Crustal and uppermost mantle structure of southern Norway: results from surface wave analysis of ambient seismic noise and earthquake data

Köhler, Andreas; Weidle, Christian; Maupin, Valérie

doi:10.1111/j.1365-246x.2012.05698.x

Cited by 15 publications

(15 citation statements)

References 40 publications

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“…Average faster velocities from the EQM in comparison to the ANM have also been reported by Zhou et al (2012) curves) -all taken around 30 s. Without stating whether the discrepancy is positive or negative, Köhler et al (2012) also find residuals of up to 1.5 per cent at 25 s. To our knowledge, there are no studies that show faster measurements from the ANM, which leads us to believe that this discrepancy is systematic. There are several possible reasons for the bias between ambient-noise and earthquake results: In Fig.…”

Section: Dispersion Curvesmentioning

confidence: 68%

“…A similar approach was followed before by Harmon et al (2008), Yang et al (2008a,b), Yao et al (2008), Ritzwoller et al (2011), Köhler et al (2012), Zhou et al (2012) and Shen et al (2013). Yao et al (2008) present a direct comparison of phase-velocity dispersion curves.…”

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confidence: 99%

“…Udías 1999), making ambient-noise studies ideal to assess the structure of the crust and upper mantle. Recordings of earthquake-generated teleseismic surface waves are dominated by lowerfrequency signal and thus sensitive to larger depths; their combination with ambient-noise data results in a data set that is sensitive to a broader depth range than ever previously achieved (Yao et al 2006(Yao et al , 2008Ritzwoller et al 2011;Köhler et al 2012;Zhou et al 2012). We only treat surface-wave phase velocity in this work, which has the advantage that group velocity can be derived from it, while the opposite is not possible.…”

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confidence: 99%

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Two-receiver measurements of phase velocity: cross-validation of ambient-noise and earthquake-based observations

Kästle¹,

Soomro

Weemstra

et al. 2016

Geophys. J. Int.

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S U M M A R YPhase velocities derived from ambient-noise cross-correlation are compared with phase velocities calculated from cross-correlations of waveform recordings of teleseismic earthquakes whose epicentres are approximately on the station-station great circle. The comparison is conducted both for Rayleigh and Love waves using over 1000 station pairs in central Europe. We describe in detail our signal-processing method which allows for automated processing of large amounts of data. Ambient-noise data are collected in the 5-80 s period range, whereas teleseismic data are available between about 8 and 250 s, resulting in a broad common period range between 8 and 80 s. At intermediate periods around 30 s and for shorter interstation distances, phase velocities measured from ambient noise are on average between 0.5 per cent and 1.5 per cent lower than those observed via the earthquake-based method. This discrepancy is small compared to typical phase-velocity heterogeneities (10 per cent peak-to-peak or more) observed in this period range.We nevertheless conduct a suite of synthetic tests to evaluate whether known biases in ambient-noise cross-correlation measurements could account for this discrepancy; we specifically evaluate the effects of heterogeneities in source distribution, of azimuthal anisotropy in surface-wave velocity and of the presence of near-field, rather than far-field only, sources of seismic noise. We find that these effects can be quite important comparing individual station pairs. The systematic discrepancy is presumably due to a combination of factors, related to differences in sensitivity of earthquake versus noise data to lateral heterogeneity. The data sets from both methods are used to create some preliminary tomographic maps that are characterized by velocity heterogeneities of similar amplitude and pattern, confirming the overall agreement between the two measurement methods.

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Section: Dispersion Curvesmentioning

confidence: 68%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Two-receiver measurements of phase velocity: cross-validation of ambient-noise and earthquake-based observations

Kästle¹,

Soomro

Weemstra

et al. 2016

Geophys. J. Int.

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“…Other studies have detected the particularly low S velocities below southern Norway using teleseismic tomography (Wawerzinek et al 2013), surface wave tomography (Weidle & Maupin 2008;Maupin 2011;Köhler et al 2012) (Rickers et al 2013). Rickers et al (2013) interpret this anomaly as being connected westwards to the 'Iceland -Jan Mayen plume system'.…”

Section: Svecofennian Sveconorwegian and Caledonian Unitsmentioning

confidence: 98%

“…1a) by running north into southern Norway near the Oslo Graben. That study also outlined a P-wave low-velocity uppermost mantle below most of southern Norway, an area also characterized by low S-wave velocities, as shown by both S-wave traveltime tomography (Wawerzinek et al 2013) and surface wave analysis (Weidle & Maupin 2008;Maupin 2011;Köhler et al 2012). The above studies with results for southern Norway included data from the MAGNUS project (Weidle et al 2010) and formed part of the TopoScandiaDeep project (for a review see Maupin et al 2013), a component of the TOPOEUROPE program.…”

