Reflection seismic studies over the end-glacial Burträsk fault, Skellefteå, Sweden

Juhlin, Christopher; Lund, Björn

doi:10.5194/se-2-9-2011

Cited by 32 publications

(20 citation statements)

References 22 publications

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“…Computational geophysics is essential to study the structure of the earth on the basis of seismic forward modeling, inversion and interpretation (Zappone, 1994;Long and Silver, 2009;Juhlin and Lund, 2011). In particular, grid methods are required for simulating wave propagation in heterogeneous realistic models (e.g., Carcione et al, 2002;Seriani et al, 1992).…”

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confidence: 99%

Simulation of seismic waves at the earth's crust (brittle–ductile transition) based on the Burgers model

et al. 2014

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Abstract. The earth's crust presents two dissimilar rheological behaviors depending on the in situ stress-temperature conditions. The upper, cooler part is brittle, while deeper zones are ductile. Seismic waves may reveal the presence of the transition but a proper characterization is required. We first obtain a stress-strain relation, including the effects of shear seismic attenuation and ductility due to shear deformations and plastic flow. The anelastic behavior is based on the Burgers mechanical model to describe the effects of seismic attenuation and steady-state creep flow. The shear Lamé constant of the brittle and ductile media depends on the in situ stress and temperature through the shear viscosity, which is obtained by the Arrhenius equation and the octahedral stress criterion. The P and S wave velocities decrease as depth and temperature increase due to the geothermal gradient, an effect which is more pronounced for shear waves. We then obtain the P -S and SH equations of motion recast in the velocity-stress formulation, including memory variables to avoid the computation of time convolutions. The equations correspond to isotropic anelastic and inhomogeneous media and are solved by a direct grid method based on the Runge-Kutta time stepping technique and the Fourier pseudospectral method. The algorithm is tested with success against known analytical solutions for different shear viscosities. A realistic example illustrates the computation of surface and reverse-VSP synthetic seismograms in the presence of an abrupt brittle-ductile transition.

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confidence: 99%

Simulation of seismic waves at the earth's crust (brittle–ductile transition) based on the Burgers model

et al. 2014

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“…No outcrops of basement rocks are found in the vicinity of the scarp, hence no fault or fault plane and sense of movement can be directly associated with the scarp. However, most glacially induced faults appear to be dominantly reverse, dipping between 50 and 60 • (Juhlin et al, 2010;Juhlin and Lund, 2011;Ahmadi et al, 2015) and associated with zones of weakness in the bedrock (e.g. shear zones or at rock contacts).…”

Section: Geological Backgroundmentioning

confidence: 99%

“…1). Based on the results from a reflection seismic survey, Ahmadi et al (2015) reported on the Pärvie post-glacial fault in Sweden, which they imaged down to about 8 km depth (see also Juhlin et al, 2010;Juhlin and Lund, 2011;Lindblom et al, 2015). To the best of our knowledge all known post-glacial faults have been reported to be associated with pre-existing structures (e.g.…”

Section: Introductionmentioning

confidence: 99%

Post-glacial reactivation of the Bollnäs fault, central Sweden – a multidisciplinary geophysical investigation

