Shear velocity structure beneath the central United States from the inversion of Rayleigh wave phase velocities

2021 ◽  
Author(s):  
Yu Geng ◽  
URBI BASU ◽  
Christine A. Powell
Keyword(s):  
United States ◽  
Rayleigh Wave ◽  
Velocity Structure ◽  
Shear Velocity ◽  
Phase Velocities ◽  
Wave Phase ◽  
Central United States

scholarly journals Shear velocity structure of the Mariana mantle wedge from Rayleigh wave phase velocities

2010 ◽  
Vol 115 (B11) ◽  
Author(s):  
Moira L. Pyle ◽  
Douglas A. Wiens ◽  
Dayanthie S. Weeraratne ◽  
Patrick J. Shore ◽  
Hajime Shiobara ◽  
...  
Keyword(s):  
Rayleigh Wave ◽  
Mantle Wedge ◽  
Velocity Structure ◽  
Shear Velocity ◽  
Phase Velocities ◽  
Wave Phase

scholarly journals Azimuthal anisotropy of Rayleigh-wave phase velocities in the east-central United States

2008 ◽  
Vol 173 (3) ◽  
pp. 827-843 ◽  
Author(s):  
Frédéric Deschamps ◽  
Sergei Lebedev ◽  
Thomas Meier ◽  
Jeannot Trampert
Keyword(s):  
United States ◽  
Rayleigh Wave ◽  
Azimuthal Anisotropy ◽  
East Central ◽  
Phase Velocities ◽  
Wave Phase ◽  
Central United States

scholarly journals Shear velocity structure beneath the central United States: implications for the origin of the Illinois Basin and intraplate seismicity

2016 ◽  
Vol 17 (3) ◽  
pp. 1020-1041 ◽  
Author(s):  
Chen Chen ◽  
Hersh Gilbert ◽  
Christopher Andronicos ◽  
Michael W. Hamburger ◽  
Timothy Larson ◽  
...  
Keyword(s):  
United States ◽  
Velocity Structure ◽  
Shear Velocity ◽  
Illinois Basin ◽  
Intraplate Seismicity ◽  
Central United States

Wave propagation and subsurface velocity structure at the Virgo gravitational wave detector (Italy)

2020 ◽  
Author(s):  
Gilberto Saccorotti ◽  
Sonja Gaviano ◽  
Carlo Giunchi ◽  
Irene Fiori ◽  
Soumen Koley ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Phase Velocity ◽  
Rayleigh Wave ◽  
Gravitational Wave ◽  
Rayleigh Waves ◽  
Velocity Structure ◽  
Band Frequency ◽  
Frequency Bands ◽  
Phase Velocities ◽  
Wave Phase

<p>The performances and sensitivity of gravitational wave (GW) detectors are significantly affected by the seismic environment. In particular, the seismic displacements and density fluctuations of the ground due to seismic-wave propagation introduce noise in the detector output signal; this noise is referred to as gravity-gradient noise, or Newtonian Noise (NN). The development of effective strategies for mitigating the effects of NN requires, therefore, a thorough assessment of seismic wavefields and medium properties at and around the GW detector. In this work, we investigate wave propagation and the subsurface velocity structure at the Virgo GW detector (Italy), using data from a temporary, 50-element array of vertical seismometers. In particular, we analyze the recordings from the catastrophic Mw=6.2 earthquake which struck Central Italy on August 24, 2016, and six of the following aftershocks.  The general kinematic properties of the earthquake wavefields are retrieved from the application of a broad-band, frequency-domain beam-forming technique. This method allows measuring the propagation direction and horizontal slowness of the incoming signal; it is applied to short time windows sliding along the array seismograms, using different subarrays whose aperture was selected in order to match different frequency bands. For the Rayleigh-wave arrivals, velocities range between 0.5 km/s and 5 km/s, suggesting the interference of different wave types and/or multiple propagation modes. For those same time intervals, the propagation directions are scattered throughout a wide angular range, indicating marked propagation effects associated with geological and topographical complexities. These results suggest that deterministic methods are not appropriate for estimating Rayleigh waves phase velocities. By assuming that the gradient of the displacement is constant throughout the array, we then attempt the estimation of ground rotations around an axis parallel to the surface (tilt), which is in turn linearly related to the phase velocity of Rayleigh waves. We calculate the ground tilt over subsequent, narrow frequency bands. Individual frequency intervals are investigated using sub-arrays with aperture specifically tailored to the frequency (wavelength) under examination. From the scaled average of the velocity-to-rotation ratios, we obtain estimates of the Rayleigh-wave phase velocities, which finally allow computing a dispersion relationship. Due to their diffusive nature, earthquake coda waves are ideally suited for the application of Aki’s autocorrelation method (SPAC). We use SPAC and a non-linear fitting of correlation functions to derive the dispersion properties of Rayleigh wave for all the 1225 independent inter-station paths. The array-averaged SPAC dispersion is consistent with that inferred from ground rotations, and with previous estimates from seismic noise analysis.  Using both a semi-analytical and perturbational approaches, this averaged dispersion is inverted to obtain a shear wave velocity profile down to ~1000m depth. Finally, we also perform an inversion of the frequency-dependent travel times associated with individual station pairs to obtain 2-D, Rayleigh wave phase velocity maps spanning the 0.5-3Hz frequency interval. </p>