Section: Previous Studiesmentioning

confidence: 99%

Upper-mantleP- andS-wave velocities across the Northern Tornquist Zone from traveltime tomography

et al. 2015

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S U M M A R YThis study presents P-and S-wave velocity variations for the upper mantle in southern Scandinavia and northern Germany based on teleseismic traveltime tomography. Tectonically, this region includes the entire northern part of the prominent Tornquist Zone which follows along the transition from old Precambrian shield units to the east to younger Phanerozoic deep sedimentary basins to the southwest. We combine data from several separate temporary arrays/profiles (276 stations) deployed over a period of about 15 yr and permanent networks (31 stations) covering the areas of Denmark, northern Germany, southern Sweden and southern Norway. By performing an integrated P-and S-traveltime analysis, we obtain the first high-resolution combined 3-D V P and V S models, including variations in the V P /V S ratio, for the whole of this region of study. Relative station mean traveltime residuals vary within ±1 s for P wave and ±2 s for S wave, with early arrivals in shield areas of southern Sweden and later arrivals in the Danish and North German Basins, as well as in most of southern Norway. In good accordance with previous, mainly P-velocity models, a marked upper-mantle velocity boundary (UMVB) is accurately delineated between shield areas (with high seismic mantle velocity) and basins (with lower velocity). It continues northwards into southern Norway near the Oslo Graben area and further north across the Southern Scandes Mountains. This main boundary, extending to a depth of at least 300 km, is even more pronounced in our new S-velocity model, with velocity contrasts of up to ±2-3 per cent. It is also clearly reflected in the V P /V S ratio. Differences in this ratio of up to about ±2 per cent are observed across the boundary, with generally low values in shield areas to the east and relatively higher values in basin areas to the southwest and in most of southern Norway. Differences in the V P /V S ratio are believed to be a rather robust indicator of upper-mantle compositional differences. For the depth interval of about 100-300 km, thick, depleted, relatively cold shield lithosphere is indicated in southern Sweden, contrasting with more fertile, warm mantle asthenosphere beneath most of the basins in Denmark and northern Germany. Both compositional and temperature differences seem to play a significant role in explaining the UMVB between southern Norway and southern Sweden. In addition to the main regional upper-mantle velocity contrasts, a number of more local anomaly features are also outlined and discussed.

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Upper and Middle Crustal Velocity Structure of the Colombian Andes From Ambient Noise Tomography: Investigating Subduction‐Related Magmatism in the Overriding Plate

et al. 2018

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New maps of S velocity variation for the upper and middle crust making up the northwestern most corner of South America have been developed from cross correlation of ambient seismic noise at 52 broadband stations in the region. Over 1,300 empirical Green's functions, reconstructing the Rayleigh wave portion of the seismic wavefield, were obtained after time and frequency‐domain normalization of the ambient noise recordings and stacking of 48 months of normalized data. Interstation phase and group velocity curves were then measured in the 6–38 s period range and tomographically inverted to produce maps of phase and group velocity variation in a 0.5° × 0.5° grid. Velocity‐depth profiles were developed for each node after simultaneously inverting phase and group velocity curves and combined to produce 3‐D maps of S velocity variation for the region. The S velocity models reveal a ~7 km thick sedimentary cover in the Caribbean region, the Magdalena Valley, and the Cordillera Oriental, as well as crustal thicknesses in the Pacific and Caribbean region under ~35 km, consistent with previous studies. They also display zones of slow velocity at 25–35 km depth under regions of both active and inactive volcanism, suggesting the presence of melts that carry the signature of segmented subduction into the overriding plate. A low‐velocity zone in the same depth range is imaged under the Lower Magdalena Basin in the Caribbean region, which may represent either sublithospheric melts ponding at midcrustal levels after breaching through a fractured Caribbean flat slab or fluid migration through major faults within the Caribbean crust.

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Crustal and uppermost mantle structure of southern Norway: results from surface wave analysis of ambient seismic noise and earthquake data

Cited by 15 publications

References 40 publications

Two-receiver measurements of phase velocity: cross-validation of ambient-noise and earthquake-based observations

Two-receiver measurements of phase velocity: cross-validation of ambient-noise and earthquake-based observations

Upper-mantleP- andS-wave velocities across the Northern Tornquist Zone from traveltime tomography

Upper and Middle Crustal Velocity Structure of the Colombian Andes From Ambient Noise Tomography: Investigating Subduction‐Related Magmatism in the Overriding Plate

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