High resolution reflection seismic imaging of the Ullared Deformation Zone, southern Sweden

Lundberg, Emil; Juhlin, Christopher

doi:10.1016/j.precamres.2011.07.012

Cited by 20 publications

(13 citation statements)

References 30 publications

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“…It consists of an hydraulic hammer mounted on a tractor and a computer control system. This type of source has been used in other studies in Sweden with good results (e.g., Juhlin et al, , 2010Juhlin and Palm, 2005;Dehghannejad et al, 2010;Lundberg and Juhlin, 2011;Malehmir et al, 2011). It is generally preferred to explosives due to its lower cost and uniform source signature .…”

Section: Seismic Reflection Data Acquisitionmentioning

confidence: 99%

“…Instead, if stacking is carried out along CDP bins rotated to coincide with the strike direction of the reflectors, stronger and more continuous reflections are to be expected. Thus, by examining stacked sections with systematically rotated CDP bins, it is possible to obtain not only sharper and more coherent reflections, but also an estimate of the strike of the reflectors (Tsumura et al, 2009;Kashubin and Juhlin, 2010;Lundberg and Juhlin, 2011).…”

Section: Azimuthal Binningmentioning

confidence: 99%

“…The estimation of the necessary cross-dip angle ϕ i , can be done by visually inspecting stacked sections cross-dip corrected with different ϕ i (e.g., Wu et al, 1995;O'Dowd et al, 2004;Rodriguez-Tablante et al, 2007;Dehghannejad et al, 2010;Lundberg and Juhlin, 2011). In our case, because the azimuth of the CDP bins is not perpendicular to the staking line (see previous section), the transverse offset, Y ij , is not the shortest distance to the stacking line, but the distance along the rotated CDP bins.…”

Section: B68mentioning

confidence: 99%

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MT and reflection seismics in northwestern Skellefte Ore District, Sweden

et al. 2013

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A seismic reflection and MT survey was carried out along a 27-km long transect in northwestern Skellefte District, as part of a bigger 3D modeling project. The main motivation for the data acquisition is to elucidate the geologic relationship between the known mineralizations in the Adak mining camp to the north and in the well studied Kristineberg area south of the transect. The seismic reflection data were acquired with a VIBSIST system, and show reflectivity down to 3 s. Apart from the conventional processing for crystalline environments, the seismic data was also subject to an azimuthal binning procedure and crossdip analysis, allowing the orientation of planar reflectors in 3D. Regarding the MT data, it is primarily of good quality along the 17 installed sites. The inversion of the determinant of the impedance tensor yielded a stable 2D resistivity model, dominated by resistors corresponding to the postorogenic intrusions along the transect. Adding the location of the analyzed seismic reflectors in the MT inversion rendered an integrated model that facilitated a preliminary joint interpretation of the data sets. Overall, the results are in good agreement with surface observations and reveal a crude configuration of the geologic units below the transect. The most prominent outcomes are the lateral and depth extent of the large postorogenic intrusions in the area reaching to 5-or 6-km depth, the dimensions of the nearly vertical Brännäs gabbro extending to 6-km depth, and the presence of enhanced conductivities along the transect at about 10 km depth. The latter is probably related to the deep conductor previously identified in the district.

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Section: Seismic Reflection Data Acquisitionmentioning

confidence: 99%

Section: Azimuthal Binningmentioning

confidence: 99%

Section: B68mentioning

confidence: 99%

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MT and reflection seismics in northwestern Skellefte Ore District, Sweden

et al. 2013

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“…This system has proven to be useful for imaging fault zones, deformation zones and the upper crust in crystalline environments (e.g. Dehghannejad et al, 2010;Juhlin et al, 2010;Juhlin and Lund, 2011;Lundberg and Juhlin, 2011). The system consists of a hydraulic breaking hammer mounted on a tractor or excavator.…”

Section: Data Acquisitionmentioning

confidence: 99%

“…Therefore, we tested both an azimuthal binning procedure and a cross-dip analysis method, as described in e.g. Lundberg and Juhlin (2011). These tests were designed to improve the coherency of reflections that originate from out-of-the-plane of the profile.…”

