Shear-Wave Velocity Model of the Bohemian Massif Crust from Ambient Noise Tomography

The current knowledge of the structure of the Bohemian Massif (BM) crust is mostly based on interpretation of refraction and reflection seismic experiments performed along 2D profiles. The recent development of ambient noise tomography, in combination with dense networks of permanent seismic stations and arrays of passive seismic experiments, provides unique opportunity to build the high-resolution 3D velocity model of the BM crust from long sequences of ambient seismic noise data.The new 3D shear-wave velocity model is built from surface-wave group-velocity dispersion measurements derived from ambient seismic noise cross-correlations by conventional two-step inversion approach. First, the 2D fast marching travel time tomography is applied to regularise velocity dispersions. Second, the stochastic inversion is applied to compute 1D shear-wave velocity profiles beneath each location of the processing grid.We processed continuous waveform data from 404 seismic stations (permanent and temporary stations of passive experiments BOHEMA I-IV, PASSEQ, EGER RIFT, ALPARRAY-EASI and ALPARRAY-AASN) in a broader region of the BM (in an area of 46-540 N 7-210 E). The overlapping period of each possible station-pair and cross-correlation quality review resulted in more than 21,000 dispersion curves, which further served as an input for surface-wave inversion at high-density grid with the cell size of 22 km. We present the new high-resolution 3D shear-wave velocity model of the BM crust and uppermost mantle with preliminary tectonic interpretations. We compare this model with a compiled P-wave velocity model from the 2D seismic refraction and wide-angle reflection experiments and with the crustal thickness (Moho depth) extracted from P-wave receiver functions (see Kampfov&#225; Exnerov&#225; et al., EGU2020_SM4.3). 1D velocity profiles resulting from the stochastic inversions exhibit regional variations, which are characteristic for individual units of the BM. Velocities within the upper crust of the BM are ~0.2 km/s higher than those in its surroundings. The highest crustal velocities occur in its southern part (Moldanubian unit). The velocity model confirms, in accord with results from receiver functions and other seismic studies, a relatively thin crust in the Saxothuringian unit, whilst thickness of the Moldanubian crust is at least 36 km in its central and southern parts. The most distinct interface with a velocity inversion at the depth of about 20 to 25 km occurs in the Moldanubian unit. The velocity decrease in the lower crust reflects probably its transversely isotropic structure.

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Shallow Shear-Wave Velocity Structure in Oklahoma Based on the Joint Inversion of Ambient Noise Dispersion and Teleseismic P-Wave Receiver Functions

Bulletin of the Seismological Society of America ◽

10.1785/0120200246 ◽

2020 ◽

Author(s):

Jiayan Tan ◽

Charles A. Langston ◽

Sidao Ni

Keyword(s):

Surface Wave ◽

Shear Wave ◽

Wave Velocity ◽

Shear Wave Velocity ◽

Ambient Noise ◽

Sedimentary Basins ◽

Velocity Model ◽

Receiver Functions ◽

P Wave ◽

Velocity Models

ABSTRACT Ambient noise cross-correlations, used to obtain fundamental-mode Rayleigh-wave group velocity estimates, and teleseismic P-wave receiver functions are jointly modeled to obtain a 3D shear-wave velocity model for the crust and upper mantle of Oklahoma. Broadband data from 82 stations of EarthScope Transportable Array, the U.S. National Seismic Network, and the Oklahoma Geological Survey are used. The period range for surface-wave ambient noise Green’s functions is from 4.5 to 30.5 s constraining shear-wave velocity to a depth of 50 km. We also compute high-frequency receiver functions at these stations from 214 teleseismic earthquakes to constrain individual 1D velocity models inferred from the surface-wave tomography. Receiver functions reveal Ps conversions from the Moho, intracrustal interfaces, and shallow sedimentary basins. Shallow low-velocity zones in the model correlate with the large sedimentary basins of Oklahoma. The velocity model significantly improves the agreement of synthetic and observed seismograms from the 6 November 2011 Mw 5.7 Prague, Oklahoma earthquake suggesting that it can be used to improve earthquake location and moment tensor inversion of local and regional earthquakes.

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First step towards an integrated geophysical-geological model of the W-Alps: A new Vs model from transdimensional ambient-noise tomography

10.5194/egusphere-egu21-3197 ◽

2021 ◽

Author(s):

Ahmed Nouibat ◽

Laurent Stehly ◽

Anne Paul ◽

Romain Brossier ◽

Thomas Bodin ◽

...