et al. 2016

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Abstract. Glacially induced intraplate faults are conspicuous in Fennoscandia where they reach trace lengths of up to 155 km with estimated magnitudes up to 8 for the associated earthquakes. While they are typically found in northern parts of Fennoscandia, there are a number of published accounts claiming their existence further south and even in northern central Europe. This study focuses on a prominent scarp discovered recently in lidar (light detection and ranging) imagery hypothesized to be from a post-glacial fault and located about 250 km north of Stockholm near the town of Bollnäs. The Bollnäs scarp strikes approximately northsouth for about 12 km. The maximum vertical offset in the sediments across the scarp is 4-5 m with the western block being elevated relative to the eastern block. To investigate potential displacement in the bedrock and identify structures in it that are related to the scarp, we conducted a multidisciplinary geophysical investigation that included gravity and magnetic measurements, high-resolution seismics, radio-magnetotellurics (RMT), electrical resistivity tomography (ERT) and ground-penetrating radar (GPR). Results of the investigations suggest a zone of low-velocity and highconductivity in the bedrock associated with a magnetic lineament that is offset horizontally about 50 m to the west of the scarp. The top of the bedrock is found ∼ 10 m below the surface on the eastern side of the scarp and about ∼ 20 m below on its western side. This difference is due to the different thicknesses of the overlying sediments accounting for the surface topography, while the bedrock surface is likely to be more or less at the same topographic level on both sides of the scarp; else the difference is not resolvable by the methods used. To explain the difference in the sediment covers, we suggest that the Bollnäs scarp is associated with an earlier deformation zone, within a wide (> 150 m), highly fractured, water-bearing zone that became active as a reverse fault after the latest Weichselian deglaciation.

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“…The length of the PGFs may vary from 2 to 150 km and the maximum height of the fault scarps from 1 to 12 m, and up to 30 m in the extreme cases (see compilation in Olesen et al, 2004). However, postglacial faulting is not confined to northern Fennoscandia, but has also been reported in northernmost Germany (Brandes et al, 2012) and central parts of Sweden and Finland (Malehmir et al, 2016;Mikko et al, 2015;Palmu et al, 2015;Juhlin and Lund, 2011;Juhlin et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Structure of the Suasselkä postglacial fault in northern Finland obtained by analysis of local events and ambient seismic noise

et al. 2017

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Abstract. Understanding the inner structure of seismogenic faults and their ability to reactivate is particularly important in investigating the continental intraplate seismicity regime. In our study we address this problem using analysis of local seismic events and ambient seismic noise recorded by the temporary DAFNE array in the northern Fennoscandian Shield. The main purpose of the DAFNE/FINLAND passive seismic array experiment was to characterize the presentday seismicity of the Suasselkä postglacial fault (SPGF), which was proposed as one potential target for the DAFNE (Drilling Active Faults in Northern Europe) project. The DAFNE/FINLAND array comprised an area of about 20 to 100 km and consisted of eight short-period and four broadband three-component autonomous seismic stations installed in the close vicinity of the fault area. The array recorded continuous seismic data during September 2011-May 2013. Recordings of the array have being analysed in order to identify and locate natural earthquakes from the fault area and to discriminate them from the blasts in the Kittilä gold mine. As a result, we found a number of natural seismic events originating from the fault area, which proves that the fault is still seismically active. In order to study the inner structure of the SPGF we use cross-correlation of ambient seismic noise recorded by the array. Analysis of azimuthal distribution of noise sources demonstrated that during the time interval under consideration the distribution of noise sources is close to the uniform one. The continuous data were processed in several steps including single-station data analysis, instrument response removal and time-domain stacking. The data were used to estimate empirical Green's functions between pairs of stations in the frequency band of 0.1-1 Hz and to calculate corresponding surface wave dispersion curves. The Swave velocity models were obtained as a result of dispersion curve inversion. The results suggest that the area of the SPGF corresponds to a narrow region of low S-wave velocities surrounded by rocks with high S-wave velocities. We interpret this low-velocity region as a non-healed mechanically weak fault damage zone (FDZ) formed due to the last major earthquake that occurred after the last glaciation.

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Reflection seismic studies over the end-glacial Burträsk fault, Skellefteå, Sweden

Cited by 32 publications

References 22 publications

Simulation of seismic waves at the earth's crust (brittle–ductile transition) based on the Burgers model

Simulation of seismic waves at the earth's crust (brittle–ductile transition) based on the Burgers model

Post-glacial reactivation of the Bollnäs fault, central Sweden – a multidisciplinary geophysical investigation

Structure of the Suasselkä postglacial fault in northern Finland obtained by analysis of local events and ambient seismic noise

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