Section: Processingmentioning

confidence: 99%

High resolution reflection seismic profiling over the Tjellefonna fault in the Møre-Trøndelag Fault Complex, Norway

2012

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Abstract. The Møre-Trøndelag Fault Complex (MTFC) is one of the most prominent fault zones of Norway, both onshore and offshore. In spite of its importance, very little is known of the deeper structure of the individual fault segments comprising the fault complex. Most seismic lines have been recorded offshore or focused on deeper structures. This paper presents results from two reflection seismic profiles, located on each side of the Tingvollfjord, acquired over the Tjellefonna fault in the southeastern part of the MTFC. Possible kilometer scale vertical offsets, reflecting large scale northwest-dipping normal faulting, separating the high topography to the southeast from lower topography to the northwest have been proposed for the Tjellefonna fault or the Baeverdalen lineament. In this study, however, the Tjellefonna fault is interpreted to dip approximately 50-60 • towards the southeast to depths of at least 1.3 km. Travel-time modeling of reflections associated with the fault was used to establish the geometry of the fault structure at depth, while detailed analysis of first P-wave arrivals in shot gathers, together with resistivity profiles, were used to define the near surface geometry of the fault zone. A continuation of the structure on the northeastern side of the Tingvollfjord is suggested by correlation of an in strike direction P-S converted reflection (generated by a fracture zone) seen on the reflection data from that side of the Tingvollfjord. The reflection seismic data correlate well with resistivity profiles and recently published near surface geophysical data. A highly reflective package forming a gentle antiform structure was also identified on both seismic profiles. This structure could be related to the folded amphibolite lenses seen on the surface or possibly by an important boundary within the gneissic basement rocks of the Western Gneiss Region. The fold hinge line of the structure is parallel with the Tjellefonna fault trace suggesting that the folding and faulting may have been related.

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Delineating fracture zones using surface‐tunnel‐surface seismic data, P‐S, and S‐P mode conversions

2017

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A surface‐tunnel‐surface seismic experiment was conducted at the Äspö Hard Rock Laboratory to study the seismic response of major fracture systems intersecting the tunnel. A newly developed three‐component microelectromechanical sensor‐based seismic landstreamer was deployed inside the noisy tunnel along with conventional seismic receivers. In addition to these, wireless recorders were placed on the surface. This combination enabled simultaneous recording of the seismic wavefield both inside the tunnel and on the surface. The landstreamer was positioned between two geophone‐based line segments, along the interval where known fracture systems intersect the tunnel. First arrival tomography produced a velocity model of the rock mass between the tunnel and the surface with anomalous low‐velocity zones correlating well with locations of known fracture systems. Prominent wave mode converted direct and reflected signals, P‐S and S‐P waves, were observed in numerous source gathers recorded inside the tunnel. Forward travel time and 2‐D finite difference elastic modeling, based on the known geometry of the fracture systems, show that the converted waves are generated at these systems. Additionally, the landstreamer data were used to estimate Vp/Vs, Poisson's ratio, and seismic attenuation factors (Qp and Qs) over fracture sets that have different hydraulic conductivities. The low‐conductivity fracture sets have greater reductions in P wave velocities and Poisson's ratio and are more attenuating than the highly hydraulically conductive fracture set. Our investigations contribute to fracture zone characterization on a scale corresponding to seismic exploration wavelengths.

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High resolution reflection seismic imaging of the Ullared Deformation Zone, southern Sweden

Cited by 20 publications

References 30 publications

MT and reflection seismics in northwestern Skellefte Ore District, Sweden

MT and reflection seismics in northwestern Skellefte Ore District, Sweden

High resolution reflection seismic profiling over the Tjellefonna fault in the Møre-Trøndelag Fault Complex, Norway

Delineating fracture zones using surface‐tunnel‐surface seismic data, P‐S, and S‐P mode conversions

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