Keyword(s):

Group Velocity ◽

Shear Wave ◽

Wave Velocity ◽

Shear Wave Velocity ◽

Ambient Noise ◽

Receiver Functions ◽

Time Inversion ◽

Geological Model ◽

Ambient Noise Tomography ◽

Low Velocity

We have successfully derived a new 3-D high resolution shear wave velocity model of the crust and uppermost mantle of a large part of W-Europe from transdimensional ambient-noise tomography. This model is intended to contribute to the development of the first 3-D crustal-scale integrated geophysical-geological model of the W-Alps to deepen understanding of orogenesis and its relationship to mantle dynamics. We used an exceptional dataset of 4 years of vertical-component, daily seismic noise records (2015 - 2019) of more than 950 permanent broadband seismic stations located in and around the Greater Alpine region, complemented by 490 temporary stations from the AlpArray sea-land seismic network and 110 stations from Cifalps dense deployments.We firstly performed a 2-D data-driven transdimensional travel time inversion for group velocity maps from 4 to 150 s (Bodin & Sambridge, 2009). The data noise level was treated as a parameter of the inversion problem, and determined within a Hierarchical Bayes method. We used Fast Marching Eikonal solver (Rawlinson & Sambridge, 2005) jointly with the reversible jump algorithm to update raypath geometry during inversion. In the inversion of group velocity maps for shear-wave velocity, we set up a new formulation of the approach proposed by Lu et al (2018) by including group velocity uncertainties. Posterior probability distributions on Vs and interfaces were estimated by exploring a set of 130 millions synthetic 4-layer 1-D Vs models that allow for low-velocity zones. The obtained probabilistic model was refined using a linearized inversion. For the ocean-bottom seismometers of the Ligurian-Provencal basin, we applied a specific processing to clean daily noise signals from instrumental and oceanic noises (Crawford & Webb, 2000) and adapted the inversion for Vs to include the water column.Our Vs model evidences strong variations of the crustal structure along strike, particulary in the subduction complex. The European crust includes lower crustal low-velocity zones and a Moho jump of ~8-12 km beneath the W-boundary of the external crystalline massifs. We observe a deep LVZ structure (50 - 80 km) in the prolongation of the European continental subduction beneath the Ivrea body. The striking fit between the receiver functions ccp migrated section across the Cifalps profile and this new Vs model validate its reliability.

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3-D crustal structure of the Iran plateau using phase velocity ambient noise tomography

Geophysical Journal International ◽

10.1093/gji/ggz537 ◽

2019 ◽

Vol 220 (3) ◽

pp. 1555-1568 ◽

Cited By ~ 2

Author(s):

R Movaghari ◽

G Javan Doloei

Keyword(s):

Phase Velocity ◽

Shear Wave ◽

Wave Velocity ◽

Crustal Structure ◽

Shear Wave Velocity ◽

Ambient Noise ◽

Velocity Model ◽

Central Iran ◽

Ambient Noise Tomography ◽

Iran Plateau

SUMMARY More accurate crustal structure models will help us to better understand the tectonic convergence between Arabian and Eurasian plates in the Iran plateau. In this study, the crustal and uppermost mantle velocity structure of the Iran plateau is investigated using ambient noise tomography. Three years of continuous data are correlated to retrieve Rayleigh wave empirical Green's functions, and phase velocity dispersion curves are extracted using the spectral method. High-resolution Rayleigh wave phase velocity maps are presented at periods of 8–60 s. The tomographic maps show a clear consistency with geological structures such as sedimentary basins and seismotectonic zones, especially at short periods. A quasi-3-D shear wave velocity model is determined from the surface down to 100 km beneath the Iran plateau. A transect of the shear wave velocity model has been considered along with a profile extending across the southern Zagros, the Sanandaj-Sirjan Zone (SSZ), the Urumieh-Dokhtar Magmatic Arc (UDMA) and Central Iran and Kopeh-Dagh (KD). Obvious crustal thinning and thickening are observable along the transect of the shear wave velocity model beneath Central Iran and the SSZ, respectively. The observed shear wave velocities beneath the Iran plateau, specifically Central Iran, support the slab break-off idea in which low density asthenospheric materials drive towards the upper layers, replacing materials in the subcrustal lithosphere.