Upper mantle shear velocity structure beneath the equatorial East Pacific Rise from array-based teleseismic surface-wave dispersion analysis

2019 ◽  
Author(s):  
Qiushi Zhai ◽  
Huajian Yao ◽  
Zhigang Peng
Keyword(s):  
Phase Velocity ◽  
Rayleigh Wave ◽  
Upper Mantle ◽  
Velocity Dispersion ◽  
Velocity Structure ◽  
Shear Velocity ◽  
Wave Phase ◽  
Phase Velocity Dispersion ◽  
Wave Phase Velocity ◽  
Rayleigh Wave Phase Velocity

Summary The Discovery/Gofar transform faults system is associated with a fast-spreading center on the equatorial East Pacific Rise. Most previous studies focus on its regular seismic cycle and crustal fault zone structure, but the characteristics of the upper mantle structure beneath this mid-ocean ridge system are not well known. Here we invert upper mantle shear velocity structure in this region using both teleseismic surface waves and ambient seismic noise from 24 ocean bottom seismometers (OBSs) deployed in this region in 2008. We develop an array analysis method with multi-dimensional stacking and tracing to determine the average fundamental mode Rayleigh wave phase-velocity dispersion curve (period band 20–100 s) for 94 teleseismic events distributed along the E-W array direction. Then, we combine with the previously measured Rayleigh wave phase-velocity dispersion (period band 2–25 s) from ambient seismic noise to obtain the average fundamental mode (period band 2–100 s) and the first-higher mode (period band 3–7 s) Rayleigh wave phase-velocity dispersion. The average dispersion data are inverted for the 1-D average shear wave velocity (Vs) structure from crust to 200-km depth in the upper mantle beneath our study region. The average Vs between the Moho and 200-km depth of the final model is about 4.18 km/s. There exists an ∼5-km thickness high-velocity lid (LID) beneath the Moho with the maximum Vs of 4.37 km/s. Below the LID, the Vs of a pronounced low-velocity zone (LVZ) in the uppermost mantle (15–60 km depth) is 4.03–4.23 km/s (∼10 per cent lower than the global average). This pronounced LVZ is thinner and shallower than the LVZs beneath other oceanic areas with older lithospheric ages. We infer that partial melting (0.5–5 per cent) mainly occurs in the shallow upper mantle zone beneath this young (0–2 Myr) oceanic region. In the deeper portion (60–200 km depth), the Vs of a weak LVZ is 4.15–4.27 km/s (∼5 per cent lower than the global average). Furthermore, the inferred lithosphere-asthenosphere boundary (LAB) with ∼15-km thickness can fit well with the conductive cooling model. These results are useful for understanding the depth distribution and melting characteristics of the upper mantle lithosphere and asthenosphere in this active ridge-transform fault region.

Shear-wave velocity structure beneath Alaska from a Bayesian joint inversion of Sp receiver functions and Rayleigh wave phase velocities

2021 ◽  
Vol 560 ◽  
pp. 116785
Author(s):  
Isabella Gama ◽  
Karen M. Fischer ◽  
Zachary Eilon ◽  
Hannah E. Krueger ◽  
Colleen A. Dalton ◽  
...  
Keyword(s):  
Rayleigh Wave ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Velocity Structure ◽  
Joint Inversion ◽  
Receiver Functions ◽  
Phase Velocities ◽  
Wave Phase ◽  
Shear Wave Velocity Structure
Sign in / Sign up

Export Citation Format

Share Document