seismic imaging

et al. 2015

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“…In the Vihanti area, ore-hosting skarn, cordierite gneisses and mafic volcanic rocks have high acoustic impedances and distinct contrast against the surrounding, low acoustic impedance, intermediate tuffites. This suggests that the host rocks of the deposit could be traced in the subsurface with reflection soundings (Kukkonen et al 2011;Heinonen et al 2013). In addition, the magnetic anomalies in aeromagnetic maps are associated with the Lampinsaari and Kuuhkamo Zn deposits in the Vihanti area.…”

Section: Potential Resources Assessmentmentioning

confidence: 99%

The Vihanti-Pyhäsalmi Area

Laine

Luukas

Mäki

et al. 2015

Mineral Resource Reviews

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The Vihanti-Pyhäsalmi district is located at the border zone between the Archaean craton in the northeast and the Palaeoproterozoic Svecofennian domain in central Finland. It is part of the Savo belt and contains one operating and four past mines and several uneconomic VHMS (Volcanic Hosted Massive Sulphide) deposits. Regional, semi-regional and mine scale 3D models of the Vihanti-Pyhäsalmi area were built in order to understand the formation of the VHMS deposit and accordingly map the ore critical geological formations and structures. In addition to the 3D modelling of the present day geology, structural geological inference was used to build 3D geological models visualizing the main deformational stages in past. The used data and information consisted of geological maps and reports, drill core logs, lithogeochemistry, reflection seismic profiles, potential field measurements and electromagnetic surveys. The geophysical 2D and 3D inversion were used to assist the 3D geological modelling seeking for continuity of the surficial structures especially in areas with only few or no drill core data. As a result, regional and semi-regional 3D models of the Vihanti-Pyhäsalmi area were obtained and new zones with VHMS exploration potential were identified in the vicinity of the Pyhäsalmi mine.

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Enhancing hardrock seismic images: Reprocessing of high resolution seismic reflection data from Vihanti, Finland

Cited by 11 publications

References 24 publications

Shear Modulus Dispersion in Cracked and Fluid‐Saturated Quartzites: Experimental Observations and Modeling

Shear Modulus Dispersion in Cracked and Fluid‐Saturated Quartzites: Experimental Observations and Modeling

Constraints on the geometry of the Suasselkä post-glacial fault, northern Finland, based on reflection seismic imaging

The Vihanti-Pyhäsalmi Area

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