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Shallow velocity model in the area of Pozzo Pitarrone, Mt. Etna, from single station, array methods and borehole data

Annals of Geophysics ◽

10.4401/ag-7086 ◽

2016 ◽

Vol 59 (4) ◽

Author(s):

Luciano Zuccarello ◽

Mario Paratore ◽

Mario La Rocca ◽

Ferruccio Ferrari ◽

Alfio Messina ◽

...

Keyword(s):

Shear Wave ◽

Wave Velocity ◽

Shear Wave Velocity ◽

Seismic Noise ◽

Velocity Model ◽

P Wave ◽

Borehole Data ◽

P Wave Velocity ◽

Single Station ◽

Mt Etna

Seismic noise recorded by a temporary array installed around Pozzo Pitarrone, NE flank of Mt. Etna, have been analysed with several techniques. Single station HVSR method and SPAC array method have been applied to stationary seismic noise to investigate the local shallow structure. The inversion of dispersion curves produced a shear wave velocity model of the area reliable down to depth of about 130 m. A comparison of such model with the stratigraphic information available for the investigated area shows a good qualitative agreement. Taking advantage of a borehole station installed at 130 m depth, we could estimate also the P-wave velocity by comparing the borehole recordings of local earthquakes with the same event recorded at surface. Further insight on the P-wave velocity in the upper 130 m layer comes from the surface reflected wave observable in some cases at the borehole station. From this analysis we obtained an average P-wave velocity of about 1.2 km/s, compatible with the shear wave velocity found from the analysis of seismic noise.

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Shear wave velocity model beneath CBJI station West Java, Indonesia from joint inversion of teleseismic receiver functions and surface wave dispersion

Journal of Physics Conference Series ◽

10.1088/1742-6596/985/1/012015 ◽

2018 ◽

Vol 985 ◽

pp. 012015

Author(s):

R H Simanungkalit ◽

T Anggono ◽

Syuhada ◽

A Amran ◽

Supriyanto

Keyword(s):

Surface Wave ◽

Shear Wave ◽

Wave Velocity ◽

Shear Wave Velocity ◽

Joint Inversion ◽

Wave Dispersion ◽

Velocity Model ◽

Receiver Functions ◽

Surface Wave Dispersion ◽

West Java

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Shear wave velocity model of the ABANICO formation underlying The santiago City Metropolitan Area, chile, using ambient seismic noise tomography

Geophysical Journal International ◽

10.1093/gji/ggaa600 ◽

2020 ◽

Author(s):

J Salomón ◽

C Pastén ◽

S Ruiz ◽

F Leyton ◽

M Sáez ◽

...

Keyword(s):

Shear Wave ◽

Wave Velocity ◽

Metropolitan Area ◽

Shear Wave Velocity ◽

Seismic Noise ◽

Velocity Model ◽

Dispersion Curves ◽

Ambient Seismic Noise ◽

Travel Times ◽

Abanico Formation

Summary The seismic response of the Santiago City, the capital of Chile with more than 5.5 million inhabitants, is controlled by the properties of the shallower quaternary deposits and the impedance contrast with the underlying Abanico formation, among other factors. In this study, we process continuous records of ambient seismic noise to perform an ambient seismic noise tomography with the aim of defining the shallower structure of the Abanico formation underneath the densely populated metropolitan area of Santiago, Chile. The seismic signals were recorded by a network consisting of 29 broadband seismological stations and 12 accelerograph stations, located in a 35 × 35 km2 quadrant. We used the average coherency of the vertical components to calculate dispersion curves from 0.1 to 5 Hz and Bootstrap resampling to estimate the variance of the travel times. The reliable frequency band of the dispersion curves was defined by an empirical method based on sign normalization of the coherency real part. The ambient noise tomography was solved on a domain discretized into 256 2 × 2 km2 cells. Using a regularized weighted least squares inversion, we inverted the observed travel-times between stations, assuming straight ray paths, in order to obtain 2D phase velocity maps from 0.2 Hz to 1.1 Hz, linearly spaced every 0.05 Hz, in 157 of the 256 square cells of the domain. In each square cell with information, dispersion curves were assembled and used to invert shear wave velocity profiles, which were interpolated using the ordinary Kriging method to obtain a 3D shear wave velocity model valid from 0.6 to 5 km depth. The 3D velocity model shows that the Abanico formation is stiffer in the south of the study area with larger velocity anomalies towards the shallower part of the model. The value of the shear wave velocity narrows with depth, reaching an average value of 3.5 km/s from 3 to 5 km depth.

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